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<article data-swiftype-index='true'>
<a class='edit-link' href="https://github.com/apache/ignite/tree/IGNITE-7595/docs/_docs/events/listening-to-events.adoc" target="_blank">Edit</a>
<h1>Working with Events</h1>
<div class="sect1">
<h2 id="overview">Overview</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Ignite can generate events for a variety of operations happening in the cluster and notify your application about those operations. There are many types of events, including cache events, node discovery events, distributed task execution events, and many more.</p>
</div>
<div class="paragraph">
<p>The list of events is available in the <a href="/docs/latest/events/events">Events</a> section.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="enabling-events">Enabling Events</h2>
<div class="sectionbody">
<div class="paragraph">
<p>By default, events are disabled, and you have to enable each event type explicitly if you want to use it in your application.
To enable specific event types, list them in the <code>includeEventTypes</code> property of <code>IgniteConfiguration</code> as shown below:</p>
</div>
<code-tabs><code-tab data-tab='XML'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="xml"><span class="cp">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</span>
<span class="c">&lt;!--
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements. See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
--&gt;</span>
<span class="nt">&lt;beans</span> <span class="na">xmlns=</span><span class="s">"http://www.springframework.org/schema/beans"</span>
<span class="na">xmlns:util=</span><span class="s">"http://www.springframework.org/schema/util"</span>
<span class="na">xmlns:xsi=</span><span class="s">"http://www.w3.org/2001/XMLSchema-instance"</span>
<span class="na">xsi:schemaLocation=</span><span class="s">" http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/util
http://www.springframework.org/schema/util/spring-util.xsd"</span><span class="nt">&gt;</span>
<span class="nt">&lt;bean</span> <span class="na">class=</span><span class="s">"org.apache.ignite.configuration.IgniteConfiguration"</span><span class="nt">&gt;</span>
<span class="nt">&lt;property</span> <span class="na">name=</span><span class="s">"includeEventTypes"</span><span class="nt">&gt;</span>
<span class="nt">&lt;list&gt;</span>
<span class="nt">&lt;util:constant</span> <span class="na">static-field=</span><span class="s">"org.apache.ignite.events.EventType.EVT_CACHE_OBJECT_PUT"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;util:constant</span> <span class="na">static-field=</span><span class="s">"org.apache.ignite.events.EventType.EVT_CACHE_OBJECT_READ"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;util:constant</span> <span class="na">static-field=</span><span class="s">"org.apache.ignite.events.EventType.EVT_CACHE_OBJECT_REMOVED"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;util:constant</span> <span class="na">static-field=</span><span class="s">"org.apache.ignite.events.EventType.EVT_NODE_LEFT"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;util:constant</span> <span class="na">static-field=</span><span class="s">"org.apache.ignite.events.EventType.EVT_NODE_JOINED"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;/list&gt;</span>
<span class="nt">&lt;/property&gt;</span>
<span class="nt">&lt;/bean&gt;</span>
<span class="nt">&lt;/beans&gt;</span></code></pre>
</div>
</div></code-tab><code-tab data-tab='Java'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="java"><span class="nc">IgniteConfiguration</span> <span class="n">cfg</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">IgniteConfiguration</span><span class="o">();</span>
<span class="c1">// Enable cache events.</span>
<span class="n">cfg</span><span class="o">.</span><span class="na">setIncludeEventTypes</span><span class="o">(</span><span class="nc">EventType</span><span class="o">.</span><span class="na">EVT_CACHE_OBJECT_PUT</span><span class="o">,</span> <span class="nc">EventType</span><span class="o">.</span><span class="na">EVT_CACHE_OBJECT_READ</span><span class="o">,</span>
