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| <a href="/docs/2.9.0/distributed-computing/fault-tolerance" |
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| <li><a href="/docs/2.9.0//machine-learning/ensemble-methods/random-forest" class=''>Random Forest</a></li> |
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| <a href="/docs/2.9.0/thin-clients/cpp-thin-client" |
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| >C++ Thin Client</a> |
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| <a href="/docs/2.9.0/thin-clients/python-thin-client" |
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| class='' |
| >Python Thin Client</a> |
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| <a href="/docs/2.9.0/thin-clients/php-thin-client" |
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| >PHP Thin Client</a> |
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| <li><a href="/docs/2.9.0//binary-client-protocol/binary-client-protocol" class=''>Binary Client Protocol</a></li> |
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| <li><a href="/docs/2.9.0//binary-client-protocol/data-format" class=''>Data Format</a></li> |
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| <li><a href="/docs/2.9.0//binary-client-protocol/key-value-queries" class=''>Key-Value Queries</a></li> |
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| <li><a href="/docs/2.9.0//binary-client-protocol/sql-and-scan-queries" class=''>SQL and Scan Queries</a></li> |
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| <li><a href="/docs/2.9.0//binary-client-protocol/binary-type-metadata" class=''>Binary Types Metadata</a></li> |
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| <li><a href="/docs/2.9.0//binary-client-protocol/cache-configuration" class=''>Cache Configuration</a></li> |
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| <a href="/docs/2.9.0/SQL/ODBC/odbc-driver" |
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| <a href="/docs/2.9.0/SQL/ODBC/connection-string-dsn" |
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| class='' |
| >Connection String and DSN</a> |
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| <li> |
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| <a href="/docs/2.9.0/SQL/ODBC/querying-modifying-data" |
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| class='' |
| >Querying and Modifying Data</a> |
| |
| </li> |
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| <li> |
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| <a href="/docs/2.9.0/SQL/ODBC/specification" |
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| class='' |
| >Specification</a> |
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| <li> |
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| <a href="/docs/2.9.0/SQL/ODBC/data-types" |
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| class='' |
| >Data Types</a> |
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| </li> |
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| <li> |
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| <article data-swiftype-index='true'> |
| <a class='edit-link' href="https://github.com/apache/ignite/tree/IGNITE-7595/docs/_docs/distributed-computing/map-reduce.adoc" target="_blank">Edit</a> |
| |
| <h1>MapReduce API</h1> |
| |
| <div class="sect1"> |
| <h2 id="overview">Overview</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>Ignite provides an API for performing simplified MapReduce operations. |
| The MapReduce pattern is based on the assumption that the task that you |
| want to execute can be split into multiple jobs (the mapping phase), |
| with each job executed separately. The results produced by each job are |
| aggregated into the final results (the reducing phase).</p> |
| </div> |
| <div class="paragraph"> |
| <p>In a distributed system such as Ignite, the jobs are distributed between |
| the nodes according to the preconfigured <a href="/docs/2.9.0/distributed-computing/load-balancing">load balancing strategy</a> and the results are aggregated on the node that submitted the task.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The MapReduce pattern is provided by the <code>ComputeTask</code> interface.</p> |
| </div> |
| <div class="admonitionblock note"> |
| <table> |
| <tr> |
| <td class="icon"> |
| <div class="title">Note</div> |
| </td> |
| <td class="content"> |
| <div class="paragraph"> |
| <p>Use <code>ComputeTask</code> only when you need fine-grained control over the |
| job-to-node mapping, or custom fail-over logic. For all other cases you |
| should use <a href="/docs/2.9.0/distributed-computing/distributed-computing#executing-an-igniteclosure">simple closures</a>.</p> |
| </div> |
| </td> |
| </tr> |
