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Posted to commits@rocketmq.apache.org by li...@apache.org on 2017/06/08 10:10:00 UTC
[05/15] incubator-rocketmq-site git commit: Revert CSS
http://git-wip-us.apache.org/repos/asf/incubator-rocketmq-site/blob/af2718af/content/feed.xml
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- <?xml version="1.0" encoding="utf-8"?><feed xmlns="http://www.w3.org/2005/Atom" ><generator uri="https://jekyllrb.com/" version="3.4.3">Jekyll</generator><link href="/feed.xml" rel="self" type="application/atom+xml" /><link href="/" rel="alternate" type="text/html" /><updated>2017-06-08T17:34:10+08:00</updated><id>/</id><title type="html">Apache RocketMQ</title><subtitle>The homepage of RocketMQ.</subtitle><author><name>{"name"=>nil, "avatar"=>"/assets/images/rmq-logo.png", "bio"=>"A fast, low latency, reliable, scalable, distributed MOM.", "location"=>"Hangzhou, China", "email"=>"dev@rocketmq.incubator.apache.org", "uri"=>"http://incubator.staging.apache.org/projects/rocketmq.html", "bitbucket"=>nil, "codepen"=>nil, "dribbble"=>nil, "flickr"=>nil, "facebook"=>nil, "foursquare"=>
nil, "github"=>"apache/incubator-rocketmq", "google_plus"=>nil, "keybase"=>nil, "instagram"=>nil, "lastfm"=>nil, "linkedin"=>nil, "pinterest"=>nil, "soundcloud"=>nil, "stackoverflow"=>"questions/tagged/rocketmq", "steam"=>nil, "tumblr"=>nil, "twitter"=>"ApacheRocketMQ", "vine"=>nil, "weibo"=>nil, "xing"=>nil, "youtube"=>nil, "quora"=>"topic/RocketMQ"}</name><email>dev@rocketmq.incubator.apache.org</email><uri>http://incubator.staging.apache.org/projects/rocketmq.html</uri></author><entry><title type="html">Release Notes - Apache RocketMQ - Version 4.1.0-incubating</title><link href="/release-notes-4.1.0-incubating/" rel="alternate" type="text/html" title="Release Notes - Apache RocketMQ - Version 4.1.0-incubating" /><published
>2017-06-02T00:00:00+08:00</published><updated>2017-06-02T00:00:00+08:00</updated><id>/release-notes-4.1.0-incubating</id><content type="html" xml:base="/release-notes-4.1.0-incubating/"><p>Release Notes - Apache RocketMQ - Version 4.1.0-incubating</p>
++<?xml version="1.0" encoding="utf-8"?><feed xmlns="http://www.w3.org/2005/Atom" ><generator uri="https://jekyllrb.com/" version="3.4.3">Jekyll</generator><link href="/feed.xml" rel="self" type="application/atom+xml" /><link href="/" rel="alternate" type="text/html" /><updated>2017-06-08T18:09:33+08:00</updated><id>/</id><title type="html">Apache RocketMQ</title><subtitle>The homepage of RocketMQ.</subtitle><author><name>{"name"=>nil, "avatar"=>"/assets/images/rmq-logo.png", "bio"=>"A fast, low latency, reliable, scalable, distributed MOM.", "location"=>"Hangzhou, China", "email"=>"dev@rocketmq.incubator.apache.org", "uri"=>"http://incubator.staging.apache.org/projects/rocketmq.html", "bitbucket"=>nil, "codepen"=>nil, "dribbble"=>nil, "flickr"=>nil, "facebook"=>nil, "foursquare"=>
nil, "github"=>"apache/incubator-rocketmq", "google_plus"=>nil, "keybase"=>nil, "instagram"=>nil, "lastfm"=>nil, "linkedin"=>nil, "pinterest"=>nil, "soundcloud"=>nil, "stackoverflow"=>"questions/tagged/rocketmq", "steam"=>nil, "tumblr"=>nil, "twitter"=>"ApacheRocketMQ", "vine"=>nil, "weibo"=>nil, "xing"=>nil, "youtube"=>nil, "quora"=>"topic/RocketMQ"}</name><email>dev@rocketmq.incubator.apache.org</email><uri>http://incubator.staging.apache.org/projects/rocketmq.html</uri></author><entry><title type="html">Release Notes - Apache RocketMQ - Version 4.1.0-incubating</title><link href="/release-notes-4.1.0-incubating/" rel="alternate" type="text/html" title="Release Notes - Apache RocketMQ - Version 4.1.0-incubating" /><published
>2017-06-02T00:00:00+08:00</published><updated>2017-06-02T00:00:00+08:00</updated><id>/release-notes-4.1.0-incubating</id><content type="html" xml:base="/release-notes-4.1.0-incubating/"><p>Release Notes - Apache RocketMQ - Version 4.1.0-incubating</p>
+
+<h2 id="new-feature">New Feature</h2>
+
+<ul>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-80">ROCKETMQ-80</a>] - Add batch feature</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-121">ROCKETMQ-121</a>] - Support message filtering based on SQL92</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-194">ROCKETMQ-194</a>] - log appender using rocketmq</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-186">ROCKETMQ-186</a>] - Implement the OpenMessaging specification 0.1.0-alpha version</li>
+</ul>
+
+<h2 id="improvement">Improvement</h2>
+
+<ul>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-67">ROCKETMQ-67</a>] - Consistent Hash allocate strategy support</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-99">ROCKETMQ-99</a>] - Add scripts for Windows platform</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-36">ROCKETMQ-36</a>] - Improve broker’s GC logs storing</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-39">ROCKETMQ-39</a>] - Duplicated codes in both filtersrv and namesrv modules</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-86">ROCKETMQ-86</a>] - Polish the release file format</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-88">ROCKETMQ-88</a>] - Polish the developer list in pom.xml</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-90">ROCKETMQ-90</a>] - Include client IP per message queue of consumer progress command output</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-114">ROCKETMQ-114</a>] - Add javadoc to codebase</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-138">ROCKETMQ-138</a>] - Add AuthenticationException class to remove hard coded Aliyun authentication class</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-139">ROCKETMQ-139</a>] - Degrade the client related modules’ JDK version to 1.6</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-144">ROCKETMQ-144</a>] - Aggregate distribution specific files to a new module</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-154">ROCKETMQ-154</a>] - Add a newline after help info</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-160">ROCKETMQ-160</a>] - SendHeartBeart log may not be triggered in the same expected period</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-161">ROCKETMQ-161</a>] - Update runbroker.sh and runserver.sh to support user defined jvm memory flag</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-168">ROCKETMQ-168</a>] - Duplicated calls of life cycle in Maven.</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-172">ROCKETMQ-172</a>] - log improvement for rocketmq client</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-176">ROCKETMQ-176</a>] - Improvement the Maven Central Badge in readme</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-187">ROCKETMQ-187</a>] - Measure the code coverage for Integration Tests</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-148">ROCKETMQ-148</a>] - Migrate all relevant docs from the old Github project’s wiki to the ASF site</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-218">ROCKETMQ-218</a>] - Add IT test for Filter By SQL 92</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-219">ROCKETMQ-219</a>] - Add Batch Example</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-220">ROCKETMQ-220</a>] - README.md update, remove some github links</li>
+</ul>
+
+<h2 id="bug">Bug</h2>
+
