From b7f30ca2ee4b46d496b2756261229a4b0da13a2f Mon Sep 17 00:00:00 2001
From: Mahadev Konar <mahadev@apache.org>
Date: Wed, 18 Nov 2009 19:06:39 +0000
Subject: [PATCH] ZOOKEEPER-368. Observers: core functionality (henry robinson
via mahadev)
git-svn-id: https://svn.apache.org/repos/asf/hadoop/zookeeper/trunk@881882 13f79535-47bb-0310-9956-ffa450edef68
---
CHANGES.txt | 2 +
docs/bookkeeperConfig.html | 3 +
docs/bookkeeperOverview.html | 3 +
docs/bookkeeperProgrammer.html | 3 +
docs/bookkeeperStarted.html | 3 +
docs/index.html | 6 +
docs/index.pdf | 91 ++--
docs/javaExample.html | 3 +
docs/linkmap.html | 9 +
docs/linkmap.pdf | 32 +-
docs/recipes.html | 3 +
docs/releasenotes.html | 3 +
docs/zookeeperAdmin.html | 3 +
docs/zookeeperHierarchicalQuorums.html | 3 +
docs/zookeeperInternals.html | 3 +
docs/zookeeperJMX.html | 3 +
docs/zookeeperObservers.html | 399 ++++++++++++++++++
docs/zookeeperObservers.pdf | 276 ++++++++++++
docs/zookeeperOver.html | 3 +
docs/zookeeperProgrammers.html | 3 +
docs/zookeeperQuotas.html | 3 +
docs/zookeeperStarted.html | 3 +
docs/zookeeperTutorial.html | 3 +
.../src/documentation/content/xdocs/index.xml | 1 +
.../src/documentation/content/xdocs/site.xml | 1 +
.../content/xdocs/zookeeperObservers.xml | 174 ++++++++
.../apache/zookeeper/server/ObserverBean.java | 45 ++
.../server/quorum/AuthFastLeaderElection.java | 18 +-
.../server/quorum/FastLeaderElection.java | 2 +-
.../zookeeper/server/quorum/Leader.java | 59 ++-
.../server/quorum/LeaderElection.java | 39 +-
.../server/quorum/LearnerHandler.java | 21 +-
.../zookeeper/server/quorum/Observer.java | 147 +++++++
.../server/quorum/ObserverMXBean.java | 37 ++
.../quorum/ObserverRequestProcessor.java | 123 ++++++
.../quorum/ObserverZooKeeperServer.java | 114 +++++
.../server/quorum/QuorumCnxManager.java | 7 +-
.../zookeeper/server/quorum/QuorumPeer.java | 146 ++++++-
.../server/quorum/QuorumPeerConfig.java | 46 +-
.../server/quorum/QuorumPeerMain.java | 1 +
.../zookeeper/server/quorum/QuorumStats.java | 5 +-
.../zookeeper/server/quorum/ObserverTest.java | 236 +++++++++++
.../server/quorum/QuorumPeerMainTest.java | 64 +--
.../server/quorum/QuorumPeerTestBase.java | 100 +++++
.../zookeeper/test/AsyncHammerTest.java | 20 +
.../test/HierarchicalQuorumTest.java | 70 ++-
.../test/ObserverHierarchicalQuorumTest.java | 59 +++
.../test/ObserverQuorumHammerTest.java | 43 ++
.../apache/zookeeper/test/ObserverTest.java | 242 +++++++++++
.../org/apache/zookeeper/test/QuorumBase.java | 23 +-
.../zookeeper/test/QuorumHammerTest.java | 6 +-
51 files changed, 2523 insertions(+), 189 deletions(-)
create mode 100644 docs/zookeeperObservers.html
create mode 100644 docs/zookeeperObservers.pdf
create mode 100644 src/docs/src/documentation/content/xdocs/zookeeperObservers.xml
create mode 100644 src/java/main/org/apache/zookeeper/server/ObserverBean.java
create mode 100644 src/java/main/org/apache/zookeeper/server/quorum/Observer.java
create mode 100644 src/java/main/org/apache/zookeeper/server/quorum/ObserverMXBean.java
create mode 100644 src/java/main/org/apache/zookeeper/server/quorum/ObserverRequestProcessor.java
create mode 100644 src/java/main/org/apache/zookeeper/server/quorum/ObserverZooKeeperServer.java
create mode 100644 src/java/test/org/apache/zookeeper/server/quorum/ObserverTest.java
create mode 100644 src/java/test/org/apache/zookeeper/server/quorum/QuorumPeerTestBase.java
create mode 100644 src/java/test/org/apache/zookeeper/test/ObserverHierarchicalQuorumTest.java
create mode 100644 src/java/test/org/apache/zookeeper/test/ObserverQuorumHammerTest.java
create mode 100644 src/java/test/org/apache/zookeeper/test/ObserverTest.java
diff --git a/CHANGES.txt b/CHANGES.txt
index 85eb0439..a31b4d04 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -152,6 +152,8 @@ NEW FEATURES:
ZOOKEEPER-550. Java Queue Recipe. (steven cheng via mahadev)
+ ZOOKEEPER-368. Observers: core functionality (henry robinson via mahadev)
+
Release 3.2.0 - 2009-06-30
Non-backward compatible changes:
diff --git a/docs/bookkeeperConfig.html b/docs/bookkeeperConfig.html
index 42c92cab..cb20eb13 100644
--- a/docs/bookkeeperConfig.html
+++ b/docs/bookkeeperConfig.html
@@ -161,6 +161,9 @@ document.write("Last Published: " + document.lastModified);
<div class="menuitem">
<a href="zookeeperJMX.html">JMX</a>
</div>
+<div class="menuitem">
+<a href="zookeeperObservers.html">Observers Guide</a>
+</div>
</div>
<div onclick="SwitchMenu('menu_1.5', 'skin/')" id="menu_1.5Title" class="menutitle">Contributor</div>
<div id="menu_1.5" class="menuitemgroup">
diff --git a/docs/bookkeeperOverview.html b/docs/bookkeeperOverview.html
index 90d6c6a5..36898b7f 100644
--- a/docs/bookkeeperOverview.html
+++ b/docs/bookkeeperOverview.html
@@ -161,6 +161,9 @@ document.write("Last Published: " + document.lastModified);
<div class="menuitem">
<a href="zookeeperJMX.html">JMX</a>
</div>
+<div class="menuitem">
+<a href="zookeeperObservers.html">Observers Guide</a>
+</div>
</div>
<div onclick="SwitchMenu('menu_1.5', 'skin/')" id="menu_1.5Title" class="menutitle">Contributor</div>
<div id="menu_1.5" class="menuitemgroup">
diff --git a/docs/bookkeeperProgrammer.html b/docs/bookkeeperProgrammer.html
index f7cbf9d4..7b0f50af 100644
--- a/docs/bookkeeperProgrammer.html
+++ b/docs/bookkeeperProgrammer.html
@@ -161,6 +161,9 @@ document.write("Last Published: " + document.lastModified);
<div class="menuitem">
<a href="zookeeperJMX.html">JMX</a>
</div>
+<div class="menuitem">
+<a href="zookeeperObservers.html">Observers Guide</a>
+</div>
</div>
<div onclick="SwitchMenu('menu_1.5', 'skin/')" id="menu_1.5Title" class="menutitle">Contributor</div>
<div id="menu_1.5" class="menuitemgroup">
diff --git a/docs/bookkeeperStarted.html b/docs/bookkeeperStarted.html
index 0698f313..ad0a354b 100644
--- a/docs/bookkeeperStarted.html
+++ b/docs/bookkeeperStarted.html
@@ -161,6 +161,9 @@ document.write("Last Published: " + document.lastModified);
<div class="menuitem">
<a href="zookeeperJMX.html">JMX</a>
</div>
+<div class="menuitem">
+<a href="zookeeperObservers.html">Observers Guide</a>
+</div>
</div>
<div onclick="SwitchMenu('menu_1.5', 'skin/')" id="menu_1.5Title" class="menutitle">Contributor</div>
<div id="menu_1.5" class="menuitemgroup">
diff --git a/docs/index.html b/docs/index.html
index 7ee1b6d2..da3c6e9d 100644
--- a/docs/index.html
+++ b/docs/index.html
@@ -161,6 +161,9 @@ document.write("Last Published: " + document.lastModified);
<div class="menuitem">
<a href="zookeeperJMX.html">JMX</a>
</div>
+<div class="menuitem">
+<a href="zookeeperObservers.html">Observers Guide</a>
+</div>
</div>
<div onclick="SwitchMenu('menu_1.5', 'skin/')" id="menu_1.5Title" class="menutitle">Contributor</div>
<div id="menu_1.5" class="menuitemgroup">
@@ -288,6 +291,9 @@ document.write("Last Published: " + document.lastModified);
<a href="zookeeperHierarchicalQuorums.html">Hierarchical quorums</a>
</li>
+<li>
+<a href="zookeeperObservers.html">Observers</a> - non-voting ensemble members that easily improve ZooKeeper's scalability</li>
+
</ul>
</li>
diff --git a/docs/index.pdf b/docs/index.pdf
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diff --git a/docs/javaExample.html b/docs/javaExample.html
index 51334e91..23efc2d2 100644
--- a/docs/javaExample.html
+++ b/docs/javaExample.html
@@ -161,6 +161,9 @@ document.write("Last Published: " + document.lastModified);
<div class="menuitem">
<a href="zookeeperJMX.html">JMX</a>
</div>
+<div class="menuitem">
+<a href="zookeeperObservers.html">Observers Guide</a>
+</div>
</div>
<div onclick="SwitchMenu('menu_1.5', 'skin/')" id="menu_1.5Title" class="menutitle">Contributor</div>
<div id="menu_1.5" class="menuitemgroup">
diff --git a/docs/linkmap.html b/docs/linkmap.html
index 5aee0a26..4a5ba1ea 100644
--- a/docs/linkmap.html
+++ b/docs/linkmap.html
@@ -161,6 +161,9 @@ document.write("Last Published: " + document.lastModified);
<div class="menuitem">
<a href="zookeeperJMX.html">JMX</a>
</div>
+<div class="menuitem">
+<a href="zookeeperObservers.html">Observers Guide</a>
+</div>
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+ +-->
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+</div>
+<!--+
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+ +-->
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+ +-->
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+</div>
+<!--+
+ |end group logo
+ +-->
+<!--+
+ |start Project Logo
+ +-->
+<div class="projectlogo">
+<a href="http://hadoop.apache.org/zookeeper/"><img class="logoImage" alt="ZooKeeper" src="images/zookeeper_small.gif" title="ZooKeeper: distributed coordination"></a>
+</div>
+<!--+
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+ +-->
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+ +-->
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+<div class="menuitem">
+<a href="index.html">Welcome</a>
+</div>
+<div class="menuitem">
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+</div>
+<div class="menuitem">
+<a href="zookeeperStarted.html">Getting Started</a>
+</div>
+<div class="menuitem">
+<a href="releasenotes.html">Release Notes</a>
+</div>
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+</div>
+<div class="menuitem">
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+</div>
+<div class="menuitem">
+<a href="javaExample.html">Java Example</a>
+</div>
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+</div>
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+<div onclick="SwitchMenu('menu_1.3', 'skin/')" id="menu_1.3Title" class="menutitle">BookKeeper</div>
+<div id="menu_1.3" class="menuitemgroup">
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+<a href="bookkeeperStarted.html">Getting started</a>
+</div>
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+<div id="menu_1.5" class="menuitemgroup">
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+<a href="http://wiki.apache.org/hadoop/ZooKeeper/FAQ">FAQ</a>
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+ PDF</a>
+</div>
+<h1>ZooKeeper Observers</h1>
+<div id="minitoc-area">
+<ul class="minitoc">
+<li>
+<a href="#ch_Introduction">Observers: Scaling ZooKeeper Without Hurting Write Performance
+ </a>
+</li>
+<li>
+<a href="#sc_UsingObservers">How to use Observers</a>
+</li>
+<li>
+<a href="#ch_UseCases">Example use cases</a>
+</li>
+</ul>
+</div>
+
+
+
+
+
+<a name="N10009"></a><a name="ch_Introduction"></a>
+<h2 class="h3">Observers: Scaling ZooKeeper Without Hurting Write Performance
+ </h2>
+<div class="section">
+<p>
+
+<em>
+ Please note: the Observers feature currently only works with the basic
+ leader election protocol, not fast leader election or authenticated fast
+ leader election. This will be remedied when a bug in the leader election
+ protocol code is fixed in the near future. An exception will be thrown
+ if you try to start a cluster containing Observers without
+ electionAlg=0. See below for more details.
+ </em>
+
+</p>
+<p>
+ Although ZooKeeper performs very well by having clients connect directly
+ to voting members of the ensemble, this architecture makes it hard to
+ scale out to huge numbers of clients. The problem is that as we add more
+ voting members, the write performance drops. This is due to the fact that
+ a write operation requires the agreement of (in general) at least half the
+ nodes in an ensemble and therefore the cost of a vote can increase
+ significantly as more voters are added.
+ </p>
+<p>
+ We have introduced a new type of ZooKeeper node called
+ an <em>Observer</em> which helps address this problem and
+ further improves ZooKeeper's scalability. Observers are non-voting members
+ of an ensemble which only hear the results of votes, not the agreement
+ protocol that leads up to them. Other than this simple distinction,
+ Observers function exactly the same as Followers - clients may connect to
+ them and send read and write requests to them. Observers forward these
+ requests to the Leader like Followers do, but they then simply wait to
+ hear the result of the vote. Because of this, we can increase the number
+ of Observers as much as we like without harming the performance of votes.
+ </p>
+<p>
+ Observers have other advantages. Because they do not vote, they are not a
+ critical part of the ZooKeeper ensemble. Therefore they can fail, or be
+ disconnected from the cluster, without harming the availability of the
+ ZooKeeper service. The benefit to the user is that Observers may connect
+ over less reliable network links than Followers. In fact, Observers may be
+ used to talk to a ZooKeeper server from another data center. Clients of
+ the Observer will see fast reads, as all reads are served locally, and
+ writes result in minimal network traffic as the number of messages
+ required in the absence of the vote protocol is smaller.
+ </p>
+</div>
+
+<a name="N10022"></a><a name="sc_UsingObservers"></a>
+<h2 class="h3">How to use Observers</h2>
+<div class="section">
+<p>
+
+<em>
+ Note that
+ until <a href="https://issues.apache.org/jira/browse/ZOOKEEPER-578">ZOOKEEPER-578</a>
+ is resolved, you must set electionAlg=0 in every server configuration
+ file. Otherwise an exception will be thrown when you try to start your
+ ensemble.