| </table> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="understanding-compute-task-interface">Understanding Compute Task Interface</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>The <code>ComputeTask</code> interface provides a way to implement custom map and reduce logic. The interface has three methods: <code>map(…​)</code>, <code>result()</code>, and <code>reduce()</code>.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The <code>map()</code> method should be implemented to create the compute jobs based on the input parameter and map them to worker nodes. The method receives the collection of cluster nodes on which the task is to be run and the task’s input parameter. The method returns a map with jobs as keys and mapped worker nodes as values. The jobs are then sent to the mapped nodes and executed there.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The <code>result()</code> method is called after completion of each job and returns an instance of <code>ComputeJobResultPolicy</code> indicating how to proceed with the task. The method receives the results of the job and the list of all the job results received so far. The method may return one of the following values:</p> |
| </div> |
| <div class="ulist"> |
| <ul> |
| <li> |
| <p><code>WAIT</code> - wait for all remaining jobs to complete (if any);</p> |
| </li> |
| <li> |
| <p><code>REDUCE</code> - immediately move to the reduce step, discarding all the remaining jobs and results not yet received;</p> |
| </li> |
| <li> |
| <p><code>FAILOVER</code> - failover the job to another node (see <a href="/docs/2.9.0/distributed-computing/fault-tolerance">Fault Tolerance</a>).</p> |
| </li> |
| </ul> |
| </div> |
| <div class="paragraph"> |
| <p>The <code>reduce()</code> method is called during the reduce step, when all the jobs have completed (or the <code>result()</code> method returned the <code>REDUCE</code> result policy for a particular job). The method receives a list with all completed results and returns the final result of the computation.</p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="executing-a-compute-task">Executing a Compute Task</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>To execute a compute task, call the <code>IgniteCompute.execute(…​)</code> method and pass the input parameter for the compute task as the last argument.</p> |
| </div> |
| <code-tabs><code-tab data-tab='Java'><div class="listingblock"> |
| <div class="content"> |
| <pre class="rouge highlight"><code data-lang="java"><span class="nc">Ignite</span> <span class="n">ignite</span> <span class="o">=</span> <span class="nc">Ignition</span><span class="o">.</span><span class="na">start</span><span class="o">();</span> |
| |
| <span class="nc">IgniteCompute</span> <span class="n">compute</span> <span class="o">=</span> <span class="n">ignite</span><span class="o">.</span><span class="na">compute</span><span class="o">();</span> |
| |
| <span class="kt">int</span> <span class="n">count</span> <span class="o">=</span> <span class="n">compute</span><span class="o">.</span><span class="na">execute</span><span class="o">(</span><span class="k">new</span> <span class="nc">CharacterCountTask</span><span class="o">(),</span> <span class="s">"Hello Grid Enabled World!"</span><span class="o">);</span></code></pre> |
| </div> |
| </div></code-tab><code-tab data-tab='C#/.NET'><div class="listingblock"> |
| <div class="content"> |
| <pre class="rouge highlight"><code data-lang="csharp"><span class="k">class</span> <span class="nc">CharCountComputeJob</span> <span class="p">:</span> <span class="n">IComputeJob</span><span class="p"><</span><span class="kt">int</span><span class="p">></span> |
| <span class="p">{</span> |
| <span class="k">private</span> <span class="k">readonly</span> <span class="kt">string</span> <span class="n">_arg</span><span class="p">;</span> |
| |
| <span class="k">public</span> <span class="nf">CharCountComputeJob</span><span class="p">(</span><span class="kt">string</span> <span class="n">arg</span><span class="p">)</span> |
| <span class="p">{</span> |
| <span class="n">Console</span><span class="p">.</span><span class="nf">WriteLine</span><span class="p">(</span><span class="s">">>> Printing '"</span> <span class="p">+</span> <span class="n">arg</span> <span class="p">+</span> <span class="s">"' from compute job."</span><span class="p">);</span> |
| <span class="k">this</span><span class="p">.</span><span class="n">_arg</span> <span class="p">=</span> <span class="n">arg</span><span class="p">;</span> |
| <span class="p">}</span> |
| |
| <span class="k">public</span> <span class="kt">int</span> <span class="nf">Execute</span><span class="p">()</span> |
| <span class="p">{</span> |
| <span class="k">return</span> <span class="n">_arg</span><span class="p">.</span><span class="n">Length</span><span class="p">;</span> |
| <span class="p">}</span> |
| |
| <span class="k">public</span> <span class="k">void</span> <span class="nf">Cancel</span><span class="p">()</span> |
| <span class="p">{</span> |
| <span class="k">throw</span> <span class="k">new</span> <span class="n">System</span><span class="p">.</span><span class="nf">NotImplementedException</span><span class="p">();</span> |
| <span class="p">}</span> |
| <span class="p">}</span> |
| |
| |
| <span class="k">class</span> <span class="nc">CharCountTask</span> <span class="p">:</span> <span class="n">IComputeTask</span><span class="p"><</span><span class="kt">string</span><span class="p">,</span> <span class="kt">int</span><span class="p">,</span> <span class="kt">int</span><span class="p">></span> |
| <span class="p">{</span> |