+<ul>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-77">ROCKETMQ-77</a>] - [TEST] org.apache.rocketmq.tools.* have NPEs</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-89">ROCKETMQ-89</a>] - WS_DOMAIN_NAME, SUBGROUP default values overrides custom values passed by java options</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-95">ROCKETMQ-95</a>] - The config files of client log have been damaged</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-98">ROCKETMQ-98</a>] - Risk of unable to release putMessage Lock forever</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-101">ROCKETMQ-101</a>] - Possible NullPointerException when retry in send Async way</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-107">ROCKETMQ-107</a>] - Access ServiceState is not thread safe when start() or shutdown()</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-119">ROCKETMQ-119</a>] - Shutdown PullMessageService properly</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-140">ROCKETMQ-140</a>] - Register higher version broker against old name servers</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-143">ROCKETMQ-143</a>] - Update fastjson from 1.2.12 to 1.2.29</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-153">ROCKETMQ-153</a>] - Fetch name server address dynamically</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-155">ROCKETMQ-155</a>] - Fix typo in ClientConfig</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-165">ROCKETMQ-165</a>] - Maximum pull batch size hard-coded restricted</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-175">ROCKETMQ-175</a>] - Consumer may miss messages because of inconsistent subscription</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-178">ROCKETMQ-178</a>] - Broker -m -p options are broken</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-179">ROCKETMQ-179</a>] - Fix errors of test cases</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-188">ROCKETMQ-188</a>] - RemotingExecption is not consistent between invoke async and invoke oneway</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-189">ROCKETMQ-189</a>] - Misleading tip on consumeTimestamp and wrong consumeTimestamp exception message</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-191">ROCKETMQ-191</a>] - Fix incorret socket option</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-199">ROCKETMQ-199</a>] - consumers can not receive stock information.</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-200">ROCKETMQ-200</a>] - Cluster name is always missing when fetch ClusterInfo from name server</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-206">ROCKETMQ-206</a>] - Load JSON config file error if non-1byte character exists</li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-208">ROCKETMQ-208</a>] - incompatibility problem found in enviroment of JDK 1.7 when running client</li>
+</ul></content><author><name>{"name"=>nil, "avatar"=>"/assets/images/rmq-logo.png", "bio"=>"A fast, low latency, reliable, scalable, distributed MOM.", "location"=>"Hangzhou, China", "email"=>"dev@rocketmq.incubator.apache.org", "uri"=>"http://incubator.staging.apache.org/projects/rocketmq.html", "bitbucket"=>nil, "codepen"=>nil, "dribbble"=>nil, "flickr"=>nil, "facebook"=>nil, "foursquare"=>nil, "github"=>"apache/incubator-rocketmq", "google_plus"=>nil, "keybase"=>nil, "instagram"=>nil, "lastfm"=>nil, "linkedin"=>nil, "pinterest"=>nil, "soundcloud"=>nil, "stackoverflow"=>"questions/tagged/rocketmq", "steam"=>nil, "tumblr
"=>nil, "twitter"=>"ApacheRocketMQ", "vine"=>nil, "weibo"=>nil, "xing"=>nil, "youtube"=>nil, "quora"=>"topic/RocketMQ"}</name><email>dev@rocketmq.incubator.apache.org</email><uri>http://incubator.staging.apache.org/projects/rocketmq.html</uri></author><summary type="html">Release Notes - Apache RocketMQ - Version 4.1.0-incubating</summary></entry><entry><title type="html">Filter Messages By SQL92 In RocketMQ</title><link href="/rocketmq/filter-messages-by-sql92-in-rocketmq/" rel="alternate" type="text/html" title="Filter Messages By SQL92 In RocketMQ" /><published>2017-04-26T00:00:00+08:00</published><updated>2017-04-26T00:00:00+08:00</updated><id>/rocketmq/filter-messages-by-sql92-in-rocketmq</id><content type="html" xml:base="/rocketmq/filter-messages-by-sql92-in-rocketmq/"><p>So far, RocketMQ only support message filtering feature by <code class="highlighter-rou
ge">TAG</code>, but one message only can own one tag, this is too limited to meet complex business requirements.</p>
+
+<p>So, we want to define and implement a reasonable filter language based on a subset of the SQL 92 expression syntax to support customized message filtering.</p>
+
+<h3 id="why-subset-of-sql92">Why Subset Of SQL92</h3>
+
+<p>Let RocketMQ has the ability of message filtering is the purpose of this issue, and as we know, SQL92 is used widely and most persons are familiar with it.It’s resonable to select it as RocketMQ’s grammar.</p>
+
+<p>As I know, ActiveMQ already impllement this functionality based on JavaCC, it’s simple and exntensible.So I just extract it and integrate into RocketMQ, only some grammars:</p>
+
+<ol>
+ <li>Numeric comparison, like <code class="highlighter-rouge">&gt;</code>, <code class="highlighter-rouge">&gt;=</code>, <code class="highlighter-rouge">&lt;</code>, <code class="highlighter-rouge">&lt;=</code>, <code class="highlighter-rouge">BETWEEN</code>, <code class="highlighter-rouge">=</code>;</li>
+ <li>Character comparison, like <code class="highlighter-rouge">=</code>, <code class="highlighter-rouge">&lt;&gt;</code>, <code class="highlighter-rouge">IN</code>;</li>
+ <li><code class="highlighter-rouge">IS NULL</code> or <code class="highlighter-rouge">IS NOT NULL</code>;</li>
+ <li>Logical <code class="highlighter-rouge">AND</code>, logical <code class="highlighter-rouge">OR</code>, logical <code class="highlighter-rouge">NOT</code>;</li>
+</ol>
+
+<p>Constant type are:</p>
+
+<ol>
+ <li>Numeric, like 123, 3.1415;</li>
+ <li>Character, like ‘abc’, must be maked with single quotes;</li>
+ <li><code class="highlighter-rouge">NULL</code>, special constant;</li>
+ <li>Boolean, <code class="highlighter-rouge">TRUE</code> or <code class="highlighter-rouge">FALSE</code>;</li>
+</ol>
+
+<h3 id="design">Design</h3>
+<ul>
+ <li>Structure</li>
+</ul>
+
+<p><img src="/assets/images/blog/filter_structure_apach.png" alt="screenshot" /></p>
+
+<ol>
+ <li>Broker collects the expression of consumer through heartbeat request, and saved in <code class="highlighter-rouge">ConsumerFilterManager</code>.</li>
+ <li>When consumer pulls messages, broker will construct a <code class="highlighter-rouge">MessageFilter</code>(an interface) with compiled expression and subscription data to select matched messages in <code class="highlighter-rouge">CommitLog</code>.</li>
+</ol>
+
+<p>The main logic is simple.</p>
+
+<ul>
+ <li>New Module, rocketmq-filter</li>
+</ul>
+
+<p>The implementation of SQL92 language is placed in this module which have dependency on common module.</p>
+
+<p>Broker compile or evaluate expression through the interface of <code class="highlighter-rouge">FilterSpi</code> contained in <code class="highlighter-rouge">FilterFactory</code> that manage all <code class="highlighter-rouge">FilterSpi</code> and also support new one to register.</p>
+
+<ul>
+ <li>How to manage consumer’s expression data</li>
+</ul>
+
+<p>Different from tag filtering, expression of SQL92 should be compiled first to check whether is leagal and then use the complied expression to compute. This procedure is designed to take place at broker.</p>
+
+<p><code class="highlighter-rouge">ConsumerManager</code> manage the suscriptions of push consumer, and <code class="highlighter-rouge">ConsumerFilterManager</code> manage the expression info of push consumer who wish to filter message by special language, the info includes data version, expression, compiled expression, alive time and etc.</p>
+
+<ul>
+ <li>How to filter message by expression</li>
+</ul>
+