+ </em>
+
+</p>
+<p>
+
+<em>
+ The reason: because Observers do not participate in leader elections,
+ they rely on voting Followers to inform them of changes to the
+ Leader. Currently, only the basic leader election algorithm starts a
+ thread that responds to requests from Observers to identify the current
+ Leader. Work is in progress on other JIRAs to bring this functionality
+ to all leader election protocols.
+ </em>
+
+</p>
+<p>Setting up a ZooKeeper ensemble that uses Observers is very simple,
+ and requires just two changes to your config files. Firstly, in the config
+ file of every node that is to be an Observer, you must place this line:
+ </p>
+<pre class="code">
+ peerType=observer
+ </pre>
+<p>
+ This line tells ZooKeeper that the server is to be an Observer. Secondly,
+ in every server config file, you must add :observer to the server
+ definition line of each Observer. For example:
+ </p>
+<pre class="code">
+ server.1:localhost:2181:3181:observer
+ </pre>
+<p>
+ This tells every other server that server.1 is an Observer, and that they
+ should not expect it to vote. This is all the configuration you need to do
+ to add an Observer to your ZooKeeper cluster. Now you can connect to it as
+ though it were an ordinary Follower. Try it out, by running:</p>
+<pre class="code">
+ bin/zkCli.sh -server localhost:2181
+ </pre>
+<p>
+ where localhost:2181 is the hostname and port number of the Observer as
+ specified in every config file. You should see a command line prompt
+ through which you can issue commands like <em>ls</em> to query
+ the ZooKeeper service.
+ </p>
+</div>
+
+
+<a name="N10051"></a><a name="ch_UseCases"></a>
+<h2 class="h3">Example use cases</h2>
+<div class="section">
+<p>
+ Two example use cases for Observers are listed below. In fact, wherever
+ you wish to scale the numbe of clients of your ZooKeeper ensemble, or
+ where you wish to insulate the critical part of an ensemble from the load
+ of dealing with client requests, Observers are a good architectural
+ choice.
+ </p>
+<ul>
+
+<li>
+
+<p> As a datacenter bridge: Forming a ZK ensemble between two
+ datacenters is a problematic endeavour as the high variance in latency
+ between the datacenters could lead to false positive failure detection
+ and partitioning. However if the ensemble runs entirely in one
+ datacenter, and the second datacenter runs only Observers, partitions
+ aren't problematic as the ensemble remains connected. Clients of the
+ Observers may still see and issue proposals.</p>
+
+</li>
+
+<li>
+
+<p>As a link to a message bus: Some companies have expressed an
+ interest in using ZK as a component of a persistent reliable message
+ bus. Observers would give a natural integration point for this work: a
+ plug-in mechanism could be used to attach the stream of proposals an
+ Observer sees to a publish-subscribe system, again without loading the
+ core ensemble.
+ </p>
+
+</li>
+
+</ul>
+</div>
+
+<p align="right">
+<font size="-2"></font>
+</p>
+</div>
+<!--+
+ |end content
+ +-->
+<div class="clearboth"> </div>
+</div>
+<div id="footer">
+<!--+
+ |start bottomstrip
+ +-->
+<div class="lastmodified">
+<script type="text/javascript"><!--
+document.write("Last Published: " + document.lastModified);
+// --></script>
+</div>
+<div class="copyright">
+ Copyright ©
+ 2008 <a href="http://www.apache.org/licenses/">The Apache Software Foundation.</a>
+</div>
+<!--+
+ |end bottomstrip
+ +-->
+</div>
+</body>
+</html>
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diff --git a/docs/zookeeperOver.html b/docs/zookeeperOver.html
index eaec7f1b..7ceef77e 100644
--- a/docs/zookeeperOver.html
+++ b/docs/zookeeperOver.html
@@ -161,6 +161,9 @@ document.write("Last Published: " + document.lastModified);
<div class="menuitem">
<a href="zookeeperJMX.html">JMX</a>
</div>
+<div class="menuitem">
+<a href="zookeeperObservers.html">Observers Guide</a>
+</div>
</div>
<div onclick="SwitchMenu('menu_1.5', 'skin/')" id="menu_1.5Title" class="menutitle">Contributor</div>
<div id="menu_1.5" class="menuitemgroup">
diff --git a/docs/zookeeperProgrammers.html b/docs/zookeeperProgrammers.html
index 8018a348..21cee903 100644
--- a/docs/zookeeperProgrammers.html
+++ b/docs/zookeeperProgrammers.html
@@ -161,6 +161,9 @@ document.write("Last Published: " + document.lastModified);
<div class="menuitem">
<a href="zookeeperJMX.html">JMX</a>
</div>
+<div class="menuitem">
+<a href="zookeeperObservers.html">Observers Guide</a>
+</div>
</div>
<div onclick="SwitchMenu('menu_1.5', 'skin/')" id="menu_1.5Title" class="menutitle">Contributor</div>
<div id="menu_1.5" class="menuitemgroup">
diff --git a/docs/zookeeperQuotas.html b/docs/zookeeperQuotas.html
index 1165b799..e848fb01 100644
--- a/docs/zookeeperQuotas.html
+++ b/docs/zookeeperQuotas.html
@@ -161,6 +161,9 @@ document.write("Last Published: " + document.lastModified);
<div class="menuitem">
<a href="zookeeperJMX.html">JMX</a>
</div>
+<div class="menuitem">
+<a href="zookeeperObservers.html">Observers Guide</a>
+</div>
</div>
<div onclick="SwitchMenu('menu_1.5', 'skin/')" id="menu_1.5Title" class="menutitle">Contributor</div>
<div id="menu_1.5" class="menuitemgroup">
diff --git a/docs/zookeeperStarted.html b/docs/zookeeperStarted.html
index 92c8906a..f1666401 100644
--- a/docs/zookeeperStarted.html
+++ b/docs/zookeeperStarted.html
@@ -161,6 +161,9 @@ document.write("Last Published: " + document.lastModified);
<div class="menuitem">
<a href="zookeeperJMX.html">JMX</a>
</div>
+<div class="menuitem">
+<a href="zookeeperObservers.html">Observers Guide</a>
+</div>
</div>
<div onclick="SwitchMenu('menu_1.5', 'skin/')" id="menu_1.5Title" class="menutitle">Contributor</div>
<div id="menu_1.5" class="menuitemgroup">
diff --git a/docs/zookeeperTutorial.html b/docs/zookeeperTutorial.html
index 0fb9172f..fceba36e 100644
--- a/docs/zookeeperTutorial.html
+++ b/docs/zookeeperTutorial.html
@@ -161,6 +161,9 @@ document.write("Last Published: " + document.lastModified);
<div class="menuitem">
<a href="zookeeperJMX.html">JMX</a>
</div>
+<div class="menuitem">
+<a href="zookeeperObservers.html">Observers Guide</a>
+</div>
</div>
<div onclick="SwitchMenu('menu_1.5', 'skin/')" id="menu_1.5Title" class="menutitle">Contributor</div>
<div id="menu_1.5" class="menuitemgroup">
diff --git a/src/docs/src/documentation/content/xdocs/index.xml b/src/docs/src/documentation/content/xdocs/index.xml
index 76b51524..266db171 100644
--- a/src/docs/src/documentation/content/xdocs/index.xml
+++ b/src/docs/src/documentation/content/xdocs/index.xml
@@ -64,6 +64,7 @@
<li><a href="zookeeperQuotas.html">Quota Guide</a> - a guide for system administrators on Quotas in ZooKeeper. </li>
<li><a href="zookeeperJMX.html">JMX</a> - how to enable JMX in ZooKeeper</li>
<li><a href="zookeeperHierarchicalQuorums.html">Hierarchical quorums</a></li>
+ <li><a href="zookeeperObservers.html">Observers</a> - non-voting ensemble members that easily improve ZooKeeper's scalability</li>
</ul>
</li>
diff --git a/src/docs/src/documentation/content/xdocs/site.xml b/src/docs/src/documentation/content/xdocs/site.xml
index 4ac950d3..34ac4b3b 100644
--- a/src/docs/src/documentation/content/xdocs/site.xml
+++ b/src/docs/src/documentation/content/xdocs/site.xml
@@ -57,6 +57,7 @@ See http://forrest.apache.org/docs/linking.html for more info.
<admin label="Administrator's Guide" href="zookeeperAdmin.html" />
<quota label="Quota Guide" href="zookeeperQuotas.html" />
<jmx label="JMX" href="zookeeperJMX.html" />
+ <observers label="Observers Guide" href="zookeeperObservers.html" />
</docs>
<docs label="Contributor">
diff --git a/src/docs/src/documentation/content/xdocs/zookeeperObservers.xml b/src/docs/src/documentation/content/xdocs/zookeeperObservers.xml
new file mode 100644
index 00000000..3db2cc8a
--- /dev/null
+++ b/src/docs/src/documentation/content/xdocs/zookeeperObservers.xml
@@ -0,0 +1,174 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+ Copyright 2002-2004 The Apache Software Foundation
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+-->
+
+<!DOCTYPE article PUBLIC "-//OASIS//DTD Simplified DocBook XML V1.0//EN"
+"http://www.oasis-open.org/docbook/xml/simple/1.0/sdocbook.dtd">
+<article id="bk_GettStartedGuide">
+ <title>ZooKeeper Observers</title>
+
+ <articleinfo>
+ <legalnotice>
+ <para>Licensed under the Apache License, Version 2.0 (the "License"); you
+ may not use this file except in compliance with the License. You may
+ obtain a copy of the License
+ at <ulink url="http://www.apache.org/licenses/LICENSE-2.0">http://www.apache.org/licenses/LICENSE-2.0</ulink>.</para>
+
+ <para>Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ License for the specific language governing permissions and limitations
+ under the License.</para>
+ </legalnotice>
+
+ <abstract>
+ <para>This guide contains information about using non-voting servers, or
+ observers in your ZooKeeper ensembles.</para>
+ </abstract>
+ </articleinfo>
+
+ <section id="ch_Introduction">
+ <title>Observers: Scaling ZooKeeper Without Hurting Write Performance
+ </title>
+ <para>
+ <emphasis>
+ Please note: the Observers feature currently only works with the basic
+ leader election protocol, not fast leader election or authenticated fast
+ leader election. This will be remedied when a bug in the leader election
+ protocol code is fixed in the near future. An exception will be thrown
+ if you try to start a cluster containing Observers without
+ electionAlg=0. See below for more details.
+ </emphasis>
+ </para>
+ <para>
+ Although ZooKeeper performs very well by having clients connect directly
+ to voting members of the ensemble, this architecture makes it hard to
+ scale out to huge numbers of clients. The problem is that as we add more
+ voting members, the write performance drops. This is due to the fact that
+ a write operation requires the agreement of (in general) at least half the
+ nodes in an ensemble and therefore the cost of a vote can increase
+ significantly as more voters are added.
+ </para>
+ <para>
+ We have introduced a new type of ZooKeeper node called
+ an <emphasis>Observer</emphasis> which helps address this problem and
+ further improves ZooKeeper's scalability. Observers are non-voting members
+ of an ensemble which only hear the results of votes, not the agreement
+ protocol that leads up to them. Other than this simple distinction,
+ Observers function exactly the same as Followers - clients may connect to
+ them and send read and write requests to them. Observers forward these
+ requests to the Leader like Followers do, but they then simply wait to
+ hear the result of the vote. Because of this, we can increase the number
+ of Observers as much as we like without harming the performance of votes.
+ </para>
+ <para>
+ Observers have other advantages. Because they do not vote, they are not a
+ critical part of the ZooKeeper ensemble. Therefore they can fail, or be
+ disconnected from the cluster, without harming the availability of the
+ ZooKeeper service. The benefit to the user is that Observers may connect
+ over less reliable network links than Followers. In fact, Observers may be
+ used to talk to a ZooKeeper server from another data center. Clients of
+ the Observer will see fast reads, as all reads are served locally, and
+ writes result in minimal network traffic as the number of messages
+ required in the absence of the vote protocol is smaller.
+ </para>
+ </section>
+ <section id="sc_UsingObservers">
+ <title>How to use Observers</title>
+ <para>
+ <emphasis>
+ Note that
+ until <ulink url="https://issues.apache.org/jira/browse/ZOOKEEPER-578">ZOOKEEPER-578</ulink>
+ is resolved, you must set electionAlg=0 in every server configuration
+ file. Otherwise an exception will be thrown when you try to start your
+ ensemble.
+ </emphasis>
+ </para>
+ <para>
+ <emphasis>
+ The reason: because Observers do not participate in leader elections,
+ they rely on voting Followers to inform them of changes to the
+ Leader. Currently, only the basic leader election algorithm starts a
+ thread that responds to requests from Observers to identify the current
+ Leader. Work is in progress on other JIRAs to bring this functionality
+ to all leader election protocols.
+ </emphasis>
+ </para>
+ <para>Setting up a ZooKeeper ensemble that uses Observers is very simple,
+ and requires just two changes to your config files. Firstly, in the config
+ file of every node that is to be an Observer, you must place this line:
+ </para>
+ <programlisting>
+ peerType=observer
+ </programlisting>
+
+ <para>
+ This line tells ZooKeeper that the server is to be an Observer. Secondly,
+ in every server config file, you must add :observer to the server
+ definition line of each Observer. For example:
+ </para>
+
+ <programlisting>
+ server.1:localhost:2181:3181:observer
+ </programlisting>
+
+ <para>
+ This tells every other server that server.1 is an Observer, and that they
+ should not expect it to vote. This is all the configuration you need to do
+ to add an Observer to your ZooKeeper cluster. Now you can connect to it as
+ though it were an ordinary Follower. Try it out, by running:</para>
+ <programlisting>
+ bin/zkCli.sh -server localhost:2181
+ </programlisting>
+ <para>
+ where localhost:2181 is the hostname and port number of the Observer as
+ specified in every config file. You should see a command line prompt
+ through which you can issue commands like <emphasis>ls</emphasis> to query
+ the ZooKeeper service.
+ </para>
+ </section>
+
+ <section id="ch_UseCases">
+ <title>Example use cases</title>
+ <para>
+ Two example use cases for Observers are listed below. In fact, wherever
+ you wish to scale the numbe of clients of your ZooKeeper ensemble, or
+ where you wish to insulate the critical part of an ensemble from the load
+ of dealing with client requests, Observers are a good architectural
+ choice.