| <span class="k">public</span> <span class="n">IDictionary</span><span class="p"><</span><span class="n">IComputeJob</span><span class="p"><</span><span class="kt">int</span><span class="p">>,</span> <span class="n">IClusterNode</span><span class="p">></span> <span class="nf">Map</span><span class="p">(</span><span class="n">IList</span><span class="p"><</span><span class="n">IClusterNode</span><span class="p">></span> <span class="n">subgrid</span><span class="p">,</span> <span class="kt">string</span> <span class="n">arg</span><span class="p">)</span> |
| <span class="p">{</span> |
| <span class="kt">var</span> <span class="n">map</span> <span class="p">=</span> <span class="k">new</span> <span class="n">Dictionary</span><span class="p"><</span><span class="n">IComputeJob</span><span class="p"><</span><span class="kt">int</span><span class="p">>,</span> <span class="n">IClusterNode</span><span class="p">>();</span> |
| <span class="k">using</span> <span class="p">(</span><span class="kt">var</span> <span class="n">enumerator</span> <span class="p">=</span> <span class="n">subgrid</span><span class="p">.</span><span class="nf">GetEnumerator</span><span class="p">())</span> |
| <span class="p">{</span> |
| <span class="k">foreach</span> <span class="p">(</span><span class="kt">var</span> <span class="n">s</span> <span class="k">in</span> <span class="n">arg</span><span class="p">.</span><span class="nf">Split</span><span class="p">(</span><span class="s">" "</span><span class="p">))</span> |
| <span class="p">{</span> |
| <span class="k">if</span> <span class="p">(!</span><span class="n">enumerator</span><span class="p">.</span><span class="nf">MoveNext</span><span class="p">())</span> |
| <span class="p">{</span> |
| <span class="n">enumerator</span><span class="p">.</span><span class="nf">Reset</span><span class="p">();</span> |
| <span class="n">enumerator</span><span class="p">.</span><span class="nf">MoveNext</span><span class="p">();</span> |
| <span class="p">}</span> |
| |
| <span class="n">map</span><span class="p">.</span><span class="nf">Add</span><span class="p">(</span><span class="k">new</span> <span class="nf">CharCountComputeJob</span><span class="p">(</span><span class="n">s</span><span class="p">),</span> <span class="n">enumerator</span><span class="p">.</span><span class="n">Current</span><span class="p">);</span> |
| <span class="p">}</span> |
| <span class="p">}</span> |
| |
| <span class="k">return</span> <span class="n">map</span><span class="p">;</span> |
| <span class="p">}</span> |
| |
| <span class="k">public</span> <span class="n">ComputeJobResultPolicy</span> <span class="nf">OnResult</span><span class="p">(</span><span class="n">IComputeJobResult</span><span class="p"><</span><span class="kt">int</span><span class="p">></span> <span class="n">res</span><span class="p">,</span> <span class="n">IList</span><span class="p"><</span><span class="n">IComputeJobResult</span><span class="p"><</span><span class="kt">int</span><span class="p">>></span> <span class="n">rcvd</span><span class="p">)</span> |
| <span class="p">{</span> |
| <span class="c1">// If there is no exception, wait for all job results.</span> |
| <span class="k">return</span> <span class="n">res</span><span class="p">.</span><span class="n">Exception</span> <span class="p">!=</span> <span class="k">null</span> <span class="p">?</span> <span class="n">ComputeJobResultPolicy</span><span class="p">.</span><span class="n">Failover</span> <span class="p">:</span> <span class="n">ComputeJobResultPolicy</span><span class="p">.</span><span class="n">Wait</span><span class="p">;</span> |
| <span class="p">}</span> |
| |
| <span class="k">public</span> <span class="kt">int</span> <span class="nf">Reduce</span><span class="p">(</span><span class="n">IList</span><span class="p"><</span><span class="n">IComputeJobResult</span><span class="p"><</span><span class="kt">int</span><span class="p">>></span> <span class="n">results</span><span class="p">)</span> |
| <span class="p">{</span> |
| <span class="k">return</span> <span class="n">results</span><span class="p">.</span><span class="nf">Select</span><span class="p">(</span><span class="n">res</span> <span class="p">=></span> <span class="n">res</span><span class="p">.</span><span class="n">Data</span><span class="p">).</span><span class="nf">Sum</span><span class="p">();</span> |
| <span class="p">}</span> |
| <span class="p">}</span> |
| |
| <span class="k">public</span> <span class="k">static</span> <span class="k">void</span> <span class="nf">MapReduceComputeJobDemo</span><span class="p">()</span> |
| <span class="p">{</span> |
| <span class="kt">var</span> <span class="n">ignite</span> <span class="p">=</span> <span class="n">Ignition</span><span class="p">.</span><span class="nf">Start</span><span class="p">(</span><span class="k">new</span> <span class="n">IgniteConfiguration</span> |
| <span class="p">{</span> |
| <span class="n">DiscoverySpi</span> <span class="p">=</span> <span class="k">new</span> <span class="n">TcpDiscoverySpi</span> |
| <span class="p">{</span> |
| <span class="n">LocalPort</span> <span class="p">=</span> <span class="m">48500</span><span class="p">,</span> |
| <span class="n">LocalPortRange</span> <span class="p">=</span> <span class="m">20</span><span class="p">,</span> |
| <span class="n">IpFinder</span> <span class="p">=</span> <span class="k">new</span> <span class="n">TcpDiscoveryStaticIpFinder</span> |
| <span class="p">{</span> |
| <span class="n">Endpoints</span> <span class="p">=</span> <span class="k">new</span><span class="p">[]</span> |
