You are viewing a plain text version of this content. The canonical link for it is here.
Posted to commits@samza.apache.org by ya...@apache.org on 2014/12/05 19:52:35 UTC
svn commit: r1643389 [21/27] - in /incubator/samza/site: ./ archive/
community/ contribute/ img/0.8/ img/0.8/learn/ img/0.8/learn/documentation/
img/0.8/learn/documentation/comparisons/
img/0.8/learn/documentation/container/ img/0.8/learn/documentation...
Added: incubator/samza/site/learn/documentation/0.8/container/checkpointing.html
URL: http://svn.apache.org/viewvc/incubator/samza/site/learn/documentation/0.8/container/checkpointing.html?rev=1643389&view=auto
==============================================================================
--- incubator/samza/site/learn/documentation/0.8/container/checkpointing.html (added)
+++ incubator/samza/site/learn/documentation/0.8/container/checkpointing.html Fri Dec 5 18:52:32 2014
@@ -0,0 +1,288 @@
+<!DOCTYPE html>
+<!--
+ 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.
+-->
+<html lang="en">
+ <head>
+ <meta charset="utf-8">
+ <title>Samza - Checkpointing</title>
+ <link href='/css/ropa-sans.css' rel='stylesheet' type='text/css'/>
+ <link href="/css/bootstrap.min.css" rel="stylesheet"/>
+ <link href="/css/font-awesome.min.css" rel="stylesheet"/>
+ <link href="/css/main.css" rel="stylesheet"/>
+ <link href="/css/syntax.css" rel="stylesheet"/>
+ <link rel="icon" type="image/png" href="/img/samza-icon.png">
+ <script src="/js/jquery-1.11.1.min.js"></script>
+ </head>
+ <body>
+ <div class="wrapper">
+ <div class="wrapper-content">
+
+ <div class="masthead">
+ <div class="container">
+ <div class="masthead-logo">
+ <a href="/" class="logo">samza</a>
+ </div>
+ <div class="masthead-icons">
+ <div class="pull-right">
+ <a href="/startup/download"><i class="fa fa-arrow-circle-o-down masthead-icon"></i></a>
+ <a href="https://git-wip-us.apache.org/repos/asf?p=incubator-samza.git;a=tree" target="_blank"><i class="fa fa-code masthead-icon" style="font-weight: bold;"></i></a>
+ <a href="https://twitter.com/samzastream" target="_blank"><i class="fa fa-twitter masthead-icon"></i></a>
+ <!-- this icon only shows in versioned pages -->
+
+
+
+
+ <a href="http://samza.incubator.apache.org/learn/documentation/latest/container/checkpointing.html"><i id="switch-version-button"></i></a>
+ <!-- links for the navigation bar -->
+
+
+ </div>
+ </div>
+ </div><!-- /.container -->
+ </div>
+
+ <div class="container">
+ <div class="menu">
+ <h1><i class="fa fa-rocket"></i> Getting Started</h1>
+ <ul>
+ <li><a href="/startup/hello-samza/0.8">Hello Samza</a></li>
+ <li><a href="/startup/download">Download</a></li>
+ </ul>
+
+ <h1><i class="fa fa-book"></i> Learn</h1>
+ <ul>
+ <li><a href="/learn/documentation/0.8">Documentation</a></li>
+ <li><a href="/learn/documentation/0.8/jobs/configuration-table.html">Configuration</a></li>
+ <li><a href="/learn/documentation/0.8/api/javadocs/">Javadocs</a></li>
+ <li><a href="/learn/tutorials/0.8">Tutorials</a></li>
+ <li><a href="http://wiki.apache.org/samza/FAQ">FAQ</a></li>
+ <li><a href="http://wiki.apache.org/samza">Wiki</a></li>
+ <li><a href="http://wiki.apache.org/samza/PapersAndTalks">Papers & Talks</a></li>
+ <li><a href="http://blogs.apache.org/samza">Blog</a></li>
+ </ul>
+
+ <h1><i class="fa fa-comments"></i> Community</h1>
+ <ul>
+ <li><a href="/community/mailing-lists.html">Mailing Lists</a></li>
+ <li><a href="/community/irc.html">IRC</a></li>
+ <li><a href="https://issues.apache.org/jira/browse/SAMZA">Bugs</a></li>
+ <li><a href="http://wiki.apache.org/samza/PoweredBy">Powered by</a></li>
+ <li><a href="http://wiki.apache.org/samza/Ecosystem">Ecosystem</a></li>
+ <li><a href="/community/committers.html">Committers</a></li>
+ </ul>
+
+ <h1><i class="fa fa-code"></i> Contribute</h1>
+ <ul>
+ <li><a href="/contribute/rules.html">Rules</a></li>
+ <li><a href="/contribute/coding-guide.html">Coding Guide</a></li>
+ <li><a href="/contribute/projects.html">Projects</a></li>
+ <li><a href="/contribute/design-documents.html">Design Documents</a></li>
+ <li><a href="/contribute/code.html">Code</a></li>
+ <li><a href="https://reviews.apache.org/groups/samza">Review Board</a></li>
+ <li><a href="/contribute/tests.html">Tests</a></li>
+ <li><a href="/contribute/disclaimer.html">Disclaimer</a></li>
+ </ul>
+
+ <h1><i class="fa fa-history"></i> Archive</h1>
+ <ul>
+ <li><a href="/archive/index.html#latest">latest</a></li>
+ <li><a href="/archive/index.html#08">0.8</a></li>
+ <li><a href="/archive/index.html#07">0.7</a></li>
+ </ul>
+ </div>
+
+ <div class="content">
+ <!--
+ 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.
+-->
+
+<h2>Checkpointing</h2>
+
+<!--
+ 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.
