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aria-label="Breadcrumbs"><ul class="breadcrumbs" itemscope="" itemtype="https://schema.org/BreadcrumbList"><li class="breadcrumbs__item"><a aria-label="Home page" class="breadcrumbs__link" href="/"><svg viewBox="0 0 24 24" class="breadcrumbHomeIcon_YNFT"><path d="M10 19v-5h4v5c0 .55.45 1 1 1h3c.55 0 1-.45 1-1v-7h1.7c.46 0 .68-.57.33-.87L12.67 3.6c-.38-.34-.96-.34-1.34 0l-8.36 7.53c-.34.3-.13.87.33.87H5v7c0 .55.45 1 1 1h3c.55 0 1-.45 1-1z" fill="currentColor"></path></svg></a></li><li class="breadcrumbs__item"><span class="breadcrumbs__link">Design</span><meta itemprop="position" content="1"></li><li itemscope="" itemprop="itemListElement" itemtype="https://schema.org/ListItem" class="breadcrumbs__item breadcrumbs__item--active"><span class="breadcrumbs__link" itemprop="name">Metadata storage</span><meta itemprop="position" content="2"></li></ul></nav><div class="tocCollapsible_ETCw theme-doc-toc-mobile tocMobile_ITEo"><button type="button" class="clean-btn tocCollapsibleButton_TO0P">On this page</button></div><div class="theme-doc-markdown markdown"><header><h1>Metadata storage</h1></header><p>Apache Druid relies on an external dependency for metadata storage. |
| Druid uses the metadata store to house various metadata about the system, but not to store the actual data. |
| The metadata store retains all metadata essential for a Druid cluster to work.</p><p>The metadata store includes the following:</p><ul><li>Segments records</li><li>Rule records</li><li>Configuration records</li><li>Task-related tables</li><li>Audit records</li></ul><p>Derby is the default metadata store for Druid, however, it is not suitable for production. |
| <a href="/docs/latest/development/extensions-core/mysql">MySQL</a> and <a href="/docs/latest/development/extensions-core/postgresql">PostgreSQL</a> are more production suitable metadata stores. |
| See <a href="/docs/latest/configuration/#metadata-storage">Metadata storage configuration</a> for the default configuration settings.</p><div class="theme-admonition theme-admonition-info alert alert--info admonition_LlT9"><div class="admonitionHeading_tbUL"><span class="admonitionIcon_kALy"><svg viewBox="0 0 14 16"><path fill-rule="evenodd" d="M7 2.3c3.14 0 5.7 2.56 5.7 5.7s-2.56 5.7-5.7 5.7A5.71 5.71 0 0 1 1.3 8c0-3.14 2.56-5.7 5.7-5.7zM7 1C3.14 1 0 4.14 0 8s3.14 7 7 7 7-3.14 7-7-3.14-7-7-7zm1 3H6v5h2V4zm0 6H6v2h2v-2z"></path></svg></span>info</div><div class="admonitionContent_S0QG"><p> We also recommend you set up a high availability environment because there is no way to restore lost metadata.</p></div></div><h2 class="anchor anchorWithStickyNavbar_LWe7" id="available-metadata-stores">Available metadata stores<a href="#available-metadata-stores" class="hash-link" aria-label="Direct link to Available metadata stores" title="Direct link to Available metadata stores"></a></h2><p>Druid supports Derby, MySQL, and PostgreSQL for storing metadata. </p><h3 class="anchor anchorWithStickyNavbar_LWe7" id="derby">Derby<a href="#derby" class="hash-link" aria-label="Direct link to Derby" title="Direct link to Derby"></a></h3><div class="theme-admonition theme-admonition-info alert alert--info admonition_LlT9"><div class="admonitionHeading_tbUL"><span class="admonitionIcon_kALy"><svg viewBox="0 0 14 16"><path fill-rule="evenodd" d="M7 2.3c3.14 0 5.7 2.56 5.7 5.7s-2.56 5.7-5.7 5.7A5.71 5.71 0 0 1 1.3 8c0-3.14 2.56-5.7 5.7-5.7zM7 1C3.14 1 0 4.14 0 8s3.14 7 7 7 7-3.14 7-7-3.14-7-7-7zm1 3H6v5h2V4zm0 6H6v2h2v-2z"></path></svg></span>info</div><div class="admonitionContent_S0QG"><p> For production clusters, consider using MySQL or PostgreSQL instead of Derby.</p></div></div><p>Configure metadata storage with Derby by setting the following properties in your Druid configuration.</p><div class="language-properties codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-properties codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">druid.metadata.storage.type=derby</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">druid.metadata.storage.connector.connectURI=jdbc:derby://localhost:1527//opt/var/druid_state/derby;create=true</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg viewBox="0 0 24 24" class="copyButtonIcon_y97N"><path fill="currentColor" d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg viewBox="0 0 24 24" class="copyButtonSuccessIcon_LjdS"><path fill="currentColor" d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><h3 class="anchor anchorWithStickyNavbar_LWe7" id="mysql">MySQL<a href="#mysql" class="hash-link" aria-label="Direct link to MySQL" title="Direct link to MySQL"></a></h3><p>See <a href="/docs/latest/development/extensions-core/mysql">mysql-metadata-storage extension documentation</a>.