+ </para>
+ <itemizedlist>
+ <listitem>
+ <para> As a datacenter bridge: Forming a ZK ensemble between two
+ datacenters is a problematic endeavour as the high variance in latency
+ between the datacenters could lead to false positive failure detection
+ and partitioning. However if the ensemble runs entirely in one
+ datacenter, and the second datacenter runs only Observers, partitions
+ aren't problematic as the ensemble remains connected. Clients of the
+ Observers may still see and issue proposals.</para>
+ </listitem>
+ <listitem>
+ <para>As a link to a message bus: Some companies have expressed an
+ interest in using ZK as a component of a persistent reliable message
+ bus. Observers would give a natural integration point for this work: a
+ plug-in mechanism could be used to attach the stream of proposals an
+ Observer sees to a publish-subscribe system, again without loading the
+ core ensemble.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </section>
+</article>
diff --git a/src/java/main/org/apache/zookeeper/server/ObserverBean.java b/src/java/main/org/apache/zookeeper/server/ObserverBean.java
new file mode 100644
index 00000000..4e0e82a8
--- /dev/null
+++ b/src/java/main/org/apache/zookeeper/server/ObserverBean.java
@@ -0,0 +1,45 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.zookeeper.server;
+
+import org.apache.zookeeper.server.quorum.Observer;
+import org.apache.zookeeper.server.quorum.ObserverMXBean;
+
+/**
+ * ObserverBean
+ *
+ */
+public class ObserverBean extends ZooKeeperServerBean implements ObserverMXBean{
+
+ private Observer observer;
+
+ public ObserverBean(Observer observer, ZooKeeperServer zks) {
+ super(zks);
+ this.observer = observer;
+ }
+
+ public int getPendingRevalidationCount() {
+ return this.observer.getPendingRevalidationsCount();
+ }
+
+ public String getQuorumAddress() {
+ return observer.getSocket().toString();
+ }
+
+}
diff --git a/src/java/main/org/apache/zookeeper/server/quorum/AuthFastLeaderElection.java b/src/java/main/org/apache/zookeeper/server/quorum/AuthFastLeaderElection.java
index 52291211..80668711 100644
--- a/src/java/main/org/apache/zookeeper/server/quorum/AuthFastLeaderElection.java
+++ b/src/java/main/org/apache/zookeeper/server/quorum/AuthFastLeaderElection.java
@@ -712,7 +712,7 @@ public class AuthFastLeaderElection implements Election {
t.start();
}
- for (QuorumServer server : self.quorumPeers.values()) {
+ for (QuorumServer server : self.getVotingView().values()) {
InetSocketAddress saddr = new InetSocketAddress(server.addr
.getAddress(), port);
addrChallengeMap.put(saddr, new HashMap<Long, Long>());
@@ -744,7 +744,7 @@ public class AuthFastLeaderElection implements Election {
private void starter(QuorumPeer self) {
this.self = self;
- port = self.quorumPeers.get(self.getId()).electionAddr.getPort();
+ port = self.getVotingView().get(self.getId()).electionAddr.getPort();
proposedLeader = -1;
proposedZxid = -1;
@@ -755,10 +755,10 @@ public class AuthFastLeaderElection implements Election {
e1.printStackTrace();
throw new RuntimeException();
}
- sendqueue = new LinkedBlockingQueue<ToSend>(2 * self.quorumPeers.size());
- recvqueue = new LinkedBlockingQueue<Notification>(2 * self.quorumPeers
+ sendqueue = new LinkedBlockingQueue<ToSend>(2 * self.getVotingView().size());
+ recvqueue = new LinkedBlockingQueue<Notification>(2 * self.getVotingView()
.size());
- new Messenger(self.quorumPeers.size() * 2, mySocket);
+ new Messenger(self.getVotingView().size() * 2, mySocket);
}
private void leaveInstance() {
@@ -766,12 +766,12 @@ public class AuthFastLeaderElection implements Election {
}
private void sendNotifications() {
- for (QuorumServer server : self.quorumPeers.values()) {
+ for (QuorumServer server : self.getView().values()) {
ToSend notmsg = new ToSend(ToSend.mType.notification,
AuthFastLeaderElection.sequencer++, proposedLeader,
proposedZxid, logicalclock, QuorumPeer.ServerState.LOOKING,
- self.quorumPeers.get(server.id).electionAddr);
+ self.getView().get(server.id).electionAddr);
sendqueue.offer(notmsg);
}
@@ -801,7 +801,7 @@ public class AuthFastLeaderElection implements Election {
count++;
}
- if (count > (self.quorumPeers.size() / 2))
+ if (count > (self.getVotingView().size() / 2))
return true;
else
return false;
@@ -875,7 +875,7 @@ public class AuthFastLeaderElection implements Election {
recvset.put(n.addr, new Vote(n.leader, n.zxid));
// If have received from all nodes, then terminate
- if (self.quorumPeers.size() == recvset.size()) {
+ if (self.getVotingView().size() == recvset.size()) {
self.setPeerState((proposedLeader == self.getId()) ?
ServerState.LEADING: ServerState.FOLLOWING);
// if (self.state == ServerState.FOLLOWING) {
diff --git a/src/java/main/org/apache/zookeeper/server/quorum/FastLeaderElection.java b/src/java/main/org/apache/zookeeper/server/quorum/FastLeaderElection.java
index 8bc7b8c1..fc9ad410 100644
--- a/src/java/main/org/apache/zookeeper/server/quorum/FastLeaderElection.java
+++ b/src/java/main/org/apache/zookeeper/server/quorum/FastLeaderElection.java
@@ -440,7 +440,7 @@ public class FastLeaderElection implements Election {
* Send notifications to all peers upon a change in our vote
*/
private void sendNotifications() {
- for (QuorumServer server : self.quorumPeers.values()) {
+ for (QuorumServer server : self.getVotingView().values()) {
long sid = server.id;
ToSend notmsg = new ToSend(ToSend.mType.notification,
diff --git a/src/java/main/org/apache/zookeeper/server/quorum/Leader.java b/src/java/main/org/apache/zookeeper/server/quorum/Leader.java
index e23322ac..84ba917a 100644
--- a/src/java/main/org/apache/zookeeper/server/quorum/Leader.java
+++ b/src/java/main/org/apache/zookeeper/server/quorum/Leader.java
@@ -42,6 +42,7 @@ import org.apache.log4j.Logger;
import org.apache.zookeeper.server.FinalRequestProcessor;
import org.apache.zookeeper.server.Request;
import org.apache.zookeeper.server.RequestProcessor;
+import org.apache.zookeeper.server.quorum.QuorumPeer.LearnerType;
/**
* This class has the control logic for the Leader.
@@ -79,6 +80,8 @@ public class Leader {
// list of followers that are ready to follow (i.e synced with the leader)
public HashSet<LearnerHandler> forwardingFollowers = new HashSet<LearnerHandler>();
+
+ protected HashSet<LearnerHandler> observingLearners = new HashSet<LearnerHandler>();
//Pending sync requests
public HashMap<Long,List<LearnerSyncRequest>> pendingSyncs = new HashMap<Long,List<LearnerSyncRequest>>();
@@ -146,6 +149,11 @@ public class Leader {
*/
final static int SNAP = 15;
+ /**
+ * This tells the leader that the connecting peer is actually an observer
+ */
+ final static int OBSERVERINFO = 16;
+
/**
* This message type is sent by the leader to indicate it's zxid and if
* needed, its database.
@@ -202,6 +210,11 @@ public class Leader {
* between the leader and the follower.
*/
final static int SYNC = 7;
+
+ /**
+ * This message type informs observers of a committed proposal.
+ */
+ final static int INFORM = 8;
private ConcurrentMap<Long, Proposal> outstandingProposals = new ConcurrentHashMap<Long, Proposal>();
@@ -267,9 +280,10 @@ public class Leader {
synchronized(this){
lastProposed = zk.getZxid();
}
-
+
newLeaderProposal.packet = new QuorumPacket(NEWLEADER, zk.getZxid(),
- null, null);
+ null, null);
+
if ((newLeaderProposal.packet.getZxid() & 0xffffffffL) != 0) {
LOG.info("NEWLEADER proposal has Zxid of "
@@ -346,8 +360,9 @@ public class Leader {
if (!tickSkip && !self.getQuorumVerifier().containsQuorum(syncedSet)) {
//if (!tickSkip && syncedCount < self.quorumPeers.size() / 2) {
// Lost quorum, shutdown
+ // TODO: message is wrong unless majority quorums used
shutdown("Only " + syncedCount + " followers, need "
- + (self.quorumPeers.size() / 2));
+ + (self.getVotingView().size() / 2));
// make sure the order is the same!
// the leader goes to looking
return;
@@ -362,7 +377,7 @@ public class Leader {
boolean isShutdown;
/**
- * Close down all the FollowerHandlers
+ * Close down all the LearnerHandlers
*/
void shutdown(String reason) {
if (isShutdown) {
@@ -465,6 +480,7 @@ public class Leader {
LOG.warn("Going to commmit null: " + p);
}
commit(zxid);
+ inform(p);
zk.commitProcessor.commit(p.request);
if(pendingSyncs.containsKey(zxid)){
for(LearnerSyncRequest r: pendingSyncs.remove(zxid)) {
@@ -545,6 +561,17 @@ public class Leader {
}
}
+ /**
+ * send a packet to all observers
+ */
+ void sendObserverPacket(QuorumPacket qp) {
+ synchronized(observingLearners) {
+ for (LearnerHandler f : observingLearners) {
+ f.queuePacket(qp);
+ }
+ }
+ }
+
long lastCommitted = -1;
/**
@@ -559,6 +586,17 @@ public class Leader {
QuorumPacket qp = new QuorumPacket(Leader.COMMIT, zxid, null, null);
sendPacket(qp);
}
+
+ /**
+ * Create an inform packet and send it to all observers.
+ * @param zxid
+ * @param proposal
+ */
+ public void inform(Proposal proposal) {
+ QuorumPacket qp = new QuorumPacket(Leader.INFORM, proposal.request.zxid,
+ proposal.packet.getData(), null);
+ sendObserverPacket(qp);
+ }
long lastProposed;
@@ -569,7 +607,6 @@ public class Leader {
* @return the proposal that is queued to send to all the members
*/
public Proposal propose(Request request) {
-
ByteArrayOutputStream baos = new ByteArrayOutputStream();
BinaryOutputArchive boa = BinaryOutputArchive.getArchive(baos);
try {
@@ -662,10 +699,16 @@ public class Leader {
handler.queuePacket(outstandingProposals.get(zxid).packet);
}
}
- synchronized (forwardingFollowers) {
- forwardingFollowers.add(handler);
+ if (handler.getLearnerType() == LearnerType.PARTICIPANT) {
+ synchronized (forwardingFollowers) {
+ forwardingFollowers.add(handler);
+ }
+ } else {
+ synchronized (observingLearners) {
+ observingLearners.add(handler);
+ }
}
-
+
return lastProposed;
}
diff --git a/src/java/main/org/apache/zookeeper/server/quorum/LeaderElection.java b/src/java/main/org/apache/zookeeper/server/quorum/LeaderElection.java
index 0f8c539d..d5eda76d 100644
--- a/src/java/main/org/apache/zookeeper/server/quorum/LeaderElection.java
+++ b/src/java/main/org/apache/zookeeper/server/quorum/LeaderElection.java
@@ -35,6 +35,7 @@ import org.apache.log4j.Logger;
import org.apache.zookeeper.jmx.MBeanRegistry;
import org.apache.zookeeper.server.quorum.Vote;
+import org.apache.zookeeper.server.quorum.QuorumPeer.LearnerType;
import org.apache.zookeeper.server.quorum.QuorumPeer.QuorumServer;
import org.apache.zookeeper.server.quorum.QuorumPeer.ServerState;
@@ -142,7 +143,7 @@ public class LeaderElection implements Election {
DatagramPacket responsePacket = new DatagramPacket(responseBytes,
responseBytes.length);
HashMap<InetSocketAddress, Vote> votes =
- new HashMap<InetSocketAddress, Vote>(self.quorumPeers.size());
+ new HashMap<InetSocketAddress, Vote>(self.getVotingView().size());
int xid = epochGen.nextInt();
while (self.running) {
votes.clear();
@@ -150,7 +151,7 @@ public class LeaderElection implements Election {
requestBuffer.putInt(xid);
requestPacket.setLength(4);
HashSet<Long> heardFrom = new HashSet<Long>();
- for (QuorumServer server : self.quorumPeers.values()) {
+ for (QuorumServer server : self.getVotingView().values()) {
LOG.info("Server address: " + server.addr);
try {
requestPacket.setSocketAddress(server.addr);
@@ -200,16 +201,38 @@ public class LeaderElection implements Election {
ElectionResult result = countVotes(votes, heardFrom);
if (result.winner.id >= 0) {
self.setCurrentVote(result.vote);
- if (result.winningCount > (self.quorumPeers.size() / 2)) {
+ // To do: this doesn't use a quorum verifier
+ if (result.winningCount > (self.getVotingView().size() / 2)) {
self.setCurrentVote(result.winner);
s.close();
Vote current = self.getCurrentVote();
- self.setPeerState((current.id == self.getId())
- ? ServerState.LEADING: ServerState.FOLLOWING);
- if (self.getPeerState() == ServerState.FOLLOWING) {
- Thread.sleep(100);
+ LOG.info("Found leader: my type is: " + self.getPeerType());
+ /**
+ * We want to make sure we implement the state machine
+ * correctly. If we are a PARTICIPANT, once a leader
+ * is elected we can move either to LEADING or
+ * FOLLOWING. However if we are an OBSERVER, it is an
+ * error to be elected as a Leader.
+ */
+ if (self.getPeerType() == LearnerType.OBSERVER) {
+ if (current.id == self.getId()) {
+ // This should never happen!
