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<article data-swiftype-index='true'>
<a class='edit-link' href="https://github.com/apache/ignite/tree/IGNITE-7595/docs/_docs/collocated-computations.adoc" target="_blank">Edit</a>
<h1>Colocating Computations with Data</h1>
<div id="preamble">
<div class="sectionbody">
<div class="paragraph">
<p>Colocated computation is type of distributed data processing wherein the computational task you want to perform over a specific data set is sent to the nodes where the required data is located and only the results of the computations are sent back. This approach minimizes data transfer between nodes and can significantly reduce the task execution time.</p>
</div>
<div class="paragraph">
<p>Ignite provides several ways to perform colocated computations, all of which use the affinity function to determine the location of the data.</p>
</div>
<div class="paragraph">
<p>The compute interface provides the <code>affinityCall(&#8230;&#8203;)</code> and <code>affinityRun(&#8230;&#8203;)</code> methods that colocate a task with data either by key or by partition.</p>
</div>
<div class="admonitionblock important">
<table>
<tr>
<td class="icon">
<div class="title">Important</div>
</td>
<td class="content">
<div class="paragraph">
<p>The <code>affinityCall(&#8230;&#8203;)</code> and <code>affinityRun(&#8230;&#8203;)</code> methods guarantee that the data for the given key or partition is present on the target node for the duration of the task.</p>
</div>
</td>
</tr>
</table>
</div>
<div class="admonitionblock important">
<table>
<tr>
<td class="icon">
<div class="title">Important</div>
</td>
<td class="content">
<div class="paragraph">
<p>The class definitions of the task to be executed on remote nodes must be available on the nodes.
You can ensure this in two ways:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>Add the classes to the classpath of the nodes;</p>
</li>
<li>
<p>Enable <a href="/docs/latest/peer-class-loading">peer class loading</a>.</p>
</li>
</ul>
</div>
</td>
</tr>
</table>
</div>
</div>
</div>
<div class="sect1">
<h2 id="colocating-by-key">Colocating by Key</h2>
<div class="sectionbody">
<div class="paragraph">
<p>To send a computational task to the node where a given key is located, use the following methods:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><code>IgniteCompute.affinityCall(String cacheName, Object key, IgniteCallable&lt;R&gt; job)</code></p>
</li>
<li>
<p><code>IgniteCompute.affinityRun(String cacheName, Object key, IgniteRunnable job)</code></p>
</li>
</ul>
</div>
<div class="paragraph">
<p>Ignite calls the configured affinity function to determine the location of the given key.</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">IgniteCache</span><span class="o">&lt;</span><span class="nc">Integer</span><span class="o">,</span> <span class="nc">String</span><span class="o">&gt;</span> <span class="n">cache</span> <span class="o">=</span> <span class="n">ignite</span><span class="o">.</span><span class="na">cache</span><span class="o">(</span><span class="s">"myCache"</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">key</span> <span class="o">=</span> <span class="mi">1</span><span class="o">;</span>
<span class="c1">// This closure will execute on the remote node where</span>
<span class="c1">// data for the given 'key' is located.</span>
<span class="n">compute</span><span class="o">.</span><span class="na">affinityRun</span><span class="o">(</span><span class="s">"myCache"</span><span class="o">,</span> <span class="n">key</span><span class="o">,</span> <span class="o">()</span> <span class="o">-&gt;</span> <span class="o">{</span>
<span class="c1">// Peek is a local memory lookup.</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">"Co-located [key= "</span> <span class="o">+</span> <span class="n">key</span> <span class="o">+</span> <span class="s">", value= "</span> <span class="o">+</span> <span class="n">cache</span><span class="o">.</span><span class="na">localPeek</span><span class="o">(</span><span class="n">key</span><span class="o">)</span> <span class="o">+</span> <span class="sc">']'</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">MyComputeAction</span> <span class="p">:</span> <span class="n">IComputeAction</span>
<span class="p">{</span>
<span class="p">[</span><span class="n">InstanceResource</span><span class="p">]</span> <span class="k">private</span> <span class="k">readonly</span> <span class="n">IIgnite</span> <span class="n">_ignite</span><span class="p">;</span>
<span class="k">public</span> <span class="kt">int</span> <span class="n">Key</span> <span class="p">{</span> <span class="k">get</span><span class="p">;</span> <span class="k">set</span><span class="p">;</span> <span class="p">}</span>
<span class="k">public</span> <span class="k">void</span> <span class="nf">Invoke</span><span class="p">()</span>
<span class="p">{</span>
<span class="kt">var</span> <span class="n">cache</span> <span class="p">=</span> <span class="n">_ignite</span><span class="p">.</span><span class="n">GetCache</span><span class="p">&lt;</span><span class="kt">int</span><span class="p">,</span> <span class="kt">string</span><span class="p">&gt;(</span><span class="s">"myCache"</span><span class="p">);</span>
<span class="c1">// Peek is a local memory lookup</span>
<span class="n">Console</span><span class="p">.</span><span class="nf">WriteLine</span><span class="p">(</span><span class="s">"Co-located [key= "</span> <span class="p">+</span> <span class="n">Key</span> <span class="p">+</span> <span class="s">", value= "</span> <span class="p">+</span> <span class="n">cache</span><span class="p">.</span><span class="nf">LocalPeek</span><span class="p">(</span><span class="n">Key</span><span class="p">)</span> <span class="p">+</span> <span class="sc">']'</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">AffinityRunDemo</span><span class="p">()</span>
