<!DOCTYPE html><html lang="en"><head><meta charSet="utf-8"/><meta http-equiv="X-UA-Compatible" content="IE=edge"/><title>Metadata storage · Apache Druid</title><meta name="viewport" content="width=device-width"/><link rel="canonical" href="https://druid.apache.org/docs/0.18.0/dependencies/metadata-storage.html"/><meta name="generator" content="Docusaurus"/><meta name="description" content="&lt;!--"/><meta name="docsearch:language" content="en"/><meta name="docsearch:version" content="0.18.0" /><meta property="og:title" content="Metadata storage · Apache Druid"/><meta property="og:type" content="website"/><meta property="og:url" content="https://druid.apache.org/index.html"/><meta property="og:description" content="&lt;!--"/><meta property="og:image" content="https://druid.apache.org/img/druid_nav.png"/><meta name="twitter:card" content="summary"/><meta name="twitter:image" content="https://druid.apache.org/img/druid_nav.png"/><link rel="shortcut icon" href="/img/favicon.png"/><link rel="stylesheet" href="https://cdn.jsdelivr.net/docsearch.js/1/docsearch.min.css"/><link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/highlight.js/9.12.0/styles/default.min.css"/><script async="" src="https://www.googletagmanager.com/gtag/js?id=UA-131010415-1"></script><script>
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console</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/operations/export-metadata.html">Export Metadata Tool</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/operations/getting-started.html">Getting started with Apache Druid</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/operations/metadata-migration.html">Metadata Migration</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/operations/segment-optimization.html">Segment Size Optimization</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/operations/use_sbt_to_build_fat_jar.html">Content for build.sbt</a></li></ul></div></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle collapsible">Development<span class="arrow"><svg width="24" height="24" viewBox="0 0 24 24"><path fill="#565656" d="M7.41 15.41L12 10.83l4.59 4.58L18 14l-6-6-6 6z"></path><path d="M0 0h24v24H0z" fill="none"></path></svg></span></h3><ul class="hide"><li 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class="navListItem"><a class="navItem" href="/docs/0.18.0/comparisons/druid-vs-spark.html">Apache Druid vs Spark</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/comparisons/druid-vs-sql-on-hadoop.html">Apache Druid vs SQL-on-Hadoop</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/design/auth.html">Authentication and Authorization</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/design/broker.html">Broker</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/design/coordinator.html">Coordinator Process</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/design/historical.html">Historical Process</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/design/indexer.html">Indexer Process</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/design/indexing-service.html">Indexing Service</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/design/middlemanager.html">MiddleManager Process</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/design/overlord.html">Overlord Process</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/design/router.html">Router Process</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/design/peons.html">Peons</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/development/extensions-core/approximate-histograms.html">Approximate Histogram aggregators</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/development/extensions-core/avro.html">Apache Avro</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/development/extensions-core/azure.html">Microsoft Azure</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/development/extensions-core/bloom-filter.html">Bloom Filter</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/development/extensions-core/datasketches-extension.html">DataSketches extension</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/development/extensions-core/datasketches-hll.html">DataSketches HLL Sketch module</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/development/extensions-core/datasketches-quantiles.html">DataSketches Quantiles Sketch module</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/development/extensions-core/datasketches-theta.html">DataSketches Theta Sketch module</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/development/extensions-core/datasketches-tuple.html">DataSketches Tuple Sketch module</a></li><li class="navListItem"><a class="navItem" href="/docs/0.18.0/development/extensions-core/druid-basic-security.html">Basic Security</a></li><li class="navListItem"><a class="navItem" 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<p>The Metadata Storage is an external dependency of Apache Druid. Druid uses it to store
various metadata about the system, but not to store the actual data. There are
a number of tables used for various purposes described below.</p>
<p>Derby is the default metadata store for Druid, however, it is not suitable for production.
<a href="/docs/0.18.0/development/extensions-core/mysql.html">MySQL</a> and <a href="/docs/0.18.0/development/extensions-core/postgresql.html">PostgreSQL</a> are more production suitable metadata stores.</p>
<blockquote>
<p>The Metadata Storage stores the entire metadata which is essential for a Druid cluster to work.
For production clusters, consider using MySQL or PostgreSQL instead of Derby.