<span class="nc">EventType</span><span class="o">.</span><span class="na">EVT_CACHE_OBJECT_REMOVED</span><span class="o">,</span> <span class="nc">EventType</span><span class="o">.</span><span class="na">EVT_NODE_JOINED</span><span class="o">,</span> <span class="nc">EventType</span><span class="o">.</span><span class="na">EVT_NODE_LEFT</span><span class="o">);</span>
<span class="c1">// Start the node.</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="n">cfg</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="kt">var</span> <span class="n">cfg</span> <span class="p">=</span> <span class="k">new</span> <span class="n">IgniteConfiguration</span>
<span class="p">{</span>
<span class="n">IncludedEventTypes</span> <span class="p">=</span> <span class="k">new</span><span class="p">[]</span>
<span class="p">{</span>
<span class="n">EventType</span><span class="p">.</span><span class="n">CacheObjectPut</span><span class="p">,</span>
<span class="n">EventType</span><span class="p">.</span><span class="n">CacheObjectRead</span><span class="p">,</span>
<span class="n">EventType</span><span class="p">.</span><span class="n">CacheObjectRemoved</span><span class="p">,</span>
<span class="n">EventType</span><span class="p">.</span><span class="n">NodeJoined</span><span class="p">,</span>
<span class="n">EventType</span><span class="p">.</span><span class="n">NodeLeft</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="n">cfg</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++. You can use XML configuration.</code></pre>
</div>
</div></code-tab></code-tabs>
</div>
</div>
<div class="sect1">
<h2 id="getting-the-events-interface">Getting the Events Interface</h2>
<div class="sectionbody">
<div class="paragraph">
<p>The events functionality is available through the events interface, which provides methods for listening to cluster events. The events interface can be obtained from an instance of <code>Ignite</code> as follows:</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">IgniteEvents</span> <span class="n">events</span> <span class="o">=</span> <span class="n">ignite</span><span class="o">.</span><span class="na">events</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="kt">var</span> <span class="n">ignite</span> <span class="p">=</span> <span class="n">Ignition</span><span class="p">.</span><span class="nf">GetIgnite</span><span class="p">();</span>
<span class="kt">var</span> <span class="n">events</span> <span class="p">=</span> <span class="n">ignite</span><span class="p">.</span><span class="nf">GetEvents</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>The events interface can be associated with a <a href="/docs/latest/distributed-computing/cluster-groups">set of nodes</a>. This means that you can access events that happen on a given set of nodes. In the following example, the events interface is obtained for the set of nodes that host the data for the Person cache.</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">ignite</span><span class="o">();</span>
<span class="nc">IgniteEvents</span> <span class="n">events</span> <span class="o">=</span> <span class="n">ignite</span><span class="o">.</span><span class="na">events</span><span class="o">(</span><span class="n">ignite</span><span class="o">.</span><span class="na">cluster</span><span class="o">().</span><span class="na">forCacheNodes</span><span class="o">(</span><span class="s">"person"</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="kt">var</span> <span class="n">ignite</span> <span class="p">=</span> <span class="n">Ignition</span><span class="p">.</span><span class="nf">GetIgnite</span><span class="p">();</span>
<span class="kt">var</span> <span class="n">events</span> <span class="p">=</span> <span class="n">ignite</span><span class="p">.</span><span class="nf">GetCluster</span><span class="p">().</span><span class="nf">ForCacheNodes</span><span class="p">(</span><span class="s">"person"</span><span class="p">).</span><span class="nf">GetEvents</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="sect1">
<h2 id="listening-to-events">Listening to Events</h2>
<div class="sectionbody">
<div class="paragraph">
<p>You can listen to either local or remote events. Local events are events that are generated on the node where the listener is registered. Remote events are events that happen on other nodes.</p>
</div>
<div class="paragraph">