| <span class="p">{</span> |
| <span class="s">"127.0.0.1:48500..48520"</span> |
| <span class="p">}</span> |
| <span class="p">}</span> |
| <span class="p">}</span> |
| <span class="p">});</span> |
| |
| <span class="kt">var</span> <span class="n">compute</span> <span class="p">=</span> <span class="n">ignite</span><span class="p">.</span><span class="nf">GetCompute</span><span class="p">();</span> |
| |
| <span class="kt">var</span> <span class="n">res</span> <span class="p">=</span> <span class="n">compute</span><span class="p">.</span><span class="nf">Execute</span><span class="p">(</span><span class="k">new</span> <span class="nf">CharCountTask</span><span class="p">(),</span> <span class="s">"Hello Grid Please Count Chars In These Words"</span><span class="p">);</span> |
| |
| <span class="n">Console</span><span class="p">.</span><span class="nf">WriteLine</span><span class="p">(</span><span class="s">"res="</span> <span class="p">+</span> <span class="n">res</span><span class="p">);</span> |
| <span class="p">}</span></code></pre> |
| </div> |
| </div></code-tab><code-tab data-tab='C++' data-unavailable='true'><div class="listingblock"> |
| <div class="content"> |
| <pre class="rouge highlight"><code>This API is not presently available for C++.</code></pre> |
| </div> |
| </div></code-tab></code-tabs> |
| <div class="paragraph"> |
| <p>You can limit the execution of jobs to a subset of nodes by using a <a href="/docs/2.9.0/distributed-computing/cluster-groups">cluster group</a>.</p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="handling-job-failures">Handling Job Failures</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>If a node crashes or becomes unavailable during a task execution, all jobs scheduled for the node are automatically sent to another available node (due to the built-in failover mechanism). However, if a job throws an exception, you can treat the job as failed and fail it over to another node for re-execution. To do this, return <code>FAILOVER</code> in the <code>result(…​)</code> method:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="rouge highlight"><code data-lang="java"><span class="nd">@Override</span> |
| <span class="kd">public</span> <span class="nc">ComputeJobResultPolicy</span> <span class="nf">result</span><span class="o">(</span><span class="nc">ComputeJobResult</span> <span class="n">res</span><span class="o">,</span> <span class="nc">List</span><span class="o"><</span><span class="nc">ComputeJobResult</span><span class="o">></span> <span class="n">rcvd</span><span class="o">)</span> <span class="o">{</span> |
| <span class="nc">IgniteException</span> <span class="n">err</span> <span class="o">=</span> <span class="n">res</span><span class="o">.</span><span class="na">getException</span><span class="o">();</span> |
| |
| <span class="k">if</span> <span class="o">(</span><span class="n">err</span> <span class="o">!=</span> <span class="kc">null</span><span class="o">)</span> |
| <span class="k">return</span> <span class="nc">ComputeJobResultPolicy</span><span class="o">.</span><span class="na">FAILOVER</span><span class="o">;</span> |
| |
| <span class="c1">// If there is no exception, wait for all job results.</span> |
| <span class="k">return</span> <span class="nc">ComputeJobResultPolicy</span><span class="o">.</span><span class="na">WAIT</span><span class="o">;</span> |
| <span class="o">}</span></code></pre> |
| </div> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="compute-task-adapters">Compute Task Adapters</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>There are several helper classes that provide most commonly used implementations of the <code>result(…​)</code> and <code>map(…​)</code> methods.</p> |
| </div> |
| <div class="ulist"> |
| <ul> |
| <li> |
| <p><code>ComputeTaskAdapter</code> — This class implements the <code>result()</code> method to return the <code>FAILOVER</code> policy if a job throws an exception and the <code>WAIT</code> policy otherwise. It means that this implementation will wait for all jobs to finish with a result.</p> |
| </li> |
| <li> |
| <p><code>ComputeTaskSplitAdapter</code> — This class extends <code>ComputeTaskAdapter</code> and implements the <code>map(…​)</code> method to automatically assign jobs to nodes. It introduces a new <code>split(…​)</code> method that implements the logic of producing jobs based on the input data.</p> |
| </li> |
| </ul> |
| </div> |
| <div class="paragraph"> |
| <p>See <a href="https://github.com/apache/ignite/tree/master/modules/core/src/main/java/org/apache/ignite/compute/ComputeTaskSplitAdapter.java" target="_blank" rel="noopener">ComputeTaskSplitAdapter.java</a> and <a href="https://github.com/apache/ignite/tree/master/modules/core/src/main/java/org/apache/ignite/compute/ComputeTaskAdapter.java" target="_blank" rel="noopener">ComputeTaskAdapter.java</a> for details.</p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="distributed-task-session">Distributed Task Session</h2> |
| <div class="sectionbody"> |
| <div class="admonitionblock note"> |
| <table> |
| <tr> |
| <td class="icon"> |
| <div class="title">Note</div> |
| </td> |
| <td class="content"> |
| Not available in .NET/C#/C++. |
| </td> |
| </tr> |
| </table> |
| </div> |
