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        </script></nav></div><div class="container mainContainer"><div class="wrapper"><div class="post"><header class="postHeader"><h1 class="postHeaderTitle">Implementing a Custom Scheduler</h1></header><article><div><span><!--
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<p>To run a Heron topology, you’ll need to set up a scheduler that is responsible
for topology management. Note: one scheduler is managing only one topology,
for the purpose of better isolation. Heron currently supports the following schedulers out of the box:</p>
<ul>
<li><a href="schedulers-aurora-cluster">Aurora</a></li>
<li><a href="schedulers-k8s-by-hand">Kubernetes</a></li>
<li><a href="schedulers-k8s-with-helm">Kubernetes-Helm</a></li>
<li><a href="schedulers-nomad">Nomad</a></li>
<li><a href="schedulers-local">Local scheduler</a></li>
<li><a href="schedulers-slurm">Slurm scheduler</a></li>
</ul>
<p>If you'd like to run Heron on a not-yet-supported system, such as
<a href="https://aws.amazon.com/ecs/">Amazon ECS</a>, you can create your own scheduler
using Heron's spi, as detailed in the
sections below.</p>
<p>Java is currently the only supported language for custom schedulers. This may
change in the future.</p>
<h2><a class="anchor" aria-hidden="true" id="java-setup"></a><a href="#java-setup" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Java Setup</h2>
<p>In order to create a custom scheduler, you need to import the <code>heron-spi</code>
library into your project.</p>
<h4><a class="anchor" aria-hidden="true" id="maven"></a><a href="#maven" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Maven</h4>
<pre><code class="hljs css language-xml"><span class="hljs-tag">&lt;<span class="hljs-name">dependency</span>&gt;</span>
  <span class="hljs-tag">&lt;<span class="hljs-name">groupId</span>&gt;</span>org.apache.heron<span class="hljs-tag">&lt;/<span class="hljs-name">groupId</span>&gt;</span>
  <span class="hljs-tag">&lt;<span class="hljs-name">artifactId</span>&gt;</span>heron-spi<span class="hljs-tag">&lt;/<span class="hljs-name">artifactId</span>&gt;</span>
  <span class="hljs-tag">&lt;<span class="hljs-name">version</span>&gt;</span>0.20.0-incubating<span class="hljs-tag">&lt;/<span class="hljs-name">version</span>&gt;</span>
<span class="hljs-tag">&lt;/<span class="hljs-name">dependency</span>&gt;</span>
</code></pre>
<h4><a class="anchor" aria-hidden="true" id="gradle"></a><a href="#gradle" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Gradle</h4>
<pre><code class="hljs css language-groovy">dependencies {
  compile <span class="hljs-string">group:</span> <span class="hljs-string">"org.apache.heron"</span>, <span class="hljs-string">name:</span> <span class="hljs-string">"heron-spi"</span>, <span class="hljs-string">version:</span> <span class="hljs-string">"0.20.0-incubating"</span>
}
</code></pre>
<h2><a class="anchor" aria-hidden="true" id="interfaces"></a><a href="#interfaces" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Interfaces</h2>
<p>Creating a custom scheduler involves implementing each of the following Java
interfaces:</p>
<table>
<thead>
<tr><th style="text-align:left">Interface</th><th style="text-align:left">Role</th><th style="text-align:left">Examples</th></tr>
</thead>
<tbody>
<tr><td style="text-align:left"><a href="/api/org/apache/heron/spi/packing/IPacking.html"><code>IPacking</code></a></td><td style="text-align:left">Defines the algorithm used to generate physical plan for a topology.</td><td style="text-align:left"><a href="/api/org/apache/heron/packing/roundrobin/RoundRobinPacking.html">RoundRobin</a></td></tr>
<tr><td style="text-align:left"><a href="/api/org/apache/heron/spi/scheduler/ILauncher.html"><code>ILauncher</code></a></td><td style="text-align:left">Defines how the scheduler is launched</td><td style="text-align:left"><a href="/api/org/apache/heron/scheduler/aurora/AuroraLauncher.html">Aurora</a>, <a href="/api/org/apache/heron/scheduler/local/LocalLauncher.html">local</a></td></tr>
<tr><td style="text-align:left"><a href="/api/org/apache/heron/spi/scheduler/IScheduler.html"><code>IScheduler</code></a></td><td style="text-align:left">Defines the scheduler object used to construct topologies</td><td style="text-align:left"><a href="/api/org/apache/heron/scheduler/local/LocalScheduler.html">local</a></td></tr>
<tr><td style="text-align:left"><a href="/api/org/apache/heron/spi/uploader/IUploader.html"><code>IUploader</code></a></td><td style="text-align:left">Uploads the topology to a shared location accessible to the runtime environment of the topology</td><td style="text-align:left"><a href="/api/org/apache/heron/uploader/localfs/LocalFileSystemUploader.html">local</a> <a href="/api/org/apache/heron/uploader/hdfs/HdfsUploader.html">HDFS</a> <a href="/api/org/apache/heron/uploader/s3/S3Uploader.html">S3</a></td></tr>
</tbody>
</table>
<p>Heron provides a number of built-in implementations out of box.</p>
<h2><a class="anchor" aria-hidden="true" id="running-the-scheduler"></a><a href="#running-the-scheduler" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Running the Scheduler</h2>
<p>To run the a custom scheduler, the implementation of the interfaces above must be specified in the <a href="deployment-configuration">config</a>.
By default, the heron-cli looks for configurations under <code>${HERON_HOME}/conf/</code>. The location can be overridden using option <code>--config-path</code>.
Below is an example showing the command for <a href="user-manuals-heron-cli#submitting-a-topology">topology
submission</a>:</p>
<pre><code class="hljs css language-bash">$ heron submit [cluster-name-storing-your-new-config]/[role]/[env] \
    --config-path [config-folder-path-storing-your-new-config] \
    /path/to/topology/my-topology.jar \
    biz.acme.topologies.MyTopology 
</code></pre>
<p>The implementation for each of the interfaces listed above must be on Heron's
<a href="https://docs.oracle.com/javase/tutorial/essential/environment/paths.html">classpath</a>.</p>
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