<!DOCTYPE html><html lang="en"><head><meta charSet="utf-8"/><meta http-equiv="X-UA-Compatible" content="IE=edge"/><title>Java runtime · Apache Druid</title><meta name="viewport" content="width=device-width, initial-scale=1.0"/><link rel="canonical" href="https://druid.apache.org/docs/latest/operations/java.html"/><meta name="generator" content="Docusaurus"/><meta name="description" content="&lt;!--"/><meta name="docsearch:language" content="en"/><meta name="docsearch:version" content="25.0.0" /><meta property="og:title" content="Java runtime · 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/npm/docsearch.js@2/dist/cdn/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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model</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/ingestion/rollup.html">Data rollup</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/ingestion/partitioning.html">Partitioning</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/ingestion/ingestion-spec.html">Ingestion spec</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/ingestion/schema-design.html">Schema design tips</a></li><div class="navGroup subNavGroup"><h4 class="navGroupSubcategoryTitle">Stream ingestion</h4><ul><li class="navListItem"><a class="navItem" href="/docs/latest/development/extensions-core/kafka-ingestion.html">Apache Kafka ingestion</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/development/extensions-core/kafka-supervisor-reference.html">Apache Kafka supervisor</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/development/extensions-core/kafka-supervisor-operations.html">Apache Kafka operations</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/development/extensions-core/kinesis-ingestion.html">Amazon Kinesis</a></li></ul></div><div class="navGroup subNavGroup"><h4 class="navGroupSubcategoryTitle">Batch ingestion</h4><ul><li class="navListItem"><a class="navItem" href="/docs/latest/ingestion/native-batch.html">Native batch</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/ingestion/native-batch-input-sources.html">Native batch: input sources</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/ingestion/migrate-from-firehose.html">Migrate from firehose</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/ingestion/hadoop.html">Hadoop-based</a></li></ul></div><div class="navGroup subNavGroup"><h4 class="navGroupSubcategoryTitle">SQL-based ingestion 🆕</h4><ul><li class="navListItem"><a class="navItem" href="/docs/latest/multi-stage-query/index.html">Overview</a></li><li class="navListItem"><a 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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 class="navListItem"><a class="navItem" href="/docs/latest/data-management/index.html">Overview</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/data-management/update.html">Data updates</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/data-management/delete.html">Data deletion</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/data-management/schema-changes.html">Schema changes</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/data-management/compaction.html">Compaction</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/data-management/automatic-compaction.html">Automatic compaction</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle collapsible">Querying<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"><div class="navGroup subNavGroup"><h4 class="navGroupSubcategoryTitle">Druid SQL</h4><ul><li class="navListItem"><a class="navItem" href="/docs/latest/querying/sql.html">Overview and syntax</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/querying/sql-data-types.html">SQL data types</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/querying/sql-operators.html">Operators</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/querying/sql-scalar.html">Scalar functions</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/querying/sql-aggregations.html">Aggregation functions</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/querying/sql-multivalue-string-functions.html">Multi-value 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class="navListItem"><a class="navItem" href="/docs/latest/misc/math-expr.html">Expressions</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/querying/having.html">Having filters (groupBy)</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/querying/limitspec.html">Sorting and limiting (groupBy)</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/querying/topnmetricspec.html">Sorting (topN)</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/querying/sorting-orders.html">String comparators</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/querying/virtual-columns.html">Virtual columns</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/development/geo.html">Spatial filters</a></li></ul></div></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle