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<p>A cache implementation for Druid based on <a href="https://github.com/redis/redis">Redis</a>.</p>
<p>Below are guidance and configuration options known to this module.</p>
<h2><a class="anchor" aria-hidden="true" id="installation"></a><a href="#installation" 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>Installation</h2>
<p>Use <a href="/docs/latest/operations/pull-deps.html">pull-deps</a> tool shipped with Druid to install this <a href="/docs/latest/development/extensions.html#community-extensions">extension</a> on broker, historical and middle manager nodes.</p>
<pre><code class="hljs css language-bash">java -classpath <span class="hljs-string">"druid_dir/lib/*"</span> org.apache.druid.cli.Main tools pull-deps -c org.apache.druid.extensions.contrib:druid-redis-cache:{VERSION}
</code></pre>
<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 this extension after installation,</p>
<ol>
<li><a href="/docs/latest/development/extensions.html#loading-extensions">include</a> this <code>druid-redis-cache</code> extension</li>
<li>to enable cache on broker nodes, follow <a href="/docs/latest/configuration/index.html#broker-caching">broker caching docs</a> to set related properties</li>
<li>to enable cache on historical nodes, follow <a href="/docs/latest/configuration/index.html#historical-caching">historical caching docs</a> to set related properties</li>
<li>to enable cache on middle manager nodes, follow <a href="/docs/latest/configuration/index.html#peon-caching">peon caching docs</a> to set related properties</li>
<li>set <code>druid.cache.type</code> to <code>redis</code></li>
<li>add the following properties</li>
</ol>
<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>
<h3><a class="anchor" aria-hidden="true" id="cluster-mode"></a><a href="#cluster-mode" 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>Cluster mode</h3>
<p>To utilize a redis cluster, following properties must be set.</p>
<p>Note: some redis cloud service providers provide redis cluster service via a redis proxy, for these clusters, please follow the <a href="#standalone-mode">Standalone mode</a> configuration below.</p>
<table>
<thead>
<tr><th>Properties</th><th>Description</th><th>Default</th><th>Required</th></tr>
</thead>
<tbody>
<tr><td><code>druid.cache.cluster.nodes</code></td><td>Redis nodes in a cluster, represented in comma separated string. See example below</td><td>None</td><td>yes</td></tr>
<tr><td><code>druid.cache.cluster.maxRedirection</code></td><td>Max retry count</td><td>5</td><td>no</td></tr>
</tbody>
</table>
<h4><a class="anchor" aria-hidden="true" id="example"></a><a href="#example" 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>Example</h4>
<pre><code class="hljs css language-properties"><span class="hljs-comment"># a typical redis cluster with 6 nodes</span>
<span class="hljs-meta">druid.cache.cluster.nodes</span>=<span class="hljs-string">127.0.0.1:7001,127.0.0.1:7002,127.0.0.1:7003,127.0.0.1:7004,127.0.0.1:7005,127.0.0.1:7006</span>
</code></pre>
<h3><a class="anchor" aria-hidden="true" id="standalone-mode"></a><a href="#standalone-mode" 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>Standalone mode</h3>
<p>To use a standalone redis, following properties must be set.</p>
<table>
<thead>
<tr><th>Properties</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.database</code></td><td>Redis database index</td><td>0</td><td>no</td></tr>
</tbody>
</table>
<p>Note: if both <code>druid.cache.cluster.nodes</code> and <code>druid.cache.host</code> are provided, cluster mode is preferred.</p>
<h3><a class="anchor" aria-hidden="true" id="shared-properties"></a><a href="#shared-properties" 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>Shared Properties</h3>
<p>Except for the properties above, there are some extra properties which can be customized to meet different needs.</p>
<table>
<thead>
<tr><th>Properties</th><th>Description</th><th>Default</th><th>Required</th></tr>
</thead>
<tbody>
<tr><td><code>druid.cache.password</code></td><td>Password to access redis server/cluster</td><td>None</td><td>no</td></tr>
<tr><td><code>druid.cache.expiration</code></td><td>Expiration for cache entries</td><td>P1D</td><td>no</td></tr>
<tr><td><code>druid.cache.timeout</code></td><td>Timeout for connecting to Redis and reading entries from Redis</td><td>PT2S</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>
<p>For <code>druid.cache.expiration</code> and <code>druid.cache.timeout</code> properties, values can be format of <code>Period</code> or a number in milliseconds.</p>
<pre><code class="hljs css language-properties"><span class="hljs-comment"># Period format(recomended)</span>
<span class="hljs-comment"># cache expires after 1 hour</span>
<span class="hljs-meta">druid.cache.expiration</span>=<span class="hljs-string">PT1H</span>
<span class="hljs-comment">
# or in number(milliseconds) format</span>
<span class="hljs-comment"># 1 hour = 3_600_000 milliseconds</span>
<span class="hljs-meta">druid.cache.expiration</span>=<span class="hljs-string">3600000</span>
</code></pre>
<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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