+-->
+
+<p>Samza provides fault-tolerant processing of streams: Samza guarantees that messages won’t be lost, even if your job crashes, if a machine dies, if there is a network fault, or something else goes wrong. In order to provide this guarantee, Samza expects the <a href="streams.html">input system</a> to meet the following requirements:</p>
+
+<ul>
+<li>The stream may be sharded into one or more <em>partitions</em>. Each partition is independent from the others, and is replicated across multiple machines (the stream continues to be available, even if a machine fails).</li>
+<li>Each partition consists of a sequence of messages in a fixed order. Each message has an <em>offset</em>, which indicates its position in that sequence. Messages are always consumed sequentially within each partition.</li>
+<li>A Samza job can start consuming the sequence of messages from any starting offset.</li>
+</ul>
+
+<p>Kafka meets these requirements, but they can also be implemented with other message broker systems.</p>
+
+<p>As described in the <a href="samza-container.html">section on SamzaContainer</a>, each task instance of your job consumes one partition of an input stream. Each task has a <em>current offset</em> for each input stream: the offset of the next message to be read from that stream partition. Every time a message is read from the stream, the current offset moves forwards.</p>
+
+<p>If a Samza container fails, it needs to be restarted (potentially on another machine) and resume processing where the failed container left off. In order to enable this, a container periodically checkpoints the current offset for each task instance.</p>
+
+<p><img src="/img/0.8/learn/documentation/container/checkpointing.svg" alt="Illustration of checkpointing" class="diagram-large"></p>
+
+<p>When a Samza container starts up, it looks for the most recent checkpoint and starts consuming messages from the checkpointed offsets. If the previous container failed unexpectedly, the most recent checkpoint may be slightly behind the current offsets (i.e. the job may have consumed some more messages since the last checkpoint was written), but we can’t know for sure. In that case, the job may process a few messages again.</p>
+
+<p>This guarantee is called <em>at-least-once processing</em>: Samza ensures that your job doesn’t miss any messages, even if containers need to be restarted. However, it is possible for your job to see the same message more than once when a container is restarted. We are planning to address this in a future version of Samza, but for now it is just something to be aware of: for example, if you are counting page views, a forcefully killed container could cause events to be slightly over-counted. You can reduce duplication by checkpointing more frequently, at a slight performance cost.</p>
+
+<p>For checkpoints to be effective, they need to be written somewhere where they will survive faults. Samza allows you to write checkpoints to the file system (using FileSystemCheckpointManager), but that doesn’t help if the machine fails and the container needs to be restarted on another machine. The most common configuration is to use Kafka for checkpointing. You can enable this with the following job configuration:</p>
+
+<div class="highlight"><pre><code class="jproperties"><span class="c"># The name of your job determines the name under which checkpoints will be stored</span>
+<span class="na">job.name</span><span class="o">=</span><span class="s">example-job</span>
+
+<span class="c"># Define a system called "kafka" for consuming and producing to a Kafka cluster</span>
+<span class="na">systems.kafka.samza.factory</span><span class="o">=</span><span class="s">org.apache.samza.system.kafka.KafkaSystemFactory</span>
+
+<span class="c"># Declare that we want our job's checkpoints to be written to Kafka</span>
+<span class="na">task.checkpoint.factory</span><span class="o">=</span><span class="s">org.apache.samza.checkpoint.kafka.KafkaCheckpointManagerFactory</span>
+<span class="na">task.checkpoint.system</span><span class="o">=</span><span class="s">kafka</span>
+
+<span class="c"># By default, a checkpoint is written every 60 seconds. You can change this if you like.</span>
+<span class="na">task.commit.ms</span><span class="o">=</span><span class="s">60000</span></code></pre></div>
+
+<p>In this configuration, Samza writes checkpoints to a separate Kafka topic called __samza_checkpoint_<job-name>_<job-id> (in the example configuration above, the topic would be called __samza_checkpoint_example-job_1). Once per minute, Samza automatically sends a message to this topic, in which the current offsets of the input streams are encoded. When a Samza container starts up, it looks for the most recent offset message in this topic, and loads that checkpoint.</p>
+
+<p>Sometimes it can be useful to use checkpoints only for some input streams, but not for others. In this case, you can tell Samza to ignore any checkpointed offsets for a particular stream name:</p>
+
+<div class="highlight"><pre><code class="jproperties"><span class="c"># Ignore any checkpoints for the topic "my-special-topic"</span>
+<span class="na">systems.kafka.streams.my-special-topic.samza.reset.offset</span><span class="o">=</span><span class="s">true</span>
+
+<span class="c"># Always start consuming "my-special-topic" at the oldest available offset</span>
+<span class="na">systems.kafka.streams.my-special-topic.samza.offset.default</span><span class="o">=</span><span class="s">oldest</span></code></pre></div>
+
+<p>The following table explains the meaning of these configuration parameters:</p>
+
+<table class="table table-condensed table-bordered table-striped">
+ <thead>
+ <tr>
+ <th>Parameter name</th>
+ <th>Value</th>
+ <th>Meaning</th>
+ </tr>
+ </thead>
+ <tbody>
+ <tr>
+ <td rowspan="2" class="nowrap">systems.<system>.<br>streams.<stream>.<br>samza.reset.offset</td>
+ <td>false (default)</td>
+ <td>When container starts up, resume processing from last checkpoint</td>
+ </tr>
+ <tr>
+ <td>true</td>
+ <td>Ignore checkpoint (pretend that no checkpoint is present)</td>
+ </tr>
+ <tr>
+ <td rowspan="2" class="nowrap">systems.<system>.<br>streams.<stream>.<br>samza.offset.default</td>
+ <td>upcoming (default)</td>
+ <td>When container starts and there is no checkpoint (or the checkpoint is ignored), only process messages that are published after the job is started, but no old messages</td>
+ </tr>
+ <tr>
+ <td>oldest</td>
+ <td>When container starts and there is no checkpoint (or the checkpoint is ignored), jump back to the oldest available message in the system, and consume all messages from that point onwards (most likely this means repeated processing of messages already seen previously)</td>
+ </tr>
+ </tbody>
+</table>
+
+<p>Note that the example configuration above causes your tasks to start consuming from the oldest offset <em>every time a container starts up</em>. This is useful in case you have some in-memory state in your tasks that you need to rebuild from source data in an input stream. If you are using streams in this way, you may also find <a href="streams.html">bootstrap streams</a> useful.</p>
+
+<h3 id="manipulating-checkpoints-manually">Manipulating Checkpoints Manually</h3>
+
+<p>If you want to make a one-off change to a job’s consumer offsets, for example to force old messages to be <a href="../jobs/reprocessing.html">processed again</a> with a new version of your code, you can use CheckpointTool to inspect and manipulate the job’s checkpoint. The tool is included in Samza’s <a href="/contribute/code.html">source repository</a>.</p>
+
+<p>To inspect a job’s latest checkpoint, you need to specify your job’s config file, so that the tool knows which job it is dealing with:</p>
+
+<div class="highlight"><pre><code class="bash">samza-example/target/bin/checkpoint-tool.sh <span class="se">\</span>
+ --config-path<span class="o">=</span>file:///path/to/job/config.properties</code></pre></div>
+
+<p>This command prints out the latest checkpoint in a properties file format. You can save the output to a file, and edit it as you wish. For example, to jump back to the oldest possible point in time, you can set all the offsets to 0. Then you can feed that properties file back into checkpoint-tool.sh and save the modified checkpoint:</p>
+
+<div class="highlight"><pre><code class="bash">samza-example/target/bin/checkpoint-tool.sh <span class="se">\</span>
+ --config-path<span class="o">=</span>file:///path/to/job/config.properties <span class="se">\</span>
+ --new-offsets<span class="o">=</span>file:///path/to/new/offsets.properties</code></pre></div>
+
+<p>Note that Samza only reads checkpoints on container startup. In order for your checkpoint change to take effect, you need to first stop the job, then save the modified offsets, and then start the job again. If you write a checkpoint while the job is running, it will most likely have no effect.</p>
+
+<h2 id="state-management-»"><a href="state-management.html">State Management »</a></h2>
+
+
+ </div>
+ </div>
+
+ </div><!-- /.wrapper-content -->
+ </div><!-- /.wrapper -->
+
+ <div class="footer">
+ <div class="container">
+ <!-- nothing for now. -->
+ </div>
+ </div>
+
+
+ <script>
+ $( document ).ready(function() {
+ if ( $.fn.urlExists( "/learn/documentation/latest/container/checkpointing.html" ) ) {
+ $("#switch-version-button").addClass("fa fa-history masthead-icon");
+ }
+ });
+
+ /* a function to test whether the url exists or not */
+ (function( $ ) {
+ $.fn.urlExists = function(url) {
+ var http = new XMLHttpRequest();
+ http.open('HEAD', url, false);
+ http.send();
+ return http.status != 404;
+ };
+ }( jQuery ));
+ </script>
+
+
+ <!-- Google Analytics -->
+ <script>
+ (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
+ (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
+ m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
+ })(window,document,'script','//www.google-analytics.com/analytics.js','ga');
+
+ ga('create', 'UA-43122768-1', 'apache.org');
+ ga('send', 'pageview');
+
+ </script>
+ </body>
+</html>
Added: incubator/samza/site/learn/documentation/0.8/container/event-loop.html
URL: http://svn.apache.org/viewvc/incubator/samza/site/learn/documentation/0.8/container/event-loop.html?rev=1643389&view=auto
==============================================================================
--- incubator/samza/site/learn/documentation/0.8/container/event-loop.html (added)
+++ incubator/samza/site/learn/documentation/0.8/container/event-loop.html Fri Dec 5 18:52:32 2014
@@ -0,0 +1,230 @@
+<!DOCTYPE html>
+<!--
+ 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.