<span class="p">{</span>
<span class="kt">var</span> <span class="n">cfg</span> <span class="p">=</span> <span class="k">new</span> <span class="nf">IgniteConfiguration</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="n">cfg</span><span class="p">);</span>
<span class="kt">var</span> <span class="n">cache</span> <span class="p">=</span> <span class="n">ignite</span><span class="p">.</span><span class="n">GetOrCreateCache</span><span class="p">&lt;</span><span class="kt">int</span><span class="p">,</span> <span class="kt">string</span><span class="p">&gt;(</span><span class="s">"myCache"</span><span class="p">);</span>
<span class="n">cache</span><span class="p">.</span><span class="nf">Put</span><span class="p">(</span><span class="m">0</span><span class="p">,</span> <span class="s">"foo"</span><span class="p">);</span>
<span class="n">cache</span><span class="p">.</span><span class="nf">Put</span><span class="p">(</span><span class="m">1</span><span class="p">,</span> <span class="s">"bar"</span><span class="p">);</span>
<span class="n">cache</span><span class="p">.</span><span class="nf">Put</span><span class="p">(</span><span class="m">2</span><span class="p">,</span> <span class="s">"baz"</span><span class="p">);</span>
<span class="kt">var</span> <span class="n">keyCnt</span> <span class="p">=</span> <span class="m">3</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="k">for</span> <span class="p">(</span><span class="kt">var</span> <span class="n">key</span> <span class="p">=</span> <span class="m">0</span><span class="p">;</span> <span class="n">key</span> <span class="p">&lt;</span> <span class="n">keyCnt</span><span class="p">;</span> <span class="n">key</span><span class="p">++)</span>
<span class="p">{</span>
<span class="c1">// This closure will execute on the remote node where</span>
<span class="c1">// data for the given 'key' is located.</span>
<span class="n">compute</span><span class="p">.</span><span class="nf">AffinityRun</span><span class="p">(</span><span class="s">"myCache"</span><span class="p">,</span> <span class="n">key</span><span class="p">,</span> <span class="k">new</span> <span class="n">MyComputeAction</span> <span class="p">{</span><span class="n">Key</span> <span class="p">=</span> <span class="n">key</span><span class="p">});</span>
<span class="p">}</span>
<span class="p">}</span></code></pre>
</div>
</div></code-tab><code-tab data-tab='C++'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="cpp"><span class="cm">/*
* Function class.
*/</span>
<span class="k">struct</span> <span class="nc">FuncAffinityRun</span> <span class="o">:</span> <span class="n">compute</span><span class="o">::</span><span class="n">ComputeFunc</span><span class="o">&lt;</span><span class="kt">void</span><span class="o">&gt;</span>
<span class="p">{</span>
<span class="cm">/*
* Default constructor.
*/</span>
<span class="n">FuncAffinityRun</span><span class="p">()</span>
<span class="p">{</span>
<span class="c1">// No-op.</span>
<span class="p">}</span>
<span class="cm">/*
* Parameterized constructor.
*/</span>
<span class="n">FuncAffinityRun</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="n">cacheName</span><span class="p">,</span> <span class="kt">int32_t</span> <span class="n">key</span><span class="p">)</span> <span class="o">:</span>
<span class="n">cacheName</span><span class="p">(</span><span class="n">cacheName</span><span class="p">),</span> <span class="n">key</span><span class="p">(</span><span class="n">key</span><span class="p">)</span>
<span class="p">{</span>
<span class="c1">// No-op.</span>
<span class="p">}</span>
<span class="cm">/**
* Callback.
*/</span>
<span class="k">virtual</span> <span class="kt">void</span> <span class="n">Call</span><span class="p">()</span>
<span class="p">{</span>
<span class="n">Ignite</span><span class="o">&amp;</span> <span class="n">node</span> <span class="o">=</span> <span class="n">GetIgnite</span><span class="p">();</span>
<span class="n">Cache</span><span class="o">&lt;</span><span class="kt">int32_t</span><span class="p">,</span> <span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="o">&gt;</span> <span class="n">cache</span> <span class="o">=</span> <span class="n">node</span><span class="p">.</span><span class="n">GetCache</span><span class="o">&lt;</span><span class="kt">int32_t</span><span class="p">,</span> <span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="o">&gt;</span><span class="p">(</span><span class="n">cacheName</span><span class="p">.</span><span class="n">c_str</span><span class="p">());</span>
<span class="c1">// Peek is a local memory lookup.</span>
<span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o">&lt;&lt;</span> <span class="s">"Co-located [key= "</span> <span class="o">&lt;&lt;</span> <span class="n">key</span> <span class="o">&lt;&lt;</span> <span class="s">", value= "</span> <span class="o">&lt;&lt;</span> <span class="n">cache</span><span class="p">.</span><span class="n">LocalPeek</span><span class="p">(</span><span class="n">key</span><span class="p">,</span> <span class="n">CachePeekMode</span><span class="o">::</span><span class="n">ALL</span><span class="p">)</span> <span class="o">&lt;&lt;</span> <span class="s">"]"</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
<span class="p">}</span>
<span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="n">cacheName</span><span class="p">;</span>
<span class="kt">int32_t</span> <span class="n">key</span><span class="p">;</span>
<span class="p">};</span>
<span class="cm">/**
* Binary type structure. Defines a set of functions required for type to be serialized and deserialized.