+<p>I redesign the interface <code class="highlighter-rouge">getMessage</code> of <code class="highlighter-rouge">MessageStore</code> by replace the last parameter <code class="highlighter-rouge">SubscriptionData</code> to <code class="highlighter-rouge">MessageFilter</code> that is also refactored. The purpose is to make module <code class="highlighter-rouge">rocketmq-store</code> has no relation with protocol.</p>
+
+<p>When get message, the implementation <code class="highlighter-rouge">ExpressionMessageFilter</code> would check whether the message is matched by <code class="highlighter-rouge">BitsArray</code> which will be refered later or evaluation, just as the mechanism of tag filtering.</p>
+
+<ul>
+ <li>Optimization, pre-calculate the filtering result when build consume queue</li>
+</ul>
+
+<p>It’s poor performance to do filter when pull message:</p>
+
+<ol>
+ <li>off-heap to heap, once every consumer subscribed same topic pull message.</li>
+ <li>decode message properties, once every consumer subscribed same topic pull message.</li>
+</ol>
+
+<p><code class="highlighter-rouge">BloomFilter</code> and pre-calculation are adopted to optimize the situation:</p>
+
+<p><img src="/assets/images/blog/filter_build_cq_apache.png" alt="screenshot" /></p>
+
+<ol>
+ <li>Every consumer has been asigned some bit position of <code class="highlighter-rouge">BloomFilter</code> when register to broker.</li>
+ <li>When broker build queue after message into <code class="highlighter-rouge">CommitLog</code>, the consumer’s filtering result would be calculated, and all resuls are assembled as a <code class="highlighter-rouge">BitsArray</code> saved in <code class="highlighter-rouge">ConsumeQueueExt</code>.</li>
+ <li><code class="highlighter-rouge">ConsumeQueueExt</code> is a store file linked to <code class="highlighter-rouge">ConsumeQueue</code>, <code class="highlighter-rouge">ConsumeQueue</code> could find the data by the <code class="highlighter-rouge">tagsCode</code> whitch is already replaced by the address(for compitable, the range is Long.MIN_VALUE to Integer.MIN_VALUE) generated by <code class="highlighter-rouge">ConsumeQueueExt</code>.</li>
+ <li><code class="highlighter-rouge">ExpressionMessageFilter</code> could use the <code class="highlighter-rouge">BitsArray</code> to check whether the message is matched. Because of BloomFilter’s collision, it also need to decode properties to do calculation for matched message(may could be reduced by check the collision, not include in this edition).</li>
+</ol>
+
+<p>This optimization is suitable for:</p>
+
+<ol>
+ <li>High subscription ratio.</li>
+ <li>Large properties.</li>
+</ol>
+
+<p>This optimization is off default, it need set some configs when broker starting to switch on:</p>
+
+<ol>
+ <li>enableCalcFilterBitMap = true, means to caculate bitmap when build consume queue.</li>
+ <li>expectConsumerNumUseFilter = XX(Integer, default is 32), means estimated consumer num subscribe same topic.</li>
+ <li>maxErrorRateOfBloomFilter = XX(1~100, default is 20), means error rate of bloom filter.</li>
+ <li>enableConsumeQueueExt = true, means construct consume queue extend file.</li>
+</ol>
+
+<h3 id="interface">Interface</h3>
+
+<p>Only push consumer could filter message by SQL92 expression in this edition, the interface is:</p>
+
+<p><code class="highlighter-rouge">public void subscribe(final String topic, final MessageSelector messageSelector)</code></p>
+
+<h3 id="performance-comparison">Performance Comparison</h3>
+
+<p>Configuration of broker machine: 32 core, 128G memory, 1000Mb/s full duplex dual network</p>
+
+<p>Producer send message with 1k body and 1k properties.</p>
+
+<p>Five consumers consume message through push model, every consumer would get 1/5 messages of total.</p>
+
+<p>Cpu and gc frequency is about 30% lower when do pre-calculate filtering result.</p></content><author><name>{"name"=>nil, "avatar"=>"/assets/images/rmq-logo.png", "bio"=>"A fast, low latency, reliable, scalable, distributed MOM.", "location"=>"Hangzhou, China", "email"=>"dev@rocketmq.incubator.apache.org", "uri"=>"http://incubator.staging.apache.org/projects/rocketmq.html", "bitbucket"=>nil, "codepen"=>nil, "dribbble"=>nil, "flickr"=>nil, "facebook"=>nil, "foursquare"=>nil, "github"=>"apache/incubator-rocketmq", "google_plus"=>nil, "keybase"=>nil, "instagram"=>nil, "lastfm"=>nil, "linkedin"=>nil, "pinterest"=>nil, "soundcloud"=>nil, "stackoverflow&q
uot;=>"questions/tagged/rocketmq", "steam"=>nil, "tumblr"=>nil, "twitter"=>"ApacheRocketMQ", "vine"=>nil, "weibo"=>nil, "xing"=>nil, "youtube"=>nil, "quora"=>"topic/RocketMQ"}</name><email>dev@rocketmq.incubator.apache.org</email><uri>http://incubator.staging.apache.org/projects/rocketmq.html</uri></author><category term="RocketMQ" /><category term="Filter" /><summary type="html">So far, RocketMQ only support message filtering feature by TAG, but one message only can own one tag, this is too limited to meet complex business requirements.</summary></entry><entry><title type="html">Launch The Second RocketMQ Code Marathon</title><link href="/activity/launch-rocketmq-code-marathon/" rel="alternate" type="text/html" title="Launch The Second RocketMQ Code Marathon" /><published>2017-03-31T00:00:00+08:00</published><updated>2017-03-31T00:00:00+08:00</upd
ated><id>/activity/launch-rocketmq-code-marathon</id><content type="html" xml:base="/activity/launch-rocketmq-code-marathon/"><p><img src="/assets/images/blog/banner.jpg" alt="Banner" /></p>
+<h1 id="rocketmq-code-marathon-">ROCKETMQ CODE MARATHON <a href="/assets/attachment/launch-second-rocketmq-code-marathon.pdf"><i class="fa fa-link"></i></a></h1>
+<h5 id="march-29th-2017">March 29th 2017</h5>
+
+<h2 id="objective">Objective:</h2>
+<ol>
+ <li>Foster Community</li>
+ <li>Prosper Ecology</li>
+ <li>Incubate Committers</li>
+</ol>
+
+<h2 id="output">Output:</h2>
+<ol>
+ <li>1~3 Milestone Releases Per Project</li>
+</ol>
+
+<h2 id="rewards">Rewards:</h2>
+<ol>
+ <li>Two Potential Committers Candidates Per Project</li>
+ <li>Free Offers to Active Participants for On-Site Meetup
+ <h2 id="projects">PROJECTS</h2>
+ </li>
+</ol>
+
+<h3 id="rocketmq-big-data">RocketMQ-Big Data</h3>
+<ol>
+ <li>Integration of big data analysis framework</li>
+ <li>Rich Documentation and Good Test Cases Coverage</li>
+ <li>Apache Beam preferred</li>
+ <li>Join by Creating Pull Requests against <a href="https://github.com/apache/incubator-rocketmq-externals">RocketMQ Beam Repository</a></li>
+ <li>Join by Creating Pull Requests against <a href="https://github.com/apache/incubator-rocketmq-externals">RocketMQ Flink Repository</a></li>
+ <li>Join by Existing Pull Request against <a href="https://github.com/apache/storm/pull/2024">RocketMQ Storm Repository</a></li>
+ <li>Join by Existing Pull Request against <a href="https://github.com/apache/incubator-rocketmq-externals/pull/5">RocketMQ Spark Repository</a></li>
+</ol>
+
+<h3 id="rocketmq-client-sdk">RocketMQ-Client SDK</h3>
+<ol>
+ <li>Development of RocketMQ Client</li>
+ <li>Rich Documentation and Good Test Cases Coverage</li>
+ <li>Go preferred</li>
+ <li>Join by Creating Pull Requests against <a href="https://github.com/apache/incubator-rocketmq-externals">RocketMQ Go Repository</a></li>
+ <li>Join by Creating Pull Requests against <a href="https://github.com/apache/incubator-rocketmq-externals">RocketMQ .Net Repository</a></li>
+ <li>Join by Creating Pull Requests against <a href="https://github.com/apache/incubator-rocketmq-externals">RocketMQ PHP Repository</a></li>
+</ol>
+
+<h3 id="rocketmq-data-replication">RocketMQ-Data Replication</h3>
+<ol>
+ <li>Implement Data Replication from Database</li>
+ <li>Rich Documentation and Good Test Cases Coverage</li>
+ <li>MySQL preferred</li>