collapsible">Configuration<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 class="navListItem"><a class="navItem" href="/docs/latest/configuration/index.html">Configuration reference</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/development/extensions.html">Extensions</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/configuration/logging.html">Logging</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle collapsible">Operations<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 class="navListItem"><a class="navItem" href="/docs/latest/operations/web-console.html">Web console</a></li><li class="navListItem navListItemActive"><a class="navItem" href="/docs/latest/operations/java.html">Java runtime</a></li><div class="navGroup subNavGroup"><h4 class="navGroupSubcategoryTitle">Security</h4><ul><li class="navListItem"><a class="navItem" href="/docs/latest/operations/security-overview.html">Security overview</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/operations/security-user-auth.html">User authentication and authorization</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/operations/auth-ldap.html">LDAP auth</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/operations/password-provider.html">Password providers</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/operations/dynamic-config-provider.html">Dynamic Config Providers</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/operations/tls-support.html">TLS support</a></li></ul></div><div class="navGroup subNavGroup"><h4 class="navGroupSubcategoryTitle">Performance tuning</h4><ul><li class="navListItem"><a class="navItem" href="/docs/latest/operations/basic-cluster-tuning.html">Basic cluster tuning</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/operations/segment-optimization.html">Segment size optimization</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/operations/mixed-workloads.html">Mixed workloads</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/operations/http-compression.html">HTTP compression</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/operations/clean-metadata-store.html">Automated metadata cleanup</a></li></ul></div><div class="navGroup subNavGroup"><h4 class="navGroupSubcategoryTitle">Monitoring</h4><ul><li class="navListItem"><a class="navItem" href="/docs/latest/operations/request-logging.html">Request logging</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/operations/metrics.html">Metrics</a></li><li 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href="/docs/latest/operations/reset-cluster.html">reset-cluster tool</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/operations/insert-segment-to-db.html">insert-segment-to-db tool</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/operations/pull-deps.html">pull-deps tool</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/operations/deep-storage-migration.html">Deep storage migration</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/operations/export-metadata.html">Export Metadata Tool</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/operations/metadata-migration.html">Metadata Migration</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/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 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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 class="navListItem"><a class="navItem" href="/docs/latest/misc/papers-and-talks.html">Papers</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle collapsible">Hidden<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 class="navListItem"><a class="navItem" href="/docs/latest/comparisons/druid-vs-elasticsearch.html">Apache Druid vs Elasticsearch</a></li><li class="navListItem"><a class="navItem" href="/docs/latest/comparisons/druid-vs-key-value.html">Apache Druid vs. Key/Value Stores (HBase/Cassandra/OpenTSDB)</a></li><li class="navListItem"><a class="navItem" 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<p>Apache Druid is written in Java and requires a Java runtime. This page provides details about obtaining and configuring
a Java runtime for Druid.</p>
<h2><a class="anchor" aria-hidden="true" id="selecting-a-java-runtime"></a><a href="#selecting-a-java-runtime" 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>Selecting a Java runtime</h2>
<p>Druid fully supports Java 8 and 11, and has experimental support for <a href="#java-17">Java 17</a>.
The project team recommends Java 11.</p>
<p>The project team recommends using an OpenJDK-based Java distribution. There are many free and actively-supported
distributions available, including
<a href="https://docs.aws.amazon.com/corretto/latest/corretto-11-ug/what-is-corretto-11.html">Amazon Corretto</a>,
<a href="https://www.azul.com/downloads/?version=java-11-lts&amp;package=jdk">Azul Zulu</a>, and
<a href="https://adoptium.net/temurin/releases?version=11">Eclipse Temurin</a>.
