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Posted to dev@distributedlog.apache.org by si...@apache.org on 2017/04/26 18:56:59 UTC

[36/51] [partial] incubator-distributedlog git commit: Release 0.4.0-incubating

http://git-wip-us.apache.org/repos/asf/incubator-distributedlog/blob/ef7245e8/content/docs/0.4.0-incubating/tutorials/messaging-2.html
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+          <ul class="dropdown-menu">
+            <li class="dropdown-header"><strong>Basic</strong></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/basic-1">Write Records (via Core Library)</a></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/basic-2">Write Records (via Write Proxy)</a></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/basic-3">Write Records to multiple streams</a></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/basic-4">Atomic Write Records</a></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/basic-5">Tailing Read Records</a></li>
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+            
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+              <a href="/docs/0.4.0-incubating/tutorials/messaging-1.html">
+                Write records to partitioned streams
+              </a>
+            </li>
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/messaging-2.html">
+                Write records to multiple streams (load balancer)
+              </a>
+            </li>
+            
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+              <a href="/docs/0.4.0-incubating/tutorials/messaging-3.html">
+                At-least-once Processing
+              </a>
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+                Exact-Once Processing
+              </a>
+            </li>
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/messaging-5.html">
+                Implement a kafka-like pub/sub system
+              </a>
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+            <li class="dropdown-header"><strong>Replicated State Machines</strong></li>
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+                Build replicated state machines
+              </a>
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+            <li class="dropdown-header"><strong>Analytics</strong></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/analytics-mapreduce">Process log streams using MapReduce</a></li>
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+<div class="col-md-8 col-md-offset-2">
+  <div class="contents topic" id="messaging-tutorial-write-records-to-multiple-streams-using-a-load-balancer">
+<p class="topic-title first">Messaging Tutorial - Write records to multiple streams using a load balancer</p>
+<ul class="auto-toc simple">
+<li><a class="reference internal" href="#how-to-write-records-to-multiple-streams-using-a-load-balancer" id="id2">1&nbsp;&nbsp;&nbsp;How to write records to multiple streams using a load balancer</a><ul class="auto-toc">
+<li><a class="reference internal" href="#make-writing-to-a-stream-as-a-finagle-service" id="id3">1.1&nbsp;&nbsp;&nbsp;Make writing to a stream as a finagle service</a></li>
+<li><a class="reference internal" href="#create-a-load-balancer-from-multiple-streams" id="id4">1.2&nbsp;&nbsp;&nbsp;Create a load balancer from multiple streams</a><ul class="auto-toc">
+<li><a class="reference internal" href="#create-a-servicefactory" id="id5">1.2.1&nbsp;&nbsp;&nbsp;Create a ServiceFactory</a></li>
+<li><a class="reference internal" href="#create-the-load-balancer" id="id6">1.2.2&nbsp;&nbsp;&nbsp;Create the load balancer</a></li>
+</ul>
+</li>
+<li><a class="reference internal" href="#write-records" id="id7">1.3&nbsp;&nbsp;&nbsp;Write records</a></li>
+<li><a class="reference internal" href="#run-the-tutorial" id="id8">1.4&nbsp;&nbsp;&nbsp;Run the tutorial</a><ul class="auto-toc">
+<li><a class="reference internal" href="#start-the-local-bookkeeper-cluster" id="id9">1.4.1&nbsp;&nbsp;&nbsp;Start the local bookkeeper cluster</a></li>