<p>Note that some events may be fired on multiple nodes even if the corresponding real-world event happens only once. For example, when a node leaves the cluster, the <code>EVT_NODE_LEFT</code> event is generated on every remaining node.</p>
</div>
<div class="paragraph">
<p>Another example is when you put an object into a cache. In this case, the <code>EVT_CACHE_OBJECT_PUT</code> event occurs on the node that hosts the <a href="/docs/latest/data-modeling/data-partitioning#backup-partitions">primary partition</a> into which the object is actually written, which may be different from the node where the <code>put(&#8230;&#8203;)</code> method is called. In addition, the event is fired on all nodes that hold the <a href="/docs/latest/data-modeling/data-partitioning#backup-partitions">backup partitions</a> for the cache if they are configured.</p>
</div>
<div class="paragraph">
<p>The events interface provides methods for listening to local events only, and for listening to both local and remote events.</p>
</div>
<div class="sect2">
<h3 id="listening-to-local-events">Listening to Local Events</h3>
<div class="paragraph">
<p>To listen to local events, use the <code>localListen(listener, eventTypes&#8230;&#8203;)</code> method, as shown below. The method accepts an event listener that is called every time an event of the given type occurs on the local node.</p>
</div>
<div class="paragraph">
<p>To unregister the local listener, return <code>false</code> in its functional method.</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">IgniteEvents</span> <span class="n">events</span> <span class="o">=</span> <span class="n">ignite</span><span class="o">.</span><span class="na">events</span><span class="o">();</span>
<span class="c1">// Local listener that listens to local events.</span>
<span class="nc">IgnitePredicate</span><span class="o">&lt;</span><span class="nc">CacheEvent</span><span class="o">&gt;</span> <span class="n">localListener</span> <span class="o">=</span> <span class="n">evt</span> <span class="o">-&gt;</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">"Received event [evt="</span> <span class="o">+</span> <span class="n">evt</span><span class="o">.</span><span class="na">name</span><span class="o">()</span> <span class="o">+</span> <span class="s">", key="</span> <span class="o">+</span> <span class="n">evt</span><span class="o">.</span><span class="na">key</span><span class="o">()</span> <span class="o">+</span> <span class="s">", oldVal="</span> <span class="o">+</span> <span class="n">evt</span><span class="o">.</span><span class="na">oldValue</span><span class="o">()</span>
<span class="o">+</span> <span class="s">", newVal="</span> <span class="o">+</span> <span class="n">evt</span><span class="o">.</span><span class="na">newValue</span><span class="o">());</span>
<span class="k">return</span> <span class="kc">true</span><span class="o">;</span> <span class="c1">// Continue listening.</span>
<span class="o">};</span>
<span class="c1">// Subscribe to the cache events that are triggered on the local node.</span>
<span class="n">events</span><span class="o">.</span><span class="na">localListen</span><span class="o">(</span><span class="n">localListener</span><span class="o">,</span> <span class="nc">EventType</span><span class="o">.</span><span class="na">EVT_CACHE_OBJECT_PUT</span><span class="o">,</span> <span class="nc">EventType</span><span class="o">.</span><span class="na">EVT_CACHE_OBJECT_READ</span><span class="o">,</span>
<span class="nc">EventType</span><span class="o">.</span><span class="na">EVT_CACHE_OBJECT_REMOVED</span><span class="o">);</span></code></pre>
</div>
</div>
<div class="paragraph">
<p>The event listener is an object of the <code>IgnitePredicate&lt;T&gt;</code> class with a type argument that matches the type of events the listener is going to process.
For example, cache events (<code>EVT_CACHE_OBJECT_PUT</code>, <code>EVT_CACHE_OBJECT_READ</code>, etc.) correspond to the <a href="https://ignite.apache.org/releases/2.9.1/javadoc/org/apache/ignite/events/CacheEvent.html">CacheEvent</a> class, discovery events (<code>EVT_NODE_LEFT</code>, <code>EVT_NODE_JOINED</code>, etc.) correspond to
the <a href="https://ignite.apache.org/releases/2.9.1/javadoc/org/apache/ignite/events/DiscoveryEvent.html" target="_blank" rel="noopener">DiscoveryEvent</a> class, and so on.