+ LOG.error("OBSERVER elected as leader!");
+ Thread.sleep(100);
+ }
+ else {
+ self.setPeerState(ServerState.OBSERVING);
+ Thread.sleep(100);
+ return current;
+ }
+ } else {
+ self.setPeerState((current.id == self.getId())
+ ? ServerState.LEADING: ServerState.FOLLOWING);
+ if (self.getPeerState() == ServerState.FOLLOWING) {
+ Thread.sleep(100);
+ }
+ return current;
}
- return current;
}
}
Thread.sleep(1000);
diff --git a/src/java/main/org/apache/zookeeper/server/quorum/LearnerHandler.java b/src/java/main/org/apache/zookeeper/server/quorum/LearnerHandler.java
index 97cb2aaf..e3baf4b6 100644
--- a/src/java/main/org/apache/zookeeper/server/quorum/LearnerHandler.java
+++ b/src/java/main/org/apache/zookeeper/server/quorum/LearnerHandler.java
@@ -38,6 +38,7 @@ import org.apache.zookeeper.ZooDefs.OpCode;
import org.apache.zookeeper.server.Request;
import org.apache.zookeeper.server.ZooTrace;
import org.apache.zookeeper.server.quorum.Leader.Proposal;
+import org.apache.zookeeper.server.quorum.QuorumPeer.LearnerType;
import org.apache.zookeeper.server.util.SerializeUtils;
import org.apache.zookeeper.txn.TxnHeader;
@@ -101,7 +102,12 @@ public class LearnerHandler extends Thread {
* If this packet is queued, the sender thread will exit
*/
final QuorumPacket proposalOfDeath = new QuorumPacket();
-
+
+ private LearnerType learnerType = LearnerType.PARTICIPANT;
+ public LearnerType getLearnerType() {
+ return learnerType;
+ }
+
/**
* This method will use the thread to send packets added to the
* queuedPackets list
@@ -217,9 +223,9 @@ public class LearnerHandler extends Thread {
QuorumPacket qp = new QuorumPacket();
ia.readRecord(qp, "packet");
- if(qp.getType() != Leader.FOLLOWERINFO) {
+ if(qp.getType() != Leader.FOLLOWERINFO && qp.getType() != Leader.OBSERVERINFO){
LOG.error("First packet " + qp.toString()
- + " is not FOLLOWERINFO!");
+ + " is not FOLLOWERINFO or OBSERVERINFO!");
return;
}
if (qp.getData() != null) {
@@ -231,9 +237,11 @@ public class LearnerHandler extends Thread {
LOG.info("Follower sid: " + this.sid + " : info : "
+ leader.self.quorumPeers.get(this.sid));
+
+ if (qp.getType() == Leader.OBSERVERINFO) {
+ learnerType = LearnerType.OBSERVER;
+ }
- /* this is the last zxid from the follower but the leader might have to
- restart the follower from a different zxid depending on truncate and diff. */
long peerLastZxid = qp.getZxid();
/* the default to send to the follower */
int packetToSend = Leader.SNAP;
@@ -356,6 +364,9 @@ public class LearnerHandler extends Thread {
switch (qp.getType()) {
case Leader.ACK:
+ if (this.learnerType == LearnerType.OBSERVER) {
+ LOG.error("Received ACK from Observer " + this.sid);
+ }
leader.processAck(this.sid, qp.getZxid(), sock.getLocalSocketAddress());
break;
case Leader.PING:
diff --git a/src/java/main/org/apache/zookeeper/server/quorum/Observer.java b/src/java/main/org/apache/zookeeper/server/quorum/Observer.java
new file mode 100644
index 00000000..48bc02a1
--- /dev/null
+++ b/src/java/main/org/apache/zookeeper/server/quorum/Observer.java
@@ -0,0 +1,147 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.zookeeper.server.quorum;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.net.InetSocketAddress;
+
+import org.apache.jute.BinaryInputArchive;
+import org.apache.jute.Record;
+import org.apache.zookeeper.server.ObserverBean;
+import org.apache.zookeeper.server.Request;
+import org.apache.zookeeper.server.util.SerializeUtils;
+import org.apache.zookeeper.txn.TxnHeader;
+
+/**
+ * Observers are peers that do not take part in the atomic broadcast protocol.
+ * Instead, they are informed of successful proposals by the Leader. Observers
+ * therefore naturally act as a relay point for publishing the proposal stream
+ * and can relieve Followers of some of the connection load. Observers may
+ * submit proposals, but do not vote in their acceptance.
+ *
+ * See ZOOKEEPER-368 for a discussion of this feature.
+ */
+public class Observer extends Learner{
+
+ Observer(QuorumPeer self,ObserverZooKeeperServer observerZooKeeperServer) {
+ this.self = self;
+ this.zk=observerZooKeeperServer;
+ }
+
+ @Override
+ public String toString() {
+ StringBuffer sb = new StringBuffer();
+ sb.append("Observer ").append(sock);
+ sb.append(" pendingRevalidationCount:")
+ .append(pendingRevalidations.size());
+ return sb.toString();
+ }
+
+ /**
+ * the main method called by the observer to observe the leader
+ *
+ * @throws InterruptedException
+ */
+ void observeLeader() throws InterruptedException {
+ zk.registerJMX(new ObserverBean(this, zk), self.jmxLocalPeerBean);
+
+ try {
+ InetSocketAddress addr = findLeader();
+ LOG.info("Observing " + addr);
+ try {
+ connectToLeader(addr);
+ long newLeaderZxid = registerWithLeader(Leader.OBSERVERINFO);
+
+ syncWithLeader(newLeaderZxid);
+ QuorumPacket qp = new QuorumPacket();
+ while (self.running) {
+ readPacket(qp);
+ processPacket(qp);
+ }
+ } catch (IOException e) {
+ LOG.warn("Exception when observing the leader", e);
+ try {
+ sock.close();
+ } catch (IOException e1) {
+ e1.printStackTrace();
+ }
+
+ synchronized (pendingRevalidations) {
+ // clear pending revalidations
+ pendingRevalidations.clear();
+ pendingRevalidations.notifyAll();
+ }
+ }
+ } finally {
+ zk.unregisterJMX(this);
+ }
+ }
+
+ /**
+ * Controls the response of an observer to the receipt of a quorumpacket
+ * @param qp
+ * @throws IOException
+ */
+ protected void processPacket(QuorumPacket qp) throws IOException{
+ switch (qp.getType()) {
+ case Leader.PING:
+ ping(qp);
+ break;
+ case Leader.PROPOSAL:
+ LOG.warn("Ignoring proposal");
+ break;
+ case Leader.COMMIT:
+ LOG.warn("Ignoring commit");
+ break;
+ case Leader.UPTODATE:
+ zk.takeSnapshot();
+ self.cnxnFactory.setZooKeeperServer(zk);
+ break;
+ case Leader.REVALIDATE:
+ revalidate(qp);
+ break;
+ case Leader.SYNC:
+ ((ObserverZooKeeperServer)zk).sync();
+ break;
+ case Leader.INFORM:
+ TxnHeader hdr = new TxnHeader();
+ BinaryInputArchive ia = BinaryInputArchive
+ .getArchive(new ByteArrayInputStream(qp.getData()));
+ Record txn = SerializeUtils.deserializeTxn(ia, hdr);
+ Request request = new Request (null, hdr.getClientId(),
+ hdr.getCxid(),
+ hdr.getType(), null, null);
+ request.txn = txn;
+ request.hdr = hdr;
+ ObserverZooKeeperServer obs = (ObserverZooKeeperServer)zk;
+ obs.commitRequest(request);
+ break;
+ }
+ }
+
+ /**
+ * Shutdown the Observer.
+ */
+ public void shutdown() {
+ LOG.info("shutdown called", new Exception("shutdown Observer"));
+ super.shutdown();
+ }
+}
+
diff --git a/src/java/main/org/apache/zookeeper/server/quorum/ObserverMXBean.java b/src/java/main/org/apache/zookeeper/server/quorum/ObserverMXBean.java
new file mode 100644
index 00000000..2c1799ab
--- /dev/null
+++ b/src/java/main/org/apache/zookeeper/server/quorum/ObserverMXBean.java
@@ -0,0 +1,37 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.zookeeper.server.quorum;
+
+import org.apache.zookeeper.server.ZooKeeperServerMXBean;
+
+/**
+ * Observer MX Bean interface, implemented by ObserverBean
+ *
+ */
+public interface ObserverMXBean extends ZooKeeperServerMXBean {
+ /**
+ * @return count of pending revalidations
+ */
+ public int getPendingRevalidationCount();
+
+ /**
+ * @return socket address
+ */
+ public String getQuorumAddress();
+}
diff --git a/src/java/main/org/apache/zookeeper/server/quorum/ObserverRequestProcessor.java b/src/java/main/org/apache/zookeeper/server/quorum/ObserverRequestProcessor.java
new file mode 100644
index 00000000..eac747fb
--- /dev/null
+++ b/src/java/main/org/apache/zookeeper/server/quorum/ObserverRequestProcessor.java
@@ -0,0 +1,123 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.zookeeper.server.quorum;
+
+import java.util.concurrent.LinkedBlockingQueue;
+
+import org.apache.log4j.Logger;
+
+import org.apache.zookeeper.ZooDefs.OpCode;
+import org.apache.zookeeper.server.RequestProcessor;
+import org.apache.zookeeper.server.Request;
+import org.apache.zookeeper.server.ZooTrace;
+
+/**
+ * This RequestProcessor forwards any requests that modify the state of the
+ * system to the Leader.
+ */
+public class ObserverRequestProcessor extends Thread implements
+ RequestProcessor {
+ private static final Logger LOG = Logger.getLogger(ObserverRequestProcessor.class);
+
+ ObserverZooKeeperServer zks;
+
+ RequestProcessor nextProcessor;
+
+ // We keep a queue of requests. As requests get submitted they are
+ // stored here. The queue is drained in the run() method.
+ LinkedBlockingQueue<Request> queuedRequests = new LinkedBlockingQueue<Request>();
+
+ boolean finished = false;
+
+ /**
+ * Constructor - takes an ObserverZooKeeperServer to associate with
+ * and the next processor to pass requests to after we're finished.
+ * @param zks
+ * @param nextProcessor
+ */
+ public ObserverRequestProcessor(ObserverZooKeeperServer zks,
+ RequestProcessor nextProcessor) {
+ super("ObserverRequestProcessor:" + zks.getServerId());
+ this.zks = zks;
+ this.nextProcessor = nextProcessor;
+ }
+
+ @Override
+ public void run() {
+ try {
+ while (!finished) {
+ Request request = queuedRequests.take();
+ if (LOG.isTraceEnabled()) {
+ ZooTrace.logRequest(LOG, ZooTrace.CLIENT_REQUEST_TRACE_MASK,
+ 'F', request, "");
+ }
+ if (request == Request.requestOfDeath) {
+ break;
+ }
+ // We want to queue the request to be processed before we submit
+ // the request to the leader so that we are ready to receive
+ // the response
+ nextProcessor.processRequest(request);
+
+ // We now ship the request to the leader. As with all
+ // other quorum operations, sync also follows this code
+ // path, but different from others, we need to keep track
+ // of the sync operations this Observer has pending, so we
+ // add it to pendingSyncs.
+ switch (request.type) {
+ case OpCode.sync:
+ zks.pendingSyncs.add(request);
+ zks.getObserver().request(request);
+ break;
+ case OpCode.create:
+ case OpCode.delete:
+ case OpCode.setData:
+ case OpCode.setACL:
+ case OpCode.createSession:
+ case OpCode.closeSession:
+ zks.getObserver().request(request);
+ break;
+ }
+ }
+ } catch (Exception e) {
+ LOG.error("Unexpected exception causing exit", e);
+ }
+ LOG.info("ObserverRequestProcessor exited loop!");
+ }
+
+ /**
+ * Simply queue the request, which will be processed in FIFO order.
+ */
+ public void processRequest(Request request) {
+ if (!finished) {
+ queuedRequests.add(request);
+ }
+ }
+
+ /**
+ * Shutdown the processor.
+ */
+ public void shutdown() {
+ finished = true;
+ queuedRequests.clear();
+ queuedRequests.add(Request.requestOfDeath);
+ nextProcessor.shutdown();
+ }
+
+}
diff --git a/src/java/main/org/apache/zookeeper/server/quorum/ObserverZooKeeperServer.java b/src/java/main/org/apache/zookeeper/server/quorum/ObserverZooKeeperServer.java
new file mode 100644
index 00000000..f336c6e3
--- /dev/null
+++ b/src/java/main/org/apache/zookeeper/server/quorum/ObserverZooKeeperServer.java
@@ -0,0 +1,114 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.zookeeper.server.quorum;
+
+import java.io.IOException;
+import java.util.concurrent.ConcurrentLinkedQueue;
+
+import org.apache.log4j.Logger;
+import org.apache.zookeeper.server.FinalRequestProcessor;
+import org.apache.zookeeper.server.Request;
+import org.apache.zookeeper.server.RequestProcessor;
+import org.apache.zookeeper.server.SyncRequestProcessor;
+import org.apache.zookeeper.server.persistence.FileTxnSnapLog;
+
+/**
+ * A ZooKeeperServer for the Observer node type. Not much is different, but
+ * we anticipate specializing the request processors in the future.
+ *
+ */
+public class ObserverZooKeeperServer extends LearnerZooKeeperServer {
+ private static final Logger LOG = Logger.getLogger(ObserverZooKeeperServer.class);
+
+ /*
+ * Request processors
+ */
+ private CommitProcessor commitProcessor;
+ private SyncRequestProcessor syncProcessor;
+
+ /*
+ * Pending sync requests
+ */
+ ConcurrentLinkedQueue<Request> pendingSyncs =
+ new ConcurrentLinkedQueue<Request>();
+
+ ObserverZooKeeperServer(FileTxnSnapLog logFactory, QuorumPeer self,
+ DataTreeBuilder treeBuilder) throws IOException {
+ super(logFactory, self.tickTime, treeBuilder);
+ this.self = self;
+ }
+
+ public Observer getObserver() {
+ return self.observer;
+ }
+
+ @Override
+ public Learner getLearner() {
+ return self.observer;
+ }
+
+ /**
+ * Unlike a Follower, which sees a full request only during the PROPOSAL
+ * phase, Observers get all the data required with the INFORM packet.
+ * This method commits a request that has been unpacked by from an INFORM
+ * received from the Leader.
+ *
+ * @param request
+ */
+ public void commitRequest(Request request) {
+ commitProcessor.commit(request);
+ }
+
+ /**
+ * Set up the request processors for an Observer:
+ * firstProcesor->commitProcessor->finalProcessor
+ */
+ @Override
+ protected void setupRequestProcessors() {
+ // We might consider changing the processor behaviour of
+ // Observers to, for example, remove the disk sync requirements.
+ // Currently, they behave almost exactly the same as followers.