+-->
+<html lang="en">
+ <head>
+ <meta charset="utf-8">
+ <title>Samza - Event Loop</title>
+ <link href='/css/ropa-sans.css' rel='stylesheet' type='text/css'/>
+ <link href="/css/bootstrap.min.css" rel="stylesheet"/>
+ <link href="/css/font-awesome.min.css" rel="stylesheet"/>
+ <link href="/css/main.css" rel="stylesheet"/>
+ <link href="/css/syntax.css" rel="stylesheet"/>
+ <link rel="icon" type="image/png" href="/img/samza-icon.png">
+ <script src="/js/jquery-1.11.1.min.js"></script>
+ </head>
+ <body>
+ <div class="wrapper">
+ <div class="wrapper-content">
+
+ <div class="masthead">
+ <div class="container">
+ <div class="masthead-logo">
+ <a href="/" class="logo">samza</a>
+ </div>
+ <div class="masthead-icons">
+ <div class="pull-right">
+ <a href="/startup/download"><i class="fa fa-arrow-circle-o-down masthead-icon"></i></a>
+ <a href="https://git-wip-us.apache.org/repos/asf?p=incubator-samza.git;a=tree" target="_blank"><i class="fa fa-code masthead-icon" style="font-weight: bold;"></i></a>
+ <a href="https://twitter.com/samzastream" target="_blank"><i class="fa fa-twitter masthead-icon"></i></a>
+ <!-- this icon only shows in versioned pages -->
+
+
+
+
+ <a href="http://samza.incubator.apache.org/learn/documentation/latest/container/event-loop.html"><i id="switch-version-button"></i></a>
+ <!-- links for the navigation bar -->
+
+
+ </div>
+ </div>
+ </div><!-- /.container -->
+ </div>
+
+ <div class="container">
+ <div class="menu">
+ <h1><i class="fa fa-rocket"></i> Getting Started</h1>
+ <ul>
+ <li><a href="/startup/hello-samza/0.8">Hello Samza</a></li>
+ <li><a href="/startup/download">Download</a></li>
+ </ul>
+
+ <h1><i class="fa fa-book"></i> Learn</h1>
+ <ul>
+ <li><a href="/learn/documentation/0.8">Documentation</a></li>
+ <li><a href="/learn/documentation/0.8/jobs/configuration-table.html">Configuration</a></li>
+ <li><a href="/learn/documentation/0.8/api/javadocs/">Javadocs</a></li>
+ <li><a href="/learn/tutorials/0.8">Tutorials</a></li>
+ <li><a href="http://wiki.apache.org/samza/FAQ">FAQ</a></li>
+ <li><a href="http://wiki.apache.org/samza">Wiki</a></li>
+ <li><a href="http://wiki.apache.org/samza/PapersAndTalks">Papers & Talks</a></li>
+ <li><a href="http://blogs.apache.org/samza">Blog</a></li>
+ </ul>
+
+ <h1><i class="fa fa-comments"></i> Community</h1>
+ <ul>
+ <li><a href="/community/mailing-lists.html">Mailing Lists</a></li>
+ <li><a href="/community/irc.html">IRC</a></li>
+ <li><a href="https://issues.apache.org/jira/browse/SAMZA">Bugs</a></li>
+ <li><a href="http://wiki.apache.org/samza/PoweredBy">Powered by</a></li>
+ <li><a href="http://wiki.apache.org/samza/Ecosystem">Ecosystem</a></li>
+ <li><a href="/community/committers.html">Committers</a></li>
+ </ul>
+
+ <h1><i class="fa fa-code"></i> Contribute</h1>
+ <ul>
+ <li><a href="/contribute/rules.html">Rules</a></li>
+ <li><a href="/contribute/coding-guide.html">Coding Guide</a></li>
+ <li><a href="/contribute/projects.html">Projects</a></li>
+ <li><a href="/contribute/design-documents.html">Design Documents</a></li>
+ <li><a href="/contribute/code.html">Code</a></li>
+ <li><a href="https://reviews.apache.org/groups/samza">Review Board</a></li>
+ <li><a href="/contribute/tests.html">Tests</a></li>
+ <li><a href="/contribute/disclaimer.html">Disclaimer</a></li>
+ </ul>
+
+ <h1><i class="fa fa-history"></i> Archive</h1>
+ <ul>
+ <li><a href="/archive/index.html#latest">latest</a></li>
+ <li><a href="/archive/index.html#08">0.8</a></li>
+ <li><a href="/archive/index.html#07">0.7</a></li>
+ </ul>
+ </div>
+
+ <div class="content">
+ <!--
+ 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.
+-->
+
+<h2>Event Loop</h2>
+
+<!--
+ 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.
+-->
+
+<p>The event loop is the <a href="samza-container.html">container</a>’s single thread that is in charge of <a href="streams.html">reading and writing messages</a>, <a href="metrics.html">flushing metrics</a>, <a href="checkpointing.html">checkpointing</a>, and <a href="windowing.html">windowing</a>.</p>
+
+<p>Samza uses a single thread because every container is designed to use a single CPU core; to get more parallelism, simply run more containers. This uses a bit more memory than multithreaded parallelism, because each JVM has some overhead, but it simplifies resource management and improves isolation between jobs. This helps Samza jobs run reliably on a multitenant cluster, where many different jobs written by different people are running at the same time.</p>
+
+<p>You are strongly discouraged from using threads in your job’s code. Samza uses multiple threads internally for communicating with input and output streams, but all message processing and user code runs on a single-threaded event loop. In general, Samza is not thread-safe.</p>
+
+<h3 id="event-loop-internals">Event Loop Internals</h3>
+
+<p>A container may have multiple <a href="../api/javadocs/org/apache/samza/system/SystemConsumer.html">SystemConsumers</a> for consuming messages from different input systems. Each SystemConsumer reads messages on its own thread, but writes messages into a shared in-process message queue. The container uses this queue to funnel all of the messages into the event loop.</p>
+
+<p>The event loop works as follows:</p>
+
+<ol>
+<li>Take a message from the incoming message queue;</li>
+<li>Give the message to the appropriate <a href="samza-container.html">task instance</a> by calling process() on it;</li>
+<li>Call window() on the task instance if it implements <a href="../api/javadocs/org/apache/samza/task/WindowableTask.html">WindowableTask</a>, and the window time has expired;</li>
+<li>Send any output from the process() and window() calls to the appropriate <a href="../api/javadocs/org/apache/samza/system/SystemProducer.html">SystemProducers</a>;</li>
+<li>Write checkpoints for any tasks whose <a href="checkpointing.html">commit interval</a> has elapsed.</li>
+</ol>
+
+<p>The container does this, in a loop, until it is shut down. Note that although there can be multiple task instances within a container (depending on the number of input stream partitions), their process() and window() methods are all called on the same thread, never concurrently on different threads.</p>
+
+<h3 id="lifecycle-listeners">Lifecycle Listeners</h3>
+
+<p>Sometimes, you need to run your own code at specific points in a task’s lifecycle. For example, you might want to set up some context in the container whenever a new message arrives, or perform some operations on startup or shutdown.</p>
+
+<p>To receive notifications when such events happen, you can implement the <a href="../api/javadocs/org/apache/samza/task/TaskLifecycleListenerFactory.html">TaskLifecycleListenerFactory</a> interface. It returns a <a href="../api/javadocs/org/apache/samza/task/TaskLifecycleListener.html">TaskLifecycleListener</a>, whose methods are called by Samza at the appropriate times.</p>
+
+<p>You can then tell Samza to use your lifecycle listener with the following properties in your job configuration:</p>
+
+<div class="highlight"><pre><code class="jproperties"><span class="c"># Define a listener called "my-listener" by giving the factory class name</span>
+<span class="na">task.lifecycle.listener.my-listener.class</span><span class="o">=</span><span class="s">com.example.foo.MyListenerFactory</span>
+
+<span class="c"># Enable it in this job (multiple listeners can be separated by commas)</span>
+<span class="na">task.lifecycle.listeners</span><span class="o">=</span><span class="s">my-listener</span></code></pre></div>
+
+<p>The Samza container creates one instance of your <a href="../api/javadocs/org/apache/samza/task/TaskLifecycleListener.html">TaskLifecycleListener</a>. If the container has multiple task instances (processing different input stream partitions), the beforeInit, afterInit, beforeClose and afterClose methods are called for each task instance. The <a href="../api/javadocs/org/apache/samza/task/TaskContext.html">TaskContext</a> argument of those methods gives you more information about the partitions.</p>
+
+<h2 id="jmx-»"><a href="jmx.html">JMX »</a></h2>
+
+
+ </div>
+ </div>
+
+ </div><!-- /.wrapper-content -->
+ </div><!-- /.wrapper -->
+
+ <div class="footer">
+ <div class="container">
+ <!-- nothing for now. -->
+ </div>
+ </div>
+
+
+ <script>
+ $( document ).ready(function() {
+ if ( $.fn.urlExists( "/learn/documentation/latest/container/event-loop.html" ) ) {
+ $("#switch-version-button").addClass("fa fa-history masthead-icon");
+ }
+ });
+
+ /* a function to test whether the url exists or not */
+ (function( $ ) {
+ $.fn.urlExists = function(url) {
+ var http = new XMLHttpRequest();
+ http.open('HEAD', url, false);
+ http.send();
+ return http.status != 404;
+ };
+ }( jQuery ));
+ </script>
+
+
+ <!-- Google Analytics -->
+ <script>
+ (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
+ (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
+ m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
+ })(window,document,'script','//www.google-analytics.com/analytics.js','ga');
+
+ ga('create', 'UA-43122768-1', 'apache.org');
+ ga('send', 'pageview');
+
+ </script>
+ </body>
+</html>
Added: incubator/samza/site/learn/documentation/0.8/container/jmx.html
URL: http://svn.apache.org/viewvc/incubator/samza/site/learn/documentation/0.8/container/jmx.html?rev=1643389&view=auto
==============================================================================
--- incubator/samza/site/learn/documentation/0.8/container/jmx.html (added)
+++ incubator/samza/site/learn/documentation/0.8/container/jmx.html Fri Dec 5 18:52:32 2014
@@ -0,0 +1,207 @@
+<!DOCTYPE html>
+<!--
+ 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.