</p><h3 class="anchor anchorWithStickyNavbar_LWe7" id="postgresql">PostgreSQL<a href="#postgresql" class="hash-link" aria-label="Direct link to PostgreSQL" title="Direct link to PostgreSQL"></a></h3><p>See <a href="/docs/latest/development/extensions-core/postgresql">postgresql-metadata-storage</a>.</p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="adding-custom-dbcp-properties">Adding custom DBCP properties<a href="#adding-custom-dbcp-properties" class="hash-link" aria-label="Direct link to Adding custom DBCP properties" title="Direct link to Adding custom DBCP properties"></a></h2><p>You can add custom properties to customize the database connection pool (DBCP) for connecting to the metadata store. |
| Define these properties with a <code>druid.metadata.storage.connector.dbcp.</code> prefix. |
| For example:</p><div class="language-properties codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-properties codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">druid.metadata.storage.connector.dbcp.maxConnLifetimeMillis=1200000</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">druid.metadata.storage.connector.dbcp.defaultQueryTimeout=30000</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg viewBox="0 0 24 24" class="copyButtonIcon_y97N"><path fill="currentColor" d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg viewBox="0 0 24 24" class="copyButtonSuccessIcon_LjdS"><path fill="currentColor" d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>Certain properties cannot be set through <code>druid.metadata.storage.connector.dbcp.</code> and must be set with the prefix <code>druid.metadata.storage.connector.</code>:</p><ul><li><code>username</code></li><li><code>password</code></li><li><code>connectURI</code></li><li><code>validationQuery</code></li><li><code>testOnBorrow</code></li></ul><p>See <a href="https://commons.apache.org/proper/commons-dbcp/configuration" target="_blank" rel="noopener noreferrer">BasicDataSource Configuration</a> for a full list of configurable properties.</p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="metadata-storage-tables">Metadata storage tables<a href="#metadata-storage-tables" class="hash-link" aria-label="Direct link to Metadata storage tables" title="Direct link to Metadata storage tables"></a></h2><p>This section describes the various tables in metadata storage.</p><h3 class="anchor anchorWithStickyNavbar_LWe7" id="segments-table">Segments table<a href="#segments-table" class="hash-link" aria-label="Direct link to Segments table" title="Direct link to Segments table"></a></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 |
| "used segments" elsewhere in the documentation and throughout the project.) The table is polled by the |
| <a href="/docs/latest/design/coordinator">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 "used" 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). The <code>used</code> column has a corresponding <code>used_status_last_updated</code> column which denotes the time |
| when the <code>used</code> status of the segment was last updated. This information can be used by the Coordinator to determine if |
| a segment is a candidate for deletion (if automated segment killing is enabled).</p><p>The <code>payload</code> column stores a JSON blob that has all of the metadata for the segment. |
| Some of the data in the <code>payload</code> column intentionally duplicates data from other columns in the segments table. |
| As an example, the <code>payload</code> column may take the following form:</p><div class="language-json codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-json codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token punctuation" style="color:rgb(199, 146, 234)">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </span><span class="token property">"dataSource"</span><span class="token operator" style="color:rgb(137, 221, 255)">:</span><span class="token string" style="color:rgb(195, 232, 141)">"wikipedia"</span><span class="token punctuation" style="color:rgb(199, 146, 234)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </span><span class="token property">"interval"</span><span class="token operator" style="color:rgb(137, 221, 255)">:</span><span class="token string" style="color:rgb(195, 232, 141)">"2012-05-23T00:00:00.000Z/2012-05-24T00:00:00.000Z"</span><span class="token punctuation" style="color:rgb(199, 146, 234)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </span><span class="token property">"version"</span><span class="token