+ <li>Join by Creating Pull Requests against <a href="https://github.com/apache/incubator-rocketmq-externals">RocketMQ MySQL Repository</a></li>
+ <li>Join by Creating Pull Requests against <a href="https://github.com/apache/incubator-rocketmq-externals">RocketMQ Redis Repository</a></li>
+ <li>Join by Creating Pull Requests against <a href="https://github.com/apache/incubator-rocketmq-externals">RocketMQ MongoDB Repository</a></li>
+</ol></content><author><name>{"name"=>nil, "avatar"=>"/assets/images/rmq-logo.png", "bio"=>"A fast, low latency, reliable, scalable, distributed MOM.", "location"=>"Hangzhou, China", "email"=>"dev@rocketmq.incubator.apache.org", "uri"=>"http://incubator.staging.apache.org/projects/rocketmq.html", "bitbucket"=>nil, "codepen"=>nil, "dribbble"=>nil, "flickr"=>nil, "facebook"=>nil, "foursquare"=>nil, "github"=>"apache/incubator-rocketmq", "google_plus"=>nil, "keybase"=>nil, "instagram"=>nil, "lastfm"=>nil, "linkedin"=>nil, "pinterest"=>nil, "soundcloud"=>nil, "stackoverflow"=>"questions/tagged/rocketmq", "steam"=>nil, "tumblr
"=>nil, "twitter"=>"ApacheRocketMQ", "vine"=>nil, "weibo"=>nil, "xing"=>nil, "youtube"=>nil, "quora"=>"topic/RocketMQ"}</name><email>dev@rocketmq.incubator.apache.org</email><uri>http://incubator.staging.apache.org/projects/rocketmq.html</uri></author><category term="Activity" /><category term="Code" /><category term="Marathon" /><summary type="html">ROCKETMQ CODE MARATHON March 29th 2017</summary></entry><entry><title type="html">The Correct Posture Of Submitting Pull Request</title><link href="/the-correct-posture-of-submitting-pull-request/" rel="alternate" type="text/html" title="The Correct Posture Of Submitting Pull Request" /><published>2017-03-24T00:00:00+08:00</published><updated>2017-03-24T00:00:00+08:00</updated><id>/the-correct-posture-of-submitting-pull-request</id><content type="html" xml:base="/the-correct-posture-of-submitting-pull-request/"><h2 id="the-c
orrect-posture-of-submitting-a-pr">The correct posture of submitting a PR</h2>
+
+<h3 id="prepare-the-repo">Prepare the repo</h3>
+<ul>
+ <li>fork the apache repo on Github
+<img src="http://img3.tbcdn.cn/5476e8b07b923/TB17G5kQpXXXXcUapXXXXXXXXXX" alt="" />
+Click the “fork” button, a forked repo will be added to your repo list.</li>
+ <li>clone the forked repo, here take “foo” as example
+ <blockquote>
+ <p>git clone https://github.com/foo/incubator-rocketmq.git</p>
+ </blockquote>
+ </li>
+ <li>add apache remote repo
+ <blockquote>
+ <p>git remote add apache https://github.com/apache/incubator-rocketmq.git</p>
+ </blockquote>
+ </li>
+ <li>show the remote repos
+ <blockquote>
+ <p>git remote -v<br />
+apache https://github.com/apache/incubator-rocketmq.git (fetch)<br />
+apache https://github.com/apache/incubator-rocketmq.git (push)<br />
+origin https://github.com/foo/incubator-rocketmq.git (fetch)<br />
+origin https://github.com/foo/incubator-rocketmq.git (push)</p>
+ </blockquote>
+ </li>
+</ul>
+
+<p><strong>Note</strong>: https://github.com/apache/incubator-rocketmq.git is a read-only repo, mirrored from git://git.apache.org/incubator-rocketmq.git. For submitting PR, fork this read-only repo on Github is OK.</p>
+
+<h3 id="use-a-new-branch-to-write-your-own-code-and-commit">Use a new branch to write your own code and commit</h3>
+<p>you’d better use a new branch for each PR, for it is convenient to manage your code and commits</p>
+<blockquote>
+ <p>git checkout -b new_pr<br />
+//do something and commit</p>
+</blockquote>
+
+<h3 id="important-rebase-instead-of-merge">[Important] Rebase instead of merge</h3>
+<blockquote>
+ <p>git fetch apache<br />
+git rebase apache/develop</p>
+</blockquote>
+
+<p>Note: if using merge, it will dirty the commits</p>
+
+<p>the difference between rebase and merge can refer to:<br />
+<a href="https://www.atlassian.com/git/tutorials/merging-vs-rebasing">https://www.atlassian.com/git/tutorials/merging-vs-rebasing</a></p>
+
+<h3 id="suggestedsquash-the-commits">[Suggested]Squash the commits</h3>
+<p>you can code and commit as usual. But when you think it is time to submit a PR, it is better to squash your commits into single one, for that others can easily identify your PR from the history commits.
+you can squash as follows:</p>
+<blockquote>
+ <p>gt reset &lt;the latest commit that dose not belong to you PR&gt;<br />
+git add –all<br />
+git commit -m “attach the issue or jira”<br />
+git push (if the commits have been already pushed to your remote repo, git push will fail , use git push -f instead)</p>
+</blockquote>
+
+<p>For example:</p>
+<blockquote>
+ <p>git log</p>
+</blockquote>
+
+<p><img src="https://lh3.googleusercontent.com/-xYoltD_ZDhE/WNTONuq58WI/AAAAAAAAABo/zWZdGVxNVa8/I/14864352604541.jpg" alt="" /></p>
+
+<blockquote>
+ <p>git resset b4108d2d9d3b1522e45ac5e7ea37106f2135bfa0 <br />
+git commit -m ‘Add batch feature’<br />
+git log</p>
+</blockquote>
+
+<p><img src="https://lh3.googleusercontent.com/-Pe_xYIiPAGE/WNTOOHEUd1I/AAAAAAAAABs/VfuT_wBQ5QI/I/14864353798102.jpg" alt="" /></p>
+<blockquote>
+ <p>git push</p>
+</blockquote>
+
+<h3 id="attach-jira-or-issue">Attach jira or issue</h3>
+<p>For now, we have finished the preparations of a PR. It is time to create it. For apache projects, we could attach the jira issue using specific title like “[XXX] add something”, such as “[ROCKETMQ-80] Add batch feature”, the “XXX” represents the the name of the jira issue.
+you could refer to:</p>
+
+<p><a href="https://github.com/apache/incubator-rocketmq/pull/53">https://github.com/apache/incubator-rocketmq/pull/53</a></p></content><author><name>{"name"=>nil, "avatar"=>"/assets/images/rmq-logo.png", "bio"=>"A fast, low latency, reliable, scalable, distributed MOM.", "location"=>"Hangzhou, China", "email"=>"dev@rocketmq.incubator.apache.org", "uri"=>"http://incubator.staging.apache.org/projects/rocketmq.html", "bitbucket"=>nil, "codepen"=>nil, "dribbble"=>nil, "flickr"=>nil, "facebook"=>nil, "foursquare"=>nil, "github"=>"apache/incubator-rocketmq", "google_plus"=>nil, "keybase"=>nil, "instagram"=>nil, "lastfm"=>nil, "linkedin"=>nil, "pinterest"=
>nil, "soundcloud"=>nil, "stackoverflow"=>"questions/tagged/rocketmq", "steam"=>nil, "tumblr"=>nil, "twitter"=>"ApacheRocketMQ", "vine"=>nil, "weibo"=>nil, "xing"=>nil, "youtube"=>nil, "quora"=>"topic/RocketMQ"}</name><email>dev@rocketmq.incubator.apache.org</email><uri>http://incubator.staging.apache.org/projects/rocketmq.html</uri></author><summary type="html">The correct posture of submitting a PR</summary></entry><entry><title type="html">Four Methods to Feed Name Server Address List</title><link href="/rocketmq/four-methods-to-feed-name-server-address-list/" rel="alternate" type="text/html" title="Four Methods to Feed Name Server Address List" /><published>2017-02-10T00:00:00+08:00</published><updated>2017-02-10T00:00:00+08:00</updated><id>/rocketmq/four-methods-to-feed-name-server-address-list</id><content type="html
" xml:base="/rocketmq/four-methods-to-feed-name-server-address-list/"><p>In Apache RocketMQ, name servers are designed to coordinate each component of the distributed system
+and fulfill much of this responsibility through managing topic route information.</p>
+
+<p>The management, roughly speaking, consists two parts:</p>
+<ul>
+ <li>Brokers periodically renew meta data, including topics they have, which are kept in every name servers.</li>
+ <li>Name servers are serving clients, including producers, consumers and command line clients with the latest routing information.</li>
+</ul>
+
+<p>Therefore, before launching brokers and clients, we need to tell them how to reach name servers by feeding them with a name server address list.