*/</span>
<span class="k">namespace</span> <span class="n">ignite</span>
<span class="p">{</span>
<span class="k">namespace</span> <span class="n">binary</span>
<span class="p">{</span>
<span class="k">template</span><span class="o">&lt;</span><span class="p">&gt;</span>
<span class="k">struct</span> <span class="nc">BinaryType</span><span class="o">&lt;</span><span class="n">FuncAffinityRun</span><span class="o">&gt;</span>
<span class="p">{</span>
<span class="k">static</span> <span class="kt">int32_t</span> <span class="n">GetTypeId</span><span class="p">()</span>
<span class="p">{</span>
<span class="k">return</span> <span class="n">GetBinaryStringHashCode</span><span class="p">(</span><span class="s">"FuncAffinityRun"</span><span class="p">);</span>
<span class="p">}</span>
<span class="k">static</span> <span class="kt">void</span> <span class="n">GetTypeName</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="o">&amp;</span> <span class="n">dst</span><span class="p">)</span>
<span class="p">{</span>
<span class="n">dst</span> <span class="o">=</span> <span class="s">"FuncAffinityRun"</span><span class="p">;</span>
<span class="p">}</span>
<span class="k">static</span> <span class="kt">int32_t</span> <span class="n">GetFieldId</span><span class="p">(</span><span class="k">const</span> <span class="kt">char</span><span class="o">*</span> <span class="n">name</span><span class="p">)</span>
<span class="p">{</span>
<span class="k">return</span> <span class="n">GetBinaryStringHashCode</span><span class="p">(</span><span class="n">name</span><span class="p">);</span>
<span class="p">}</span>
<span class="k">static</span> <span class="kt">int32_t</span> <span class="n">GetHashCode</span><span class="p">(</span><span class="k">const</span> <span class="n">FuncAffinityRun</span><span class="o">&amp;</span> <span class="n">obj</span><span class="p">)</span>
<span class="p">{</span>
<span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
<span class="p">}</span>
<span class="k">static</span> <span class="kt">bool</span> <span class="n">IsNull</span><span class="p">(</span><span class="k">const</span> <span class="n">FuncAffinityRun</span><span class="o">&amp;</span> <span class="n">obj</span><span class="p">)</span>
<span class="p">{</span>
<span class="k">return</span> <span class="nb">false</span><span class="p">;</span>
<span class="p">}</span>
<span class="k">static</span> <span class="kt">void</span> <span class="n">GetNull</span><span class="p">(</span><span class="n">FuncAffinityRun</span><span class="o">&amp;</span> <span class="n">dst</span><span class="p">)</span>
<span class="p">{</span>
<span class="n">dst</span> <span class="o">=</span> <span class="n">FuncAffinityRun</span><span class="p">();</span>
<span class="p">}</span>
<span class="k">static</span> <span class="kt">void</span> <span class="n">Write</span><span class="p">(</span><span class="n">BinaryWriter</span><span class="o">&amp;</span> <span class="n">writer</span><span class="p">,</span> <span class="k">const</span> <span class="n">FuncAffinityRun</span><span class="o">&amp;</span> <span class="n">obj</span><span class="p">)</span>
<span class="p">{</span>
<span class="n">writer</span><span class="p">.</span><span class="n">WriteString</span><span class="p">(</span><span class="s">"cacheName"</span><span class="p">,</span> <span class="n">obj</span><span class="p">.</span><span class="n">cacheName</span><span class="p">);</span>
<span class="n">writer</span><span class="p">.</span><span class="n">WriteInt32</span><span class="p">(</span><span class="s">"key"</span><span class="p">,</span> <span class="n">obj</span><span class="p">.</span><span class="n">key</span><span class="p">);</span>
<span class="p">}</span>
<span class="k">static</span> <span class="kt">void</span> <span class="n">Read</span><span class="p">(</span><span class="n">BinaryReader</span><span class="o">&amp;</span> <span class="n">reader</span><span class="p">,</span> <span class="n">FuncAffinityRun</span><span class="o">&amp;</span> <span class="n">dst</span><span class="p">)</span>
<span class="p">{</span>
<span class="n">dst</span><span class="p">.</span><span class="n">cacheName</span> <span class="o">=</span> <span class="n">reader</span><span class="p">.</span><span class="n">ReadString</span><span class="p">(</span><span class="s">"cacheName"</span><span class="p">);</span>
<span class="n">dst</span><span class="p">.</span><span class="n">key</span> <span class="o">=</span> <span class="n">reader</span><span class="p">.</span><span class="n">ReadInt32</span><span class="p">(</span><span class="s">"key"</span><span class="p">);</span>
<span class="p">}</span>
<span class="p">};</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="kt">int</span> <span class="nf">main</span><span class="p">()</span>
<span class="p">{</span>
<span class="n">IgniteConfiguration</span> <span class="n">cfg</span><span class="p">;</span>
<span class="n">cfg</span><span class="p">.</span><span class="n">springCfgPath</span> <span class="o">=</span> <span class="s">"/path/to/configuration.xml"</span><span class="p">;</span>
<span class="n">Ignite</span> <span class="n">ignite</span> <span class="o">=</span> <span class="n">Ignition</span><span class="o">::</span><span class="n">Start</span><span class="p">(</span><span class="n">cfg</span><span class="p">);</span>
<span class="c1">// Get cache instance.</span>
<span class="n">Cache</span><span class="o">&lt;</span><span class="kt">int32_t</span><span class="p">,</span> <span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="o">&gt;</span> <span class="n">cache</span> <span class="o">=</span> <span class="n">ignite</span><span class="p">.</span><span class="n">GetOrCreateCache</span><span class="o">&lt;</span><span class="kt">int32_t</span><span class="p">,</span> <span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="o">&gt;</span><span class="p">(</span><span class="s">"myCache"</span><span class="p">);</span>
<span class="c1">// Get binding instance.</span>