+<li><a class="reference internal" href="#start-the-write-proxy" id="id10">1.4.2&nbsp;&nbsp;&nbsp;Start the write proxy</a></li>
+<li><a class="reference internal" href="#create-the-stream" id="id11">1.4.3&nbsp;&nbsp;&nbsp;Create the stream</a></li>
+<li><a class="reference internal" href="#tail-the-streams" id="id12">1.4.4&nbsp;&nbsp;&nbsp;Tail the streams</a></li>
+<li><a class="reference internal" href="#id1" id="id13">1.4.5&nbsp;&nbsp;&nbsp;Write records</a></li>
+<li><a class="reference internal" href="#check-the-results" id="id14">1.4.6&nbsp;&nbsp;&nbsp;Check the results</a></li>
+</ul>
+</li>
+</ul>
+</li>
+</ul>
+</div>
+<div class="section" id="how-to-write-records-to-multiple-streams-using-a-load-balancer">
+<h2><a class="toc-backref" href="#id2">1&nbsp;&nbsp;&nbsp;How to write records to multiple streams using a load balancer</a></h2>
+<p>If applications does not care about ordering and they just want use multiple streams to transform messages, it is easier
+to use a load balancer to balancing the writes among the multiple streams.</p>
+<p>This tutorial shows how to build a multi-streams writer, which ues a finagle load balancer to balancing traffic among multiple streams.</p>
+<div class="section" id="make-writing-to-a-stream-as-a-finagle-service">
+<h3><a class="toc-backref" href="#id3">1.1&nbsp;&nbsp;&nbsp;Make writing to a stream as a finagle service</a></h3>
+<p>In order to leverage the finagle load balancer to balancing traffic among multiple streams, we have to make writing
+to a stream as a finagle service.</p>
+<pre class="literal-block">
+class StreamWriter&lt;VALUE&gt; extends Service&lt;VALUE, DLSN&gt; {
+
+    private final String stream;
+    private final DistributedLogClient client;
+
+    StreamWriter(String stream,
+                 DistributedLogClient client) {
+        this.stream = stream;
+        this.client = client;
+    }
+
+    &#64;Override
+    public Future&lt;DLSN&gt; apply(VALUE request) {
+        return client.write(stream, ByteBuffer.wrap(request.toString().getBytes(UTF_8)));
+    }
+}
+</pre>
+</div>
+<div class="section" id="create-a-load-balancer-from-multiple-streams">
+<h3><a class="toc-backref" href="#id4">1.2&nbsp;&nbsp;&nbsp;Create a load balancer from multiple streams</a></h3>
+<div class="section" id="create-a-servicefactory">
+<h4><a class="toc-backref" href="#id5">1.2.1&nbsp;&nbsp;&nbsp;Create a ServiceFactory</a></h4>
+<p>Create a set of finagle <cite>ServiceFactory</cite> over multiple streams.</p>
+<pre class="literal-block">
+String[] streams;
+Set&lt;ServiceFactory&lt;VALUE, DLSN&gt;&gt; serviceFactories = Sets.newHashSet();
+for (String stream : streams) {
+    Service&lt;VALUE, DLSN&gt; service = new StreamWriter(stream, client);
+    serviceFactories.add(new SingletonFactory&lt;VALUE, DLSN&gt;(service));
+}
+</pre>
+</div>
+<div class="section" id="create-the-load-balancer">
+<h4><a class="toc-backref" href="#id6">1.2.2&nbsp;&nbsp;&nbsp;Create the load balancer</a></h4>
+<pre class="literal-block">
+Service&lt;VALUE, DLSN&gt; writeSerivce =
+    Balancers.heap(new scala.util.Random(System.currentTimeMillis()))
+        .newBalancer(
+                Activity.value(scalaSet),
+                NullStatsReceiver.get(),
+                new NoBrokersAvailableException(&quot;No partitions available&quot;)
+        ).toService();
+</pre>
+</div>
+</div>
+<div class="section" id="write-records">
+<h3><a class="toc-backref" href="#id7">1.3&nbsp;&nbsp;&nbsp;Write records</a></h3>
+<p>Once the balancer service is initialized, we can write records through the balancer service.</p>
+<pre class="literal-block">
+Future&lt;DLSN&gt; writeFuture = writeSerivce.write(...);
+</pre>
+</div>
+<div class="section" id="run-the-tutorial">
+<h3><a class="toc-backref" href="#id8">1.4&nbsp;&nbsp;&nbsp;Run the tutorial</a></h3>
+<p>Run the example in the following steps:</p>
+<div class="section" id="start-the-local-bookkeeper-cluster">
+<h4><a class="toc-backref" href="#id9">1.4.1&nbsp;&nbsp;&nbsp;Start the local bookkeeper cluster</a></h4>
+<p>You can use follow command to start the distributedlog stack locally.