+In Apache RocketMQ, this can be done in four ways.</p>
+
+<ol>
+ <li>
+ <p>Programmatic Way</p>
+
+ <p>For broker, we may specify <code class="highlighter-rouge">namesrvAddr=name-server-ip1:port;name-server-ip2:port</code> in broker configuration file.</p>
+
+ <p>For producers and consumers, we may feed name server address list to them as follows:</p>
+
+ <p><code class="highlighter-rouge">
+DefaultMQProducer producer = new DefaultMQProducer("please_rename_unique_group_name");
+producer.setNamesrvAddr("name-server1-ip:port;name-server2-ip:port");</code></p>
+
+ <p><code class="highlighter-rouge">
+DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("please_rename_unique_group_name");
+consumer.setNamesrvAddr("name-server1-ip:port;name-server2-ip:port");</code></p>
+
+ <p>If you use admin command line from shell, you may specify this way:
+<code class="highlighter-rouge">sh mqadmin command-name -n name-server-ip1:port;name-server-ip2:port -X OTHER-OPTION</code></p>
+
+ <p>a simple example is:
+<code class="highlighter-rouge">sh mqadmin -n localhost:9876 clusterList</code>
+assuming to query cluster info on the name server node.</p>
+
+ <p>If integrating admin tool into your own dashboard, you may
+<code class="highlighter-rouge">DefaultMQAdminExt defaultMQAdminExt = new DefaultMQAdminExt("please_rename_unique_group_name");
+ defaultMQAdminExt.setNamesrvAddr("name-server1-ip:port;name-server2-ip:port");</code></p>
+ </li>
+ <li>
+ <p>Java Options</p>
+
+ <p>Name server address list may also be fed to your application through specifying the sequel java option
+ <code class="highlighter-rouge">rocketmq.namesrv.addr</code> before launching.</p>
+ </li>
+ <li>
+ <p>Environment Variable</p>
+
+ <p>You can export <code class="highlighter-rouge">NAMESRV_ADDR</code> environment variable. Brokers and clients will examine and use its value if set.</p>
+ </li>
+ <li>
+ <p>HTTP Endpoint</p>
+
+ <p>If you do not specify name server address list using previously mentioned methods, Apache RocketMQ will access
+ the following HTTP end point to acquire and update name server address list every two minutes with initial delay of
+ ten seconds.</p>
+
+ <p>On default, the end point is:</p>
+
+ <p><code class="highlighter-rouge">http://jmenv.tbsite.net:8080/rocketmq/nsaddr</code></p>
+
+ <p>You may override <code class="highlighter-rouge">jmenv.tbsite.net</code> by this java option: <code class="highlighter-rouge">rocketmq.namesrv.domain</code>,
+ You may also override <code class="highlighter-rouge">nsaddr</code> part by this java option: <code class="highlighter-rouge">rocketmq.namesrv.domain.subgroup</code></p>
+
+ <p>If you are running Apache RocketMQ in production, this method is recommended because it gives you maximum flexibility
+ – you can dynamically add or remove name server nodes without necessity of rebooting your brokers and clients
+ according to your name servers’ system load.</p>
+ </li>
+</ol>
+
+<ul>
+ <li>
+ <p>Priority</p>
+
+ <p>Methods introduced first take precedence over the latter, namely, <br />
+ <code class="highlighter-rouge">Programmatic Way &gt; Java Options &gt; Environment Variable &gt; HTTP Endpoint</code></p>
+ </li>
+</ul></content><author><name>{"name"=>nil, "avatar"=>"/assets/images/rmq-logo.png", "bio"=>"A fast, low latency, reliable, scalable, distributed MOM.", "location"=>"Hangzhou, China", "email"=>"dev@rocketmq.incubator.apache.org", "uri"=>"http://incubator.staging.apache.org/projects/rocketmq.html", "bitbucket"=>nil, "codepen"=>nil, "dribbble"=>nil, "flickr"=>nil, "facebook"=>nil, "foursquare"=>nil, "github"=>"apache/incubator-rocketmq", "google_plus"=>nil, "keybase"=>nil, "instagram"=>nil, "lastfm"=>nil, "linkedin"=>nil, "pinterest"=>nil, "soundcloud"=>nil, "stackoverflow"=>"questions/tagged/rocketmq", "steam"=>nil, "tumblr
"=>nil, "twitter"=>"ApacheRocketMQ", "vine"=>nil, "weibo"=>nil, "xing"=>nil, "youtube"=>nil, "quora"=>"topic/RocketMQ"}</name><email>dev@rocketmq.incubator.apache.org</email><uri>http://incubator.staging.apache.org/projects/rocketmq.html</uri></author><category term="RocketMQ" /><category term="Name Server" /><summary type="html">In Apache RocketMQ, name servers are designed to coordinate each component of the distributed system and fulfill much of this responsibility through managing topic route information.</summary></entry><entry><title type="html">Release Notes - Apache RocketMQ - Version 4.0.0-incubating</title><link href="/release_notes/release-notes-4.0.0-incubating/" rel="alternate" type="text/html" title="Release Notes - Apache RocketMQ - Version 4.0.0-incubating" /><published>2017-01-24T00:00:00+08:00</published><updated>2017-01-24T00:00:00+08:00</updated><id>/release_
notes/release-notes-4.0.0-incubating</id><content type="html" xml:base="/release_notes/release-notes-4.0.0-incubating/"><p>Below is a summary of the JIRA issues addressed in the 4.0.0-incubating release of RocketMQ. For full documentation of the release, a guide to get started, please refer to <a href="/docs/quick-start/">Quick Start</a>.</p>
+
+<h2> Download the 4.0.0-incubating release
+</h2>
+
+<ul>
+ <li>Source: <a href="https://www.apache.org/dyn/closer.cgi?path=incubator/rocketmq/4.0.0-incubating/rocketmq-all-4.0.0-incubating-source-release.zip">rocketmq-all-4.0.0-incubating-source-release.zip</a> [<a href="https://www.apache.org/dist/incubator/rocketmq/4.0.0-incubating/rocketmq-all-4.0.0-incubating-source-release.zip.asc">PGP</a>] [<a href="https://www.apache.org/dist/incubator/rocketmq/4.0.0-incubating/rocketmq-all-4.0.0-incubating-source-release.zip.md5">MD5</a>] [<a href="https://www.apache.org/dist/incubator/rocketmq/4.0.0-incubating/rocketmq-all-4.0.0-incubating-source-release.zip.sha1">SHA1</a>]</li>
+ <li>Binary: <a href="https://www.apache.org/dyn/closer.cgi?path=incubator/rocketmq/4.0.0-incubating/rocketmq-all-4.0.0-incubating-bin-release.zip">rocketmq-all-4.0.0-incubating-bin-release.zip</a> [<a href="https://www.apache.org/dist/incubator/rocketmq/4.0.0-incubating/rocketmq-all-4.0.0-incubating-bin-release.zip.asc">PGP</a>] [<a href="https://www.apache.org/dist/incubator/rocketmq/4.0.0-incubating/rocketmq-all-4.0.0-incubating-bin-release.zip.md5">MD5</a>] [<a href="https://www.apache.org/dist/incubator/rocketmq/4.0.0-incubating/rocketmq-all-4.0.0-incubating-bin-release.zip.sha1">SHA1</a>]</li>
+</ul>
+
+<h2> Bug
+</h2>
+<ul>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-2">ROCKETMQ-2</a>] - Broker tests fail with &quot;Address
+ already in use&quot;
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-5">ROCKETMQ-5</a>] - Avoid creating directories in
+ UtilAll#getDiskPartitionSpaceUsedPercent()
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-19">ROCKETMQ-19</a>] - Thread-unsafe in
+ MQAdminImpl#queryMessage
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-22">ROCKETMQ-22</a>] - new funciton &#39;printWaterMark&#39;
+ in version 3.5.8(4.0.0) will cause a ClassCastException
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-25">ROCKETMQ-25</a>] - Query Msg by key: Possible
+ concurrent access to LinkedList
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-30">ROCKETMQ-30</a>] - Message Filter example has
+ incorrect method signature
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-31">ROCKETMQ-31</a>] - Deletion needed for
+ `$HOME/rmq_bk_gc.log` in `bin/mqbroker`
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-33">ROCKETMQ-33</a>] - CPU Occupy 100%
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-34">ROCKETMQ-34</a>] - Potential NPE in
+ NettyConnetManageHandler#connect
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-35">ROCKETMQ-35</a>] - Consumer client can’t persist
+ consume offset table to Broker
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-45">ROCKETMQ-45</a>] - Delete consume queue hang file
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-47">ROCKETMQ-47</a>] - Broker updates NameServer
+ address list on startup twice
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-59">ROCKETMQ-59</a>] - Charset misusage in
+ RocketMQSerializable
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-64">ROCKETMQ-64</a>] - Remove duplication code line in
+ BrokerOuterAPI.registerBroker method
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-70">ROCKETMQ-70</a>] - Duplicate methods in
+ NettyRemotingClient
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-74">ROCKETMQ-74</a>] - DataVersion equals not working
+ as expected.
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-83">ROCKETMQ-83</a>] - Fail in quickstart-sample
+ </li>
+</ul>
+
+<h2> Improvement
+</h2>
+<ul>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-8">ROCKETMQ-8</a>] - Standardize build script using
+ maven wrapper
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-11">ROCKETMQ-11</a>] - Improve concision - Reuse local
+ variable &#39;brokerAddrs&#39; in RouteInfoManager.getSystemTopicList method
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-14">ROCKETMQ-14</a>] - Remoting invoke callback shoule
+ be invoked in an executor rather than in current thread.