+ RequestProcessor finalProcessor = new FinalRequestProcessor(this);
+ commitProcessor = new CommitProcessor(finalProcessor,
+ Long.toString(getServerId()), true);
+ commitProcessor.start();
+ firstProcessor = new ObserverRequestProcessor(this, commitProcessor);
+ ((ObserverRequestProcessor) firstProcessor).start();
+ syncProcessor = new SyncRequestProcessor(this,
+ new SendAckRequestProcessor(getObserver()));
+ syncProcessor.start();
+ }
+
+ /*
+ * Process a sync request
+ */
+ synchronized public void sync(){
+ if(pendingSyncs.size() ==0){
+ LOG.warn("Not expecting a sync.");
+ return;
+ }
+
+ Request r = pendingSyncs.remove();
+ commitProcessor.commit(r);
+ }
+
+ @Override
+ public String getState() {
+ return "observer";
+ };
+}
diff --git a/src/java/main/org/apache/zookeeper/server/quorum/QuorumCnxManager.java b/src/java/main/org/apache/zookeeper/server/quorum/QuorumCnxManager.java
index 557fd65a..10a55250 100644
--- a/src/java/main/org/apache/zookeeper/server/quorum/QuorumCnxManager.java
+++ b/src/java/main/org/apache/zookeeper/server/quorum/QuorumCnxManager.java
@@ -126,7 +126,7 @@ public class QuorumCnxManager {
SocketChannel channel;
LOG.debug("Opening channel to server " + sid);
channel = SocketChannel
- .open(self.quorumPeers.get(sid).electionAddr);
+ .open(self.getVotingView().get(sid).electionAddr);
channel.socket().setTcpNoDelay(true);
initiateConnection(channel, sid);
}
@@ -327,7 +327,8 @@ public class QuorumCnxManager {
try {
SocketChannel channel;
LOG.debug("Opening channel to server " + sid);
- channel = SocketChannel.open(electionAddr);
+ channel = SocketChannel
+ .open(self.getView().get(sid).electionAddr);
channel.socket().setTcpNoDelay(true);
initiateConnection(channel, sid);
} catch (UnresolvedAddressException e) {
@@ -510,7 +511,7 @@ public class QuorumCnxManager {
LOG.warn("Exception while closing socket");
}
//channel = null;
-
+
this.interrupt();
if (recvWorker != null)
recvWorker.finish();
diff --git a/src/java/main/org/apache/zookeeper/server/quorum/QuorumPeer.java b/src/java/main/org/apache/zookeeper/server/quorum/QuorumPeer.java
index 7b5213b7..e49c9027 100644
--- a/src/java/main/org/apache/zookeeper/server/quorum/QuorumPeer.java
+++ b/src/java/main/org/apache/zookeeper/server/quorum/QuorumPeer.java
@@ -25,6 +25,8 @@ import java.net.InetSocketAddress;
import java.net.SocketException;
import java.nio.ByteBuffer;
import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
import java.util.List;
import java.util.Map;
@@ -93,22 +95,54 @@ public class QuorumPeer extends Thread implements QuorumStats.Provider {
this.electionAddr = null;
}
+ public QuorumServer(long id, InetSocketAddress addr,
+ InetSocketAddress electionAddr, LearnerType type) {
+ this.id = id;
+ this.addr = addr;
+ this.electionAddr = electionAddr;
+ this.type = type;
+ }
+
public InetSocketAddress addr;
public InetSocketAddress electionAddr;
public long id;
+
+ public LearnerType type = LearnerType.PARTICIPANT;
}
public enum ServerState {
- LOOKING, FOLLOWING, LEADING;
+ LOOKING, FOLLOWING, LEADING, OBSERVING;
+ }
+
+ /**
+ * A peer can either be participating, which implies that it is willing to
+ * both vote in instances of consensus and to elect or become a Leader, or
+ * it may be observing in which case it isn't.
+ *
+ * We need this distinction to decide which ServerState to move to when
+ * conditions change (e.g. which state to become after LOOKING).
+ */
+ public enum LearnerType {
+ PARTICIPANT, OBSERVER;
+ }
+
+ private LearnerType peerType = LearnerType.PARTICIPANT;
+
+ public LearnerType getPeerType() {
+ return peerType;
+ }
+
+ public void setPeerType(LearnerType p) {
+ peerType = p;
}
/**
* The servers that make up the cluster
*/
- Map<Long, QuorumServer> quorumPeers;
+ protected Map<Long, QuorumServer> quorumPeers;
public int getQuorumSize(){
- return quorumPeers.size();
+ return getVotingView().size();
}
/**
@@ -226,6 +260,11 @@ public class QuorumPeer extends Thread implements QuorumStats.Provider {
// This can happen in state transitions,
// just ignore the request
}
+ break;
+ case OBSERVING:
+ // Do nothing, Observers keep themselves to
+ // themselves.
+ break;
}
packet.setData(b);
udpSocket.send(packet);
@@ -233,7 +272,7 @@ public class QuorumPeer extends Thread implements QuorumStats.Provider {
packet.setLength(b.length);
}
} catch (Exception e) {
- LOG.warn("Unexpected exception",e);
+ LOG.warn("Unexpected exception in ResponderThread",e);
} finally {
LOG.warn("QuorumPeer responder thread exited");
}
@@ -282,7 +321,8 @@ public class QuorumPeer extends Thread implements QuorumStats.Provider {
long myid, int tickTime, int initLimit, int syncLimit,
NIOServerCnxn.Factory cnxnFactory) throws IOException {
this(quorumPeers, dataDir, dataLogDir, electionType, myid, tickTime,
- initLimit, syncLimit, cnxnFactory, new QuorumMaj(quorumPeers.size()));
+ initLimit, syncLimit, cnxnFactory,
+ new QuorumMaj(countParticipants(quorumPeers)));
}
public QuorumPeer(Map<Long, QuorumServer> quorumPeers, File dataDir,
@@ -300,7 +340,7 @@ public class QuorumPeer extends Thread implements QuorumStats.Provider {
this.syncLimit = syncLimit;
this.logFactory = new FileTxnSnapLog(dataLogDir, dataDir);
if(quorumConfig == null)
- this.quorumConfig = new QuorumMaj(quorumPeers.size());
+ this.quorumConfig = new QuorumMaj(countParticipants(quorumPeers));
else this.quorumConfig = quorumConfig;
}
@@ -310,8 +350,10 @@ public class QuorumPeer extends Thread implements QuorumStats.Provider {
@Override
public synchronized void start() {
- cnxnFactory.start();
- startLeaderElection();
+ cnxnFactory.start();
+ if (getPeerType() == LearnerType.PARTICIPANT) {
+ startLeaderElection();
+ }
super.start();
}
@@ -323,7 +365,7 @@ public class QuorumPeer extends Thread implements QuorumStats.Provider {
}
synchronized public void startLeaderElection() {
currentVote = new Vote(myid, getLastLoggedZxid());
- for (QuorumServer p : quorumPeers.values()) {
+ for (QuorumServer p : getView().values()) {
if (p.id == myid) {
myQuorumAddr = p.addr;
break;
@@ -344,6 +386,20 @@ public class QuorumPeer extends Thread implements QuorumStats.Provider {
this.electionAlg = createElectionAlgorithm(electionType);
}
+ /**
+ * Count the number of nodes in the map that could be followers.
+ * @param peers
+ * @return The number of followers in the map
+ */
+ protected static int countParticipants(Map<Long,QuorumServer> peers) {
+ int count = 0;
+ for (QuorumServer q : peers.values()) {
+ if (q.type == LearnerType.PARTICIPANT) {
+ count++;
+ }
+ }
+ return count;
+ }
/**
* This constructor is only used by the existing unit test code.
@@ -357,7 +413,7 @@ public class QuorumPeer extends Thread implements QuorumStats.Provider {
this(quorumPeers, snapDir, logDir, electionAlg,
myid,tickTime, initLimit,syncLimit,
new NIOServerCnxn.Factory(clientPort),
- new QuorumMaj(quorumPeers.size()));
+ new QuorumMaj(countParticipants(quorumPeers)));
}
/**
@@ -380,6 +436,7 @@ public class QuorumPeer extends Thread implements QuorumStats.Provider {
}
public Follower follower;
public Leader leader;
+ public Observer observer;
protected Follower makeFollower(FileTxnSnapLog logFactory) throws IOException {
return new Follower(this, new FollowerZooKeeperServer(logFactory,
@@ -390,9 +447,15 @@ public class QuorumPeer extends Thread implements QuorumStats.Provider {
return new Leader(this, new LeaderZooKeeperServer(logFactory,
this,new ZooKeeperServer.BasicDataTreeBuilder()));
}
+
+ protected Observer makeObserver(FileTxnSnapLog logFactory) throws IOException {
+ return new Observer(this, new ObserverZooKeeperServer(logFactory,
+ this, new ZooKeeperServer.BasicDataTreeBuilder()));
+ }
private Election createElectionAlgorithm(int electionAlgorithm){
Election le=null;
+
//TODO: use a factory rather than a switch
switch (electionAlgorithm) {
case 0:
@@ -423,6 +486,8 @@ public class QuorumPeer extends Thread implements QuorumStats.Provider {
protected Election makeLEStrategy(){
LOG.debug("Initializing leader election protocol...");
+ // LeaderElection is the only implementation that correctly
+ // transitions between LOOKING and OBSERVER
if(electionAlg==null)
return new LeaderElection(this);
return electionAlg;
@@ -435,12 +500,18 @@ public class QuorumPeer extends Thread implements QuorumStats.Provider {
synchronized protected void setFollower(Follower newFollower){
follower=newFollower;
}
+
+ synchronized protected void setObserver(Observer newObserver){
+ observer=newObserver;
+ }
synchronized public ZooKeeperServer getActiveServer(){
if(leader!=null)
return leader.zk;
else if(follower!=null)
return follower.zk;
+ else if (observer != null)
+ return observer.zk;
return null;
}
@@ -491,6 +562,19 @@ public class QuorumPeer extends Thread implements QuorumStats.Provider {
setPeerState(ServerState.LOOKING);
}
break;
+ case OBSERVING:
+ try {
+ LOG.info("OBSERVING");
+ setObserver(makeObserver(logFactory));
+ observer.observeLeader();
+ } catch (Exception e) {
+ LOG.warn("Unexpected exception",e );
+ } finally {
+ observer.shutdown();
+ setObserver(null);
+ setPeerState(ServerState.LOOKING);
+ }
+ break;
case FOLLOWING:
try {
LOG.info("FOLLOWING");
@@ -549,11 +633,42 @@ public class QuorumPeer extends Thread implements QuorumStats.Provider {
}
/**
- * A 'view' is a node's current opinion of the membership of the
- * ensemble.
+ * A 'view' is a node's current opinion of the membership of the entire
+ * ensemble.
*/
public Map<Long,QuorumPeer.QuorumServer> getView() {
- return this.quorumPeers;
+ return Collections.unmodifiableMap(this.quorumPeers);
+ }
+
+ /**
+ * Observers are not contained in this view, only nodes with
+ * PeerType=PARTICIPANT.
+ */
+ public Map<Long,QuorumPeer.QuorumServer> getVotingView() {
+ Map<Long,QuorumPeer.QuorumServer> ret =
+ new HashMap<Long, QuorumPeer.QuorumServer>();
+ Map<Long,QuorumPeer.QuorumServer> view = getView();
+ for (QuorumServer server : view.values()) {
+ if (server.type == LearnerType.PARTICIPANT) {
+ ret.put(server.id, server);
+ }
+ }
+ return ret;
+ }
+
+ /**
+ * Returns only observers, no followers.