<span class="n">IgniteBinding</span> <span class="n">binding</span> <span class="o">=</span> <span class="n">ignite</span><span class="p">.</span><span class="n">GetBinding</span><span class="p">();</span>
<span class="c1">// Registering our class as a compute function.</span>
<span class="n">binding</span><span class="p">.</span><span class="n">RegisterComputeFunc</span><span class="o">&lt;</span><span class="n">FuncAffinityRun</span><span class="o">&gt;</span><span class="p">();</span>
<span class="c1">// Get compute instance.</span>
<span class="n">compute</span><span class="o">::</span><span class="n">Compute</span> <span class="n">compute</span> <span class="o">=</span> <span class="n">ignite</span><span class="p">.</span><span class="n">GetCompute</span><span class="p">();</span>
<span class="kt">int</span> <span class="n">key</span> <span class="o">=</span> <span class="mi">1</span><span class="p">;</span>
<span class="c1">// This closure will execute on the remote node where</span>
<span class="c1">// data for the given 'key' is located.</span>
<span class="n">compute</span><span class="p">.</span><span class="n">AffinityRun</span><span class="p">(</span><span class="n">cache</span><span class="p">.</span><span class="n">GetName</span><span class="p">(),</span> <span class="n">key</span><span class="p">,</span> <span class="n">FuncAffinityRun</span><span class="p">(</span><span class="n">cache</span><span class="p">.</span><span class="n">GetName</span><span class="p">(),</span> <span class="n">key</span><span class="p">));</span>
<span class="p">}</span></code></pre>
</div>
</div></code-tab></code-tabs>
</div>
</div>
<div class="sect1">
<h2 id="colocating-by-partition">Colocating by Partition</h2>
<div class="sectionbody">
<div class="paragraph">
<p>The <code>affinityCall(Collection&lt;String&gt; cacheNames, int partId, IgniteRunnable job)</code> and <code>affinityRun(Collection&lt;String&gt; cacheNames, int partId, IgniteRunnable job)</code> send a given task to the node where the partition with a given ID is located. This is useful when you need to retrieve objects for multiple keys and you know that the keys belong to the same partition. In this case, you can create one task instead of multiple task for each key.</p>
</div>
<div class="paragraph">
<p>For example, let&#8217;s say you want to calculate the arithmetic mean of a specific field for a specific subset of keys.
If you want to distribute the computation, you can group the keys by partitions and send each group of keys to the node where the partition is located to get the values.
The number of groups and, therefore, the number of tasks is no more than the total number of partitions (default is 1024).
Below is a code snippet that illustrates this example.</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="c1">// this task sums up the values of the salary field for the given set of keys</span>
<span class="kd">private</span> <span class="kd">static</span> <span class="kd">class</span> <span class="nc">SumTask</span> <span class="kd">implements</span> <span class="nc">IgniteCallable</span><span class="o">&lt;</span><span class="nc">BigDecimal</span><span class="o">&gt;</span> <span class="o">{</span>
<span class="kd">private</span> <span class="nc">Set</span><span class="o">&lt;</span><span class="nc">Long</span><span class="o">&gt;</span> <span class="n">keys</span><span class="o">;</span>
<span class="kd">public</span> <span class="nf">SumTask</span><span class="o">(</span><span class="nc">Set</span><span class="o">&lt;</span><span class="nc">Long</span><span class="o">&gt;</span> <span class="n">keys</span><span class="o">)</span> <span class="o">{</span>
<span class="k">this</span><span class="o">.</span><span class="na">keys</span> <span class="o">=</span> <span class="n">keys</span><span class="o">;</span>
<span class="o">}</span>
<span class="nd">@IgniteInstanceResource</span>
<span class="kd">private</span> <span class="nc">Ignite</span> <span class="n">ignite</span><span class="o">;</span>
<span class="nd">@Override</span>
<span class="kd">public</span> <span class="nc">BigDecimal</span> <span class="nf">call</span><span class="o">()</span> <span class="kd">throws</span> <span class="nc">Exception</span> <span class="o">{</span>
<span class="nc">IgniteCache</span><span class="o">&lt;</span><span class="nc">Long</span><span class="o">,</span> <span class="nc">BinaryObject</span><span class="o">&gt;</span> <span class="n">cache</span> <span class="o">=</span> <span class="n">ignite</span><span class="o">.</span><span class="na">cache</span><span class="o">(</span><span class="s">"person"</span><span class="o">).</span><span class="na">withKeepBinary</span><span class="o">();</span>
<span class="nc">BigDecimal</span> <span class="n">sum</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">BigDecimal</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="kt">long</span> <span class="n">k</span> <span class="o">:</span> <span class="n">keys</span><span class="o">)</span> <span class="o">{</span>
<span class="nc">BinaryObject</span> <span class="n">person</span> <span class="o">=</span> <span class="n">cache</span><span class="o">.</span><span class="na">localPeek</span><span class="o">(</span><span class="n">k</span><span class="o">,</span> <span class="nc">CachePeekMode</span><span class="o">.</span><span class="na">PRIMARY</span><span class="o">);</span>
<span class="k">if</span> <span class="o">(</span><span class="n">person</span> <span class="o">!=</span> <span class="kc">null</span><span class="o">)</span>
<span class="n">sum</span> <span class="o">=</span> <span class="n">sum</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="k">new</span> <span class="nc">BigDecimal</span><span class="o">((</span><span class="kt">float</span><span class="o">)</span> <span class="n">person</span><span class="o">.</span><span class="na">field</span><span class="o">(</span><span class="s">"salary"</span><span class="o">)));</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">calculateAverage</span><span class="o">(</span><span class="nc">Ignite</span> <span class="n">ignite</span><span class="o">,</span> <span class="nc">Set</span><span class="o">&lt;</span><span class="nc">Long</span><span class="o">&gt;</span> <span class="n">keys</span><span class="o">)</span> <span class="o">{</span>