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-16">ROCKETMQ-16</a>] - Improve the codes of setting
+ topic.json&#39;s and subscriptionGroup.json&#39;s path
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-18">ROCKETMQ-18</a>] - Repackage com.alibaba to
+ org.apache and change maven coordinate
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-20">ROCKETMQ-20</a>] - Default &#39;consumeFromWhere&#39;
+ is inconsist with example&#39;s
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-29">ROCKETMQ-29</a>] -
+ org.apache.rocketmq.common.help.FAQUrl refers to docs in Chinese
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-32">ROCKETMQ-32</a>] - Improve concision - Reuse local
+ variable &#39;brokerAddrs&#39; in RouteInfoManager.getSystemTopicList method
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-37">ROCKETMQ-37</a>] - Log output information is not
+ accurate
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-43">ROCKETMQ-43</a>] - code style file didn&#39;t match
+ check-style in typecast
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-50">ROCKETMQ-50</a>] - Polish unit tests for RocketMQ
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-60">ROCKETMQ-60</a>] - Checklist review for
+ 4.0.0-incubating release
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-69">ROCKETMQ-69</a>] - Add link to RocketMQ web page
+ into README.md
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-85">ROCKETMQ-85</a>] - Polish README file and remove
+ all the 3rd party links in it.
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-87">ROCKETMQ-87</a>] - Polish the LICENSE and NOTICE
+ files to match all the dependencies
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-1">ROCKETMQ-1</a>] - Update build and clean up ip for
+ 4.0.0-incubating
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-38">ROCKETMQ-38</a>] - Polish unit tests for
+ rocketmq-remoting
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-51">ROCKETMQ-51</a>] - Polish unit tests for
+ rocketmq-broker
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-52">ROCKETMQ-52</a>] - Polish unit tests for
+ rocketmq-client
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-53">ROCKETMQ-53</a>] - Polish unit tests for
+ rocketmq-commons
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-54">ROCKETMQ-54</a>] - Polish unit tests for
+ rocketmq-namesrv
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-56">ROCKETMQ-56</a>] - Polish unit tests for
+ rocketmq-store
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-57">ROCKETMQ-57</a>] - Polish unit tests for
+ rocketmq-tools
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-58">ROCKETMQ-58</a>] - Add integration test for
+ RocketMQ
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-62">ROCKETMQ-62</a>] - Polish Maven assembly release
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-3">ROCKETMQ-3</a>] - Clean up the unit test of rocketmq
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-13">ROCKETMQ-13</a>] - Wrong log level for
+ AcceptSocketService termination
+ </li>
+ <li>[<a href="https://issues.apache.org/jira/browse/ROCKETMQ-9">ROCKETMQ-9</a>] - Errors in rocketmq-store module
+ </li>
+</ul></content><author><name>{"name"=>nil, "avatar"=>"/assets/images/rmq-logo.png", "bio"=>"A fast, low latency, reliable, scalable, distributed MOM.", "location"=>"Hangzhou, China", "email"=>"dev@rocketmq.incubator.apache.org", "uri"=>"http://incubator.staging.apache.org/projects/rocketmq.html", "bitbucket"=>nil, "codepen"=>nil, "dribbble"=>nil, "flickr"=>nil, "facebook"=>nil, "foursquare"=>nil, "github"=>"apache/incubator-rocketmq", "google_plus"=>nil, "keybase"=>nil, "instagram"=>nil, "lastfm"=>nil, "linkedin"=>nil, "pinterest"=>nil, "soundcloud"=>nil, "stackoverflow"=>"questions/tagged/rocketmq", "steam"=>nil, "tumblr
"=>nil, "twitter"=>"ApacheRocketMQ", "vine"=>nil, "weibo"=>nil, "xing"=>nil, "youtube"=>nil, "quora"=>"topic/RocketMQ"}</name><email>dev@rocketmq.incubator.apache.org</email><uri>http://incubator.staging.apache.org/projects/rocketmq.html</uri></author><category term="Release_Notes" /><category term="RocketMQ" /><category term="Version" /><summary type="html">Below is a summary of the JIRA issues addressed in the 4.0.0-incubating release of RocketMQ. For full documentation of the release, a guide to get started, please refer to Quick Start.</summary></entry><entry><title type="html">Launch RocketMQ Code Marathon</title><link href="/activity/launch-rocketmq-code-marathon/" rel="alternate" type="text/html" title="Launch RocketMQ Code Marathon" /><published>2017-01-05T00:00:00+08:00</published><updated>2017-01-05T00:00:00+08:00</updated><id>/activity/launch-rocketmq-code-marathon</i
d><content type="html" xml:base="/activity/launch-rocketmq-code-marathon/"><p><img src="/assets/images/blog/banner.jpg" alt="Banner" /></p>
+<h1 id="rocketmq-code-marathon-">ROCKETMQ CODE MARATHON <a href="/assets/attachment/launch-rocketmq-code-marathon.pdf"><i class="fa fa-link"></i></a></h1>
+<h5 id="january-5th-2017">January 5th 2017</h5>
+
+<h2 id="objective">Objective:</h2>
+<ol>
+ <li>Foster Community</li>
+ <li>Prosper Ecology</li>
+ <li>Incubate Committers</li>
+</ol>
+
+<h2 id="output">Output:</h2>
+<ol>
+ <li>1~3 Milestone Releases Per Project</li>
+</ol>
+
+<h2 id="rewards">Rewards:</h2>
+<ol>
+ <li>Two Potential Committers Per Project</li>
+ <li>Free Offers to Active Participants for On-Site Meetup</li>
+ <li>PMC Memberships for Qualified Committers</li>
+</ol>
+
+<h2 id="projects">PROJECTS</h2>
+
+<h3 id="rocketmq-console">RocketMQ-Console</h3>
+<ol>
+ <li>Brand New UI</li>
+ <li>I18n Support</li>
+ <li><a href="https://projects.spring.io/spring-boot/">Spring Boot</a> + <a href="http://getbootstrap.com/">Bootstrap</a> Recommended</li>
+ <li>Join by Creating Pull Requests against <a href="https://github.com/apache/incubator-rocketmq-externals/tree/master/rocketmq-console">RocketMQ Console Repository</a></li>
+</ol>
+
+<h3 id="rocketmq-jms">RocketMQ-JMS</h3>
+<ol>
+ <li>Supporting JMS 2.0 Protocol</li>
+ <li>Rich Documentation and Good Test Cases Coverage</li>
+ <li>Join by Creating Pull Requests against <a href="https://github.com/apache/incubator-rocketmq-externals/tree/master/rocketmq-jms">RocketMQ JMS Repository</a></li>
+</ol>
+
+<h3 id="rocketmq-flume">RocketMQ-Flume</h3>
+<ol>
+ <li>Supporting Latest <a href="http://flume.apache.org/">Flume</a></li>
+ <li>Rich Documentation and Good Test Cases Coverage</li>
+ <li>Join by Creating Pull Requests against <a href="https://github.com/apache/incubator-rocketmq-externals/tree/master/rocketmq-flume">RocketMQ Flume Repository</a></li>
+</ol></content><author><name>{"name"=>nil, "avatar"=>"/assets/images/rmq-logo.png", "bio"=>"A fast, low latency, reliable, scalable, distributed MOM.", "location"=>"Hangzhou, China", "email"=>"dev@rocketmq.incubator.apache.org", "uri"=>"http://incubator.staging.apache.org/projects/rocketmq.html", "bitbucket"=>nil, "codepen"=>nil, "dribbble"=>nil, "flickr"=>nil, "facebook"=>nil, "foursquare"=>nil, "github"=>"apache/incubator-rocketmq", "google_plus"=>nil, "keybase"=>nil, "instagram"=>nil, "lastfm"=>nil, "linkedin"=>nil, "pinterest"=>nil, "soundcloud"=>nil, "stackoverflow"=>"questions/tagged/rocketmq", "steam"=>nil, "tumblr
"=>nil, "twitter"=>"ApacheRocketMQ", "vine"=>nil, "weibo"=>nil, "xing"=>nil, "youtube"=>nil, "quora"=>"topic/RocketMQ"}</name><email>dev@rocketmq.incubator.apache.org</email><uri>http://incubator.staging.apache.org/projects/rocketmq.html</uri></author><category term="Activity" /><category term="Code" /><category term="Marathon" /><summary type="html">ROCKETMQ CODE MARATHON January 5th 2017</summary></entry><entry><title type="html">Mastering Component Compatible Dependency</title><link href="/maven/mastering-component-compatible-dependency/" rel="alternate" type="text/html" title="Mastering Component Compatible Dependency" /><published>2016-12-23T00:00:00+08:00</published><updated>2016-12-23T00:00:00+08:00</updated><id>/maven/mastering-component-compatible-dependency</id><content type="html" xml:base="/maven/mastering-component-compatible-dependency/"><p>This article mainl
y includes three parts.at first,I will introduce compatibility principle(more details see <a href="http://blog.csdn.net/fengjia10/article/details/7799227">here</a>) briefly.followed by a detailed elaborating about Java component compatible dependency,including the interface-oriented programming,single component signature protection,single component compatibility protection and multi-component compatibility compile time checking.Finally is the review and prospect,especially about <strong>Dependency Mediator</strong> project.</p>
+
+<aside class="sidebar__right">
+<nav class="toc">
+ <header><h4 class="nav__title"><i class="fa fa-file-text"></i> On This Page</h4></header>
+<ul class="toc__menu" id="markdown-toc">
+ <li><a href="#compatibility" id="markdown-toc-compatibility">Compatibility</a></li>
+ <li><a href="#component-compatible-dependency" id="markdown-toc-component-compatible-dependency">Component Compatible Dependency</a> <ul>
+ <li><a href="#interface-oriented-programming" id="markdown-toc-interface-oriented-programming">Interface-oriented programming</a></li>
+ <li><a href="#single-component-signature-protection" id="markdown-toc-single-component-signature-protection">Single component signature protection</a></li>
+ <li><a href="#single-component-compatibility-protection" id="markdown-toc-single-component-compatibility-protection">Single component compatibility protection</a></li>
+ <li><a href="#multi-component-compatibility-compile-time-checking" id="markdown-toc-multi-component-compatibility-compile-time-checking">Multi-component compatibility compile time checking</a></li>
+ </ul>
+ </li>
+ <li><a href="#summary" id="markdown-toc-summary">Summary</a></li>
+</ul>
+
+ </nav>
+</aside>
+
+<h1 id="compatibility">Compatibility</h1>
+