+ */
+ public Map<Long,QuorumPeer.QuorumServer> getObservingView() {
+ Map<Long,QuorumPeer.QuorumServer> ret =
+ new HashMap<Long, QuorumPeer.QuorumServer>();
+ Map<Long,QuorumPeer.QuorumServer> view = getView();
+ for (QuorumServer server : view.values()) {
+ if (server.type == LearnerType.OBSERVER) {
+ ret.put(server.id, server);
+ }
+ }
+ return ret;
}
/**
@@ -565,6 +680,9 @@ public class QuorumPeer extends Thread implements QuorumStats.Provider {
return this.quorumPeers.containsKey(sid);
}
+ /**
+ * Only used by QuorumStats at the moment
+ */
public String[] getQuorumPeers() {
List<String> l = new ArrayList<String>();
synchronized (this) {
@@ -594,6 +712,8 @@ public class QuorumPeer extends Thread implements QuorumStats.Provider {
return QuorumStats.Provider.LEADING_STATE;
case FOLLOWING:
return QuorumStats.Provider.FOLLOWING_STATE;
+ case OBSERVING:
+ return QuorumStats.Provider.OBSERVING_STATE;
}
return QuorumStats.Provider.UNKNOWN_STATE;
}
diff --git a/src/java/main/org/apache/zookeeper/server/quorum/QuorumPeerConfig.java b/src/java/main/org/apache/zookeeper/server/quorum/QuorumPeerConfig.java
index dbb1e159..dc6b86e8 100644
--- a/src/java/main/org/apache/zookeeper/server/quorum/QuorumPeerConfig.java
+++ b/src/java/main/org/apache/zookeeper/server/quorum/QuorumPeerConfig.java
@@ -33,6 +33,7 @@ import java.util.Map.Entry;
import org.apache.log4j.Logger;
import org.apache.zookeeper.server.ZooKeeperServer;
import org.apache.zookeeper.server.quorum.QuorumPeer.QuorumServer;
+import org.apache.zookeeper.server.quorum.QuorumPeer.LearnerType;
import org.apache.zookeeper.server.quorum.flexible.QuorumVerifier;
import org.apache.zookeeper.server.quorum.flexible.QuorumMaj;
import org.apache.zookeeper.server.quorum.flexible.QuorumHierarchical;
@@ -52,12 +53,16 @@ public class QuorumPeerConfig {
protected int maxClientCnxns = 10;
protected final HashMap<Long,QuorumServer> servers =
new HashMap<Long, QuorumServer>();
+ protected final HashMap<Long,QuorumServer> observers =
+ new HashMap<Long, QuorumServer>();
protected long serverId;
protected HashMap<Long, Long> serverWeight = new HashMap<Long, Long>();
protected HashMap<Long, Long> serverGroup = new HashMap<Long, Long>();
protected int numGroups = 0;
protected QuorumVerifier quorumVerifier;
+
+ protected LearnerType peerType = LearnerType.PARTICIPANT;
@SuppressWarnings("serial")
public static class ConfigException extends Exception {
@@ -128,13 +133,23 @@ public class QuorumPeerConfig {
electionAlg = Integer.parseInt(value);
} else if (key.equals("maxClientCnxns")) {
maxClientCnxns = Integer.parseInt(value);
+ } else if (key.equals("peerType")) {
+ if (value.toLowerCase().equals("observer")) {
+ peerType = LearnerType.OBSERVER;
+ } else if (value.toLowerCase().equals("participant")) {
+ peerType = LearnerType.PARTICIPANT;
+ } else
+ {
+ throw new ConfigException("Unrecognised peertype: " + value);
+ }
} else if (key.startsWith("server.")) {
int dot = key.indexOf('.');
long sid = Long.parseLong(key.substring(dot + 1));
String parts[] = value.split(":");
- if ((parts.length != 2) && (parts.length != 3)) {
+ if ((parts.length != 2) && (parts.length != 3) && (parts.length !=4)) {
LOG.error(value
- + " does not have the form host:port or host:port:port");
+ + " does not have the form host:port or host:port:port " +
+ " or host:port:port:type");
}
InetSocketAddress addr = new InetSocketAddress(parts[0],
Integer.parseInt(parts[1]));
@@ -145,6 +160,21 @@ public class QuorumPeerConfig {
parts[0], Integer.parseInt(parts[2]));
servers.put(Long.valueOf(sid), new QuorumServer(sid, addr,
electionAddr));
+ } else if (parts.length == 4) {
+ InetSocketAddress electionAddr = new InetSocketAddress(
+ parts[0], Integer.parseInt(parts[2]));
+ LearnerType type = LearnerType.PARTICIPANT;
+ if (parts[3].toLowerCase().equals("observer")) {
+ type = LearnerType.OBSERVER;
+ observers.put(Long.valueOf(sid), new QuorumServer(sid, addr,
+ electionAddr,type));
+ } else if (parts[3].toLowerCase().equals("participant")) {
+ type = LearnerType.PARTICIPANT;
+ servers.put(Long.valueOf(sid), new QuorumServer(sid, addr,
+ electionAddr,type));
+ } else {
+ throw new ConfigException("Unrecognised peertype: " + value);
+ }
}
} else if (key.startsWith("group")) {
int dot = key.indexOf('.');
@@ -169,6 +199,10 @@ public class QuorumPeerConfig {
System.setProperty("zookeeper." + key, value);
}
}
+ if (observers.size() > 0 && electionAlg != 0) {
+ throw new IllegalArgumentException("Observers must currently be used with simple leader election" +
+ " (set electionAlg=0)");
+ }
if (dataDir == null) {
throw new IllegalArgumentException("dataDir is not set");
}
@@ -233,6 +267,10 @@ public class QuorumPeerConfig {
quorumVerifier = new QuorumMaj(servers.size());
}
+ // Now add observers to servers, once the quorums have been
+ // figured out
+ servers.putAll(observers);
+
File myIdFile = new File(dataDir, "myid");
if (!myIdFile.exists()) {
throw new IllegalArgumentException(myIdFile.toString()
@@ -276,4 +314,8 @@ public class QuorumPeerConfig {
public long getServerId() { return serverId; }
public boolean isDistributed() { return servers.size() > 1; }
+
+ public LearnerType getPeerType() {
+ return peerType;
+ }
}
diff --git a/src/java/main/org/apache/zookeeper/server/quorum/QuorumPeerMain.java b/src/java/main/org/apache/zookeeper/server/quorum/QuorumPeerMain.java
index 7ed148ac..0dc158a3 100644
--- a/src/java/main/org/apache/zookeeper/server/quorum/QuorumPeerMain.java
+++ b/src/java/main/org/apache/zookeeper/server/quorum/QuorumPeerMain.java
@@ -133,6 +133,7 @@ public class QuorumPeerMain {
quorumPeer.setSyncLimit(config.getSyncLimit());
quorumPeer.setQuorumVerifier(config.getQuorumVerifier());
quorumPeer.setCnxnFactory(cnxnFactory);
+ quorumPeer.setPeerType(config.getPeerType());
quorumPeer.start();
quorumPeer.join();
diff --git a/src/java/main/org/apache/zookeeper/server/quorum/QuorumStats.java b/src/java/main/org/apache/zookeeper/server/quorum/QuorumStats.java
index 06ca1fb5..b6c62e44 100644
--- a/src/java/main/org/apache/zookeeper/server/quorum/QuorumStats.java
+++ b/src/java/main/org/apache/zookeeper/server/quorum/QuorumStats.java
@@ -26,7 +26,7 @@ public class QuorumStats {
static public final String LOOKING_STATE = "leaderelection";
static public final String LEADING_STATE = "leading";
static public final String FOLLOWING_STATE = "following";
-
+ static public final String OBSERVING_STATE = "observing";
public String[] getQuorumPeers();
public String getServerState();
}
@@ -53,7 +53,8 @@ public class QuorumStats {
sb.append(" ").append(f);
}
sb.append("\n");
- }else if(state.equals(Provider.FOLLOWING_STATE)){
+ }else if(state.equals(Provider.FOLLOWING_STATE)
+ || state.equals(Provider.OBSERVING_STATE)){
sb.append("Leader: ");
String[] ldr=getQuorumPeers();
if(ldr.length>0)
diff --git a/src/java/test/org/apache/zookeeper/server/quorum/ObserverTest.java b/src/java/test/org/apache/zookeeper/server/quorum/ObserverTest.java
new file mode 100644
index 00000000..72b05c96
--- /dev/null
+++ b/src/java/test/org/apache/zookeeper/server/quorum/ObserverTest.java
@@ -0,0 +1,236 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.zookeeper.server.quorum;
+
+import static org.apache.zookeeper.test.ClientBase.CONNECTION_TIMEOUT;
+
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.util.concurrent.CountDownLatch;
+
+import org.apache.log4j.Logger;
+import org.apache.zookeeper.CreateMode;
+import org.apache.zookeeper.WatchedEvent;
+import org.apache.zookeeper.Watcher;
+import org.apache.zookeeper.ZooKeeper;
+import org.apache.zookeeper.Watcher.Event.KeeperState;
+import org.apache.zookeeper.ZooDefs.Ids;
+import org.apache.zookeeper.ZooKeeper.States;
+
+import org.apache.zookeeper.AsyncCallback.VoidCallback;
+import org.apache.zookeeper.KeeperException.ConnectionLossException;
+
+import org.apache.zookeeper.server.quorum.QuorumPeerConfig.ConfigException;
+import org.apache.zookeeper.test.ClientBase;
+import org.junit.Test;
+
+/**
+ * Test Observer behaviour and specific code paths.
+ *
+ */
+public class ObserverTest extends QuorumPeerTestBase implements Watcher{
+ protected static final Logger LOG =
+ Logger.getLogger(ObserverTest.class);
+
+ // We expect two notifications before we want to continue
+ CountDownLatch latch = new CountDownLatch(2);
+ ZooKeeper zk;
+ WatchedEvent lastEvent = null;
+
+ /**
+ * This test ensures two things:
+ * 1. That Observers can successfully proxy requests to the ensemble.
+ * 2. That Observers don't participate in leader elections.
+ * The second is tested by constructing an ensemble where a leader would
+ * be elected if and only if an Observer voted.
+ * @throws Exception
+ */
+ @Test
+ public void testObserver() throws Exception {
+ ClientBase.setupTestEnv();
+ final int CLIENT_PORT_QP1 = 3181;
+ final int CLIENT_PORT_QP2 = CLIENT_PORT_QP1 + 3;
+ final int CLIENT_PORT_OBS = CLIENT_PORT_QP2 + 3;
+
+ String quorumCfgSection =
+ "electionAlg=0\n" +
+ "server.1=localhost:" + (CLIENT_PORT_QP1 + 1)
+ + ":" + (CLIENT_PORT_QP1 + 2)
+ + "\nserver.2=localhost:" + (CLIENT_PORT_QP2 + 1)
+ + ":" + (CLIENT_PORT_QP2 + 2)
+ + "\nserver.3=localhost:"
+ + (CLIENT_PORT_OBS+1)+ ":" + (CLIENT_PORT_OBS + 2) + ":observer";
+ String obsCfgSection = quorumCfgSection + "\npeerType=observer";
+ MainThread q1 = new MainThread(1, CLIENT_PORT_QP1, quorumCfgSection);
+ MainThread q2 = new MainThread(2, CLIENT_PORT_QP2, quorumCfgSection);
+ MainThread q3 = new MainThread(3, CLIENT_PORT_OBS, obsCfgSection);
+ q1.start();
+ q2.start();
+ q3.start();
+ assertTrue("waiting for server 1 being up",
+ ClientBase.waitForServerUp("localhost:" + CLIENT_PORT_QP1,
+ CONNECTION_TIMEOUT));
+ assertTrue("waiting for server 2 being up",
+ ClientBase.waitForServerUp("localhost:" + CLIENT_PORT_QP2,
+ CONNECTION_TIMEOUT));
+ assertTrue("waiting for server 3 being up",
+ ClientBase.waitForServerUp("localhost:" + CLIENT_PORT_OBS,
+ CONNECTION_TIMEOUT));
+
+ zk = new ZooKeeper("localhost:" + CLIENT_PORT_OBS,
+ ClientBase.CONNECTION_TIMEOUT, this);
+ zk.create("/obstest", "test".getBytes(),Ids.OPEN_ACL_UNSAFE,
+ CreateMode.PERSISTENT);
+
+ // Assert that commands are getting forwarded correctly
+ assertEquals(new String(zk.getData("/obstest", null, null)), "test");
+
+ // Now check that other commands don't blow everything up
+ zk.sync("/", null, null);
+ zk.setData("/obstest", "test2".getBytes(), -1);
+ zk.getChildren("/", false);
+
+ assertEquals(zk.getState(), States.CONNECTED);
+
+ // Now kill one of the other real servers
+ q2.shutdown();
+
+ assertTrue("Waiting for server 2 to shut down",
+ ClientBase.waitForServerDown("localhost:"+CLIENT_PORT_QP2,
+ ClientBase.CONNECTION_TIMEOUT));
+
+ // Now the resulting ensemble shouldn't be quorate
+ latch.await();
+ assertNotSame("zk should not be connected", KeeperState.SyncConnected,lastEvent.getState());
+
+ try {
+ assertFalse("Shouldn't get a response when cluster not quorate!",
+ new String(zk.getData("/obstest", null, null)).equals("test"));
+ }
+ catch (ConnectionLossException c) {
+ LOG.info("Connection loss exception caught - ensemble not quorate (this is expected)");
+ }
+
+ latch = new CountDownLatch(1);
+
+ // Bring it back
+ q2 = new MainThread(2, CLIENT_PORT_QP2, quorumCfgSection);
+ q2.start();
+ assertTrue("waiting for server 2 being up",
+ ClientBase.waitForServerUp("localhost:" + CLIENT_PORT_QP2,
+ CONNECTION_TIMEOUT));
+
+ latch.await();
+ // It's possible our session expired - but this is ok, shows we
+ // were able to talk to the ensemble
+ assertTrue("Didn't reconnect",
+ (KeeperState.SyncConnected==lastEvent.getState() ||
+ KeeperState.Expired==lastEvent.getState()));
+
+ q1.shutdown();
+ q2.shutdown();
+ q3.shutdown();
+
+ zk.close();
+ assertTrue("Waiting for server 1 to shut down",
+ ClientBase.waitForServerDown("localhost:"+CLIENT_PORT_QP1,
+ ClientBase.CONNECTION_TIMEOUT));
+ assertTrue("Waiting for server 2 to shut down",
+ ClientBase.waitForServerDown("localhost:"+CLIENT_PORT_QP2,
+ ClientBase.CONNECTION_TIMEOUT));
+ assertTrue("Waiting for server 3 to shut down",
+ ClientBase.waitForServerDown("localhost:"+CLIENT_PORT_OBS,
+ ClientBase.CONNECTION_TIMEOUT));
+
+ }
+
+ public void process(WatchedEvent event) {
+ latch.countDown();
+ lastEvent = event;
+ }
+
+ /**
+ * This test ensures that an Observer does not elect itself as a leader, or
+ * indeed come up properly, if it is the lone member of an ensemble.
+ * @throws IOException
+ */
+ @Test
+ public void testSingleObserver() throws IOException{
+ ClientBase.setupTestEnv();
+ final int CLIENT_PORT_QP1 = 3181;
+
+ String quorumCfgSection =
+ "server.1=localhost:" + (CLIENT_PORT_QP1 + 1)
+ + ":" + (CLIENT_PORT_QP1 + 2) + "\npeerType=observer";
+
+ MainThread q1 = new MainThread(1, CLIENT_PORT_QP1, quorumCfgSection);
+ q1.start();
+ assertFalse("Observer shouldn't come up",
+ ClientBase.waitForServerUp("localhost:" + CLIENT_PORT_QP1,
+ CONNECTION_TIMEOUT));
+
+ q1.shutdown();
+ }
+
+ @Test
+ public void testLeaderElectionFail() throws Exception {
+ ClientBase.setupTestEnv();
+ final int CLIENT_PORT_QP1 = 3181;
+ final int CLIENT_PORT_QP2 = CLIENT_PORT_QP1 + 3;
+ final int CLIENT_PORT_OBS = CLIENT_PORT_QP2 + 3;
+
+ String quorumCfgSection =
+ "electionAlg=1\n" +
+ "server.1=localhost:" + (CLIENT_PORT_QP1 + 1)
+ + ":" + (CLIENT_PORT_QP1 + 2)
+ + "\nserver.2=localhost:" + (CLIENT_PORT_QP2 + 1)
+ + ":" + (CLIENT_PORT_QP2 + 2)
+ + "\nserver.3=localhost:"
+ + (CLIENT_PORT_OBS+1)+ ":" + (CLIENT_PORT_OBS + 2) + ":observer";
+ QuorumPeerConfig qpc = new QuorumPeerConfig();
+
+ File tmpDir = ClientBase.createTmpDir();
+ File confFile = new File(tmpDir, "zoo.cfg");
+
+ FileWriter fwriter = new FileWriter(confFile);
+ fwriter.write("tickTime=2000\n");
+ fwriter.write("initLimit=10\n");
+ fwriter.write("syncLimit=5\n");
+
+ File dataDir = new File(tmpDir, "data");
+ if (!dataDir.mkdir()) {
+ throw new IOException("Unable to mkdir " + dataDir);
+ }
+ fwriter.write("dataDir=" + dataDir.toString() + "\n");
+
+ fwriter.write("clientPort=" + CLIENT_PORT_QP1 + "\n");
+ fwriter.write(quorumCfgSection + "\n");
+ fwriter.flush();
+ fwriter.close();
+ try {
+ qpc.parse(confFile.toString());
+ } catch (ConfigException e) {
+ LOG.info("Config exception caught as expected: " + e.getCause());
+ return;
+ }
+
+ assertTrue("Didn't get the expected config exception", false);
+ }
+}
diff --git a/src/java/test/org/apache/zookeeper/server/quorum/QuorumPeerMainTest.java b/src/java/test/org/apache/zookeeper/server/quorum/QuorumPeerMainTest.java
index 4c7723e6..9d102c92 100644
--- a/src/java/test/org/apache/zookeeper/server/quorum/QuorumPeerMainTest.java
+++ b/src/java/test/org/apache/zookeeper/server/quorum/QuorumPeerMainTest.java
@@ -55,63 +55,8 @@ import org.junit.Test;
* Test stand-alone server.