| <div class="paragraph"> |
| <p>For each task, Ignite creates a distributed session that holds information about the task and is visible to the task itself and to all jobs spawned by it. You can use this session to share attributes between jobs. Attributes can be assigned before or during job execution and become visible to other jobs in the same order in which they were set.</p> |
| </div> |
| <code-tabs><code-tab data-tab='Java'><div class="listingblock"> |
| <div class="content"> |
| <pre class="rouge highlight"><code data-lang="java"><span class="nd">@ComputeTaskSessionFullSupport</span> |
| <span class="kd">private</span> <span class="kd">static</span> <span class="kd">class</span> <span class="nc">TaskSessionAttributesTask</span> <span class="kd">extends</span> <span class="nc">ComputeTaskSplitAdapter</span><span class="o"><</span><span class="nc">Object</span><span class="o">,</span> <span class="nc">Object</span><span class="o">></span> <span class="o">{</span> |
| |
| <span class="nd">@Override</span> |
| <span class="kd">protected</span> <span class="nc">Collection</span><span class="o"><?</span> <span class="kd">extends</span> <span class="nc">ComputeJob</span><span class="o">></span> <span class="nf">split</span><span class="o">(</span><span class="kt">int</span> <span class="n">gridSize</span><span class="o">,</span> <span class="nc">Object</span> <span class="n">arg</span><span class="o">)</span> <span class="o">{</span> |
| <span class="nc">Collection</span><span class="o"><</span><span class="nc">ComputeJob</span><span class="o">></span> <span class="n">jobs</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">LinkedList</span><span class="o"><>();</span> |
| |
| <span class="c1">// Generate jobs by number of nodes in the grid.</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"><</span> <span class="n">gridSize</span><span class="o">;</span> <span class="n">i</span><span class="o">++)</span> <span class="o">{</span> |
| <span class="n">jobs</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="k">new</span> <span class="nc">ComputeJobAdapter</span><span class="o">(</span><span class="n">arg</span><span class="o">)</span> <span class="o">{</span> |
| <span class="c1">// Auto-injected task session.</span> |
| <span class="nd">@TaskSessionResource</span> |
| <span class="kd">private</span> <span class="nc">ComputeTaskSession</span> <span class="n">ses</span><span class="o">;</span> |
| |
| <span class="c1">// Auto-injected job context.</span> |
| <span class="nd">@JobContextResource</span> |
| <span class="kd">private</span> <span class="nc">ComputeJobContext</span> <span class="n">jobCtx</span><span class="o">;</span> |
| |
| <span class="nd">@Override</span> |
| <span class="kd">public</span> <span class="nc">Object</span> <span class="nf">execute</span><span class="o">()</span> <span class="o">{</span> |
| <span class="c1">// Perform STEP1.</span> |
| <span class="c1">// ...</span> |
| |
| <span class="c1">// Tell other jobs that STEP1 is complete.</span> |
| <span class="n">ses</span><span class="o">.</span><span class="na">setAttribute</span><span class="o">(</span><span class="n">jobCtx</span><span class="o">.</span><span class="na">getJobId</span><span class="o">(),</span> <span class="s">"STEP1"</span><span class="o">);</span> |
| |
| <span class="c1">// Wait for other jobs to complete STEP1.</span> |
| <span class="k">for</span> <span class="o">(</span><span class="nc">ComputeJobSibling</span> <span class="n">sibling</span> <span class="o">:</span> <span class="n">ses</span><span class="o">.</span><span class="na">getJobSiblings</span><span class="o">())</span> |
| <span class="k">try</span> <span class="o">{</span> |
| <span class="n">ses</span><span class="o">.</span><span class="na">waitForAttribute</span><span class="o">(</span><span class="n">sibling</span><span class="o">.</span><span class="na">getJobId</span><span class="o">(),</span> <span class="s">"STEP1"</span><span class="o">,</span> <span class="mi">0</span><span class="o">);</span> |
| <span class="o">}</span> <span class="k">catch</span> <span class="o">(</span><span class="nc">InterruptedException</span> <span class="n">e</span><span class="o">)</span> <span class="o">{</span> |
| <span class="n">e</span><span class="o">.</span><span class="na">printStackTrace</span><span class="o">();</span> |
| <span class="o">}</span> |
| |
| <span class="c1">// Move on to STEP2.</span> |
| <span class="c1">// ...</span> |
| |
| <span class="k">return</span> <span class="o">...</span> |
| |
| <span class="o">}</span> |
| <span class="o">});</span> |
| <span class="o">}</span> |
| <span class="k">return</span> <span class="n">jobs</span><span class="o">;</span> |
| <span class="o">}</span> |
| |
| <span class="nd">@Override</span> |
| <span class="kd">public</span> <span class="nc">Object</span> <span class="nf">reduce</span><span class="o">(</span><span class="nc">List</span><span class="o"><</span><span class="nc">ComputeJobResult</span><span class="o">></span> <span class="n">results</span><span class="o">)</span> <span class="o">{</span> |
| <span class="c1">// No-op.</span> |
| <span class="k">return</span> <span class="kc">null</span><span class="o">;</span> |
| <span class="o">}</span> |
| |
| <span class="o">}</span></code></pre> |
| </div> |
