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class="breadcrumbs__link">Design</span><meta itemprop="position" content="1"></li><li class="breadcrumbs__item"><span class="breadcrumbs__link">Services</span><meta itemprop="position" content="2"></li><li itemscope="" itemprop="itemListElement" itemtype="https://schema.org/ListItem" class="breadcrumbs__item breadcrumbs__item--active"><span class="breadcrumbs__link" itemprop="name">Overlord</span><meta itemprop="position" content="3"></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>Overlord service</h1></header><p>The Overlord service is responsible for accepting tasks, coordinating task distribution, creating locks around tasks, and returning statuses to callers. The Overlord can be configured to run in one of two modes - local or remote (local being default). |
| In local mode, the Overlord is also responsible for creating Peons for executing tasks. When running the Overlord in local mode, all Middle Manager and Peon configurations must be provided as well. |
| Local mode is typically used for simple workflows. In remote mode, the Overlord and Middle Manager are run in separate services and you can run each on a different server. |
| This mode is recommended if you intend to use the indexing service as the single endpoint for all Druid indexing.</p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="configuration">Configuration<a href="#configuration" class="hash-link" aria-label="Direct link to Configuration" title="Direct link to Configuration"></a></h2><p>For Apache Druid Overlord service configuration, see <a href="/docs/31.0.0/configuration/#overlord">Overlord Configuration</a>.</p><p>For basic tuning guidance for the Overlord service, see <a href="/docs/31.0.0/operations/basic-cluster-tuning#overlord">Basic cluster tuning</a>.</p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="http-endpoints">HTTP endpoints<a href="#http-endpoints" class="hash-link" aria-label="Direct link to HTTP endpoints" title="Direct link to HTTP endpoints"></a></h2><p>For a list of API endpoints supported by the Overlord, please see the <a href="/docs/31.0.0/api-reference/service-status-api#overlord">Service status API reference</a>.</p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="blacklisted-workers">Blacklisted workers<a href="#blacklisted-workers" class="hash-link" aria-label="Direct link to Blacklisted workers" title="Direct link to Blacklisted workers"></a></h2><p>If a Middle Manager has task failures above a threshold, the Overlord will blacklist these Middle Managers. No more than 20% of the Middle Managers can be blacklisted. Blacklisted Middle Managers will be periodically whitelisted.</p><p>The following variables can be used to set the threshold and blacklist timeouts.</p><div class="codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-text codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain">druid.indexer.runner.maxRetriesBeforeBlacklist</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">druid.indexer.runner.workerBlackListBackoffTime</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">druid.indexer.runner.workerBlackListCleanupPeriod</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain">druid.indexer.runner.maxPercentageBlacklistWorkers</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><h2 class="anchor anchorWithStickyNavbar_LWe7" id="autoscaling">Autoscaling<a href="#autoscaling" class="hash-link" aria-label="Direct link to Autoscaling" title="Direct link to Autoscaling"></a></h2><p>The autoscaling mechanisms currently in place are tightly coupled with our deployment infrastructure but the framework should be in place for other implementations. We are highly open to new implementations or extensions of the existing mechanisms. In our own deployments, Middle Manager services are Amazon AWS EC2 nodes and they are provisioned to register themselves in a <a href="https://github.com/ning/galaxy" target="_blank" rel="noopener noreferrer">galaxy</a> environment.</p><p>If autoscaling is enabled, new Middle Managers may be added when a task has been in pending state for too long. Middle Managers may be terminated if they have not run any tasks for a period of time.</p></div></article><nav class="pagination-nav docusaurus-mt-lg" aria-label="Docs pages"><a class="pagination-nav__link pagination-nav__link--prev" href="/docs/31.0.0/design/coordinator"><div class="pagination-nav__sublabel">Previous</div><div class="pagination-nav__label">Coordinator</div></a><a class="pagination-nav__link pagination-nav__link--next" href="/docs/31.0.0/design/broker"><div class="pagination-nav__sublabel">Next</div><div class="pagination-nav__label">Broker</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="#configuration" class="table-of-contents__link toc-highlight">Configuration</a></li><li><a href="#http-endpoints" class="table-of-contents__link toc-highlight">HTTP endpoints</a></li><li><a href="#blacklisted-workers" class="table-of-contents__link toc-highlight">Blacklisted workers</a></li><li><a href="#autoscaling" class="table-of-contents__link toc-highlight">Autoscaling</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. 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