If you want to listen to events of different types, you can use the generic <a href="https://ignite.apache.org/releases/2.9.1/javadoc/org/apache/ignite/events/Event.html" target="_blank" rel="noopener">Event</a> interface:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="java"><span class="nc">IgnitePredicate</span><span class="o">&lt;</span><span class="nc">Event</span><span class="o">&gt;</span> <span class="n">localListener</span> <span class="o">=</span> <span class="n">evt</span> <span class="o">-&gt;</span> <span class="o">{</span>
<span class="c1">// process the event</span>
<span class="k">return</span> <span class="kc">true</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">LocalListener</span> <span class="p">:</span> <span class="n">IEventListener</span><span class="p">&lt;</span><span class="n">CacheEvent</span><span class="p">&gt;</span>
<span class="p">{</span>
<span class="k">public</span> <span class="kt">bool</span> <span class="nf">Invoke</span><span class="p">(</span><span class="n">CacheEvent</span> <span class="n">evt</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">"Received event [evt="</span> <span class="p">+</span> <span class="n">evt</span><span class="p">.</span><span class="n">Name</span> <span class="p">+</span> <span class="s">", key="</span> <span class="p">+</span> <span class="n">evt</span><span class="p">.</span><span class="n">Key</span> <span class="p">+</span> <span class="s">", oldVal="</span> <span class="p">+</span> <span class="n">evt</span><span class="p">.</span><span class="n">OldValue</span>
<span class="p">+</span> <span class="s">", newVal="</span> <span class="p">+</span> <span class="n">evt</span><span class="p">.</span><span class="n">NewValue</span><span class="p">);</span>
<span class="k">return</span> <span class="k">true</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">LocalListenDemo</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="n">IgniteConfiguration</span>
<span class="p">{</span>
<span class="n">IncludedEventTypes</span> <span class="p">=</span> <span class="k">new</span><span class="p">[]</span>
<span class="p">{</span>
<span class="n">EventType</span><span class="p">.</span><span class="n">CacheObjectPut</span><span class="p">,</span>
<span class="n">EventType</span><span class="p">.</span><span class="n">CacheObjectRead</span><span class="p">,</span>
<span class="n">EventType</span><span class="p">.</span><span class="n">CacheObjectRemoved</span><span class="p">,</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="n">cfg</span><span class="p">);</span>
<span class="kt">var</span> <span class="n">events</span> <span class="p">=</span> <span class="n">ignite</span><span class="p">.</span><span class="nf">GetEvents</span><span class="p">();</span>
<span class="n">events</span><span class="p">.</span><span class="nf">LocalListen</span><span class="p">(</span><span class="k">new</span> <span class="nf">LocalListener</span><span class="p">(),</span> <span class="n">EventType</span><span class="p">.</span><span class="n">CacheObjectPut</span><span class="p">,</span> <span class="n">EventType</span><span class="p">.</span><span class="n">CacheObjectRead</span><span class="p">,</span>
<span class="n">EventType</span><span class="p">.</span><span class="n">CacheObjectRemoved</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="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="m">1</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="m">2</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 class="sect2">
<h3 id="listening-to-remote-events">Listening to Remote Events</h3>
<div class="paragraph">
<p>The <code>IgniteEvents.remoteListen(localListener, filter, types)</code> method can be used to register a listener that listens for both remote and local events.
It accepts a local listener, a filter, and a list of event types you want to listen to.</p>
</div>
<div class="paragraph">
<p>The filter is deployed to all the nodes associated with the events interface, including the local node. The events that pass the filter are sent to the local listener.</p>
</div>
<div class="paragraph">
<p>The method returns a unique identifier that can be used to unregister the listener and filters. To do this, call <code>IgniteEvents.stopRemoteListen(uuid)</code>. Another way to unregister the listener is to return <code>false</code> in the <code>apply()</code> method.</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">IgniteEvents</span> <span class="n">events</span> <span class="o">=</span> <span class="n">ignite</span><span class="o">.</span><span class="na">events</span><span class="o">();</span>