| </div></code-tab><code-tab data-tab='C#/.NET' data-unavailable='true'><div class="listingblock"> |
| <div class="content"> |
| <pre class="rouge highlight"><code>This API is not presently available for C#/.NET.</code></pre> |
| </div> |
| </div></code-tab><code-tab data-tab='C++' data-unavailable='true'><div class="listingblock"> |
| <div class="content"> |
| <pre class="rouge highlight"><code>This API is not presently available for C++.</code></pre> |
| </div> |
| </div></code-tab></code-tabs> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="compute-task-example">Compute Task Example</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>The following example demonstrates a simple character counting application that splits a given string into words and calculates the length of each word in an individual job. The jobs are distributed to all cluster nodes.</p> |
| </div> |
| <code-tabs><code-tab data-tab='Java'><div class="listingblock"> |
| <div class="content"> |
| <pre class="rouge highlight"><code data-lang="java"><span class="kd">public</span> <span class="kd">class</span> <span class="nc">ComputeTaskExample</span> <span class="o">{</span> |
| <span class="kd">public</span> <span class="kd">static</span> <span class="kd">class</span> <span class="nc">CharacterCountTask</span> <span class="kd">extends</span> <span class="nc">ComputeTaskSplitAdapter</span><span class="o"><</span><span class="nc">String</span><span class="o">,</span> <span class="nc">Integer</span><span class="o">></span> <span class="o">{</span> |
| <span class="c1">// 1. Splits the received string into words</span> |
| <span class="c1">// 2. Creates a child job for each word</span> |
| <span class="c1">// 3. Sends the jobs to other nodes for processing.</span> |
| <span class="nd">@Override</span> |
| <span class="kd">public</span> <span class="nc">List</span><span class="o"><</span><span class="nc">ComputeJob</span><span class="o">></span> <span class="nf">split</span><span class="o">(</span><span class="kt">int</span> <span class="n">gridSize</span><span class="o">,</span> <span class="nc">String</span> <span class="n">arg</span><span class="o">)</span> <span class="o">{</span> |
| <span class="nc">String</span><span class="o">[]</span> <span class="n">words</span> <span class="o">=</span> <span class="n">arg</span><span class="o">.</span><span class="na">split</span><span class="o">(</span><span class="s">" "</span><span class="o">);</span> |
| |
| <span class="nc">List</span><span class="o"><</span><span class="nc">ComputeJob</span><span class="o">></span> <span class="n">jobs</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">ArrayList</span><span class="o"><>(</span><span class="n">words</span><span class="o">.</span><span class="na">length</span><span class="o">);</span> |
| |
| <span class="k">for</span> <span class="o">(</span><span class="kd">final</span> <span class="nc">String</span> <span class="n">word</span> <span class="o">:</span> <span class="n">words</span><span class="o">)</span> <span class="o">{</span> |
| <span class="n">jobs</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="k">new</span> <span class="nc">ComputeJobAdapter</span><span class="o">()</span> <span class="o">{</span> |
| <span class="nd">@Override</span> |
| <span class="kd">public</span> <span class="nc">Object</span> <span class="nf">execute</span><span class="o">()</span> <span class="o">{</span> |
| <span class="nc">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="s">">>> Printing '"</span> <span class="o">+</span> <span class="n">word</span> <span class="o">+</span> <span class="s">"' on from compute job."</span><span class="o">);</span> |
| |
| <span class="c1">// Return the number of letters in the word.</span> |
| <span class="k">return</span> <span class="n">word</span><span class="o">.</span><span class="na">length</span><span class="o">();</span> |
| <span class="o">}</span> |
| <span class="o">});</span> |
| <span class="o">}</span> |
| |
| <span class="k">return</span> <span class="n">jobs</span><span class="o">;</span> |
| <span class="o">}</span> |
| |
| <span class="nd">@Override</span> |
| <span class="kd">public</span> <span class="nc">Integer</span> <span class="nf">reduce</span><span class="o">(</span><span class="nc">List</span><span class="o"><</span><span class="nc">ComputeJobResult</span><span class="o">></span> <span class="n">results</span><span class="o">)</span> <span class="o">{</span> |
| <span class="kt">int</span> <span class="n">sum</span> <span class="o">=</span> <span class="mi">0</span><span class="o">;</span> |
| |
| <span class="k">for</span> <span class="o">(</span><span class="nc">ComputeJobResult</span> <span class="n">res</span> <span class="o">:</span> <span class="n">results</span><span class="o">)</span> |
| <span class="n">sum</span> <span class="o">+=</span> <span class="n">res</span><span class="o">.<</span><span class="nc">Integer</span><span class="o">></span><span class="n">getData</span><span class="o">();</span> |
| |
| <span class="k">return</span> <span class="n">sum</span><span class="o">;</span> |
| <span class="o">}</span> |
| <span class="o">}</span> |
| |
| <span class="kd">public</span> <span class="kd">static</span> <span class="kt">void</span> <span class="nf">main</span><span class="o">(</span><span class="nc">String</span><span class="o">[]</span> <span class="n">args</span><span class="o">)</span> <span class="o">{</span> |