+After the distributedlog cluster is started, you could access it using
+distributedlog uri <em>distributedlog://127.0.0.1:7000/messaging/distributedlog</em>.</p>
+<pre class="literal-block">
+// dlog local ${zk-port}
+./distributedlog-core/bin/dlog local 7000
+</pre>
+</div>
+<div class="section" id="start-the-write-proxy">
+<h4><a class="toc-backref" href="#id10">1.4.2&nbsp;&nbsp;&nbsp;Start the write proxy</a></h4>
+<p>Start the write proxy, listening on port 8000.</p>
+<pre class="literal-block">
+// DistributedLogServerApp -p ${service-port} --shard-id ${shard-id} -sp ${stats-port} -u {distributedlog-uri} -mx -c ${conf-file}
+./distributedlog-service/bin/dlog org.apache.distributedlog.service.DistributedLogServerApp -p 8000 --shard-id 1 -sp 8001 -u distributedlog://127.0.0.1:7000/messaging/distributedlog -mx -c ${distributedlog-repo}/distributedlog-service/conf/distributedlog_proxy.conf
+</pre>
+</div>
+<div class="section" id="create-the-stream">
+<h4><a class="toc-backref" href="#id11">1.4.3&nbsp;&nbsp;&nbsp;Create the stream</a></h4>
+<p>Create the stream under the distributedlog uri.</p>
+<pre class="literal-block">
+// Create Stream `messaging-stream-{1,5}`
+// dlog tool create -u ${distributedlog-uri} -r ${stream-prefix} -e ${stream-regex}
+./distributedlog-core/bin/dlog tool create -u distributedlog://127.0.0.1:7000/messaging/distributedlog -r messaging-stream- -e 1-5
+</pre>
+</div>
+<div class="section" id="tail-the-streams">
+<h4><a class="toc-backref" href="#id12">1.4.4&nbsp;&nbsp;&nbsp;Tail the streams</a></h4>
+<p>Tailing the streams using <cite>MultiReader</cite> to wait for new records.</p>
+<pre class="literal-block">
+// Tailing Stream `messaging-stream-{1,5}`
+// runner run org.apache.distributedlog.basic.MultiReader ${distributedlog-uri} ${stream}[, ${stream}]
+./distributedlog-tutorials/distributedlog-basic/bin/runner run org.apache.distributedlog.basic.MultiReader distributedlog://127.0.0.1:7000/messaging/distributedlog messaging-stream-1,messaging-stream-2,messaging-stream-3,messaging-stream-4,messaging-stream-5
+</pre>
+</div>
+<div class="section" id="id1">
+<h4><a class="toc-backref" href="#id13">1.4.5&nbsp;&nbsp;&nbsp;Write records</a></h4>
+<p>Run the example to write records to multiple stream in a console.</p>
+<pre class="literal-block">
+// Write Records into Stream `messaging-stream-{1,5}`
+// runner run org.apache.distributedlog.messaging.ConsoleProxyRRMultiWriter ${distributedlog-uri} ${stream}[, ${stream}]
+./distributedlog-tutorials/distributedlog-messaging/bin/runner run org.apache.distributedlog.messaging.ConsoleProxyRRMultiWriter 'inet!127.0.0.1:8000' messaging-stream-1,messaging-stream-2,messaging-stream-3,messaging-stream-4,messaging-stream-5
+</pre>
+</div>
+<div class="section" id="check-the-results">
+<h4><a class="toc-backref" href="#id14">1.4.6&nbsp;&nbsp;&nbsp;Check the results</a></h4>
+<p>Example output from <cite>ConsoleProxyRRMultiWriter</cite> and <cite>MultiReader</cite>.</p>
+<pre class="literal-block">
+// Output of `ConsoleProxyRRMultiWriter`
+Picked up JAVA_TOOL_OPTIONS: -Dfile.encoding=utf8
+May 08, 2016 1:22:35 PM com.twitter.finagle.BaseResolver$$anonfun$resolvers$1 apply
+INFO: Resolver[inet] = com.twitter.finagle.InetResolver(com.twitter.finagle.InetResolver&#64;6c4cbf96)
+May 08, 2016 1:22:35 PM com.twitter.finagle.BaseResolver$$anonfun$resolvers$1 apply