+-->
+<html lang="en">
+ <head>
+ <meta charset="utf-8">
+ <title>Samza - JMX</title>
+ <link href='/css/ropa-sans.css' rel='stylesheet' type='text/css'/>
+ <link href="/css/bootstrap.min.css" rel="stylesheet"/>
+ <link href="/css/font-awesome.min.css" rel="stylesheet"/>
+ <link href="/css/main.css" rel="stylesheet"/>
+ <link href="/css/syntax.css" rel="stylesheet"/>
+ <link rel="icon" type="image/png" href="/img/samza-icon.png">
+ <script src="/js/jquery-1.11.1.min.js"></script>
+ </head>
+ <body>
+ <div class="wrapper">
+ <div class="wrapper-content">
+
+ <div class="masthead">
+ <div class="container">
+ <div class="masthead-logo">
+ <a href="/" class="logo">samza</a>
+ </div>
+ <div class="masthead-icons">
+ <div class="pull-right">
+ <a href="/startup/download"><i class="fa fa-arrow-circle-o-down masthead-icon"></i></a>
+ <a href="https://git-wip-us.apache.org/repos/asf?p=incubator-samza.git;a=tree" target="_blank"><i class="fa fa-code masthead-icon" style="font-weight: bold;"></i></a>
+ <a href="https://twitter.com/samzastream" target="_blank"><i class="fa fa-twitter masthead-icon"></i></a>
+ <!-- this icon only shows in versioned pages -->
+
+
+
+
+ <a href="http://samza.incubator.apache.org/learn/documentation/latest/container/jmx.html"><i id="switch-version-button"></i></a>
+ <!-- links for the navigation bar -->
+
+
+ </div>
+ </div>
+ </div><!-- /.container -->
+ </div>
+
+ <div class="container">
+ <div class="menu">
+ <h1><i class="fa fa-rocket"></i> Getting Started</h1>
+ <ul>
+ <li><a href="/startup/hello-samza/0.8">Hello Samza</a></li>
+ <li><a href="/startup/download">Download</a></li>
+ </ul>
+
+ <h1><i class="fa fa-book"></i> Learn</h1>
+ <ul>
+ <li><a href="/learn/documentation/0.8">Documentation</a></li>
+ <li><a href="/learn/documentation/0.8/jobs/configuration-table.html">Configuration</a></li>
+ <li><a href="/learn/documentation/0.8/api/javadocs/">Javadocs</a></li>
+ <li><a href="/learn/tutorials/0.8">Tutorials</a></li>
+ <li><a href="http://wiki.apache.org/samza/FAQ">FAQ</a></li>
+ <li><a href="http://wiki.apache.org/samza">Wiki</a></li>
+ <li><a href="http://wiki.apache.org/samza/PapersAndTalks">Papers & Talks</a></li>
+ <li><a href="http://blogs.apache.org/samza">Blog</a></li>
+ </ul>
+
+ <h1><i class="fa fa-comments"></i> Community</h1>
+ <ul>
+ <li><a href="/community/mailing-lists.html">Mailing Lists</a></li>
+ <li><a href="/community/irc.html">IRC</a></li>
+ <li><a href="https://issues.apache.org/jira/browse/SAMZA">Bugs</a></li>
+ <li><a href="http://wiki.apache.org/samza/PoweredBy">Powered by</a></li>
+ <li><a href="http://wiki.apache.org/samza/Ecosystem">Ecosystem</a></li>
+ <li><a href="/community/committers.html">Committers</a></li>
+ </ul>
+
+ <h1><i class="fa fa-code"></i> Contribute</h1>
+ <ul>
+ <li><a href="/contribute/rules.html">Rules</a></li>
+ <li><a href="/contribute/coding-guide.html">Coding Guide</a></li>
+ <li><a href="/contribute/projects.html">Projects</a></li>
+ <li><a href="/contribute/design-documents.html">Design Documents</a></li>
+ <li><a href="/contribute/code.html">Code</a></li>
+ <li><a href="https://reviews.apache.org/groups/samza">Review Board</a></li>
+ <li><a href="/contribute/tests.html">Tests</a></li>
+ <li><a href="/contribute/disclaimer.html">Disclaimer</a></li>
+ </ul>
+
+ <h1><i class="fa fa-history"></i> Archive</h1>
+ <ul>
+ <li><a href="/archive/index.html#latest">latest</a></li>
+ <li><a href="/archive/index.html#08">0.8</a></li>
+ <li><a href="/archive/index.html#07">0.7</a></li>
+ </ul>
+ </div>
+
+ <div class="content">
+ <!--
+ 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.
+-->
+
+<h2>JMX</h2>
+
+<!--
+ 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.
