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<p>To use this Apache Druid (incubating) extension, make sure to <a href="/docs/latest/development/extensions.html#loading-extensions">include</a> <code>druid-redis-cache</code> extension.</p>
<p>A cache implementation for Druid based on <a href="https://github.com/antirez/redis">Redis</a>.</p>
<p>Below are the configuration options known to this module.</p>
<p>Note that just adding these properties does not enable the cache. You still need to add the <code>druid.&lt;process-type&gt;.cache.useCache</code> and <code>druid.&lt;process-type&gt;.cache.populateCache</code> properties for the processes you want to enable the cache on as described in the <a href="../../configuration/index.html#cache-configuration">cache configuration docs</a>.</p>
<p>A possible configuration would be to keep the properties below in your <code>common.runtime.properties</code> file (present on all processes) and then add <code>druid.&lt;nodetype&gt;.cache.useCache</code> and <code>druid.&lt;nodetype&gt;.cache.populateCache</code> in the <code>runtime.properties</code> file of the process types you want to enable caching on.</p>
<h2><a class="anchor" aria-hidden="true" id="configuration"></a><a href="#configuration" 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>Configuration</h2>
<table>
<thead>
<tr><th><code>common.runtime.properties</code></th><th>Description</th><th>Default</th><th>Required</th></tr>
</thead>
<tbody>
<tr><td><code>druid.cache.host</code></td><td>Redis server host</td><td>None</td><td>yes</td></tr>
<tr><td><code>druid.cache.port</code></td><td>Redis server port</td><td>None</td><td>yes</td></tr>
<tr><td><code>druid.cache.expiration</code></td><td>Expiration(in milliseconds) for cache entries</td><td>24 * 3600 * 1000</td><td>no</td></tr>
<tr><td><code>druid.cache.timeout</code></td><td>Timeout(in milliseconds) for get cache entries from Redis</td><td>2000</td><td>no</td></tr>
<tr><td><code>druid.cache.maxTotalConnections</code></td><td>Max total connections to Redis</td><td>8</td><td>no</td></tr>
<tr><td><code>druid.cache.maxIdleConnections</code></td><td>Max idle connections to Redis</td><td>8</td><td>no</td></tr>
<tr><td><code>druid.cache.minIdleConnections</code></td><td>Min idle connections to Redis</td><td>0</td><td>no</td></tr>
</tbody>
</table>
<h2><a class="anchor" aria-hidden="true" id="enabling"></a><a href="#enabling" 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>Enabling</h2>
<p>To enable the redis cache, include this module on the loadList and set <code>druid.cache.type</code> to <code>redis</code> in your properties.</p>
<h2><a class="anchor" aria-hidden="true" id="metrics"></a><a href="#metrics" 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>Metrics</h2>
<p>In addition to the normal cache metrics, the redis cache implementation also reports the following in both <code>total</code> and <code>delta</code></p>
<table>
<thead>
<tr><th>Metric</th><th>Description</th><th>Normal value</th></tr>
</thead>
<tbody>
<tr><td><code>query/cache/redis/*/requests</code></td><td>Count of requests to redis cache</td><td>whatever request to redis will increase request count by 1</td></tr>
</tbody>
</table>
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