<span class="c1">// get the affinity function configured for the cache</span>
<span class="nc">Affinity</span><span class="o">&lt;</span><span class="nc">Long</span><span class="o">&gt;</span> <span class="n">affinityFunc</span> <span class="o">=</span> <span class="n">ignite</span><span class="o">.</span><span class="na">affinity</span><span class="o">(</span><span class="s">"person"</span><span class="o">);</span>
<span class="c1">// this map stores collections of keys for each partition</span>
<span class="nc">HashMap</span><span class="o">&lt;</span><span class="nc">Integer</span><span class="o">,</span> <span class="nc">Set</span><span class="o">&lt;</span><span class="nc">Long</span><span class="o">&gt;&gt;</span> <span class="n">partMap</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">HashMap</span><span class="o">&lt;&gt;();</span>
<span class="n">keys</span><span class="o">.</span><span class="na">forEach</span><span class="o">(</span><span class="n">k</span> <span class="o">-&gt;</span> <span class="o">{</span>
<span class="kt">int</span> <span class="n">partId</span> <span class="o">=</span> <span class="n">affinityFunc</span><span class="o">.</span><span class="na">partition</span><span class="o">(</span><span class="n">k</span><span class="o">);</span>
<span class="nc">Set</span><span class="o">&lt;</span><span class="nc">Long</span><span class="o">&gt;</span> <span class="n">keysByPartition</span> <span class="o">=</span> <span class="n">partMap</span><span class="o">.</span><span class="na">computeIfAbsent</span><span class="o">(</span><span class="n">partId</span><span class="o">,</span> <span class="n">key</span> <span class="o">-&gt;</span> <span class="k">new</span> <span class="nc">HashSet</span><span class="o">&lt;</span><span class="nc">Long</span><span class="o">&gt;());</span>
<span class="n">keysByPartition</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="n">k</span><span class="o">);</span>
<span class="o">});</span>
<span class="nc">BigDecimal</span> <span class="n">total</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">BigDecimal</span><span class="o">(</span><span class="mi">0</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="nc">List</span><span class="o">&lt;</span><span class="nc">String</span><span class="o">&gt;</span> <span class="n">caches</span> <span class="o">=</span> <span class="nc">Arrays</span><span class="o">.</span><span class="na">asList</span><span class="o">(</span><span class="s">"person"</span><span class="o">);</span>
<span class="c1">// iterate over all partitions</span>
<span class="k">for</span> <span class="o">(</span><span class="nc">Map</span><span class="o">.</span><span class="na">Entry</span><span class="o">&lt;</span><span class="nc">Integer</span><span class="o">,</span> <span class="nc">Set</span><span class="o">&lt;</span><span class="nc">Long</span><span class="o">&gt;&gt;</span> <span class="n">pair</span> <span class="o">:</span> <span class="n">partMap</span><span class="o">.</span><span class="na">entrySet</span><span class="o">())</span> <span class="o">{</span>
<span class="c1">// send a task that gets specific keys for the partition</span>
<span class="nc">BigDecimal</span> <span class="n">sum</span> <span class="o">=</span> <span class="n">compute</span><span class="o">.</span><span class="na">affinityCall</span><span class="o">(</span><span class="n">caches</span><span class="o">,</span> <span class="n">pair</span><span class="o">.</span><span class="na">getKey</span><span class="o">().</span><span class="na">intValue</span><span class="o">(),</span> <span class="k">new</span> <span class="nc">SumTask</span><span class="o">(</span><span class="n">pair</span><span class="o">.</span><span class="na">getValue</span><span class="o">()));</span>
<span class="n">total</span> <span class="o">=</span> <span class="n">total</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="n">sum</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">"the average salary is "</span> <span class="o">+</span> <span class="n">total</span><span class="o">.</span><span class="na">floatValue</span><span class="o">()</span> <span class="o">/</span> <span class="n">keys</span><span class="o">.</span><span class="na">size</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 class="paragraph">
<p>If you want to process all the data in the cache, you can iterate over all cache partitions and send tasks that process the data stored on each individual partition.</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="c1">// this task sums up the value of the 'salary' field for all objects stored in</span>
<span class="c1">// the given partition</span>
<span class="kd">public</span> <span class="kd">static</span> <span class="kd">class</span> <span class="nc">SumByPartitionTask</span> <span class="kd">implements</span> <span class="nc">IgniteCallable</span><span class="o">&lt;</span><span class="nc">BigDecimal</span><span class="o">&gt;</span> <span class="o">{</span>
<span class="kd">private</span> <span class="kt">int</span> <span class="n">partId</span><span class="o">;</span>
<span class="kd">public</span> <span class="nf">SumByPartitionTask</span><span class="o">(</span><span class="kt">int</span> <span class="n">partId</span><span class="o">)</span> <span class="o">{</span>
<span class="k">this</span><span class="o">.</span><span class="na">partId</span> <span class="o">=</span> <span class="n">partId</span><span class="o">;</span>
<span class="o">}</span>
<span class="nd">@IgniteInstanceResource</span>
<span class="kd">private</span> <span class="nc">Ignite</span> <span class="n">ignite</span><span class="o">;</span>
<span class="nd">@Override</span>