+-->
+
+<p>Samza’s containers and YARN ApplicationMaster enable <a href="http://docs.oracle.com/javase/tutorial/jmx/">JMX</a> by default. JMX can be used for managing the JVM; for example, you can connect to it using <a href="http://docs.oracle.com/javase/7/docs/technotes/guides/management/jconsole.html">jconsole</a>, which is included in the JDK.</p>
+
+<p>You can tell Samza to publish its internal <a href="metrics.html">metrics</a>, and any custom metrics you define, as JMX MBeans. To enable this, set the following properties in your job configuration:</p>
+
+<div class="highlight"><pre><code class="jproperties"><span class="c"># Define a Samza metrics reporter called "jmx", which publishes to JMX</span>
+<span class="na">metrics.reporter.jmx.class</span><span class="o">=</span><span class="s">org.apache.samza.metrics.reporter.JmxReporterFactory</span>
+
+<span class="c"># Use it (if you have multiple reporters defined, separate them with commas)</span>
+<span class="na">metrics.reporters</span><span class="o">=</span><span class="s">jmx</span></code></pre></div>
+
+<p>JMX needs to be configured to use a specific port, but in a distributed environment, there is no way of knowing in advance which ports are available on the machines running your containers. Therefore Samza chooses the JMX port randomly. If you need to connect to it, you can find the port by looking in the container’s logs, which report the JMX server details as follows:</p>
+<div class="highlight"><pre><code class="language-text" data-lang="text">2014-06-02 21:50:17 JmxServer [INFO] According to InetAddress.getLocalHost.getHostName we are samza-grid-1234.example.com
+2014-06-02 21:50:17 JmxServer [INFO] Started JmxServer registry port=50214 server port=50215 url=service:jmx:rmi://localhost:50215/jndi/rmi://localhost:50214/jmxrmi
+2014-06-02 21:50:17 JmxServer [INFO] If you are tunneling, you might want to try JmxServer registry port=50214 server port=50215 url=service:jmx:rmi://samza-grid-1234.example.com:50215/jndi/rmi://samza-grid-1234.example.com:50214/jmxrmi
+</code></pre></div>
+<h2 id="jobrunner-»"><a href="../jobs/job-runner.html">JobRunner »</a></h2>
+
+
+ </div>
+ </div>
+
+ </div><!-- /.wrapper-content -->
+ </div><!-- /.wrapper -->
+
+ <div class="footer">
+ <div class="container">
+ <!-- nothing for now. -->
+ </div>
+ </div>
+
+
+ <script>
+ $( document ).ready(function() {
+ if ( $.fn.urlExists( "/learn/documentation/latest/container/jmx.html" ) ) {
+ $("#switch-version-button").addClass("fa fa-history masthead-icon");
+ }
+ });
+
+ /* a function to test whether the url exists or not */
+ (function( $ ) {
+ $.fn.urlExists = function(url) {
+ var http = new XMLHttpRequest();
+ http.open('HEAD', url, false);
+ http.send();
+ return http.status != 404;
+ };
+ }( jQuery ));
+ </script>
+
+
+ <!-- Google Analytics -->
+ <script>
+ (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
+ (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
+ m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
+ })(window,document,'script','//www.google-analytics.com/analytics.js','ga');
+
+ ga('create', 'UA-43122768-1', 'apache.org');
+ ga('send', 'pageview');
+
+ </script>
+ </body>
+</html>
Added: incubator/samza/site/learn/documentation/0.8/container/metrics.html
URL: http://svn.apache.org/viewvc/incubator/samza/site/learn/documentation/0.8/container/metrics.html?rev=1643389&view=auto
==============================================================================
--- incubator/samza/site/learn/documentation/0.8/container/metrics.html (added)
+++ incubator/samza/site/learn/documentation/0.8/container/metrics.html Fri Dec 5 18:52:32 2014
@@ -0,0 +1,266 @@
+<!DOCTYPE html>
+<!--
+ 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.
+-->
+<html lang="en">
+ <head>
+ <meta charset="utf-8">
+ <title>Samza - Metrics</title>
+ <link href='/css/ropa-sans.css' rel='stylesheet' type='text/css'/>
+ <link href="/css/bootstrap.min.css" rel="stylesheet"/>
+ <link href="/css/font-awesome.min.css" rel="stylesheet"/>
+ <link href="/css/main.css" rel="stylesheet"/>
+ <link href="/css/syntax.css" rel="stylesheet"/>
+ <link rel="icon" type="image/png" href="/img/samza-icon.png">
+ <script src="/js/jquery-1.11.1.min.js"></script>
+ </head>
+ <body>
+ <div class="wrapper">
+ <div class="wrapper-content">
+
+ <div class="masthead">
+ <div class="container">
+ <div class="masthead-logo">
+ <a href="/" class="logo">samza</a>
+ </div>
+ <div class="masthead-icons">
+ <div class="pull-right">
+ <a href="/startup/download"><i class="fa fa-arrow-circle-o-down masthead-icon"></i></a>
+ <a href="https://git-wip-us.apache.org/repos/asf?p=incubator-samza.git;a=tree" target="_blank"><i class="fa fa-code masthead-icon" style="font-weight: bold;"></i></a>
+ <a href="https://twitter.com/samzastream" target="_blank"><i class="fa fa-twitter masthead-icon"></i></a>
+ <!-- this icon only shows in versioned pages -->
+
+
+
+
+ <a href="http://samza.incubator.apache.org/learn/documentation/latest/container/metrics.html"><i id="switch-version-button"></i></a>
+ <!-- links for the navigation bar -->
+
+
+ </div>
+ </div>
+ </div><!-- /.container -->
+ </div>
+
+ <div class="container">
+ <div class="menu">
+ <h1><i class="fa fa-rocket"></i> Getting Started</h1>
+ <ul>
+ <li><a href="/startup/hello-samza/0.8">Hello Samza</a></li>
+ <li><a href="/startup/download">Download</a></li>
+ </ul>
+
+ <h1><i class="fa fa-book"></i> Learn</h1>
+ <ul>
+ <li><a href="/learn/documentation/0.8">Documentation</a></li>
+ <li><a href="/learn/documentation/0.8/jobs/configuration-table.html">Configuration</a></li>
+ <li><a href="/learn/documentation/0.8/api/javadocs/">Javadocs</a></li>
+ <li><a href="/learn/tutorials/0.8">Tutorials</a></li>
+ <li><a href="http://wiki.apache.org/samza/FAQ">FAQ</a></li>
+ <li><a href="http://wiki.apache.org/samza">Wiki</a></li>
+ <li><a href="http://wiki.apache.org/samza/PapersAndTalks">Papers & Talks</a></li>
+ <li><a href="http://blogs.apache.org/samza">Blog</a></li>
+ </ul>
+
+ <h1><i class="fa fa-comments"></i> Community</h1>
+ <ul>
+ <li><a href="/community/mailing-lists.html">Mailing Lists</a></li>
+ <li><a href="/community/irc.html">IRC</a></li>
+ <li><a href="https://issues.apache.org/jira/browse/SAMZA">Bugs</a></li>
+ <li><a href="http://wiki.apache.org/samza/PoweredBy">Powered by</a></li>
+ <li><a href="http://wiki.apache.org/samza/Ecosystem">Ecosystem</a></li>
+ <li><a href="/community/committers.html">Committers</a></li>
+ </ul>
+
+ <h1><i class="fa fa-code"></i> Contribute</h1>
+ <ul>
+ <li><a href="/contribute/rules.html">Rules</a></li>
+ <li><a href="/contribute/coding-guide.html">Coding Guide</a></li>
+ <li><a href="/contribute/projects.html">Projects</a></li>
+ <li><a href="/contribute/design-documents.html">Design Documents</a></li>
+ <li><a href="/contribute/code.html">Code</a></li>
+ <li><a href="https://reviews.apache.org/groups/samza">Review Board</a></li>
+ <li><a href="/contribute/tests.html">Tests</a></li>
+ <li><a href="/contribute/disclaimer.html">Disclaimer</a></li>
+ </ul>
+
+ <h1><i class="fa fa-history"></i> Archive</h1>
+ <ul>
+ <li><a href="/archive/index.html#latest">latest</a></li>
+ <li><a href="/archive/index.html#08">0.8</a></li>
+ <li><a href="/archive/index.html#07">0.7</a></li>
+ </ul>
+ </div>
+
+ <div class="content">
+ <!--
+ 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.
+-->
+
+<h2>Metrics</h2>
+
+<!--
+ 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.