+<p>what is compatibility？it is also the key to understanding the compatible dependency.Compatibility, often catch our eyes through two forms,<strong>binary compatibility</strong>,that means they can run the same executable code, typically machine code for a general purpose computer CPU.within the framework of Release-to-Release Binary Compatibility in SOM (Forman, Conner, Danforth, and Raper, Proceedings of OOPSLA ‘95), Java programming language binaries are binary compatible under all relevant transformations that the authors identify (with some caveats with respect to the addition of instance variables). here is a list of some important binary compatible changes that the Java programming language supports:</p>
+
+<ul>
+ <li>Reimplementing existing methods, constructors, and initializers to improve performance.</li>
+ <li>Changing methods or constructors to return values on inputs for which they previously either threw exceptions that normally should not occur or failed by going into an infinite loop or causing a deadlock.</li>
+ <li>Adding new fields, methods, or constructors to an existing class or interface.</li>
+ <li>Deleting private fields, methods, or constructors of a class.</li>
+ <li>When an entire package is updated, deleting default (package-only) access fields, methods, or constructors of classes and interfaces in the package.</li>
+ <li>Reordering the fields, methods, or constructors in an existing type declaration.</li>
+ <li>Moving a method upward in the class hierarchy.</li>
+ <li>Reordering the list of direct superinterfaces of a class or interface.</li>
+ <li>Inserting new class or interface types in the type hierarchy.</li>
+</ul>
+
+<p>Generally,java language is <strong>upwards binary-compatible</strong> with previous version,such as Java SE 6 is upwards binary-compatible with J2SE 5.0 except for some minor incompatibilities.You can get details from <a href="http://www.oracle.com/technetwork/java/javase/compatibility-137541.html#binary">here</a>.</p>
+
+<p>Another compatibility form,we call it <strong>source compatibility</strong>,meaning that recompilation is necessary.Java language does not support downward source compatibility. Such as if source files use new language features or Java SE platform APIs, they will not be usable with an earlier version of the Java platform. Usually it will throw similar error like this:</p>
+
+<div class="language-java highlighter-rouge"><pre class="highlight"><code><span class="n">java</span><span class="o">.</span><span class="na">lang</span><span class="o">.</span><span class="na">UnsupportedClassVersionError</span><span class="o">:</span> <span class="n">com</span><span class="o">.</span><span class="na">alibaba</span><span class="o">.</span><span class="na">mq</span><span class="o">.</span><span class="na">core</span><span class="o">.</span><span class="na">MessageConsumer</span> <span class="o">:</span>
+ <span class="n">Unsupported</span> <span class="n">major</span><span class="o">.</span><span class="na">minor</span> <span class="n">version</span> <span class="mf">51.0</span>
+ <span class="n">at</span> <span class="n">java</span><span class="o">.</span><span class="na">lang</span><span class="o">.</span><span class="na">ClassLoader</span><span class="o">.</span><span class="na">defineClass1</span><span class="o">(</span><span class="n">Native</span> <span class="n">Method</span><span class="o">)</span>
+ <span class="n">at</span> <span class="n">java</span><span class="o">.</span><span class="na">lang</span><span class="o">.</span><span class="na">ClassLoader</span><span class="o">.</span><span class="na">defineClassCond</span><span class="o">(</span><span class="n">Unknown</span> <span class="n">Source</span><span class="o">)</span>
+</code></pre>
+</div>
+
+<p>Java language source compatibility policy is as follows,except for any incompatibilities listed further below:</p>
+
+<ul>
+ <li>Maintenance releases (such as 1.7.25, 1.7.26) do not introduce any new language features or APIs. They will maintain source-compatibility with each other.</li>
+ <li>Functionality releases and major releases (such as 1.4.0,5.0,6.0,7.0,8.0) maintain upwards but not downwards source-compatibility.</li>
+</ul>
+
+<p>Let’s sum up before going on:</p>
+
+<ul>
+ <li>Document those incompatibility cases as much as possible, even some rare circumstances and corner cases.</li>
+ <li>Recommend developer to provide facilities that alert developers to the impact of changes on pre-existing binaries that cannot be recompiled.</li>
+ <li>Generally speaking,Binary Compatibility problems may occur in the following situations:</li>
+ <li><strong>Replacing the old with the new</strong>,such as the Java platform Profiling Architecture in the Java SE6,JVMDI was removed and JVMPI was disabled in Java SE 6.</li>
+ <li><strong>Combinatorial resolution</strong>,such as Non class files have been moved from rt.jar in Java SE 6.if -Xbootclasspath:<path to="" rt.jar=""> is specified,and request any resource files will fail since these resources now reside in a different jar file called resources.jar.</path></li>
+ <li><strong>Behavior change</strong>,such as Java SE 6 will throw an OverlappingFileLockException,if the application attempts to lock the overlapping region other instances of FileChannel that has been locked, in order to realize the backward compatibility, it provides disableSystemWideOverlappingFileLockCheck system properties. again, also in Java SE 6, jar will preserve file modification dates and times during extract, through the sun.tools.jar.useExtractionTime=true to achieve backward compatibility.</li>
+ <li><strong>Structure change</strong>,this is also the key problem to solve in <strong>Dependency Mediator</strong> project. generally speaking,modification and deletion belonging to incompatible operations.and more attentions must be paid in the RPC service maintenance, more detailed description,please refer to an <a href="http://blog.csdn.net/fengjia10/article/details/7799227">article</a> I wrote before. also you can read the the thirteenth chapter of Java language specification.</li>
+</ul>
+
+<h1 id="component-compatible-dependency">Component Compatible Dependency</h1>
+
+<p>This article don’t talk about <strong>dependency analysis</strong> and <strong>dependency decoupling</strong>,if you care these topics,please read <a href="http://java.dzone.com/articles/dependency-analysis-and-1">Dependency Analysis and the Modularisation of Java Programs</a>.highly recommending you try to dive into open source project <a href="http://xplrarc.massey.ac.nz/">Architecture Explorer</a>,through bcel technology,analyzing and measuring component’s dependency relationship.but in my opinion,<a href="http://clarkware.com/software/JDepend.html">Jdepend</a> was surely the most distinguished tool in dependency analysis and dependency decoupling area.it traverses Java class file directories and generates design quality metrics for each Java package,also allows you to automatically measure the quality of a design in terms of its extensibility, reusability, and maintainability
to manage package dependencies effectively.</p>
+
+<p>Let’s return,ask yourself，have you ever been disturbed by the following problems?</p>
+
+<ul>
+ <li>Your service depend a volatile service,volatile means your service depending neither an abstract class nor a interface,this class update at irregular intervals,you often encountered errors such as <strong>NoSuchMethodError</strong>,<strong>NoSuchFieldError</strong> and <strong>NoClassDefFoundError</strong> etc.</li>
+ <li>You are developing a new feature,but this feature can not backward compatible with previous version,
+what should you do ? How do you give a incompatible list in your release report.</li>
+ <li>Java language library is a superb collection of beautiful things,how do you make a rational dependency exclusion and effective mediate various dependency problems when developing.</li>
+</ul>
+
+<p>It is the time to introduce the key idea - <strong>Mediating Components Compatible Dependency</strong>.Specifically,it includs the following basic principles:</p>
+
+<ul>
+ <li>Interface-oriented programming</li>
+ <li>Single component signature protection</li>
+ <li>Single component compatibility protection</li>
+ <li>Multi-component compatibility compile time checking</li>
+</ul>
+
+<h2 id="interface-oriented-programming">Interface-oriented programming</h2>
+
+<p>Interface-oriented programming,It’s easier said than done.I will cite SLF4J design philosophy explain this principle.</p>
+
+<p>Differing from commons logging,SLF4J use <strong>static binder technology</strong> so as to avoid notorious <a href="http://articles.qos.ch/classloader.html">classloader problem</a>,every concrete log implementation must
+have a class named StaticLoggerBinder and implementing SLF4J spi LoggerFactoryBinder.thus you just depend SLF4J api,not concerned about underlying implementation.some people may asking,why choose SLF4J not commons logging，I can also depend commons logging api but not concret implementation？it’s not performance but classloader problem.JCL discovery process relies on classloader hacks to find the logging framework at runtime but this mechanism leads to numerous problems including unexpected behavior,hard to debug classloading problems resulting in increased complexity.This is nicely captured by Ceki (the author of Log4J, SLF4J and Logback) in Think again before adopting the commons-logging API (which also mentions memory leaks problems observed with JCL).and this is why SLF4J, which uses static bindings, has been created. Let’s see.how to find the concrete realizations in SLF4J:</p>
+
+<div class="language-java highlighter-rouge"><pre class="highlight"><code><span class="c1">// We need to use the name of the StaticLoggerBinder class, but we can't reference</span>
+<span class="c1">// the class itself.</span>
+<span class="kd">private</span> <span class="kd">static</span> <span class="n">String</span> <span class="n">STATIC_LOGGER_BINDER_PATH</span> <span class="o">=</span> <span class="s">"org/slf4j/impl/StaticLoggerBinder.class"</span><span class="o">;</span>
+ <span class="cm">/**
+ * It is LoggerFactory's responsibility to track version changes and manage
+ * the compatibility list.
