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<p>You can configure the <a href="heron-architecture#stream-manager">Stream
Manager</a> (SM) in a
topology using the parameters below, including how the SM handles <a href="#back-pressure-parameters">back
pressure</a>.</p>
<h2><a class="anchor" aria-hidden="true" id="back-pressure-parameters"></a><a href="#back-pressure-parameters" 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>Back Pressure Parameters</h2>
<table>
<thead>
<tr><th style="text-align:left">Parameter</th><th style="text-align:left">Meaning</th><th style="text-align:left">Default</th></tr>
</thead>
<tbody>
<tr><td style="text-align:left"><code>heron.streammgr.network.backpressure.threshold</code></td><td style="text-align:left">The number of times the SM should wait to see a buffer full while enqueueing data before declaring the start of backpressure</td><td style="text-align:left"><code>3</code></td></tr>
<tr><td style="text-align:left"><code>heron.streammgr.network.backpressure.highwatermark.mb</code></td><td style="text-align:left">The high water mark on the number of megabytes that can be left outstanding on a connection</td><td style="text-align:left"><code>50</code></td></tr>
<tr><td style="text-align:left"><code>heron.streammgr.network.backpressure.lowwatermark.md</code></td><td style="text-align:left">The low water mark on the number of megabytes that can be left outstanding on a connection</td><td style="text-align:left"><code>30</code></td></tr>
<tr><td style="text-align:left"><code>heron.streammgr.network.options.maximum.packet.mb</code></td><td style="text-align:left">The maximum packet size, in megabytes, for the SM's network options</td><td style="text-align:left"><code>100</code></td></tr>
</tbody>
</table>
<h2><a class="anchor" aria-hidden="true" id="timeout-interval"></a><a href="#timeout-interval" 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>Timeout Interval</h2>
<table>
<thead>
<tr><th style="text-align:left">Parameter</th><th style="text-align:left">Meaning</th><th style="text-align:left">Default</th></tr>
</thead>
<tbody>
<tr><td style="text-align:left"><code>heron.streammgr.xormgr.rotatingmap.nbuckets</code></td><td style="text-align:left">TODO</td><td style="text-align:left"><code>3</code></td></tr>
</tbody>
</table>
<h2><a class="anchor" aria-hidden="true" id="other-parameters"></a><a href="#other-parameters" 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>Other Parameters</h2>
<table>
<thead>
<tr><th style="text-align:left">Parameter</th><th style="text-align:left">Meaning</th><th style="text-align:left">Default</th></tr>
</thead>
<tbody>
<tr><td style="text-align:left"><code>heron.streammgr.packet.maximum.size.bytes</code></td><td style="text-align:left">Maximum size (in bytes) of packets sent out from the SM</td><td style="text-align:left"><code>102400</code></td></tr>
<tr><td style="text-align:left"><code>heron.streammgr.cache.drain.frequency.ms</code></td><td style="text-align:left">The frequency (in milliseconds) at which the SM's tuple cache is drained</td><td style="text-align:left"><code>10</code></td></tr>
<tr><td style="text-align:left"><code>heron.streammgr.cache.drain.size.mb</code></td><td style="text-align:left">The size threshold (in megabytes) at which the SM's tuple cache is drained</td><td style="text-align:left"><code>100</code></td></tr>
<tr><td style="text-align:left"><code>heron.streammgr.client.reconnect.interval.sec</code></td><td style="text-align:left">The reconnect interval to other SMs for the SM client (in seconds)</td><td style="text-align:left"><code>1</code></td></tr>
<tr><td style="text-align:left"><code>heron.streammgr.client.reconnect.tmanager.interval.sec</code></td><td style="text-align:left">The reconnect interval to the Topology Manager for the SM client (in seconds)</td><td style="text-align:left"><code>10</code></td></tr>
<tr><td style="text-align:left"><code>heron.streammgr.tmanager.heartbeat.interval.sec</code></td><td style="text-align:left">The interval (in seconds) at which a heartbeat is sent to the Topology Manager</td><td style="text-align:left"><code>10</code></td></tr>
<tr><td style="text-align:left"><code>heron.streammgr.connection.read.batch.size.mb</code></td><td style="text-align:left">The maximum batch size (in megabytes) at which the SM reads from the socket</td><td style="text-align:left"><code>1</code></td></tr>
<tr><td style="text-align:left"><code>heron.streammgr.connection.write.batch.size.mb</code></td><td style="text-align:left">The maximum batch size (in megabytes) to write by the stream manager to the socket</td><td style="text-align:left"><code>1</code></td></tr>
</tbody>
</table>
</span></div></article></div><div class="docs-prevnext"><a class="docs-prev button" href="/docs/next/cluster-config-metrics"><span class="arrow-prev">← </span><span>Metrics Manager</span></a><a class="docs-next button" href="/docs/next/cluster-config-tmanager"><span>Topology Manager</span><span class="arrow-next"> →</span></a></div></div></div><nav class="onPageNav"><ul class="toc-headings"><li><a href="#back-pressure-parameters">Back Pressure Parameters</a></li><li><a href="#timeout-interval">Timeout Interval</a></li><li><a href="#other-parameters">Other Parameters</a></li></ul></nav></div><footer class="nav-footer" id="footer"><div class="apache-disclaimer">Apache Heron is an effort undergoing incubation at <a target="_blank" href="https://apache.org/">The Apache Software Foundation (ASF)</a> sponsored by the Apache Incubator PMC. Incubation is required of all newly accepted projects until a further review indicates that the infrastructure, communications, and decision making process have stabilized in a manner consistent with other successful ASF projects. While incubation status is not necessarily a reflection of the completeness or stability of the code, it does indicate that the project has yet to be fully endorsed by the ASF.<br/><br/>Apache®, the names of Apache projects, and the feather logo are either <a rel="external" href="https://www.apache.org/foundation/marks/list/">registered trademarks or trademarks</a> of the Apache Software Foundation in the United States and/or other countries.<br/><br/><div class="copyright-box">Copyright © 2023 the Apache Software Foundation, Apache Heron, Heron, 
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