+-->
+
+<p>When you’re running a stream process in production, it’s important that you have good metrics to track the health of your job. In order to make this easy, Samza includes a metrics library. It is used by Samza itself to generate some standard metrics such as message throughput, but you can also use it in your task code to emit custom metrics.</p>
+
+<p>Metrics can be reported in various ways. You can expose them via <a href="jmx.html">JMX</a>, which is useful in development. In production, a common setup is for each Samza container to periodically publish its metrics to a “metrics” Kafka topic, in which the metrics from all Samza jobs are aggregated. You can then consume this stream in another Samza job, and send the metrics to your favorite graphing system such as <a href="http://graphite.wikidot.com/">Graphite</a>.</p>
+
+<p>To set up your job to publish metrics to Kafka, you can use the following configuration:</p>
+
+<div class="highlight"><pre><code class="jproperties"><span class="c"># Define a metrics reporter called "snapshot", which publishes metrics</span>
+<span class="c"># every 60 seconds.</span>
+<span class="na">metrics.reporters</span><span class="o">=</span><span class="s">snapshot</span>
+<span class="na">metrics.reporter.snapshot.class</span><span class="o">=</span><span class="s">org.apache.samza.metrics.reporter.MetricsSnapshotReporterFactory</span>
+
+<span class="c"># Tell the snapshot reporter to publish to a topic called "metrics"</span>
+<span class="c"># in the "kafka" system.</span>
+<span class="na">metrics.reporter.snapshot.stream</span><span class="o">=</span><span class="s">kafka.metrics</span>
+
+<span class="c"># Encode metrics data as JSON.</span>
+<span class="na">serializers.registry.metrics.class</span><span class="o">=</span><span class="s">org.apache.samza.serializers.MetricsSnapshotSerdeFactory</span>
+<span class="na">systems.kafka.streams.metrics.samza.msg.serde</span><span class="o">=</span><span class="s">metrics</span></code></pre></div>
+
+<p>With this configuration, the job automatically sends several JSON-encoded messages to the “metrics” topic in Kafka every 60 seconds. The messages look something like this:</p>
+
+<div class="highlight"><pre><code class="json"><span class="p">{</span>
+ <span class="nt">"header"</span><span class="p">:</span> <span class="p">{</span>
+ <span class="nt">"container-name"</span><span class="p">:</span> <span class="s2">"samza-container-0"</span><span class="p">,</span>
+ <span class="nt">"host"</span><span class="p">:</span> <span class="s2">"samza-grid-1234.example.com"</span><span class="p">,</span>
+ <span class="nt">"job-id"</span><span class="p">:</span> <span class="s2">"1"</span><span class="p">,</span>
+ <span class="nt">"job-name"</span><span class="p">:</span> <span class="s2">"my-samza-job"</span><span class="p">,</span>
+ <span class="nt">"reset-time"</span><span class="p">:</span> <span class="mi">1401729000347</span><span class="p">,</span>
+ <span class="nt">"samza-version"</span><span class="p">:</span> <span class="s2">"0.0.1"</span><span class="p">,</span>
+ <span class="nt">"source"</span><span class="p">:</span> <span class="s2">"Partition-2"</span><span class="p">,</span>
+ <span class="nt">"time"</span><span class="p">:</span> <span class="mi">1401729420566</span><span class="p">,</span>
+ <span class="nt">"version"</span><span class="p">:</span> <span class="s2">"0.0.1"</span>
+ <span class="p">},</span>
+ <span class="nt">"metrics"</span><span class="p">:</span> <span class="p">{</span>
+ <span class="nt">"org.apache.samza.container.TaskInstanceMetrics"</span><span class="p">:</span> <span class="p">{</span>
+ <span class="nt">"commit-calls"</span><span class="p">:</span> <span class="mi">7</span><span class="p">,</span>
+ <span class="nt">"commit-skipped"</span><span class="p">:</span> <span class="mi">77948</span><span class="p">,</span>
+ <span class="nt">"kafka-input-topic-offset"</span><span class="p">:</span> <span class="s2">"1606"</span><span class="p">,</span>
+ <span class="nt">"messages-sent"</span><span class="p">:</span> <span class="mi">985</span><span class="p">,</span>
+ <span class="nt">"process-calls"</span><span class="p">:</span> <span class="mi">1093</span><span class="p">,</span>
+ <span class="nt">"send-calls"</span><span class="p">:</span> <span class="mi">985</span><span class="p">,</span>
+ <span class="nt">"send-skipped"</span><span class="p">:</span> <span class="mi">76970</span><span class="p">,</span>
+ <span class="nt">"window-calls"</span><span class="p">:</span> <span class="mi">0</span><span class="p">,</span>
+ <span class="nt">"window-skipped"</span><span class="p">:</span> <span class="mi">77955</span>
+ <span class="p">}</span>
+ <span class="p">}</span>
+<span class="p">}</span></code></pre></div>
+
+<p>There is a separate message for each task instance, and the header tells you the job name, job ID and partition of the task. The metrics allow you to see how many messages have been processed and sent, the current offset in the input stream partition, and other details. There are additional messages which give you metrics about the JVM (heap size, garbage collection information, threads etc.), internal metrics of the Kafka producers and consumers, and more.</p>
+
+<p>It’s easy to generate custom metrics in your job, if there’s some value you want to keep an eye on. You can use Samza’s built-in metrics framework, which is similar in design to Coda Hale’s <a href="http://metrics.codahale.com/">metrics</a> library. </p>
+
+<p>You can register your custom metrics through a <a href="../api/javadocs/org/apache/samza/metrics/MetricsRegistry.html">MetricsRegistry</a>. Your stream task needs to implement <a href="../api/javadocs/org/apache/samza/task/InitableTask.html">InitableTask</a>, so that you can get the metrics registry from the <a href="../api/javadocs/org/apache/samza/task/TaskContext.html">TaskContext</a>. This simple example shows how to count the number of messages processed by your task:</p>
+
+<div class="highlight"><pre><code class="java"><span class="kd">public</span> <span class="kd">class</span> <span class="nc">MyJavaStreamTask</span> <span class="kd">implements</span> <span class="n">StreamTask</span><span class="o">,</span> <span class="n">InitableTask</span> <span class="o">{</span>
+ <span class="kd">private</span> <span class="n">Counter</span> <span class="n">messageCount</span><span class="o">;</span>
+
+ <span class="kd">public</span> <span class="kt">void</span> <span class="nf">init</span><span class="o">(</span><span class="n">Config</span> <span class="n">config</span><span class="o">,</span> <span class="n">TaskContext</span> <span class="n">context</span><span class="o">)</span> <span class="o">{</span>
+ <span class="k">this</span><span class="o">.</span><span class="na">messageCount</span> <span class="o">=</span> <span class="n">context</span>
+ <span class="o">.</span><span class="na">getMetricsRegistry</span><span class="o">()</span>
+ <span class="o">.</span><span class="na">newCounter</span><span class="o">(</span><span class="n">getClass</span><span class="o">().</span><span class="na">getName</span><span class="o">(),</span> <span class="s">"message-count"</span><span class="o">);</span>
+ <span class="o">}</span>
+
+ <span class="kd">public</span> <span class="kt">void</span> <span class="nf">process</span><span class="o">(</span><span class="n">IncomingMessageEnvelope</span> <span class="n">envelope</span><span class="o">,</span>
+ <span class="n">MessageCollector</span> <span class="n">collector</span><span class="o">,</span>
+ <span class="n">TaskCoordinator</span> <span class="n">coordinator</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">messageCount</span><span class="o">.</span><span class="na">inc</span><span class="o">();</span>
+ <span class="o">}</span>
+<span class="o">}</span></code></pre></div>
+
+<p>Samza currently supports two kind of metrics: <a href="../api/javadocs/org/apache/samza/metrics/Counter.html">counters</a> and <a href="../api/javadocs/org/apache/samza/metrics/Gauge.html">gauges</a>. Use a counter when you want to track how often something occurs, and a gauge when you want to report the level of something, such as the size of a buffer. Each task instance (for each input stream partition) gets its own set of metrics.</p>
+
+<p>If you want to report metrics in some other way, e.g. directly to a graphing system (without going via Kafka), you can implement a <a href="../api/javadocs/org/apache/samza/metrics/MetricsReporterFactory.html">MetricsReporterFactory</a> and reference it in your job configuration.</p>
+
+<h2 id="windowing-»"><a href="windowing.html">Windowing »</a></h2>
+
+
+ </div>
+ </div>
+
+ </div><!-- /.wrapper-content -->
+ </div><!-- /.wrapper -->
+
+ <div class="footer">
+ <div class="container">
+ <!-- nothing for now. -->
+ </div>
+ </div>
+
+
+ <script>
+ $( document ).ready(function() {
+ if ( $.fn.urlExists( "/learn/documentation/latest/container/metrics.html" ) ) {
+ $("#switch-version-button").addClass("fa fa-history masthead-icon");
+ }
+ });
+
+ /* a function to test whether the url exists or not */
+ (function( $ ) {
+ $.fn.urlExists = function(url) {
+ var http = new XMLHttpRequest();
+ http.open('HEAD', url, false);
+ http.send();
+ return http.status != 404;
+ };
+ }( jQuery ));
+ </script>
+
+
+ <!-- Google Analytics -->
+ <script>
+ (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
+ (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
+ m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
+ })(window,document,'script','//www.google-analytics.com/analytics.js','ga');
+
+ ga('create', 'UA-43122768-1', 'apache.org');
+ ga('send', 'pageview');
+
+ </script>
+ </body>
+</html>
Added: incubator/samza/site/learn/documentation/0.8/container/samza-container.html
URL: http://svn.apache.org/viewvc/incubator/samza/site/learn/documentation/0.8/container/samza-container.html?rev=1643389&view=auto
==============================================================================
--- incubator/samza/site/learn/documentation/0.8/container/samza-container.html (added)
+++ incubator/samza/site/learn/documentation/0.8/container/samza-container.html Fri Dec 5 18:52:32 2014
@@ -0,0 +1,275 @@
+<!DOCTYPE html>
+<!--
+ 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.