+INFO: Resolver[fixedinet] = com.twitter.finagle.FixedInetResolver(com.twitter.finagle.FixedInetResolver&#64;57052dc3)
+May 08, 2016 1:22:35 PM com.twitter.finagle.BaseResolver$$anonfun$resolvers$1 apply
+INFO: Resolver[neg] = com.twitter.finagle.NegResolver$(com.twitter.finagle.NegResolver$&#64;14ff89d7)
+May 08, 2016 1:22:35 PM com.twitter.finagle.BaseResolver$$anonfun$resolvers$1 apply
+INFO: Resolver[nil] = com.twitter.finagle.NilResolver$(com.twitter.finagle.NilResolver$&#64;14b28d06)
+May 08, 2016 1:22:35 PM com.twitter.finagle.BaseResolver$$anonfun$resolvers$1 apply
+INFO: Resolver[fail] = com.twitter.finagle.FailResolver$(com.twitter.finagle.FailResolver$&#64;56488f87)
+May 08, 2016 1:22:35 PM com.twitter.finagle.Init$$anonfun$1 apply$mcV$sp
+INFO: Finagle version media-platform-tools/release-20160330-1117-sgerstein-9-g2dcdd6c (rev=2dcdd6c866f9bd3599ed49568d651189735e8ad6) built at 20160330-160058
+[dlog] &gt; message-1
+[dlog] &gt; message-2
+[dlog] &gt; message-3
+[dlog] &gt; message-4
+[dlog] &gt; message-5
+[dlog] &gt;
+
+
+// Output of `MultiReader`
+Opening log stream messaging-stream-1
+Opening log stream messaging-stream-2
+Opening log stream messaging-stream-3
+Opening log stream messaging-stream-4
+Opening log stream messaging-stream-5
+Log stream messaging-stream-2 is empty.
+Wait for records from messaging-stream-2 starting from DLSN{logSegmentSequenceNo=1, entryId=0, slotId=0}
+Open reader to read records from stream messaging-stream-2
+Log stream messaging-stream-1 is empty.
+Wait for records from messaging-stream-1 starting from DLSN{logSegmentSequenceNo=1, entryId=0, slotId=0}
+Open reader to read records from stream messaging-stream-1
+Log stream messaging-stream-3 is empty.
+Wait for records from messaging-stream-3 starting from DLSN{logSegmentSequenceNo=1, entryId=0, slotId=0}
+Open reader to read records from stream messaging-stream-3
+Log stream messaging-stream-4 is empty.
+Wait for records from messaging-stream-4 starting from DLSN{logSegmentSequenceNo=1, entryId=0, slotId=0}
+Open reader to read records from stream messaging-stream-4
+Log stream messaging-stream-5 is empty.
+Wait for records from messaging-stream-5 starting from DLSN{logSegmentSequenceNo=1, entryId=0, slotId=0}
+Open reader to read records from stream messaging-stream-5
+Received record DLSN{logSegmentSequenceNo=1, entryId=2, slotId=0} from stream messaging-stream-3
+&quot;&quot;&quot;
+message-1
+&quot;&quot;&quot;
+Received record DLSN{logSegmentSequenceNo=1, entryId=2, slotId=0} from stream messaging-stream-2
+&quot;&quot;&quot;
+message-2
+&quot;&quot;&quot;
+Received record DLSN{logSegmentSequenceNo=1, entryId=4, slotId=0} from stream messaging-stream-2
+&quot;&quot;&quot;
+message-3
+&quot;&quot;&quot;
+Received record DLSN{logSegmentSequenceNo=1, entryId=2, slotId=0} from stream messaging-stream-4
+&quot;&quot;&quot;
+message-4
+&quot;&quot;&quot;
+Received record DLSN{logSegmentSequenceNo=1, entryId=6, slotId=0} from stream messaging-stream-2
+&quot;&quot;&quot;
+message-5
+&quot;&quot;&quot;
+</pre>
+</div>
+</div>
+</div>
+
+
+</div>
+
+
+
+      </div>
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+  <div class="row">
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+                  <a href="http://www.apache.org">The Apache Software Foundation.</a> All Rights Reserved.