<span class="kd">public</span> <span class="nc">BigDecimal</span> <span class="nf">call</span><span class="o">()</span> <span class="kd">throws</span> <span class="nc">Exception</span> <span class="o">{</span>
<span class="c1">// use binary objects to avoid deserialization</span>
<span class="nc">IgniteCache</span><span class="o">&lt;</span><span class="nc">Long</span><span class="o">,</span> <span class="nc">BinaryObject</span><span class="o">&gt;</span> <span class="n">cache</span> <span class="o">=</span> <span class="n">ignite</span><span class="o">.</span><span class="na">cache</span><span class="o">(</span><span class="s">"person"</span><span class="o">).</span><span class="na">withKeepBinary</span><span class="o">();</span>
<span class="nc">BigDecimal</span> <span class="n">total</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">BigDecimal</span><span class="o">(</span><span class="mi">0</span><span class="o">);</span>
<span class="k">try</span> <span class="o">(</span><span class="nc">QueryCursor</span><span class="o">&lt;</span><span class="nc">Cache</span><span class="o">.</span><span class="na">Entry</span><span class="o">&lt;</span><span class="nc">Long</span><span class="o">,</span> <span class="nc">BinaryObject</span><span class="o">&gt;&gt;</span> <span class="n">cursor</span> <span class="o">=</span> <span class="n">cache</span>
<span class="o">.</span><span class="na">query</span><span class="o">(</span><span class="k">new</span> <span class="nc">ScanQuery</span><span class="o">&lt;</span><span class="nc">Long</span><span class="o">,</span> <span class="nc">BinaryObject</span><span class="o">&gt;(</span><span class="n">partId</span><span class="o">).</span><span class="na">setLocal</span><span class="o">(</span><span class="kc">true</span><span class="o">)))</span> <span class="o">{</span>
<span class="k">for</span> <span class="o">(</span><span class="nc">Cache</span><span class="o">.</span><span class="na">Entry</span><span class="o">&lt;</span><span class="nc">Long</span><span class="o">,</span> <span class="nc">BinaryObject</span><span class="o">&gt;</span> <span class="n">entry</span> <span class="o">:</span> <span class="n">cursor</span><span class="o">)</span> <span class="o">{</span>
<span class="n">total</span> <span class="o">=</span> <span class="n">total</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="k">new</span> <span class="nc">BigDecimal</span><span class="o">((</span><span class="kt">float</span><span class="o">)</span> <span class="n">entry</span><span class="o">.</span><span class="na">getValue</span><span class="o">().</span><span class="na">field</span><span class="o">(</span><span class="s">"salary"</span><span class="o">)));</span>
<span class="o">}</span>
<span class="o">}</span>
<span class="k">return</span> <span class="n">total</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 class="admonitionblock important">
<table>
<tr>
<td class="icon">
<div class="title">Important</div>
</td>
<td class="content">
<h3 id="performance-considerations" class="discrete">Performance Considerations</h3>
<div class="paragraph">
<p>Colocated computations yield performance benefits when the amount of the data you want to process is sufficiently large. In some cases, when the amount of data is small, a <a href="/docs/latest/key-value-api/using-scan-queries">scan query</a> may perform better.</p>
</div>
</td>
</tr>
</table>
</div>
</div>
</div>
<div class="sect1">
<h2 id="entry-processor">Entry Processor</h2>
<div class="sectionbody">
<div class="paragraph">
<p>An entry processor is used to process cache entries on the nodes where they are stored and return the result of the processing. With an entry processor, you do not have to transfer the entire object to perform an operation with it, you can perform the operation remotely and only transfer the results.</p>
</div>
<div class="paragraph">
<p>If an entry processor sets the value for an entry that does not exist, the entry is added to the cache.</p>
</div>
<div class="paragraph">
<p>Entry processors are executed atomically within a lock on the given cache key.</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">IgniteCache</span><span class="o">&lt;</span><span class="nc">String</span><span class="o">,</span> <span class="nc">Integer</span><span class="o">&gt;</span> <span class="n">cache</span> <span class="o">=</span> <span class="n">ignite</span><span class="o">.</span><span class="na">cache</span><span class="o">(</span><span class="s">"mycache"</span><span class="o">);</span>
<span class="c1">// Increment the value for a specific key by 1.</span>
<span class="c1">// The operation will be performed on the node where the key is stored.</span>
<span class="c1">// Note that if the cache does not contain an entry for the given key, it will</span>
<span class="c1">// be created.</span>
<span class="n">cache</span><span class="o">.</span><span class="na">invoke</span><span class="o">(</span><span class="s">"mykey"</span><span class="o">,</span> <span class="o">(</span><span class="n">entry</span><span class="o">,</span> <span class="n">args</span><span class="o">)</span> <span class="o">-&gt;</span> <span class="o">{</span>
<span class="nc">Integer</span> <span class="n">val</span> <span class="o">=</span> <span class="n">entry</span><span class="o">.</span><span class="na">getValue</span><span class="o">();</span>
<span class="n">entry</span><span class="o">.</span><span class="na">setValue</span><span class="o">(</span><span class="n">val</span> <span class="o">==</span> <span class="kc">null</span> <span class="o">?</span> <span class="mi">1</span> <span class="o">:</span> <span class="n">val</span> <span class="o">+</span> <span class="mi">1</span><span class="o">);</span>
<span class="k">return</span> <span class="kc">null</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">void</span> <span class="nf">CacheInvoke</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="kt">var</span> <span class="n">cache</span> <span class="p">=</span> <span class="n">ignite</span><span class="p">.</span><span class="n">GetOrCreateCache</span><span class="p">&lt;</span><span class="kt">int</span><span class="p">,</span> <span class="kt">int</span><span class="p">&gt;(</span><span class="s">"myCache"</span><span class="p">);</span>