| |
| <span class="nc">Ignite</span> <span class="n">ignite</span> <span class="o">=</span> <span class="nc">Ignition</span><span class="o">.</span><span class="na">start</span><span class="o">();</span> |
| |
| <span class="nc">IgniteCompute</span> <span class="n">compute</span> <span class="o">=</span> <span class="n">ignite</span><span class="o">.</span><span class="na">compute</span><span class="o">();</span> |
| |
| <span class="c1">// Execute the task on the cluster and wait for its completion.</span> |
| <span class="kt">int</span> <span class="n">cnt</span> <span class="o">=</span> <span class="n">compute</span><span class="o">.</span><span class="na">execute</span><span class="o">(</span><span class="nc">CharacterCountTask</span><span class="o">.</span><span class="na">class</span><span class="o">,</span> <span class="s">"Hello Grid Enabled World!"</span><span class="o">);</span> |
| |
| <span class="nc">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="s">">>> Total number of characters in the phrase is '"</span> <span class="o">+</span> <span class="n">cnt</span> <span class="o">+</span> <span class="s">"'."</span><span class="o">);</span> |
| <span class="o">}</span> |
| <span class="o">}</span></code></pre> |
| </div> |
| </div></code-tab><code-tab data-tab='C#/.NET'><div class="listingblock"> |
| <div class="content"> |
| <pre class="rouge highlight"><code data-lang="csharp"><span class="k">class</span> <span class="nc">CharCountComputeJob</span> <span class="p">:</span> <span class="n">IComputeJob</span><span class="p"><</span><span class="kt">int</span><span class="p">></span> |
| <span class="p">{</span> |
| <span class="k">private</span> <span class="k">readonly</span> <span class="kt">string</span> <span class="n">_arg</span><span class="p">;</span> |
| |
| <span class="k">public</span> <span class="nf">CharCountComputeJob</span><span class="p">(</span><span class="kt">string</span> <span class="n">arg</span><span class="p">)</span> |
| <span class="p">{</span> |
| <span class="n">Console</span><span class="p">.</span><span class="nf">WriteLine</span><span class="p">(</span><span class="s">">>> Printing '"</span> <span class="p">+</span> <span class="n">arg</span> <span class="p">+</span> <span class="s">"' from compute job."</span><span class="p">);</span> |
| <span class="k">this</span><span class="p">.</span><span class="n">_arg</span> <span class="p">=</span> <span class="n">arg</span><span class="p">;</span> |
| <span class="p">}</span> |
| |
| <span class="k">public</span> <span class="kt">int</span> <span class="nf">Execute</span><span class="p">()</span> |
| <span class="p">{</span> |
| <span class="k">return</span> <span class="n">_arg</span><span class="p">.</span><span class="n">Length</span><span class="p">;</span> |
| <span class="p">}</span> |
| |
| <span class="k">public</span> <span class="k">void</span> <span class="nf">Cancel</span><span class="p">()</span> |
| <span class="p">{</span> |
| <span class="k">throw</span> <span class="k">new</span> <span class="n">System</span><span class="p">.</span><span class="nf">NotImplementedException</span><span class="p">();</span> |
| <span class="p">}</span> |
| <span class="p">}</span> |
| |
| <span class="k">public</span> <span class="k">class</span> <span class="nc">ComputeTaskExample</span> |
| <span class="p">{</span> |
| <span class="k">private</span> <span class="k">class</span> <span class="nc">CharacterCountTask</span> <span class="p">:</span> <span class="n">ComputeTaskSplitAdapter</span><span class="p"><</span><span class="kt">string</span><span class="p">,</span> <span class="kt">int</span><span class="p">,</span> <span class="kt">int</span><span class="p">></span> |
| <span class="p">{</span> |
| <span class="k">public</span> <span class="k">override</span> <span class="kt">int</span> <span class="nf">Reduce</span><span class="p">(</span><span class="n">IList</span><span class="p"><</span><span class="n">IComputeJobResult</span><span class="p"><</span><span class="kt">int</span><span class="p">>></span> <span class="n">results</span><span class="p">)</span> |
| <span class="p">{</span> |
| <span class="k">return</span> <span class="n">results</span><span class="p">.</span><span class="nf">Select</span><span class="p">(</span><span class="n">res</span> <span class="p">=></span> <span class="n">res</span><span class="p">.</span><span class="n">Data</span><span class="p">).</span><span class="nf">Sum</span><span class="p">();</span> |
| <span class="p">}</span> |
| |
| <span class="k">protected</span> <span class="k">override</span> <span class="n">ICollection</span><span class="p"><</span><span class="n">IComputeJob</span><span class="p"><</span><span class="kt">int</span><span class="p">>></span> <span class="nf">Split</span><span class="p">(</span><span class="kt">int</span> <span class="n">gridSize</span><span class="p">,</span> <span class="kt">string</span> <span class="n">arg</span><span class="p">)</span> |
| <span class="p">{</span> |
| <span class="k">return</span> <span class="n">arg</span><span class="p">.</span><span class="nf">Split</span><span class="p">(</span><span class="s">" "</span><span class="p">)</span> |