<span class="nc">IgnitePredicate</span><span class="o">&lt;</span><span class="nc">CacheEvent</span><span class="o">&gt;</span> <span class="n">filter</span> <span class="o">=</span> <span class="n">evt</span> <span class="o">-&gt;</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">"remote event: "</span> <span class="o">+</span> <span class="n">evt</span><span class="o">.</span><span class="na">name</span><span class="o">());</span>
<span class="k">return</span> <span class="kc">true</span><span class="o">;</span>
<span class="o">};</span>
<span class="c1">// Subscribe to the cache events on all nodes where the cache is hosted.</span>
<span class="no">UUID</span> <span class="n">uuid</span> <span class="o">=</span> <span class="n">events</span><span class="o">.</span><span class="na">remoteListen</span><span class="o">(</span><span class="k">new</span> <span class="nc">IgniteBiPredicate</span><span class="o">&lt;</span><span class="no">UUID</span><span class="o">,</span> <span class="nc">CacheEvent</span><span class="o">&gt;()</span> <span class="o">{</span>
<span class="nd">@Override</span>
<span class="kd">public</span> <span class="kt">boolean</span> <span class="nf">apply</span><span class="o">(</span><span class="no">UUID</span> <span class="n">uuid</span><span class="o">,</span> <span class="nc">CacheEvent</span> <span class="n">e</span><span class="o">)</span> <span class="o">{</span>
<span class="c1">// process the event</span>
<span class="k">return</span> <span class="kc">true</span><span class="o">;</span> <span class="c1">//continue listening</span>
<span class="o">}</span>
<span class="o">},</span> <span class="n">filter</span><span class="o">,</span> <span class="nc">EventType</span><span class="o">.</span><span class="na">EVT_CACHE_OBJECT_PUT</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 class="sect2">
<h3 id="batching-events">Batching Events</h3>
<div class="paragraph">
<p>Each activity in a cache can result in an event notification being generated and sent. For systems with high cache activity, getting notified for every event could be network intensive, possibly leading to a decreased performance of cache operations.</p>
</div>
<div class="paragraph">
<p>Event notifications can be grouped together and sent in batches or timely intervals to mitigate the impact on performance. Here is an example of how this can be done:</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">ignite</span><span class="o">();</span>
<span class="c1">// Get an instance of the cache.</span>
<span class="kd">final</span> <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">"cacheName"</span><span class="o">);</span>
<span class="c1">// Sample remote filter which only accepts events for the keys</span>
<span class="c1">// that are greater than or equal to 10.</span>
<span class="nc">IgnitePredicate</span><span class="o">&lt;</span><span class="nc">CacheEvent</span><span class="o">&gt;</span> <span class="n">rmtLsnr</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">IgnitePredicate</span><span class="o">&lt;</span><span class="nc">CacheEvent</span><span class="o">&gt;()</span> <span class="o">{</span>
<span class="nd">@Override</span>
<span class="kd">public</span> <span class="kt">boolean</span> <span class="nf">apply</span><span class="o">(</span><span class="nc">CacheEvent</span> <span class="n">evt</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">"Cache event: "</span> <span class="o">+</span> <span class="n">evt</span><span class="o">);</span>
<span class="kt">int</span> <span class="n">key</span> <span class="o">=</span> <span class="n">evt</span><span class="o">.</span><span class="na">key</span><span class="o">();</span>
<span class="k">return</span> <span class="n">key</span> <span class="o">&gt;=</span> <span class="mi">10</span><span class="o">;</span>
<span class="o">}</span>
<span class="o">};</span>
<span class="c1">// Subscribe to the cache events that are triggered on all nodes</span>
<span class="c1">// that host the cache.</span>
<span class="c1">// Send notifications in batches of 10.</span>
<span class="n">ignite</span><span class="o">.</span><span class="na">events</span><span class="o">(</span><span class="n">ignite</span><span class="o">.</span><span class="na">cluster</span><span class="o">().</span><span class="na">forCacheNodes</span><span class="o">(</span><span class="s">"cacheName"</span><span class="o">)).</span><span class="na">remoteListen</span><span class="o">(</span><span class="mi">10</span> <span class="cm">/* batch size */</span><span class="o">,</span>