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http://git-wip-us.apache.org/repos/asf/incubator-distributedlog/blob/ef7245e8/content/docs/0.4.0-incubating/tutorials/messaging-3.html
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+            <li class="dropdown-header"><strong>Basic</strong></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/basic-1">Write Records (via Core Library)</a></li>
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+            <li><a href="/docs/0.4.0-incubating/tutorials/basic-3">Write Records to multiple streams</a></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/basic-4">Atomic Write Records</a></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/basic-5">Tailing Read Records</a></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/basic-6">Rewind Read Records</a></li>
+            <li role="separator" class="divider"></li>
+            <li class="dropdown-header"><strong>Messaging</strong></li>
+            
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/messaging-1.html">
+                Write records to partitioned streams
+              </a>
+            </li>
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/messaging-2.html">
+                Write records to multiple streams (load balancer)
+              </a>
+            </li>
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/messaging-3.html">
+                At-least-once Processing
+              </a>
+            </li>
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/messaging-4.html">
+                Exact-Once Processing
+              </a>
+            </li>
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/messaging-5.html">
+                Implement a kafka-like pub/sub system
+              </a>
+            </li>
+            
+            <li role="separator" class="divider"></li>
+            <li class="dropdown-header"><strong>Replicated State Machines</strong></li>
+            
+            
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+              <a href="/docs/0.4.0-incubating/tutorials/replicatedstatemachines.html">
+                Build replicated state machines
+              </a>
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+            <li class="dropdown-header"><strong>Analytics</strong></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/analytics-mapreduce">Process log streams using MapReduce</a></li>
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+
+<div class="col-md-8 col-md-offset-2">
+  <div class="contents topic" id="messaging-tutorial-at-least-once-processing">
+<p class="topic-title first">Messaging Tutorial - At-least-once Processing</p>
+<ul class="auto-toc simple">
+<li><a class="reference internal" href="#at-least-once-processing" id="id1">1&nbsp;&nbsp;&nbsp;At-least-once Processing</a><ul class="auto-toc">
+<li><a class="reference internal" href="#how-to-track-reading-positions" id="id2">1.1&nbsp;&nbsp;&nbsp;How to track reading positions</a><ul class="auto-toc">
+<li><a class="reference internal" href="#open-the-offset-store" id="id3">1.1.1&nbsp;&nbsp;&nbsp;Open the offset store</a></li>
+<li><a class="reference internal" href="#read-the-reader-read-position" id="id4">1.1.2&nbsp;&nbsp;&nbsp;Read the reader read position</a></li>
+<li><a class="reference internal" href="#read-records" id="id5">1.1.3&nbsp;&nbsp;&nbsp;Read records</a></li>
+<li><a class="reference internal" href="#track-read-position" id="id6">1.1.4&nbsp;&nbsp;&nbsp;Track read position</a></li>
+<li><a class="reference internal" href="#record-read-position" id="id7">1.1.5&nbsp;&nbsp;&nbsp;Record read position</a></li>
+</ul>
+</li>
+</ul>
+</li>
+</ul>
+</div>
+<div class="section" id="at-least-once-processing">
+<h2><a class="toc-backref" href="#id1">1&nbsp;&nbsp;&nbsp;At-least-once Processing</a></h2>
+<p>Applications typically choose between <cite>at-least-once</cite> and <cite>exactly-once</cite> processing semantics.