| <span class="p">.</span><span class="nf">Select</span><span class="p">(</span><span class="n">word</span> <span class="p">=></span> <span class="k">new</span> <span class="nf">CharCountComputeJob</span><span class="p">(</span><span class="n">word</span><span class="p">))</span> |
| <span class="p">.</span><span class="n">Cast</span><span class="p"><</span><span class="n">IComputeJob</span><span class="p"><</span><span class="kt">int</span><span class="p">>>()</span> |
| <span class="p">.</span><span class="nf">ToList</span><span class="p">();</span> |
| <span class="p">}</span> |
| <span class="p">}</span> |
| |
| <span class="k">public</span> <span class="k">static</span> <span class="k">void</span> <span class="nf">RunComputeTaskExample</span><span class="p">()</span> |
| <span class="p">{</span> |
| <span class="kt">var</span> <span class="n">ignite</span> <span class="p">=</span> <span class="n">Ignition</span><span class="p">.</span><span class="nf">Start</span><span class="p">(</span><span class="k">new</span> <span class="n">IgniteConfiguration</span> |
| <span class="p">{</span> |
| <span class="n">DiscoverySpi</span> <span class="p">=</span> <span class="k">new</span> <span class="n">TcpDiscoverySpi</span> |
| <span class="p">{</span> |
| <span class="n">LocalPort</span> <span class="p">=</span> <span class="m">48500</span><span class="p">,</span> |
| <span class="n">LocalPortRange</span> <span class="p">=</span> <span class="m">20</span><span class="p">,</span> |
| <span class="n">IpFinder</span> <span class="p">=</span> <span class="k">new</span> <span class="n">TcpDiscoveryStaticIpFinder</span> |
| <span class="p">{</span> |
| <span class="n">Endpoints</span> <span class="p">=</span> <span class="k">new</span><span class="p">[]</span> |
| <span class="p">{</span> |
| <span class="s">"127.0.0.1:48500..48520"</span> |
| <span class="p">}</span> |
| <span class="p">}</span> |
| <span class="p">}</span> |
| <span class="p">});</span> |
| |
| <span class="kt">var</span> <span class="n">cnt</span> <span class="p">=</span> <span class="n">ignite</span><span class="p">.</span><span class="nf">GetCompute</span><span class="p">().</span><span class="nf">Execute</span><span class="p">(</span><span class="k">new</span> <span class="nf">CharacterCountTask</span><span class="p">(),</span> <span class="s">"Hello Grid Enabled World!"</span><span class="p">);</span> |
| <span class="n">Console</span><span class="p">.</span><span class="nf">WriteLine</span><span class="p">(</span><span class="s">">>> Total number of characters in the phrase is '"</span> <span class="p">+</span> <span class="n">cnt</span> <span class="p">+</span> <span class="s">"'."</span><span class="p">);</span> |
| <span class="p">}</span> |
| <span class="p">}</span></code></pre> |
| </div> |
| </div></code-tab><code-tab data-tab='C++' data-unavailable='true'><div class="listingblock"> |
| <div class="content"> |
| <pre class="rouge highlight"><code>This API is not presently available for C++.</code></pre> |
| </div> |
| </div></code-tab></code-tabs> |
| </div> |
| </div> |
| <div class="copyright"> |
| © 2020 The Apache Software Foundation.<br/> |
| Apache, Apache Ignite, the Apache feather and the Apache Ignite logo are either registered trademarks or trademarks of The Apache Software Foundation. |
| |
| </div> |
| |
| </article> |
| <nav class="right-nav" data-swiftype-index='false'> |
| <ul class="sectlevel1"> |
| <li><a href="#overview">Overview</a></li> |
| <li><a href="#understanding-compute-task-interface">Understanding Compute Task Interface</a></li> |
| <li><a href="#executing-a-compute-task">Executing a Compute Task</a></li> |
| <li><a href="#handling-job-failures">Handling Job Failures</a></li> |
| <li><a href="#compute-task-adapters">Compute Task Adapters</a></li> |
| <li><a href="#distributed-task-session">Distributed Task Session</a></li> |
| <li><a href="#compute-task-example">Compute Task Example</a></li> |
| </ul> |
| |
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| visible: 'always' |
| }; |
| </script> |
| <!-- load google fonts async --> |
| <script type="text/javascript"> |
| WebFontConfig = { |
| google: { families: [ 'Open+Sans:300,400,600,700&display=swap' ] } |
| }; |
| (function() { |
| var wf = document.createElement('script'); |
| wf.src = 'https://ajax.googleapis.com/ajax/libs/webfont/1/webfont.js'; |
| wf.type = 'text/javascript'; |
| wf.async = 'true'; |
| var s = document.getElementsByTagName('script')[0]; |
| s.parentNode.insertBefore(wf, s); |
| })(); </script> |
| <script src="https://cdn.jsdelivr.net/npm/docsearch.js@2/dist/cdn/docsearch.min.js"></script> |
| <script> |
| docsearch({ |
| // Your apiKey and indexName will be given to you once |
| // we create your config |
| apiKey: '3eee686c0ebe39eff3baeb18c56fa5f8', |
| indexName: 'apache_ignite', |
| // Replace inputSelector with a CSS selector |
| // matching your search input |
| inputSelector: '#search-input', |
| // algoliaOptions: { 'facetFilters': ["version:$VERSION"] }, |
| |
| // Set debug to true to inspect the dropdown |
| debug: false, |
| }); |
| </script> |
| <script type='module' src='/assets/js/index.js?1600286557' async crossorigin></script> |
| <script type='module' src='/assets/js/versioning.js?1600286557' async crossorigin></script> |
| </body> |
| |
| </html> |