<span class="kt">var</span> <span class="n">proc</span> <span class="p">=</span> <span class="k">new</span> <span class="nf">Processor</span><span class="p">();</span>
<span class="c1">// Increment cache value 10 times</span>
<span class="k">for</span> <span class="p">(</span><span class="kt">int</span> <span class="n">i</span> <span class="p">=</span> <span class="m">0</span><span class="p">;</span> <span class="n">i</span> <span class="p">&lt;</span> <span class="m">10</span><span class="p">;</span> <span class="n">i</span><span class="p">++)</span>
<span class="n">cache</span><span class="p">.</span><span class="nf">Invoke</span><span class="p">(</span><span class="m">1</span><span class="p">,</span> <span class="n">proc</span><span class="p">,</span> <span class="m">5</span><span class="p">);</span>
<span class="p">}</span>
<span class="k">class</span> <span class="nc">Processor</span> <span class="p">:</span> <span class="n">ICacheEntryProcessor</span><span class="p">&lt;</span><span class="kt">int</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="kt">int</span><span class="p">&gt;</span>
<span class="p">{</span>
<span class="k">public</span> <span class="kt">int</span> <span class="nf">Process</span><span class="p">(</span><span class="n">IMutableCacheEntry</span><span class="p">&lt;</span><span class="kt">int</span><span class="p">,</span> <span class="kt">int</span><span class="p">&gt;</span> <span class="n">entry</span><span class="p">,</span> <span class="kt">int</span> <span class="n">arg</span><span class="p">)</span>
<span class="p">{</span>
<span class="n">entry</span><span class="p">.</span><span class="n">Value</span> <span class="p">=</span> <span class="n">entry</span><span class="p">.</span><span class="n">Exists</span> <span class="p">?</span> <span class="n">arg</span> <span class="p">:</span> <span class="n">entry</span><span class="p">.</span><span class="n">Value</span> <span class="p">+</span> <span class="n">arg</span><span class="p">;</span>
<span class="k">return</span> <span class="n">entry</span><span class="p">.</span><span class="n">Value</span><span class="p">;</span>
<span class="p">}</span>
<span class="p">}</span></code></pre>
</div>
</div></code-tab><code-tab data-tab='C++'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="cpp"><span class="cm">/**
* Processor for invoke method.
*/</span>
<span class="k">class</span> <span class="nc">IncrementProcessor</span> <span class="o">:</span> <span class="k">public</span> <span class="n">cache</span><span class="o">::</span><span class="n">CacheEntryProcessor</span><span class="o">&lt;</span><span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="p">,</span> <span class="kt">int32_t</span><span class="p">,</span> <span class="kt">int32_t</span><span class="p">,</span> <span class="kt">int32_t</span><span class="o">&gt;</span>
<span class="p">{</span>
<span class="nl">public:</span>
<span class="cm">/**
* Constructor.
*/</span>
<span class="n">IncrementProcessor</span><span class="p">()</span>
<span class="p">{</span>
<span class="c1">// No-op.</span>
<span class="p">}</span>
<span class="cm">/**
* Copy constructor.
*
* @param other Other instance.
*/</span>
<span class="n">IncrementProcessor</span><span class="p">(</span><span class="k">const</span> <span class="n">IncrementProcessor</span><span class="o">&amp;</span> <span class="n">other</span><span class="p">)</span>
<span class="p">{</span>
<span class="c1">// No-op.</span>
<span class="p">}</span>
<span class="cm">/**
* Assignment operator.
*
* @param other Other instance.
* @return This instance.
*/</span>
<span class="n">IncrementProcessor</span><span class="o">&amp;</span> <span class="k">operator</span><span class="o">=</span><span class="p">(</span><span class="k">const</span> <span class="n">IncrementProcessor</span><span class="o">&amp;</span> <span class="n">other</span><span class="p">)</span>
<span class="p">{</span>
<span class="k">return</span> <span class="o">*</span><span class="k">this</span><span class="p">;</span>
<span class="p">}</span>
<span class="cm">/**
* Call instance.
*/</span>
<span class="k">virtual</span> <span class="kt">int32_t</span> <span class="n">Process</span><span class="p">(</span><span class="n">MutableCacheEntry</span><span class="o">&lt;</span><span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="p">,</span> <span class="kt">int32_t</span><span class="o">&gt;&amp;</span> <span class="n">entry</span><span class="p">,</span> <span class="k">const</span> <span class="kt">int</span><span class="o">&amp;</span> <span class="n">arg</span><span class="p">)</span>
<span class="p">{</span>
<span class="c1">// Increment the value for a specific key by 1.</span>
<span class="c1">// The operation will be performed on the node where the key is stored.</span>
<span class="c1">// Note that if the cache does not contain an entry for the given key, it will</span>
<span class="c1">// be created.</span>
<span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="n">entry</span><span class="p">.</span><span class="n">IsExists</span><span class="p">())</span>
<span class="n">entry</span><span class="p">.</span><span class="n">SetValue</span><span class="p">(</span><span class="mi">1</span><span class="p">);</span>
<span class="k">else</span>
<span class="n">entry</span><span class="p">.</span><span class="n">SetValue</span><span class="p">(</span><span class="n">entry</span><span class="p">.</span><span class="n">GetValue</span><span class="p">()</span> <span class="o">+</span> <span class="mi">1</span><span class="p">);</span>
<span class="k">return</span> <span class="n">entry</span><span class="p">.</span><span class="n">GetValue</span><span class="p">();</span>
<span class="p">}</span>
<span class="p">};</span>
<span class="cm">/**
* Binary type structure. Defines a set of functions required for type to be serialized and deserialized.