operator" style="color:rgb(137, 221, 255)">:</span><span class="token string" style="color:rgb(195, 232, 141)">"2012-05-24T00:10:00.046Z"</span><span class="token punctuation" style="color:rgb(199, 146, 234)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </span><span class="token property">"loadSpec"</span><span class="token operator" style="color:rgb(137, 221, 255)">:</span><span class="token punctuation" style="color:rgb(199, 146, 234)">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </span><span class="token property">"type"</span><span class="token operator" style="color:rgb(137, 221, 255)">:</span><span class="token string" style="color:rgb(195, 232, 141)">"s3_zip"</span><span class="token punctuation" style="color:rgb(199, 146, 234)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </span><span class="token property">"bucket"</span><span class="token operator" style="color:rgb(137, 221, 255)">:</span><span class="token string" style="color:rgb(195, 232, 141)">"bucket_for_segment"</span><span class="token punctuation" style="color:rgb(199, 146, 234)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </span><span class="token property">"key"</span><span class="token operator" style="color:rgb(137, 221, 255)">:</span><span class="token string" style="color:rgb(195, 232, 141)">"path/to/segment/on/s3"</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </span><span class="token punctuation" style="color:rgb(199, 146, 234)">}</span><span class="token punctuation" style="color:rgb(199, 146, 234)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </span><span class="token property">"dimensions"</span><span class="token operator" style="color:rgb(137, 221, 255)">:</span><span class="token string" style="color:rgb(195, 232, 141)">"comma-delimited-list-of-dimension-names"</span><span class="token punctuation" style="color:rgb(199, 146, 234)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </span><span class="token property">"metrics"</span><span class="token operator" style="color:rgb(137, 221, 255)">:</span><span class="token string" style="color:rgb(195, 232, 141)">"comma-delimited-list-of-metric-names"</span><span class="token punctuation" style="color:rgb(199, 146, 234)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </span><span class="token property">"shardSpec"</span><span class="token operator" style="color:rgb(137, 221, 255)">:</span><span class="token punctuation" style="color:rgb(199, 146, 234)">{</span><span class="token property">"type"</span><span class="token operator" style="color:rgb(137, 221, 255)">:</span><span class="token string" style="color:rgb(195, 232, 141)">"none"</span><span class="token punctuation" style="color:rgb(199, 146, 234)">}</span><span class="token punctuation" style="color:rgb(199, 146, 234)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </span><span class="token property">"binaryVersion"</span><span class="token operator" style="color:rgb(137, 221, 255)">:</span><span class="token number" style="color:rgb(247, 140, 108)">9</span><span class="token punctuation" style="color:rgb(199, 146, 234)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </span><span class="token property">"size"</span><span class="token operator" style="color:rgb(137, 221, 255)">:</span><span class="token plain">size_of_segment</span><span class="token punctuation" style="color:rgb(199, 146, 234)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </span><span class="token property">"identifier"</span><span class="token operator" style="color:rgb(137, 221, 255)">:</span><span class="token string" style="color:rgb(195, 232, 141)">"wikipedia_2012-05-23T00:00:00.000Z_2012-05-24T00:00:00.000Z_2012-05-23T00:10:00.046Z"</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"></span><span class="token punctuation" style="color:rgb(199, 146, 234)">}</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg viewBox="0 0 24 24" class="copyButtonIcon_y97N"><path fill="currentColor" d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg viewBox="0 0 24 24" class="copyButtonSuccessIcon_LjdS"><path fill="currentColor" d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><h3 class="anchor anchorWithStickyNavbar_LWe7" id="rule-table">Rule table<a href="#rule-table" class="hash-link" aria-label="Direct link to Rule table" title="Direct link to Rule table"></a></h3><p>The rule table stores the various rules about where segments should |
| land. These rules are used by the <a href="/docs/latest/design/coordinator">Coordinator</a> |