Also, it's highly recommended to set up a high availability environment
because there is no way to restore if you lose any metadata.</p>
</blockquote>
<h2><a class="anchor" aria-hidden="true" id="using-derby"></a><a href="#using-derby" 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>Using Derby</h2>
<p>Add the following to your Druid configuration.</p>
<pre><code class="hljs css language-properties"><span class="hljs-meta">druid.metadata.storage.type</span>=<span class="hljs-string">derby</span>
<span class="hljs-meta">druid.metadata.storage.connector.connectURI</span>=<span class="hljs-string">jdbc:derby://localhost:1527//opt/var/druid_state/derby;create=true</span>
</code></pre>
<h2><a class="anchor" aria-hidden="true" id="mysql"></a><a href="#mysql" 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>MySQL</h2>
<p>See <a href="/docs/0.18.0/development/extensions-core/mysql.html">mysql-metadata-storage extension documentation</a>.</p>
<h2><a class="anchor" aria-hidden="true" id="postgresql"></a><a href="#postgresql" 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>PostgreSQL</h2>
<p>See <a href="/docs/0.18.0/development/extensions-core/postgresql.html">postgresql-metadata-storage</a>.</p>
<h2><a class="anchor" aria-hidden="true" id="adding-custom-dbcp-properties"></a><a href="#adding-custom-dbcp-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>Adding custom dbcp properties</h2>
<p>NOTE: These properties are not settable through the <code>druid.metadata.storage.connector.dbcp properties</code>: <code>username</code>, <code>password</code>, <code>connectURI</code>, <code>validationQuery</code>, <code>testOnBorrow</code>. These must be set through <code>druid.metadata.storage.connector</code> properties.</p>
<p>Example supported properties:</p>
<pre><code class="hljs css language-properties"><span class="hljs-meta">druid.metadata.storage.connector.dbcp.maxConnLifetimeMillis</span>=<span class="hljs-string">1200000</span>
<span class="hljs-meta">druid.metadata.storage.connector.dbcp.defaultQueryTimeout</span>=<span class="hljs-string">30000</span>
</code></pre>
<p>See <a href="https://commons.apache.org/proper/commons-dbcp/configuration.html">BasicDataSource Configuration</a> for full list.</p>
<h2><a class="anchor" aria-hidden="true" id="metadata-storage-tables"></a><a href="#metadata-storage-tables" 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>Metadata storage tables</h2>
<h3><a class="anchor" aria-hidden="true" id="segments-table"></a><a href="#segments-table" 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>Segments table</h3>
<p>This is dictated by the <code>druid.metadata.storage.tables.segments</code> property.</p>
<p>This table stores metadata about the segments that should be available in the system. (This set of segments is called
&quot;used segments&quot; elsewhere in the documentation and throughout the project.) The table is polled by the
<a href="/docs/0.18.0/design/coordinator.html">Coordinator</a> to determine the set of segments that should be available for querying in the
system. The table has two main functional columns, the other columns are for indexing purposes.</p>
<p>Value 1 in the <code>used</code> column means that the segment should be &quot;used&quot; by the cluster (i.e., it should be loaded and
available for requests). Value 0 means that the segment should not be loaded into the cluster. We do this as a means of
unloading segments from the cluster without actually removing their metadata (which allows for simpler rolling back if
that is ever an issue).</p>
<p>The <code>payload</code> column stores a JSON blob that has all of the metadata for the segment (some of the data stored in this payload is redundant with some of the columns in the table, that is intentional). This looks something like</p>
<pre><code class="hljs css language-json">{
 <span class="hljs-attr">"dataSource"</span>:<span class="hljs-string">"wikipedia"</span>,
 <span class="hljs-attr">"interval"</span>:<span class="hljs-string">"2012-05-23T00:00:00.000Z/2012-05-24T00:00:00.000Z"</span>,
 <span class="hljs-attr">"version"</span>:<span class="hljs-string">"2012-05-24T00:10:00.046Z"</span>,
 <span class="hljs-attr">"loadSpec"</span>:{
    <span class="hljs-attr">"type"</span>:<span class="hljs-string">"s3_zip"</span>,
    <span class="hljs-attr">"bucket"</span>:<span class="hljs-string">"bucket_for_segment"</span>,
    <span class="hljs-attr">"key"</span>:<span class="hljs-string">"path/to/segment/on/s3"</span>
 },
 <span class="hljs-attr">"dimensions"</span>:<span class="hljs-string">"comma-delimited-list-of-dimension-names"</span>,
 <span class="hljs-attr">"metrics"</span>:<span class="hljs-string">"comma-delimited-list-of-metric-names"</span>,
 <span class="hljs-attr">"shardSpec"</span>:{<span class="hljs-attr">"type"</span>:<span class="hljs-string">"none"</span>},
 <span class="hljs-attr">"binaryVersion"</span>:<span class="hljs-number">9</span>,
 <span class="hljs-attr">"size"</span>:size_of_segment,
 <span class="hljs-attr">"identifier"</span>:<span class="hljs-string">"wikipedia_2012-05-23T00:00:00.000Z_2012-05-24T00:00:00.000Z_2012-05-23T00:10:00.046Z"</span>
}
</code></pre>
<p>Note that the format of this blob can and will change from time-to-time.</p>
<h3><a class="anchor" aria-hidden="true" id="rule-table"></a><a href="#rule-table" 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>Rule table</h3>
<p>The rule table is used to store the various rules about where segments should
land. These rules are used by the <a href="/docs/0.18.0/design/coordinator.html">Coordinator</a>
when making segment (re-)allocation decisions about the cluster.</p>
<h3><a class="anchor" aria-hidden="true" id="config-table"></a><a href="#config-table" 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>Config table</h3>
<p>The config table is used to store runtime configuration objects. We do not have
many of these yet and we are not sure if we will keep this mechanism going
forward, but it is the beginnings of a method of changing some configuration
parameters across the cluster at runtime.</p>
<h3><a class="anchor" aria-hidden="true" id="task-related-tables"></a><a href="#task-related-tables" 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>Task-related tables</h3>
<p>There are also a number of tables created and used by the <a href="/docs/0.18.0/design/overlord.html">Overlord</a> and <a href="/docs/0.18.0/design/middlemanager.html">MiddleManager</a> when managing tasks.</p>
<h3><a class="anchor" aria-hidden="true" id="audit-table"></a><a href="#audit-table" 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>Audit table</h3>
<p>The Audit table is used to store the audit history for configuration changes
e.g rule changes done by <a href="/docs/0.18.0/design/coordinator.html">Coordinator</a> and other
config changes.</p>
<p>##Accessed by: ##</p>
<p>The Metadata Storage is accessed only by:</p>
<ol>
<li>Indexing Service Processes (if any)</li>
<li>Realtime Processes (if any)</li>
<li>Coordinator Processes</li>
</ol>
<p>Thus you need to give permissions (e.g., in AWS Security Groups) only for these machines to access the Metadata storage.</p>
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