+-->
+<html lang="en">
+ <head>
+ <meta charset="utf-8">
+ <title>Samza - SamzaContainer</title>
+ <link href='/css/ropa-sans.css' rel='stylesheet' type='text/css'/>
+ <link href="/css/bootstrap.min.css" rel="stylesheet"/>
+ <link href="/css/font-awesome.min.css" rel="stylesheet"/>
+ <link href="/css/main.css" rel="stylesheet"/>
+ <link href="/css/syntax.css" rel="stylesheet"/>
+ <link rel="icon" type="image/png" href="/img/samza-icon.png">
+ <script src="/js/jquery-1.11.1.min.js"></script>
+ </head>
+ <body>
+ <div class="wrapper">
+ <div class="wrapper-content">
+
+ <div class="masthead">
+ <div class="container">
+ <div class="masthead-logo">
+ <a href="/" class="logo">samza</a>
+ </div>
+ <div class="masthead-icons">
+ <div class="pull-right">
+ <a href="/startup/download"><i class="fa fa-arrow-circle-o-down masthead-icon"></i></a>
+ <a href="https://git-wip-us.apache.org/repos/asf?p=incubator-samza.git;a=tree" target="_blank"><i class="fa fa-code masthead-icon" style="font-weight: bold;"></i></a>
+ <a href="https://twitter.com/samzastream" target="_blank"><i class="fa fa-twitter masthead-icon"></i></a>
+ <!-- this icon only shows in versioned pages -->
+
+
+
+
+ <a href="http://samza.incubator.apache.org/learn/documentation/latest/container/samza-container.html"><i id="switch-version-button"></i></a>
+ <!-- links for the navigation bar -->
+
+
+ </div>
+ </div>
+ </div><!-- /.container -->
+ </div>
+
+ <div class="container">
+ <div class="menu">
+ <h1><i class="fa fa-rocket"></i> Getting Started</h1>
+ <ul>
+ <li><a href="/startup/hello-samza/0.8">Hello Samza</a></li>
+ <li><a href="/startup/download">Download</a></li>
+ </ul>
+
+ <h1><i class="fa fa-book"></i> Learn</h1>
+ <ul>
+ <li><a href="/learn/documentation/0.8">Documentation</a></li>
+ <li><a href="/learn/documentation/0.8/jobs/configuration-table.html">Configuration</a></li>
+ <li><a href="/learn/documentation/0.8/api/javadocs/">Javadocs</a></li>
+ <li><a href="/learn/tutorials/0.8">Tutorials</a></li>
+ <li><a href="http://wiki.apache.org/samza/FAQ">FAQ</a></li>
+ <li><a href="http://wiki.apache.org/samza">Wiki</a></li>
+ <li><a href="http://wiki.apache.org/samza/PapersAndTalks">Papers & Talks</a></li>
+ <li><a href="http://blogs.apache.org/samza">Blog</a></li>
+ </ul>
+
+ <h1><i class="fa fa-comments"></i> Community</h1>
+ <ul>
+ <li><a href="/community/mailing-lists.html">Mailing Lists</a></li>
+ <li><a href="/community/irc.html">IRC</a></li>
+ <li><a href="https://issues.apache.org/jira/browse/SAMZA">Bugs</a></li>
+ <li><a href="http://wiki.apache.org/samza/PoweredBy">Powered by</a></li>
+ <li><a href="http://wiki.apache.org/samza/Ecosystem">Ecosystem</a></li>
+ <li><a href="/community/committers.html">Committers</a></li>
+ </ul>
+
+ <h1><i class="fa fa-code"></i> Contribute</h1>
+ <ul>
+ <li><a href="/contribute/rules.html">Rules</a></li>
+ <li><a href="/contribute/coding-guide.html">Coding Guide</a></li>
+ <li><a href="/contribute/projects.html">Projects</a></li>
+ <li><a href="/contribute/design-documents.html">Design Documents</a></li>
+ <li><a href="/contribute/code.html">Code</a></li>
+ <li><a href="https://reviews.apache.org/groups/samza">Review Board</a></li>
+ <li><a href="/contribute/tests.html">Tests</a></li>
+ <li><a href="/contribute/disclaimer.html">Disclaimer</a></li>
+ </ul>
+
+ <h1><i class="fa fa-history"></i> Archive</h1>
+ <ul>
+ <li><a href="/archive/index.html#latest">latest</a></li>
+ <li><a href="/archive/index.html#08">0.8</a></li>
+ <li><a href="/archive/index.html#07">0.7</a></li>
+ </ul>
+ </div>
+
+ <div class="content">
+ <!--
+ 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.
+-->
+
+<h2>SamzaContainer</h2>
+
+<!--
+ 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.