| when making segment (re-)allocation decisions about the cluster.</p><h3 class="anchor anchorWithStickyNavbar_LWe7" id="config-table">Config table<a href="#config-table" class="hash-link" aria-label="Direct link to Config table" title="Direct link to Config table"></a></h3><p>The config table stores 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 class="anchor anchorWithStickyNavbar_LWe7" id="task-related-tables">Task-related tables<a href="#task-related-tables" class="hash-link" aria-label="Direct link to Task-related tables" title="Direct link to Task-related tables"></a></h3><p>Task-related tables are created and used by the <a href="/docs/latest/design/overlord">Overlord</a> and <a href="/docs/latest/design/middlemanager">MiddleManager</a> when managing tasks.</p><h3 class="anchor anchorWithStickyNavbar_LWe7" id="audit-table">Audit table<a href="#audit-table" class="hash-link" aria-label="Direct link to Audit table" title="Direct link to Audit table"></a></h3><p>The audit table stores the audit history for configuration changes |
| such as rule changes done by <a href="/docs/latest/design/coordinator">Coordinator</a> and other |
| config changes.</p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="metadata-storage-access">Metadata storage access<a href="#metadata-storage-access" class="hash-link" aria-label="Direct link to Metadata storage access" title="Direct link to Metadata storage access"></a></h2><p>Only the following processes access the metadata storage:</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) for only these machines to access the metadata storage.</p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="learn-more">Learn more<a href="#learn-more" class="hash-link" aria-label="Direct link to Learn more" title="Direct link to Learn more"></a></h2><p>See the following topics for more information:</p><ul><li><a href="/docs/latest/configuration/#metadata-storage">Metadata storage configuration</a></li><li><a href="/docs/latest/operations/clean-metadata-store">Automated cleanup for metadata records</a></li></ul></div></article><nav class="pagination-nav docusaurus-mt-lg" aria-label="Docs pages"><a class="pagination-nav__link pagination-nav__link--prev" href="/docs/latest/design/deep-storage"><div class="pagination-nav__sublabel">Previous</div><div class="pagination-nav__label">Deep storage</div></a><a class="pagination-nav__link pagination-nav__link--next" href="/docs/latest/design/zookeeper"><div class="pagination-nav__sublabel">Next</div><div class="pagination-nav__label">ZooKeeper</div></a></nav></div></div><div class="col col--3"><div class="tableOfContents_bqdL thin-scrollbar theme-doc-toc-desktop"><ul class="table-of-contents table-of-contents__left-border"><li><a href="#available-metadata-stores" class="table-of-contents__link toc-highlight">Available metadata stores</a><ul><li><a href="#derby" class="table-of-contents__link toc-highlight">Derby</a></li><li><a href="#mysql" class="table-of-contents__link toc-highlight">MySQL</a></li><li><a href="#postgresql" class="table-of-contents__link toc-highlight">PostgreSQL</a></li></ul></li><li><a href="#adding-custom-dbcp-properties" class="table-of-contents__link toc-highlight">Adding custom DBCP properties</a></li><li><a href="#metadata-storage-tables" class="table-of-contents__link toc-highlight">Metadata storage tables</a><ul><li><a href="#segments-table" class="table-of-contents__link toc-highlight">Segments table</a></li><li><a href="#rule-table" class="table-of-contents__link toc-highlight">Rule table</a></li><li><a href="#config-table" class="table-of-contents__link toc-highlight">Config table</a></li><li><a href="#task-related-tables" class="table-of-contents__link toc-highlight">Task-related tables</a></li><li><a href="#audit-table" class="table-of-contents__link toc-highlight">Audit table</a></li></ul></li><li><a href="#metadata-storage-access" class="table-of-contents__link toc-highlight">Metadata storage access</a></li><li><a href="#learn-more" class="table-of-contents__link toc-highlight">Learn more</a></li></ul></div></div></div></div></main></div></div><footer class="footer"><div class="container container-fluid"><div class="footer__bottom text--center"><div class="margin-bottom--sm"><img src="/img/favicon.png" class="themedImage_ToTc themedImage--light_HNdA footer__logo"><img src="/img/favicon.png" class="themedImage_ToTc themedImage--dark_i4oU footer__logo"></div><div class="footer__copyright">Copyright © 2023 Apache Software Foundation. Except where otherwise noted, licensed under CC BY-SA 4.0. Apache Druid, Druid, and the Druid logo are either registered trademarks or trademarks of The Apache Software Foundation in the United States and other countries.</div></div></div></footer></div> |
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