*
*/
-public class QuorumPeerMainTest extends TestCase implements Watcher {
- protected static final Logger LOG =
- Logger.getLogger(QuorumPeerMainTest.class);
-
- public static class MainThread extends Thread {
- final File confFile;
- final TestQPMain main;
-
- public MainThread(int myid, int clientPort, String quorumCfgSection)
- throws IOException
- {
- super("QuorumPeer with myid:" + myid
- + " and clientPort:" + clientPort);
- File tmpDir = ClientBase.createTmpDir();
- confFile = new File(tmpDir, "zoo.cfg");
-
- FileWriter fwriter = new FileWriter(confFile);
- fwriter.write("tickTime=2000\n");
- fwriter.write("initLimit=10\n");
- fwriter.write("syncLimit=5\n");
-
- File dataDir = new File(tmpDir, "data");
- if (!dataDir.mkdir()) {
- throw new IOException("Unable to mkdir " + dataDir);
- }
- fwriter.write("dataDir=" + dataDir.toString() + "\n");
-
- fwriter.write("clientPort=" + clientPort + "\n");
- fwriter.write(quorumCfgSection + "\n");
- fwriter.flush();
- fwriter.close();
-
- File myidFile = new File(dataDir, "myid");
- fwriter = new FileWriter(myidFile);
- fwriter.write(Integer.toString(myid));
- fwriter.flush();
- fwriter.close();
-
- main = new TestQPMain();
- }
-
- public void run() {
- String args[] = new String[1];
- args[0] = confFile.toString();
- try {
- main.initializeAndRun(args);
- } catch (Exception e) {
- // test will still fail even though we just log/ignore
- LOG.error("unexpected exception in run", e);
- }
- }
-
- public void shutdown() {
- main.shutdown();
- }
- }
-
+public class QuorumPeerMainTest extends QuorumPeerTestBase {
+
public static class TestQPMain extends QuorumPeerMain {
public void shutdown() {
super.shutdown();
@@ -358,8 +303,5 @@ public class QuorumPeerMainTest extends TestCase implements Watcher {
}
assertTrue("fastleaderelection used", found);
}
-
- public void process(WatchedEvent event) {
- // ignore for this test
- }
+
}
diff --git a/src/java/test/org/apache/zookeeper/server/quorum/QuorumPeerTestBase.java b/src/java/test/org/apache/zookeeper/server/quorum/QuorumPeerTestBase.java
new file mode 100644
index 00000000..05326d2f
--- /dev/null
+++ b/src/java/test/org/apache/zookeeper/server/quorum/QuorumPeerTestBase.java
@@ -0,0 +1,100 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ *
+ */
+package org.apache.zookeeper.server.quorum;
+
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+
+import org.apache.log4j.Logger;
+import org.apache.zookeeper.WatchedEvent;
+import org.apache.zookeeper.Watcher;
+import org.apache.zookeeper.server.quorum.QuorumPeerMainTest.TestQPMain;
+import org.apache.zookeeper.test.ClientBase;
+
+import junit.framework.TestCase;
+
+/**
+ * Has some common functionality for tests that work with QuorumPeers.
+ * Override process(WatchedEvent) to implement the Watcher interface
+ */
+public class QuorumPeerTestBase extends TestCase implements Watcher {
+ protected static final Logger LOG =
+ Logger.getLogger(QuorumPeerTestBase.class);
+
+ public void process(WatchedEvent event) {
+ // ignore for this test
+ }
+
+ public static class MainThread extends Thread {
+ final File confFile;
+ final TestQPMain main;
+
+ public MainThread(int myid, int clientPort, String quorumCfgSection)
+ throws IOException
+ {
+ super("QuorumPeer with myid:" + myid
+ + " and clientPort:" + clientPort);
+ File tmpDir = ClientBase.createTmpDir();
+ confFile = new File(tmpDir, "zoo.cfg");
+
+ FileWriter fwriter = new FileWriter(confFile);
+ fwriter.write("tickTime=2000\n");
+ fwriter.write("initLimit=10\n");
+ fwriter.write("syncLimit=5\n");
+
+ File dataDir = new File(tmpDir, "data");
+ if (!dataDir.mkdir()) {
+ throw new IOException("Unable to mkdir " + dataDir);
+ }
+ fwriter.write("dataDir=" + dataDir.toString() + "\n");
+
+ fwriter.write("clientPort=" + clientPort + "\n");
+ fwriter.write(quorumCfgSection + "\n");
+ fwriter.flush();
+ fwriter.close();
+
+ File myidFile = new File(dataDir, "myid");
+ fwriter = new FileWriter(myidFile);
+ fwriter.write(Integer.toString(myid));
+ fwriter.flush();
+ fwriter.close();
+
+ main = new TestQPMain();
+ }
+
+ public void run() {
+ String args[] = new String[1];
+ args[0] = confFile.toString();
+ try {
+ main.initializeAndRun(args);
+ } catch (Exception e) {
+ // test will still fail even though we just log/ignore
+ LOG.error("unexpected exception in run", e);
+ }
+ }
+
+ public void shutdown() {
+ main.shutdown();
+ }
+ }
+}
diff --git a/src/java/test/org/apache/zookeeper/test/AsyncHammerTest.java b/src/java/test/org/apache/zookeeper/test/AsyncHammerTest.java
index 5dda8628..df30303d 100644
--- a/src/java/test/org/apache/zookeeper/test/AsyncHammerTest.java
+++ b/src/java/test/org/apache/zookeeper/test/AsyncHammerTest.java
@@ -202,6 +202,26 @@ public class AsyncHammerTest extends TestCase
LOG.info("Verifying hammers 2");
qb.verifyRootOfAllServersMatch(qb.hostPort);
}
+
+ @Test
+ public void testObserversHammer() throws Exception {
+ qb.tearDown();
+ qb.setUp(true);
+ bang = true;
+ Thread[] hammers = new Thread[100];
+ for (int i = 0; i < hammers.length; i++) {
+ hammers[i] = new HammerThread("HammerThread-" + i);
+ hammers[i].start();
+ }
+ Thread.sleep(5000); // allow the clients to run for max 5sec
+ bang = false;
+ for (int i = 0; i < hammers.length; i++) {
+ hammers[i].interrupt();
+ verifyThreadTerminated(hammers[i], 60000);
+ }
+ // before restart
+ qb.verifyRootOfAllServersMatch(qb.hostPort);
+ }
@SuppressWarnings("unchecked")
public void processResult(int rc, String path, Object ctx, String name) {
diff --git a/src/java/test/org/apache/zookeeper/test/HierarchicalQuorumTest.java b/src/java/test/org/apache/zookeeper/test/HierarchicalQuorumTest.java
index 63088041..e3107109 100644
--- a/src/java/test/org/apache/zookeeper/test/HierarchicalQuorumTest.java
+++ b/src/java/test/org/apache/zookeeper/test/HierarchicalQuorumTest.java
@@ -50,20 +50,20 @@ public class HierarchicalQuorumTest extends ClientBase {
File s1dir, s2dir, s3dir, s4dir, s5dir;
QuorumPeer s1, s2, s3, s4, s5;
- private int port1;
- private int port2;
- private int port3;
- private int port4;
- private int port5;
+ protected int port1;
+ protected int port2;
+ protected int port3;
+ protected int port4;
+ protected int port5;
- private int leport1;
- private int leport2;
- private int leport3;
- private int leport4;
- private int leport5;
+ protected int leport1;
+ protected int leport2;
+ protected int leport3;
+ protected int leport4;
+ protected int leport5;
Properties qp;
- private final ClientHammerTest cht = new ClientHammerTest();
+ protected final ClientHammerTest cht = new ClientHammerTest();
@Override
protected void setUp() throws Exception {
@@ -118,15 +118,29 @@ public class HierarchicalQuorumTest extends ClientBase {
LOG.info("Setup finished");
}
-
+ /**
+ * This method is here to keep backwards compatibility with the test code
+ * written before observers.
+ * @throws Exception
+ */
void startServers() throws Exception {
+ startServers(false);
+ }
+
+ /**
+ * Starts 5 Learners. When withObservers == false, all 5 are Followers.
+ * When withObservers == true, 3 are Followers and 2 Observers.
+ * @param withObservers
+ * @throws Exception
+ */
+ void startServers(boolean withObservers) throws Exception {
int tickTime = 2000;
int initLimit = 3;
int syncLimit = 3;
HashMap<Long,QuorumServer> peers = new HashMap<Long,QuorumServer>();
peers.put(Long.valueOf(1), new QuorumServer(1,
new InetSocketAddress("127.0.0.1", port1 + 1000),
- new InetSocketAddress("127.0.0.1", leport1 + 1000)));
+ new InetSocketAddress("127.0.0.1", leport1 + 1000)));
peers.put(Long.valueOf(2), new QuorumServer(2,
new InetSocketAddress("127.0.0.1", port2 + 1000),
new InetSocketAddress("127.0.0.1", leport2 + 1000)));
@@ -135,10 +149,14 @@ public class HierarchicalQuorumTest extends ClientBase {
new InetSocketAddress("127.0.0.1", leport3 + 1000)));
peers.put(Long.valueOf(4), new QuorumServer(4,
new InetSocketAddress("127.0.0.1", port4 + 1000),
- new InetSocketAddress("127.0.0.1", leport4 + 1000)));
+ new InetSocketAddress("127.0.0.1", leport4 + 1000),
+ withObservers ? QuorumPeer.LearnerType.OBSERVER
+ : QuorumPeer.LearnerType.PARTICIPANT));
peers.put(Long.valueOf(5), new QuorumServer(5,
new InetSocketAddress("127.0.0.1", port5 + 1000),
- new InetSocketAddress("127.0.0.1", leport5 + 1000)));
+ new InetSocketAddress("127.0.0.1", leport5 + 1000),
+ withObservers ? QuorumPeer.LearnerType.OBSERVER
+ : QuorumPeer.LearnerType.PARTICIPANT));
LOG.info("creating QuorumPeer 1 port " + port1);
QuorumHierarchical hq1 = new QuorumHierarchical(qp);
@@ -158,21 +176,37 @@ public class HierarchicalQuorumTest extends ClientBase {
LOG.info("creating QuorumPeer 4 port " + port4);
QuorumHierarchical hq4 = new QuorumHierarchical(qp);
s4 = new QuorumPeer(peers, s4dir, s4dir, port4, 3, 4, tickTime, initLimit, syncLimit, hq4);
+ if (withObservers) {
+ s4.setPeerType(QuorumPeer.LearnerType.OBSERVER);
+ }
assertEquals(port4, s4.getClientPort());
-
+
LOG.info("creating QuorumPeer 5 port " + port5);
QuorumHierarchical hq5 = new QuorumHierarchical(qp);
s5 = new QuorumPeer(peers, s5dir, s5dir, port5, 3, 5, tickTime, initLimit, syncLimit, hq5);
+ if (withObservers) {
+ s5.setPeerType(QuorumPeer.LearnerType.OBSERVER);
+ }
assertEquals(port5, s5.getClientPort());
+
+ // Observers are currently only compatible with LeaderElection
+ if (withObservers) {
+ s1.setElectionType(0);
+ s2.setElectionType(0);
+ s3.setElectionType(0);
+ s4.setElectionType(0);
+ s5.setElectionType(0);
+ }
+
LOG.info("start QuorumPeer 1");
s1.start();
LOG.info("start QuorumPeer 2");
s2.start();
LOG.info("start QuorumPeer 3");
s3.start();
- LOG.info("start QuorumPeer 4");
+ LOG.info("start QuorumPeer 4" + (withObservers ? "(observer)" : ""));
s4.start();
- LOG.info("start QuorumPeer 5");
+ LOG.info("start QuorumPeer 5" + (withObservers ? "(observer)" : ""));
s5.start();
LOG.info("started QuorumPeer 5");
diff --git a/src/java/test/org/apache/zookeeper/test/ObserverHierarchicalQuorumTest.java b/src/java/test/org/apache/zookeeper/test/ObserverHierarchicalQuorumTest.java
new file mode 100644
index 00000000..66fecc3d
--- /dev/null
+++ b/src/java/test/org/apache/zookeeper/test/ObserverHierarchicalQuorumTest.java
@@ -0,0 +1,59 @@
+/* Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.zookeeper.test;
+
+import org.apache.log4j.Logger;
+import org.apache.zookeeper.server.quorum.QuorumPeer;
+import org.junit.Test;
+
+/**
+ * Mimics QuorumHierarchical test, but on an ensemble that includes 2
+ * observers.
+ */
+
+public class ObserverHierarchicalQuorumTest extends HierarchicalQuorumTest {
+ private static final Logger LOG = Logger.getLogger(QuorumBase.class);
+
+ /**
+ * startServers(true) puts two observers into a 5 peer ensemble
+ */
+ void startServers() throws Exception {
+ startServers(true);
+ }
+
+ protected void shutdown(QuorumPeer qp) {
+ try {
+ /* TODO: when Observers are compatible with fle, shutdown
+ * the leader election */
+ LOG.info("Done with leader election");
+ qp.shutdown();
+ LOG.info("Done with quorum peer");
+ qp.join(30000);
+ if (qp.isAlive()) {
+ fail("QP failed to shutdown in 30 seconds");
+ }
+ } catch (InterruptedException e) {
+ LOG.debug("QP interrupted", e);
+ }
+ }
+
+ @Test
+ public void testHierarchicalQuorum() throws Throwable {
+ cht.runHammer(5, 10);
+ }
+}
\ No newline at end of file
diff --git a/src/java/test/org/apache/zookeeper/test/ObserverQuorumHammerTest.java b/src/java/test/org/apache/zookeeper/test/ObserverQuorumHammerTest.java
new file mode 100644
index 00000000..94ae77fc
--- /dev/null
+++ b/src/java/test/org/apache/zookeeper/test/ObserverQuorumHammerTest.java
@@ -0,0 +1,43 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.zookeeper.test;
+import org.apache.log4j.Logger;
+import org.junit.Before;
+import org.junit.Test;
+
+/**
+ * Mimics QuorumHammerTest, but with 2 observers in the 5 Learner ensemble.