+<cite>At-least-once</cite> processing guarantees that the application will process all the log records,
+however when the application resumes after failure, previously processed records may be re-processed
+if they have not been acknowledged. With at least once processing guarantees the application can store
+reader positions in an external store and update it periodically. Upon restart the application will
+reprocess messages since the last updated reader position.</p>
+<p>This tutorial shows how to do <cite>at-least-once</cite> processing by using a <cite>offset-store</cite> to track the reading positions.</p>
+<div class="section" id="how-to-track-reading-positions">
+<h3><a class="toc-backref" href="#id2">1.1&nbsp;&nbsp;&nbsp;How to track reading positions</a></h3>
+<p>Applications typically choose an external storage (e.g key/value storage) or another log stream to store their
+read positions. In this example, we used a local key/value store - <cite>LevelDB</cite> to store the read positions.</p>
+<div class="section" id="open-the-offset-store">
+<h4><a class="toc-backref" href="#id3">1.1.1&nbsp;&nbsp;&nbsp;Open the offset store</a></h4>
+<pre class="literal-block">
+String offsetStoreFile = ...;
+Options options = new Options();
+options.createIfMissing(true);
+DB offsetDB = factory.open(new File(offsetStoreFile), options);
+</pre>
+</div>
+<div class="section" id="read-the-reader-read-position">
+<h4><a class="toc-backref" href="#id4">1.1.2&nbsp;&nbsp;&nbsp;Read the reader read position</a></h4>
+<p>Read the reader read position from the offset store.</p>
+<pre class="literal-block">
+byte[] offset = offsetDB.get(readerId.getBytes(UTF_8));
+DLSN dlsn;
+if (null == offset) {
+    dlsn = DLSN.InitialDLSN;
+} else {
+    dlsn = DLSN.deserializeBytes(offset);
+}
+</pre>
+</div>
+<div class="section" id="read-records">
+<h4><a class="toc-backref" href="#id5">1.1.3&nbsp;&nbsp;&nbsp;Read records</a></h4>
+<p>Start read from the read position that recorded in offset store.</p>
+<pre class="literal-block">
+final AsyncLogReader reader = FutureUtils.result(dlm.openAsyncLogReader(dlsn));
+</pre>
+</div>
+<div class="section" id="track-read-position">
+<h4><a class="toc-backref" href="#id6">1.1.4&nbsp;&nbsp;&nbsp;Track read position</a></h4>
+<p>Track the last read position while reading using <cite>AtomicReference</cite>.</p>
+<pre class="literal-block">
+final AtomicReference&lt;DLSN&gt; lastReadDLSN = new AtomicReference&lt;DLSN&gt;(null);
+reader.readNext().addEventListener(new FutureEventListener&lt;LogRecordWithDLSN&gt;() {
+    ...
+
+    &#64;Override
+    public void onSuccess(LogRecordWithDLSN record) {
+        lastReadDLSN.set(record.getDlsn());
+        // process the record
+        ...
+        // read next record
+        reader.readNext().addEventListener(this);
+    }
+});
+</pre>
+</div>
+<div class="section" id="record-read-position">
+<h4><a class="toc-backref" href="#id7">1.1.5&nbsp;&nbsp;&nbsp;Record read position</a></h4>
+<p>Periodically update the last read position to the offset store.</p>
+<pre class="literal-block">
+final ScheduledExecutorService executorService =
+        Executors.newSingleThreadScheduledExecutor();
+executorService.scheduleAtFixedRate(new Runnable() {
+    &#64;Override
+    public void run() {
+        if (null != lastDLSN.get()) {
+            offsetDB.put(readerId.getBytes(UTF_8), lastDLSN.get().serializeBytes());
+        }
+    }
+}, 10, 10, TimeUnit.SECONDS);
+</pre>
+<p>Check <a class="reference external" href="https://github.com/apache/incubator-distributedlog/blob/master/distributedlog-tutorials/distributedlog-messaging/src/main/java/com/twitter/distributedlog/messaging/ReaderWithOffsets.java">distributedlog-tutorials/distributedlog-messaging/src/main/java/com/twitter/distributedlog/messaging/ReaderWithOffsets</a> for more details.</p>
+</div>
+</div>
+</div>
+
+
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+
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+      <div class="col-xs-12">
+          <footer>
+              <p class="text-center">&copy; Copyright 2016
+                  <a href="http://www.apache.org">The Apache Software Foundation.</a> All Rights Reserved.