*/</span>
<span class="k">namespace</span> <span class="n">ignite</span>
<span class="p">{</span>
<span class="k">namespace</span> <span class="n">binary</span>
<span class="p">{</span>
<span class="k">template</span><span class="o">&lt;</span><span class="p">&gt;</span>
<span class="k">struct</span> <span class="nc">BinaryType</span><span class="o">&lt;</span><span class="n">IncrementProcessor</span><span class="o">&gt;</span>
<span class="p">{</span>
<span class="k">static</span> <span class="kt">int32_t</span> <span class="n">GetTypeId</span><span class="p">()</span>
<span class="p">{</span>
<span class="k">return</span> <span class="n">GetBinaryStringHashCode</span><span class="p">(</span><span class="s">"IncrementProcessor"</span><span class="p">);</span>
<span class="p">}</span>
<span class="k">static</span> <span class="kt">void</span> <span class="n">GetTypeName</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="o">&amp;</span> <span class="n">dst</span><span class="p">)</span>
<span class="p">{</span>
<span class="n">dst</span> <span class="o">=</span> <span class="s">"IncrementProcessor"</span><span class="p">;</span>
<span class="p">}</span>
<span class="k">static</span> <span class="kt">int32_t</span> <span class="n">GetFieldId</span><span class="p">(</span><span class="k">const</span> <span class="kt">char</span><span class="o">*</span> <span class="n">name</span><span class="p">)</span>
<span class="p">{</span>
<span class="k">return</span> <span class="n">GetBinaryStringHashCode</span><span class="p">(</span><span class="n">name</span><span class="p">);</span>
<span class="p">}</span>
<span class="k">static</span> <span class="kt">int32_t</span> <span class="n">GetHashCode</span><span class="p">(</span><span class="k">const</span> <span class="n">IncrementProcessor</span><span class="o">&amp;</span> <span class="n">obj</span><span class="p">)</span>
<span class="p">{</span>
<span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
<span class="p">}</span>
<span class="k">static</span> <span class="kt">bool</span> <span class="n">IsNull</span><span class="p">(</span><span class="k">const</span> <span class="n">IncrementProcessor</span><span class="o">&amp;</span> <span class="n">obj</span><span class="p">)</span>
<span class="p">{</span>
<span class="k">return</span> <span class="nb">false</span><span class="p">;</span>
<span class="p">}</span>
<span class="k">static</span> <span class="kt">void</span> <span class="n">GetNull</span><span class="p">(</span><span class="n">IncrementProcessor</span><span class="o">&amp;</span> <span class="n">dst</span><span class="p">)</span>
<span class="p">{</span>
<span class="n">dst</span> <span class="o">=</span> <span class="n">IncrementProcessor</span><span class="p">();</span>
<span class="p">}</span>
<span class="k">static</span> <span class="kt">void</span> <span class="n">Write</span><span class="p">(</span><span class="n">BinaryWriter</span><span class="o">&amp;</span> <span class="n">writer</span><span class="p">,</span> <span class="k">const</span> <span class="n">IncrementProcessor</span><span class="o">&amp;</span> <span class="n">obj</span><span class="p">)</span>
<span class="p">{</span>
<span class="c1">// No-op.</span>
<span class="p">}</span>
<span class="k">static</span> <span class="kt">void</span> <span class="n">Read</span><span class="p">(</span><span class="n">BinaryReader</span><span class="o">&amp;</span> <span class="n">reader</span><span class="p">,</span> <span class="n">IncrementProcessor</span><span class="o">&amp;</span> <span class="n">dst</span><span class="p">)</span>
<span class="p">{</span>
<span class="c1">// No-op.</span>
<span class="p">}</span>
<span class="p">};</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="kt">int</span> <span class="nf">main</span><span class="p">()</span>
<span class="p">{</span>
<span class="n">IgniteConfiguration</span> <span class="n">cfg</span><span class="p">;</span>
<span class="n">cfg</span><span class="p">.</span><span class="n">springCfgPath</span> <span class="o">=</span> <span class="s">"platforms/cpp/examples/put-get-example/config/example-cache.xml"</span><span class="p">;</span>
<span class="n">Ignite</span> <span class="n">ignite</span> <span class="o">=</span> <span class="n">Ignition</span><span class="o">::</span><span class="n">Start</span><span class="p">(</span><span class="n">cfg</span><span class="p">);</span>
<span class="c1">// Get cache instance.</span>
<span class="n">Cache</span><span class="o">&lt;</span><span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="p">,</span> <span class="kt">int32_t</span><span class="o">&gt;</span> <span class="n">cache</span> <span class="o">=</span> <span class="n">ignite</span><span class="p">.</span><span class="n">GetOrCreateCache</span><span class="o">&lt;</span><span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="p">,</span> <span class="kt">int32_t</span><span class="o">&gt;</span><span class="p">(</span><span class="s">"myCache"</span><span class="p">);</span>
<span class="c1">// Get binding instance.</span>
<span class="n">IgniteBinding</span> <span class="n">binding</span> <span class="o">=</span> <span class="n">ignite</span><span class="p">.</span><span class="n">GetBinding</span><span class="p">();</span>
<span class="c1">// Registering our class as a cache entry processor.</span>
<span class="n">binding</span><span class="p">.</span><span class="n">RegisterCacheEntryProcessor</span><span class="o">&lt;</span><span class="n">IncrementProcessor</span><span class="o">&gt;</span><span class="p">();</span>
<span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="n">key</span><span class="p">(</span><span class="s">"mykey"</span><span class="p">);</span>
<span class="n">IncrementProcessor</span> <span class="n">inc</span><span class="p">;</span>
<span class="n">cache</span><span class="p">.</span><span class="n">Invoke</span><span class="o">&lt;</span><span class="kt">int32_t</span><span class="o">&gt;</span><span class="p">(</span><span class="n">key</span><span class="p">,</span> <span class="n">inc</span><span class="p">,</span> <span class="nb">NULL</span><span class="p">);</span>
<span class="p">}</span></code></pre>
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