+ */
+public class ObserverQuorumHammerTest extends QuorumHammerTest {
+ public static final long CONNECTION_TIMEOUT = ClientTest.CONNECTION_TIMEOUT;
+
+
+ @Before
+ @Override
+ protected void setUp() throws Exception {
+ qb.setUp(true);
+ cht.hostPort = qb.hostPort;
+ cht.setUpAll();
+ }
+
+ @Test
+ public void testHammerBasic() throws Throwable {
+ cht.testHammerBasic();
+ }
+}
\ No newline at end of file
diff --git a/src/java/test/org/apache/zookeeper/test/ObserverTest.java b/src/java/test/org/apache/zookeeper/test/ObserverTest.java
new file mode 100644
index 00000000..9d8ca6c1
--- /dev/null
+++ b/src/java/test/org/apache/zookeeper/test/ObserverTest.java
@@ -0,0 +1,242 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.zookeeper.test;
+
+import static org.apache.zookeeper.test.ClientBase.CONNECTION_TIMEOUT;
+
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.util.concurrent.CountDownLatch;
+
+import org.apache.log4j.Logger;
+import org.apache.zookeeper.CreateMode;
+import org.apache.zookeeper.WatchedEvent;
+import org.apache.zookeeper.Watcher;
+import org.apache.zookeeper.ZooKeeper;
+import org.apache.zookeeper.KeeperException.ConnectionLossException;
+import org.apache.zookeeper.Watcher.Event.KeeperState;
+import org.apache.zookeeper.ZooDefs.Ids;
+import org.apache.zookeeper.ZooKeeper.States;
+import org.apache.zookeeper.server.quorum.QuorumPeerConfig;
+import org.apache.zookeeper.server.quorum.QuorumPeerTestBase;
+import org.apache.zookeeper.server.quorum.QuorumPeerConfig.ConfigException;
+import org.junit.Test;
+
+/**
+ * Test Observer behaviour and specific code paths.
+ *
+ */
+public class ObserverTest extends QuorumPeerTestBase implements Watcher{
+ protected static final Logger LOG =
+ Logger.getLogger(ObserverTest.class);
+
+ // We expect two notifications before we want to continue
+ CountDownLatch latch = new CountDownLatch(2);
+ ZooKeeper zk;
+ WatchedEvent lastEvent = null;
+
+ /**
+ * This test ensures two things:
+ * 1. That Observers can successfully proxy requests to the ensemble.
+ * 2. That Observers don't participate in leader elections.
+ * The second is tested by constructing an ensemble where a leader would
+ * be elected if and only if an Observer voted.
+ * @throws Exception
+ */
+ @Test
+ public void testObserver() throws Exception {
+ ClientBase.setupTestEnv();
+ final int CLIENT_PORT_QP1 = 3181;
+ final int CLIENT_PORT_QP2 = CLIENT_PORT_QP1 + 3;
+ final int CLIENT_PORT_OBS = CLIENT_PORT_QP2 + 3;
+
+ String quorumCfgSection =
+ "electionAlg=0\n" +
+ "server.1=localhost:" + (CLIENT_PORT_QP1 + 1)
+ + ":" + (CLIENT_PORT_QP1 + 2)
+ + "\nserver.2=localhost:" + (CLIENT_PORT_QP2 + 1)
+ + ":" + (CLIENT_PORT_QP2 + 2)
+ + "\nserver.3=localhost:"
+ + (CLIENT_PORT_OBS+1)+ ":" + (CLIENT_PORT_OBS + 2) + ":observer";
+ String obsCfgSection = quorumCfgSection + "\npeerType=observer";
+ MainThread q1 = new MainThread(1, CLIENT_PORT_QP1, quorumCfgSection);
+ MainThread q2 = new MainThread(2, CLIENT_PORT_QP2, quorumCfgSection);
+ MainThread q3 = new MainThread(3, CLIENT_PORT_OBS, obsCfgSection);
+ q1.start();
+ q2.start();
+ q3.start();
+ assertTrue("waiting for server 1 being up",
+ ClientBase.waitForServerUp("localhost:" + CLIENT_PORT_QP1,
+ CONNECTION_TIMEOUT));
+ assertTrue("waiting for server 2 being up",
+ ClientBase.waitForServerUp("localhost:" + CLIENT_PORT_QP2,
+ CONNECTION_TIMEOUT));
+ assertTrue("waiting for server 3 being up",
+ ClientBase.waitForServerUp("localhost:" + CLIENT_PORT_OBS,
+ CONNECTION_TIMEOUT));
+
+ zk = new ZooKeeper("localhost:" + CLIENT_PORT_OBS,
+ ClientBase.CONNECTION_TIMEOUT, this);
+ zk.create("/obstest", "test".getBytes(),Ids.OPEN_ACL_UNSAFE,
+ CreateMode.PERSISTENT);
+
+ // Assert that commands are getting forwarded correctly
+ assertEquals(new String(zk.getData("/obstest", null, null)), "test");
+
+ // Now check that other commands don't blow everything up
+ zk.sync("/", null, null);
+ zk.setData("/obstest", "test2".getBytes(), -1);
+ zk.getChildren("/", false);
+
+ assertEquals(zk.getState(), States.CONNECTED);
+
+ // Now kill one of the other real servers
+ q2.shutdown();
+
+ assertTrue("Waiting for server 2 to shut down",
+ ClientBase.waitForServerDown("localhost:"+CLIENT_PORT_QP2,
+ ClientBase.CONNECTION_TIMEOUT));
+
+ // Now the resulting ensemble shouldn't be quorate
+ latch.await();
+ assertNotSame("zk should not be connected", KeeperState.SyncConnected,lastEvent.getState());
+
+ try {
+ assertFalse("Shouldn't get a response when cluster not quorate!",
+ new String(zk.getData("/obstest", null, null)).equals("test"));
+ }
+ catch (ConnectionLossException c) {
+ LOG.info("Connection loss exception caught - ensemble not quorate (this is expected)");
+ }
+
+ latch = new CountDownLatch(1);
+
+ // Bring it back
+ q2 = new MainThread(2, CLIENT_PORT_QP2, quorumCfgSection);
+ q2.start();
+ assertTrue("waiting for server 2 being up",
+ ClientBase.waitForServerUp("localhost:" + CLIENT_PORT_QP2,
+ CONNECTION_TIMEOUT));
+
+ latch.await();
+ // It's possible our session expired - but this is ok, shows we
+ // were able to talk to the ensemble
+ assertTrue("Didn't reconnect",
+ (KeeperState.SyncConnected==lastEvent.getState() ||
+ KeeperState.Expired==lastEvent.getState()));
+
+ q1.shutdown();
+ q2.shutdown();
+ q3.shutdown();
+
+ zk.close();
+ assertTrue("Waiting for server 1 to shut down",
+ ClientBase.waitForServerDown("localhost:"+CLIENT_PORT_QP1,
+ ClientBase.CONNECTION_TIMEOUT));
+ assertTrue("Waiting for server 2 to shut down",
+ ClientBase.waitForServerDown("localhost:"+CLIENT_PORT_QP2,
+ ClientBase.CONNECTION_TIMEOUT));
+ assertTrue("Waiting for server 3 to shut down",
+ ClientBase.waitForServerDown("localhost:"+CLIENT_PORT_OBS,
+ ClientBase.CONNECTION_TIMEOUT));
+
+ }
+
+ /**
+ * Implementation of watcher interface.
+ */
+ public void process(WatchedEvent event) {
+ latch.countDown();
+ lastEvent = event;
+ }
+
+ /**
+ * This test ensures that an Observer does not elect itself as a leader, or
+ * indeed come up properly, if it is the lone member of an ensemble.
+ * @throws IOException
+ */
+ @Test
+ public void testSingleObserver() throws IOException{
+ ClientBase.setupTestEnv();
+ final int CLIENT_PORT_QP1 = 3181;
+
+ String quorumCfgSection =
+ "server.1=localhost:" + (CLIENT_PORT_QP1 + 1)
+ + ":" + (CLIENT_PORT_QP1 + 2) + "\npeerType=observer";
+
+ MainThread q1 = new MainThread(1, CLIENT_PORT_QP1, quorumCfgSection);
+ q1.start();
+ assertFalse("Observer shouldn't come up",
+ ClientBase.waitForServerUp("localhost:" + CLIENT_PORT_QP1,
+ CONNECTION_TIMEOUT));
+
+ q1.shutdown();
+ }
+
+ /**
+ * Check that an attempt to instantiate an ensemble with observers and
+ * electionAlg != 0 fails (this will be removed when the restriction is).
+ * @throws Exception
+ */
+ @Test
+ public void testLeaderElectionFail() throws Exception {
+ ClientBase.setupTestEnv();
+ final int CLIENT_PORT_QP1 = 3181;
+ final int CLIENT_PORT_QP2 = CLIENT_PORT_QP1 + 3;
+ final int CLIENT_PORT_OBS = CLIENT_PORT_QP2 + 3;
+
+ String quorumCfgSection =
+ "electionAlg=1\n" +
+ "server.1=localhost:" + (CLIENT_PORT_QP1 + 1)
+ + ":" + (CLIENT_PORT_QP1 + 2)
+ + "\nserver.2=localhost:" + (CLIENT_PORT_QP2 + 1)
+ + ":" + (CLIENT_PORT_QP2 + 2)
+ + "\nserver.3=localhost:"
+ + (CLIENT_PORT_OBS+1)+ ":" + (CLIENT_PORT_OBS + 2) + ":observer";
+ QuorumPeerConfig qpc = new QuorumPeerConfig();
+
+ File tmpDir = ClientBase.createTmpDir();
+ File confFile = new File(tmpDir, "zoo.cfg");
+
+ FileWriter fwriter = new FileWriter(confFile);
+ fwriter.write("tickTime=2000\n");
+ fwriter.write("initLimit=10\n");
+ fwriter.write("syncLimit=5\n");
+
+ File dataDir = new File(tmpDir, "data");
+ if (!dataDir.mkdir()) {
+ throw new IOException("Unable to mkdir " + dataDir);
+ }
+ fwriter.write("dataDir=" + dataDir.toString() + "\n");
+
+ fwriter.write("clientPort=" + CLIENT_PORT_QP1 + "\n");
+ fwriter.write(quorumCfgSection + "\n");
+ fwriter.flush();
+ fwriter.close();
+ try {
+ qpc.parse(confFile.toString());
+ } catch (ConfigException e) {
+ LOG.info("Config exception caught as expected: " + e.getCause());
+ return;
+ }
+
+ assertTrue("Didn't get the expected config exception", false);
+ }
+}
diff --git a/src/java/test/org/apache/zookeeper/test/QuorumBase.java b/src/java/test/org/apache/zookeeper/test/QuorumBase.java
index 2b68e26a..1b670de8 100644
--- a/src/java/test/org/apache/zookeeper/test/QuorumBase.java
+++ b/src/java/test/org/apache/zookeeper/test/QuorumBase.java
@@ -31,6 +31,7 @@ import org.apache.log4j.Logger;
import org.apache.zookeeper.PortAssignment;
import org.apache.zookeeper.TestableZooKeeper;
import org.apache.zookeeper.server.quorum.QuorumPeer;
+import org.apache.zookeeper.server.quorum.QuorumPeer.LearnerType;
import org.apache.zookeeper.server.quorum.QuorumPeer.QuorumServer;
import org.junit.After;
@@ -49,6 +50,10 @@ public class QuorumBase extends ClientBase {
@Override
protected void setUp() throws Exception {
+ setUp(false);
+ }
+
+ protected void setUp(boolean withObservers) throws Exception {
LOG.info("STARTING " + getName());
setupTestEnv();
@@ -74,7 +79,7 @@ public class QuorumBase extends ClientBase {
s4dir = ClientBase.createTmpDir();
s5dir = ClientBase.createTmpDir();
- startServers();
+ startServers(withObservers);
OperatingSystemMXBean osMbean =
ManagementFactory.getOperatingSystemMXBean();
@@ -87,7 +92,12 @@ public class QuorumBase extends ClientBase {
LOG.info("Setup finished");
}
+
void startServers() throws Exception {
+ startServers(false);
+ }
+
+ void startServers(boolean withObservers) throws Exception {
int tickTime = 2000;
int initLimit = 3;
int syncLimit = 3;
@@ -97,6 +107,11 @@ public class QuorumBase extends ClientBase {
peers.put(Long.valueOf(3), new QuorumServer(3, new InetSocketAddress("127.0.0.1", port3 + 1000)));
peers.put(Long.valueOf(4), new QuorumServer(4, new InetSocketAddress("127.0.0.1", port4 + 1000)));
peers.put(Long.valueOf(5), new QuorumServer(5, new InetSocketAddress("127.0.0.1", port5 + 1000)));
+
+ if (withObservers) {
+ peers.get(Long.valueOf(4)).type = LearnerType.OBSERVER;
+ peers.get(Long.valueOf(5)).type = LearnerType.OBSERVER;
+ }
LOG.info("creating QuorumPeer 1 port " + port1);
s1 = new QuorumPeer(peers, s1dir, s1dir, port1, 0, 1, tickTime, initLimit, syncLimit);
@@ -113,6 +128,12 @@ public class QuorumBase extends ClientBase {
LOG.info("creating QuorumPeer 5 port " + port5);
s5 = new QuorumPeer(peers, s5dir, s5dir, port5, 0, 5, tickTime, initLimit, syncLimit);
assertEquals(port5, s5.getClientPort());
+
+ if (withObservers) {
+ s4.setPeerType(LearnerType.OBSERVER);
+ s5.setPeerType(LearnerType.OBSERVER);
+ }
+
LOG.info("start QuorumPeer 1");
s1.start();
LOG.info("start QuorumPeer 2");
diff --git a/src/java/test/org/apache/zookeeper/test/QuorumHammerTest.java b/src/java/test/org/apache/zookeeper/test/QuorumHammerTest.java
index d81b5ad8..8bbbc2e4 100644
--- a/src/java/test/org/apache/zookeeper/test/QuorumHammerTest.java
+++ b/src/java/test/org/apache/zookeeper/test/QuorumHammerTest.java
@@ -22,11 +22,11 @@ import org.junit.Before;
import org.junit.Test;
public class QuorumHammerTest extends QuorumBase {
- private static final Logger LOG = Logger.getLogger(QuorumHammerTest.class);
+ protected static final Logger LOG = Logger.getLogger(QuorumHammerTest.class);
public static final long CONNECTION_TIMEOUT = ClientTest.CONNECTION_TIMEOUT;
- private final QuorumBase qb = new QuorumBase();
- private final ClientHammerTest cht = new ClientHammerTest();
+ protected final QuorumBase qb = new QuorumBase();
+ protected final ClientHammerTest cht = new ClientHammerTest();
@Before
@Override
--
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