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+
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http://git-wip-us.apache.org/repos/asf/incubator-distributedlog/blob/ef7245e8/content/docs/0.4.0-incubating/tutorials/messaging-4.html
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+++ b/content/docs/0.4.0-incubating/tutorials/messaging-4.html
@@ -0,0 +1,395 @@
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+              <a href="/docs/0.4.0-incubating/tutorials/messaging-5.html">
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+              </a>
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+<div class="col-md-8 col-md-offset-2">
+  <div class="contents topic" id="messaging-tutorial-exact-once-processing">
+<p class="topic-title first">Messaging Tutorial - Exact-Once Processing</p>
+<ul class="simple">
+<li><a class="reference internal" href="#exact-once-processing" id="id1">Exact-Once Processing</a></li>
+</ul>
+</div>
+<div class="section" id="exact-once-processing">
+<h2><a class="toc-backref" href="#id1">Exact-Once Processing</a></h2>
+<p>Applications typically choose between <cite>at-least-once</cite> and <cite>exactly-once</cite> processing semantics.
+<cite>At-least-once</cite> processing guarantees that the application will process all the log records,
+however when the application resumes after failure, previously processed records may be re-processed
+if they have not been acknowledged. <cite>Exactly once</cite> processing is a stricter guarantee where applications
+must see the effect of processing each record exactly once. <cite>Exactly once</cite> semantics can be achieved
+by maintaining reader positions together with the application state and atomically updating both the
+reader position and the effects of the corresponding log records.</p>
+<p>This <a class="reference external" href="https://github.com/apache/incubator-distributedlog/blob/master/distributedlog-tutorials/distributedlog-messaging/src/main/java/com/twitter/distributedlog/messaging/StreamTransformer.java">tutorial</a> shows how to do <cite>exact-once</cite> processing.</p>
+</div>
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http://git-wip-us.apache.org/repos/asf/incubator-distributedlog/blob/ef7245e8/content/docs/0.4.0-incubating/tutorials/messaging-5.html
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+<!DOCTYPE html>
+<html lang="en">
+
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+  <meta http-equiv="X-UA-Compatible" content="IE=edge">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+
+  <title>Tutorials - Implement a kafka-like pub/sub system</title>
+  <meta name="description" content="Apache DistributedLog is an high performance replicated log.
+">
+
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+              <a href="/docs/0.4.0-incubating/admin_guide/performance.html">
+                Performance Tuning
+              </a>
+            </li>
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/admin_guide/loadtest.html">
+                Load Test
+              </a>
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+            
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+              <a href="/docs/0.4.0-incubating/admin_guide/hardware.html">
+                Hardware
+              </a>
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+            
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+              <a href="/docs/0.4.0-incubating/admin_guide/monitoring.html">
+                Monitoring
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+              <a href="/docs/0.4.0-incubating/admin_guide/zookeeper.html">
+                ZooKeeper
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+            
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+              <a href="/docs/0.4.0-incubating/admin_guide/bookkeeper.html">
+                BookKeeper
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+        </li>
+        <!-- Tutorials -->
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+		      <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">Tutorials<span class="caret"></span></a>
+          <ul class="dropdown-menu">
+            <li class="dropdown-header"><strong>Basic</strong></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/basic-1">Write Records (via Core Library)</a></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/basic-2">Write Records (via Write Proxy)</a></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/basic-3">Write Records to multiple streams</a></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/basic-4">Atomic Write Records</a></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/basic-5">Tailing Read Records</a></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/basic-6">Rewind Read Records</a></li>
+            <li role="separator" class="divider"></li>
+            <li class="dropdown-header"><strong>Messaging</strong></li>
+            
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/messaging-1.html">
+                Write records to partitioned streams
+              </a>
+            </li>
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/messaging-2.html">
+                Write records to multiple streams (load balancer)
+              </a>
+            </li>
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/messaging-3.html">
+                At-least-once Processing