<span class="mi">0</span> <span class="cm">/* time intervals */</span><span class="o">,</span> <span class="kc">false</span><span class="o">,</span> <span class="kc">null</span><span class="o">,</span> <span class="n">rmtLsnr</span><span class="o">,</span> <span class="nc">EventType</span><span class="o">.</span><span class="na">EVTS_CACHE</span><span class="o">);</span>
<span class="c1">// Generate cache events.</span>
<span class="k">for</span> <span class="o">(</span><span class="kt">int</span> <span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="o">;</span> <span class="n">i</span> <span class="o">&lt;</span> <span class="mi">20</span><span class="o">;</span> <span class="n">i</span><span class="o">++)</span>
<span class="n">cache</span><span class="o">.</span><span class="na">put</span><span class="o">(</span><span class="n">i</span><span class="o">,</span> <span class="nc">Integer</span><span class="o">.</span><span class="na">toString</span><span class="o">(</span><span class="n">i</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>
<div class="sect1">
<h2 id="storing-and-querying-events">Storing and Querying Events</h2>
<div class="sectionbody">
<div class="paragraph">
<p>You can configure an event storage that will keep events on the nodes where they occur. You can then query events in your application.</p>
</div>
<div class="paragraph">
<p>The event storage can be configured to keep events for a specific period, keep only the most recent events, or keep the events that satisfy a specific filter. See the <a href="https://ignite.apache.org/releases/2.9.1/javadoc/org/apache/ignite/spi/eventstorage/memory/MemoryEventStorageSpi.html" target="_blank" rel="noopener">MemoryEventStorageSpi</a> javadoc for details.</p>
</div>
<div class="paragraph">
<p>Below is an example of event storage configuration:</p>
</div>
<code-tabs><code-tab data-tab='XML'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="xml"><span class="nt">&lt;bean</span> <span class="na">class=</span><span class="s">"org.apache.ignite.configuration.IgniteConfiguration"</span><span class="nt">&gt;</span>
<span class="nt">&lt;property</span> <span class="na">name=</span><span class="s">"eventStorageSpi"</span> <span class="nt">&gt;</span>
<span class="nt">&lt;bean</span> <span class="na">class=</span><span class="s">"org.apache.ignite.spi.eventstorage.memory.MemoryEventStorageSpi"</span><span class="nt">&gt;</span>
<span class="nt">&lt;property</span> <span class="na">name=</span><span class="s">"expireAgeMs"</span> <span class="na">value=</span><span class="s">"600000"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;/bean&gt;</span>
<span class="nt">&lt;/property&gt;</span>
<span class="nt">&lt;/bean&gt;</span></code></pre>
</div>
</div></code-tab><code-tab data-tab='Java'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="java"><span class="nc">MemoryEventStorageSpi</span> <span class="n">eventStorageSpi</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">MemoryEventStorageSpi</span><span class="o">();</span>
<span class="n">eventStorageSpi</span><span class="o">.</span><span class="na">setExpireAgeMs</span><span class="o">(</span><span class="mi">600000</span><span class="o">);</span>
<span class="nc">IgniteConfiguration</span> <span class="n">igniteCfg</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">IgniteConfiguration</span><span class="o">();</span>
<span class="n">igniteCfg</span><span class="o">.</span><span class="na">setEventStorageSpi</span><span class="o">(</span><span class="n">eventStorageSpi</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="n">igniteCfg</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="kt">var</span> <span class="n">cfg</span> <span class="p">=</span> <span class="k">new</span> <span class="n">IgniteConfiguration</span>
<span class="p">{</span>
<span class="n">EventStorageSpi</span> <span class="p">=</span> <span class="k">new</span> <span class="nf">MemoryEventStorageSpi</span><span class="p">()</span>
<span class="p">{</span>
<span class="n">ExpirationTimeout</span> <span class="p">=</span> <span class="n">TimeSpan</span><span class="p">.</span><span class="nf">FromMilliseconds</span><span class="p">(</span><span class="m">600000</span><span class="p">)</span>
<span class="p">},</span>
<span class="n">IncludedEventTypes</span> <span class="p">=</span> <span class="k">new</span><span class="p">[]</span>
<span class="p">{</span>
<span class="n">EventType</span><span class="p">.</span><span class="n">CacheObjectPut</span><span class="p">,</span>
<span class="n">EventType</span><span class="p">.</span><span class="n">CacheObjectRead</span><span class="p">,</span>
<span class="n">EventType</span><span class="p">.</span><span class="n">CacheObjectRemoved</span><span class="p">,</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="n">cfg</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++. You can use XML configuration.</code></pre>