+ * It is assumed that all versions in the 1.6 are mutually compatible.
+ */</span>
+<span class="kd">static</span> <span class="kd">private</span> <span class="kd">final</span> <span class="n">String</span><span class="o">[]</span> <span class="n">API_COMPATIBILITY_LIST</span> <span class="o">=</span> <span class="k">new</span> <span class="n">String</span><span class="o">[]{</span><span class="s">"1.6"</span><span class="o">,</span> <span class="s">"1.7"</span><span class="o">};</span>
+
+<span class="c1">// private constructor prevents instantiation</span>
+<span class="kd">private</span> <span class="nf">LoggerFactory</span><span class="o">()</span> <span class="o">{}</span>
+<span class="kd">private</span> <span class="kd">final</span> <span class="kd">static</span> <span class="kt">void</span> <span class="nf">versionSanityCheck</span><span class="o">()</span> <span class="o">{</span>
+ <span class="k">try</span> <span class="o">{</span>
+ <span class="n">String</span> <span class="n">requested</span> <span class="o">=</span> <span class="n">StaticLoggerBinder</span><span class="o">.</span><span class="na">REQUESTED_API_VERSION</span><span class="o">;</span>
+ <span class="kt">boolean</span> <span class="n">match</span> <span class="o">=</span> <span class="kc">false</span><span class="o">;</span>
+ <span class="k">for</span> <span class="o">(</span><span class="kt">int</span> <span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="o">;</span> <span class="n">i</span> <span class="o">&lt;</span> <span class="n">API_COMPATIBILITY_LIST</span><span class="o">.</span><span class="na">length</span><span class="o">;</span> <span class="n">i</span><span class="o">++)</span> <span class="o">{</span>
+ <span class="k">if</span> <span class="o">(</span><span class="n">requested</span><span class="o">.</span><span class="na">startsWith</span><span class="o">(</span><span class="n">API_COMPATIBILITY_LIST</span><span class="o">[</span><span class="n">i</span><span class="o">]))</span> <span class="o">{</span>
+ <span class="n">match</span> <span class="o">=</span> <span class="kc">true</span><span class="o">;</span>
+ <span class="o">}</span>
+ <span class="o">}</span>
+ <span class="k">if</span> <span class="o">(!</span><span class="n">match</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">Util</span><span class="o">.</span><span class="na">report</span><span class="o">(</span><span class="s">"The requested version "</span> <span class="o">+</span> <span class="n">requested</span>
+ <span class="o">+</span> <span class="s">" by your slf4j binding is not compatible with "</span>
+ <span class="o">+</span> <span class="n">Arrays</span><span class="o">.</span><span class="na">asList</span><span class="o">(</span><span class="n">API_COMPATIBILITY_LIST</span><span class="o">).</span><span class="na">toString</span><span class="o">());</span>
+ <span class="n">Util</span><span class="o">.</span><span class="na">report</span><span class="o">(</span><span class="s">"See "</span> <span class="o">+</span> <span class="n">VERSION_MISMATCH</span> <span class="o">+</span> <span class="s">" for further details."</span><span class="o">);</span>
+ <span class="o">}</span>
+<span class="o">}</span> <span class="k">catch</span> <span class="o">(</span><span class="n">java</span><span class="o">.</span><span class="na">lang</span><span class="o">.</span><span class="na">NoSuchFieldError</span> <span class="n">nsfe</span><span class="o">)</span> <span class="o">{</span>
+ <span class="c1">// given our large user base and SLF4J's commitment to backward</span>
+ <span class="c1">// compatibility, we cannot cry here. Only for implementations</span>
+ <span class="c1">// which willingly declare a REQUESTED_API_VERSION field do we</span>
+ <span class="c1">// emit compatibility warnings.</span>
+<span class="o">}</span> <span class="k">catch</span> <span class="o">(</span><span class="n">Throwable</span> <span class="n">e</span><span class="o">)</span> <span class="o">{</span>
+ <span class="c1">// we should never reach here</span>
+ <span class="n">Util</span><span class="o">.</span><span class="na">report</span><span class="o">(</span><span class="s">"Unexpected problem occured during version sanity check"</span><span class="o">,</span> <span class="n">e</span><span class="o">);</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+</code></pre>
+</div>
+
+<p>you can use these skills at your library.just Let others depend on your interface package,detecting certain implementation statically.</p>
+
+<p>If you have developed an old version library,naming it as 2.x.x.next version,you hope to refactor some implementations,how to process multi-version compatibility?here is a skill from maven dependency plugin:</p>
+
+<div class="language-java highlighter-rouge"><pre class="highlight"><code><span class="n">String</span> <span class="n">hint</span> <span class="o">=</span> <span class="n">isMaven31</span><span class="o">()</span> <span class="o">?</span> <span class="s">"maven31"</span> <span class="o">:</span> <span class="n">isMaven2x</span><span class="o">()</span> <span class="o">?</span> <span class="s">"maven2"</span> <span class="o">:</span> <span class="s">"maven3"</span><span class="o">;</span>
+
+<span class="cm">/**
+* Check the current Maven version to see if it's Maven 2.x.
+*/</span>
+<span class="kd">protected</span> <span class="kd">static</span> <span class="kt">boolean</span> <span class="nf">isMaven2x</span><span class="o">()</span>
+<span class="o">{</span>
+ <span class="k">return</span> <span class="o">!</span><span class="n">canFindCoreClass</span><span class="o">(</span> <span class="s">"org.apache.maven.project.DependencyResolutionRequest"</span> <span class="o">);</span> <span class="c1">// Maven 3 specific</span>
+<span class="o">}</span>
+
+<span class="cm">/**
+* Check the current Maven version to see if it's Maven 3.1.
+*/</span>
+<span class="kd">protected</span> <span class="kd">static</span> <span class="kt">boolean</span> <span class="nf">isMaven31</span><span class="o">()</span>
+<span class="o">{</span>
+ <span class="k">return</span> <span class="nf">canFindCoreClass</span><span class="o">(</span> <span class="s">"org.eclipse.aether.artifact.Artifact"</span> <span class="o">);</span> <span class="c1">// Maven 3.1 specific</span>
+<span class="o">}</span>
+&l
<TRUNCATED>