+              </a>
+            </li>
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/messaging-4.html">
+                Exact-Once Processing
+              </a>
+            </li>
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/messaging-5.html">
+                Implement a kafka-like pub/sub system
+              </a>
+            </li>
+            
+            <li role="separator" class="divider"></li>
+            <li class="dropdown-header"><strong>Replicated State Machines</strong></li>
+            
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/replicatedstatemachines.html">
+                Build replicated state machines
+              </a>
+            </li>
+            
+            <li role="separator" class="divider"></li>
+            <li class="dropdown-header"><strong>Analytics</strong></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/analytics-mapreduce">Process log streams using MapReduce</a></li>
+          </ul>
+        </li>
+      </ul>
+    </div><!--/.nav-collapse -->
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+</nav>
+
+
+<link rel="stylesheet" href="">
+
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+
+      <div class="row">
+        
+        <!--
+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
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+
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+
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+-->
+
+<div class="col-md-8 col-md-offset-2">
+  <div class="contents topic" id="messaging-tutorial-implement-a-kafka-like-pub-sub-system">
+<p class="topic-title first">Messaging Tutorial - Implement a kafka-like pub/sub system</p>
+<ul class="simple">
+<li><a class="reference internal" href="#how-to-implement-a-kafka-like-partitioned-pub-sub-system-using-distributedlog" id="id1">How to implement a kafka-like partitioned pub/sub system using DistributedLog</a></li>
+</ul>
+</div>
+<div class="section" id="how-to-implement-a-kafka-like-partitioned-pub-sub-system-using-distributedlog">
+<h2><a class="toc-backref" href="#id1">How to implement a kafka-like partitioned pub/sub system using DistributedLog</a></h2>
+<p><a class="reference external" href="https://github.com/apache/incubator-distributedlog/tree/master/distributedlog-tutorials/distributedlog-kafka">./distributedlog-tutorials/distributedlog-kafka</a> shows how to implement a kafka-like publisher using multiple streams.
+Check <a class="reference external" href="https://github.com/apache/incubator-distributedlog/blob/master/distributedlog-tutorials/distributedlog-kafka/src/main/java/com/twitter/distributedlog/kafka/KafkaDistributedLogProducer.java">KafkaDistributedLogProducer</a> for more details.</p>
+</div>
+
+
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+              <p class="text-center">&copy; Copyright 2016
+                  <a href="http://www.apache.org">The Apache Software Foundation.</a> All Rights Reserved.
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http://git-wip-us.apache.org/repos/asf/incubator-distributedlog/blob/ef7245e8/content/docs/0.4.0-incubating/tutorials/replicatedstatemachines.html
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+<!DOCTYPE html>
+<html lang="en">
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+  <title>Tutorial - Build replicated state machines</title>
+  <meta name="description" content="Apache DistributedLog is an high performance replicated log.
+">
+
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+        <!-- Overview -->
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+            <li><a href="/docs/0.4.0-incubating/tutorials/basic-3">Write Records to multiple streams</a></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/basic-4">Atomic Write Records</a></li>
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+            <li class="dropdown-header"><strong>Messaging</strong></li>
+            
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/messaging-1.html">
+                Write records to partitioned streams
+              </a>
+            </li>
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/messaging-2.html">
+                Write records to multiple streams (load balancer)
+              </a>
+            </li>
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/messaging-3.html">
+                At-least-once Processing
+              </a>
+            </li>
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/messaging-4.html">
+                Exact-Once Processing
+              </a>
+            </li>
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/messaging-5.html">
+                Implement a kafka-like pub/sub system
+              </a>
+            </li>
+            
+            <li role="separator" class="divider"></li>
+            <li class="dropdown-header"><strong>Replicated State Machines</strong></li>
+            
+            
+            <li>
+              <a href="/docs/0.4.0-incubating/tutorials/replicatedstatemachines.html">
+                Build replicated state machines
+              </a>
+            </li>
+            
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+            <li class="dropdown-header"><strong>Analytics</strong></li>
+            <li><a href="/docs/0.4.0-incubating/tutorials/analytics-mapreduce">Process log streams using MapReduce</a></li>
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