</div>
</div></code-tab></code-tabs>
<div class="sect2">
<h3 id="querying-local-events">Querying Local Events</h3>
<div class="paragraph">
<p>The following example shows how you can query local <code>EVT_CACHE_OBJECT_PUT</code> events stored in the event storage.</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">Collection</span><span class="o">&lt;</span><span class="nc">CacheEvent</span><span class="o">&gt;</span> <span class="n">cacheEvents</span> <span class="o">=</span> <span class="n">events</span><span class="o">.</span><span class="na">localQuery</span><span class="o">(</span><span class="n">e</span> <span class="o">-&gt;</span> <span class="o">{</span>
<span class="c1">// process the event</span>
<span class="k">return</span> <span class="kc">true</span><span class="o">;</span>
<span class="o">},</span> <span class="nc">EventType</span><span class="o">.</span><span class="na">EVT_CACHE_OBJECT_PUT</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="kt">var</span> <span class="n">events</span> <span class="p">=</span> <span class="n">ignite</span><span class="p">.</span><span class="nf">GetEvents</span><span class="p">();</span>
<span class="kt">var</span> <span class="n">cacheEvents</span> <span class="p">=</span> <span class="n">events</span><span class="p">.</span><span class="nf">LocalQuery</span><span class="p">(</span><span class="n">EventType</span><span class="p">.</span><span class="n">CacheObjectPut</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 class="sect2">
<h3 id="querying-remote-events">Querying Remote Events</h3>
<div class="paragraph">
<p>Here is an example of querying remote events:</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">Collection</span><span class="o">&lt;</span><span class="nc">CacheEvent</span><span class="o">&gt;</span> <span class="n">storedEvents</span> <span class="o">=</span> <span class="n">events</span><span class="o">.</span><span class="na">remoteQuery</span><span class="o">(</span><span class="n">e</span> <span class="o">-&gt;</span> <span class="o">{</span>
<span class="c1">// process the event</span>
<span class="k">return</span> <span class="kc">true</span><span class="o">;</span>
<span class="o">},</span> <span class="mi">0</span><span class="o">,</span> <span class="nc">EventType</span><span class="o">.</span><span class="na">EVT_CACHE_OBJECT_PUT</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">EventFilter</span> <span class="p">:</span> <span class="n">IEventFilter</span><span class="p">&lt;</span><span class="n">CacheEvent</span><span class="p">&gt;</span>
<span class="p">{</span>
<span class="k">public</span> <span class="kt">bool</span> <span class="nf">Invoke</span><span class="p">(</span><span class="n">CacheEvent</span> <span class="n">evt</span><span class="p">)</span>
<span class="p">{</span>
<span class="k">return</span> <span class="k">true</span><span class="p">;</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="c1">// ....</span>
<span class="kt">var</span> <span class="n">events</span> <span class="p">=</span> <span class="n">ignite</span><span class="p">.</span><span class="nf">GetEvents</span><span class="p">();</span>
<span class="kt">var</span> <span class="n">storedEvents</span> <span class="p">=</span> <span class="n">events</span><span class="p">.</span><span class="nf">RemoteQuery</span><span class="p">(</span><span class="k">new</span> <span class="nf">EventFilter</span><span class="p">(),</span> <span class="k">null</span><span class="p">,</span> <span class="n">EventType</span><span class="p">.</span><span class="n">CacheObjectPut</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>
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© 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.
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<ul class="sectlevel1">
<li><a href="#overview">Overview</a></li>
<li><a href="#enabling-events">Enabling Events</a></li>
<li><a href="#getting-the-events-interface">Getting the Events Interface</a></li>
<li><a href="#listening-to-events">Listening to Events</a>
<ul class="sectlevel2">
<li><a href="#listening-to-local-events">Listening to Local Events</a></li>
<li><a href="#listening-to-remote-events">Listening to Remote Events</a></li>
<li><a href="#batching-events">Batching Events</a></li>
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<li><a href="#storing-and-querying-events">Storing and Querying Events</a>
<ul class="sectlevel2">
<li><a href="#querying-local-events">Querying Local Events</a></li>
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