+-->
+
+<p>The SamzaContainer is responsible for managing the startup, execution, and shutdown of one or more <a href="../api/overview.html">StreamTask</a> instances. Each SamzaContainer typically runs as an indepentent Java virtual machine. A Samza job can consist of several SamzaContainers, potentially running on different machines.</p>
+
+<p>When a SamzaContainer starts up, it does the following:</p>
+
+<ol>
+<li>Get last checkpointed offset for each input stream partition that it consumes</li>
+<li>Create a “reader” thread for every input stream partition that it consumes</li>
+<li>Start metrics reporters to report metrics</li>
+<li>Start a checkpoint timer to save your task’s input stream offsets every so often</li>
+<li>Start a window timer to trigger your task’s <a href="../api/javadocs/org/apache/samza/task/WindowableTask.html">window method</a>, if it is defined</li>
+<li>Instantiate and initialize your StreamTask once for each input stream partition</li>
+<li>Start an event loop that takes messages from the input stream reader threads, and gives them to your StreamTasks</li>
+<li>Notify lifecycle listeners during each one of these steps</li>
+</ol>
+
+<p>Let’s start in the middle, with the instantiation of a StreamTask. The following sections of the documentation cover the other steps.</p>
+
+<h3 id="tasks-and-partitions">Tasks and Partitions</h3>
+
+<p>When the container starts, it creates instances of the <a href="../api/overview.html">task class</a> that you’ve written. If the task class implements the <a href="../api/javadocs/org/apache/samza/task/InitableTask.html">InitableTask</a> interface, the SamzaContainer will also call the init() method.</p>
+
+<div class="highlight"><pre><code class="java"><span class="cm">/** Implement this if you want a callback when your task starts up. */</span>
+<span class="kd">public</span> <span class="kd">interface</span> <span class="nc">InitableTask</span> <span class="o">{</span>
+ <span class="kt">void</span> <span class="nf">init</span><span class="o">(</span><span class="n">Config</span> <span class="n">config</span><span class="o">,</span> <span class="n">TaskContext</span> <span class="n">context</span><span class="o">);</span>
+<span class="o">}</span></code></pre></div>
+
+<p>By default, how many instances of your task class are created depends on the number of partitions in the job’s input streams. If your Samza job has ten partitions, there will be ten instantiations of your task class: one for each partition. The first task instance will receive all messages for partition one, the second instance will receive all messages for partition two, and so on.</p>
+
+<p><img src="/img/0.8/learn/documentation/container/tasks-and-partitions.svg" alt="Illustration of tasks consuming partitions" class="diagram-large"></p>
+
+<p>The number of partitions in the input streams is determined by the systems from which you are consuming. For example, if your input system is Kafka, you can specify the number of partitions when you create a topic from the command line or using the num.partitions in Kafka’s server properties file.</p>
+
+<p>If a Samza job has more than one input stream, the number of task instances for the Samza job is the maximum number of partitions across all input streams. For example, if a Samza job is reading from PageViewEvent (12 partitions), and ServiceMetricEvent (14 partitions), then the Samza job would have 14 task instances (numbered 0 through 13). Task instances 12 and 13 only receive events from ServiceMetricEvent, because there is no corresponding PageViewEvent partition.</p>
+
+<p>With this default approach to assigning input streams to task instances, Samza is effectively performing a group-by operation on the input streams with their partitions as the key. Other strategies for grouping input stream partitions are possible by implementing a new <a href="../api/javadocs/org/apache/samza/container/SystemStreamPartitionGrouper.html">SystemStreamPartitionGrouper</a> and factory, and configuring the job to use it via the job.systemstreampartition.grouper.factory configuration value.</p>
+
+<p>Samza provides the above-discussed per-partition grouper as well as the <a href="../api/javadocs/org/apache/samza/container/systemstreampartition/groupers/GroupBySystemStreamPartition">GroupBySystemStreamPartitionGrouper</a>, which provides a separate task class instance for every input stream partition, effectively grouping by the input stream itself. This provides maximum scalability in terms of how many containers can be used to process those input streams and is appropriate for very high volume jobs that need no grouping of the input streams.</p>
+
+<p>Considering the above example of a PageViewEvent partitioned 12 ways and a ServiceMetricEvent partitioned 14 ways, the GroupBySystemStreamPartitionGrouper would create 12 + 14 = 26 task instances, which would then be distributed across the number of containers configured, as discussed below.</p>
+
+<p>Note that once a job has been started using a particular SystemStreamPartitionGrouper and that job is using state or checkpointing, it is not possible to change that grouping in subsequent job starts, as the previous checkpoints and state information would likely be incorrect under the new grouping approach.</p>
+
+<h3 id="containers-and-resource-allocation">Containers and resource allocation</h3>
+
+<p>Although the number of task instances is fixed — determined by the number of input partitions — you can configure how many containers you want to use for your job. If you are <a href="../jobs/yarn-jobs.html">using YARN</a>, the number of containers determines what CPU and memory resources are allocated to your job.</p>
+
+<p>If the data volume on your input streams is small, it might be sufficient to use just one SamzaContainer. In that case, Samza still creates one task instance per input partition, but all those tasks run within the same container. At the other extreme, you can create as many containers as you have partitions, and Samza will assign one task instance to each container.</p>
+
+<p>Each SamzaContainer is designed to use one CPU core, so it uses a <a href="event-loop.html">single-threaded event loop</a> for execution. It’s not advisable to create your own threads within a SamzaContainer. If you need more parallelism, please configure your job to use more containers.</p>
+
+<p>Any <a href="state-management.html">state</a> in your job belongs to a task instance, not to a container. This is a key design decision for Samza’s scalability: as your job’s resource requirements grow and shrink, you can simply increase or decrease the number of containers, but the number of task instances remains unchanged. As you scale up or down, the same state remains attached to each task instance. Task instances may be moved from one container to another, and any persistent state managed by Samza will be moved with it. This allows the job’s processing semantics to remain unchanged, even as you change the job’s parallelism.</p>
+
+<h3 id="joining-multiple-input-streams">Joining multiple input streams</h3>
+
+<p>If your job has multiple input streams, Samza provides a simple but powerful mechanism for joining data from different streams: each task instance receives messages from one partition of <em>each</em> of the input streams. For example, say you have two input streams, A and B, each with four partitions. Samza creates four task instances to process them, and assigns the partitions as follows:</p>
+
+<table class="table table-condensed table-bordered table-striped">
+ <thead>
+ <tr>
+ <th>Task instance</th>
+ <th>Consumes stream partitions</th>
+ </tr>
+ </thead>
+ <tbody>
+ <tr>
+ <td>0</td><td>stream A partition 0, stream B partition 0</td>
+ </tr>
+ <tr>
+ <td>1</td><td>stream A partition 1, stream B partition 1</td>
+ </tr>
+ <tr>
+ <td>2</td><td>stream A partition 2, stream B partition 2</td>
+ </tr>
+ <tr>
+ <td>3</td><td>stream A partition 3, stream B partition 3</td>
+ </tr>
+ </tbody>
+</table>
+
+<p>Thus, if you want two events in different streams to be processed by the same task instance, you need to ensure they are sent to the same partition number. You can achieve this by using the same partitioning key when <a href="../api/overview.html">sending the messages</a>. Joining streams is discussed in detail in the <a href="state-management.html">state management</a> section.</p>
+
+<p>There is one caveat in all of this: Samza currently assumes that a stream’s partition count will never change. Partition splitting or repartitioning is not supported. If an input stream has N partitions, it is expected that it has always had, and will always have N partitions. If you want to re-partition a stream, you can write a job that reads messages from the stream, and writes them out to a new stream with the required number of partitions. For example, you could read messages from PageViewEvent, and write them to PageViewEventRepartition.</p>
+
+<h2 id="streams-»"><a href="streams.html">Streams »</a></h2>
+
+
+ </div>
+ </div>
+
+ </div><!-- /.wrapper-content -->
+ </div><!-- /.wrapper -->
+
+ <div class="footer">
+ <div class="container">
+ <!-- nothing for now. -->
+ </div>
+ </div>
+
+
+ <script>
+ $( document ).ready(function() {
+ if ( $.fn.urlExists( "/learn/documentation/latest/container/samza-container.html" ) ) {
+ $("#switch-version-button").addClass("fa fa-history masthead-icon");
+ }
+ });
+
+ /* a function to test whether the url exists or not */
+ (function( $ ) {
+ $.fn.urlExists = function(url) {
+ var http = new XMLHttpRequest();
+ http.open('HEAD', url, false);
+ http.send();
+ return http.status != 404;
+ };
+ }( jQuery ));
+ </script>
+
+
+ <!-- Google Analytics -->
+ <script>
+ (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
+ (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
+ m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
+ })(window,document,'script','//www.google-analytics.com/analytics.js','ga');
+
+ ga('create', 'UA-43122768-1', 'apache.org');
+ ga('send', 'pageview');
+
+ </script>
+ </body>
+</html>