The project team does not recommend any specific distribution over any other.</p>
<p>Druid relies on the environment variables <code>JAVA_HOME</code> or <code>DRUID_JAVA_HOME</code> to find Java on the machine. You can set
<code>DRUID_JAVA_HOME</code> if there is more than one instance of Java. To verify Java requirements for your environment, run the
<code>bin/verify-java</code> script.</p>
<h2><a class="anchor" aria-hidden="true" id="garbage-collection"></a><a href="#garbage-collection" 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>Garbage collection</h2>
<p>In general, the project team recommends using the G1 collector with default settings. This is the default collector in
Java 11. To enable G1 on Java 8, use <code>-XX:+UseG1GC</code>. There is no harm in explicitly specifying this on Java 11 as well.</p>
<p>Garbage collector selection and tuning is a form of sport in the Java community. There may be situations where adjusting
garbage collection configuration improves or worsens performance. The project team's guidance is that most people do
not need to stray away from G1 with default settings.</p>
<h2><a class="anchor" aria-hidden="true" id="strong-encapsulation"></a><a href="#strong-encapsulation" 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>Strong encapsulation</h2>
<p>Java 9 and beyond (including Java 11) include the capability for
<a href="https://dev.java/learn/strong-encapsulation-(of-jdk-internals)/">strong encapsulation</a> of internal JDK APIs. Druid
uses certain internal JDK APIs for functionality- and performance-related reasons. In Java 11, this leads to log
messages like the following:</p>
<pre><code class="hljs"><span class="hljs-symbol">WARNING: </span>An illegal reflective access operation has occurred
<span class="hljs-symbol">WARNING: </span>Use --illegal-access=warn to enable warnings of further illegal reflective access operations
<span class="hljs-symbol">WARNING: </span>All illegal access operations will be denied in a future release
</code></pre>
<p>These warning messages are harmless, and can be ignored. However, you can avoid them entirely if you wish by adding the
following Java command line parameters. These parameters are not part of the default configurations that ship with
Druid, because Java 8 does not recognize these parameters and fails to start up if they are provided.</p>
<p>To do this, add the following lines to your <code>jvm.config</code> files:</p>
<pre><code class="hljs">--<span class="hljs-keyword">add</span>-exports=java.<span class="hljs-keyword">base</span>/jdk.<span class="hljs-keyword">internal</span>.<span class="hljs-keyword">ref</span>=ALL-UNNAMED
--<span class="hljs-keyword">add</span>-exports=java.<span class="hljs-keyword">base</span>/jdk.<span class="hljs-keyword">internal</span>.misc=ALL-UNNAMED
--<span class="hljs-keyword">add</span>-opens=java.<span class="hljs-keyword">base</span>/java.lang=ALL-UNNAMED
--<span class="hljs-keyword">add</span>-opens=java.<span class="hljs-keyword">base</span>/java.io=ALL-UNNAMED
--<span class="hljs-keyword">add</span>-opens=java.<span class="hljs-keyword">base</span>/java.nio=ALL-UNNAMED
--<span class="hljs-keyword">add</span>-opens=java.<span class="hljs-keyword">base</span>/jdk.<span class="hljs-keyword">internal</span>.<span class="hljs-keyword">ref</span>=ALL-UNNAMED
--<span class="hljs-keyword">add</span>-opens=java.<span class="hljs-keyword">base</span>/sun.nio.ch=ALL-UNNAMED
</code></pre>
<p>Additionally, tasks run by <a href="/docs/latest/design/architecture.html">MiddleManagers</a> execute in separate JVMs. The command line for
these JVMs is given by <code>druid.indexer.runner.javaOptsArray</code> or <code>druid.indexer.runner.javaOpts</code> in
<code>middleManager/runtime.properties</code>. Java command line parameters for tasks must be specified here. For example, use
a line like the following:</p>
<pre><code class="hljs"><span class="hljs-attr">druid.indexer.runner.javaOptsArray</span>=[<span class="hljs-string">"-server"</span>,<span class="hljs-string">"-Xms1g"</span>,<span class="hljs-string">"-Xmx1g"</span>,<span class="hljs-string">"-XX:MaxDirectMemorySize=1g"</span>,<span class="hljs-string">"-Duser.timezone=UTC"</span>,<span class="hljs-string">"-Dfile.encoding=UTF-8"</span>,<span class="hljs-string">"-XX:+ExitOnOutOfMemoryError"</span>,<span class="hljs-string">"-Djava.util.logging.manager=org.apache.logging.log4j.jul.LogManager"</span>,<span class="hljs-string">"--add-exports=java.base/jdk.internal.ref=ALL-UNNAMED"</span>,<span class="hljs-string">"--add-exports=java.base/jdk.internal.misc=ALL-UNNAMED"</span>,<span class="hljs-string">"--add-opens=java.base/java.lang=ALL-UNNAMED"</span>,<span class="hljs-string">"--add-opens=java.base/java.io=ALL-UNNAMED"</span>,<span class="hljs-string">"--add-opens=java.base/java.nio=ALL-UNNAMED"</span>,<span class="hljs-string">"--add-opens=java.base/jdk.internal.ref=ALL-UNNAMED"</span>,<span class="hljs-string">"--add-opens=java.base/sun.nio.ch=ALL-UNNAMED"</span>]
</code></pre>
<p>The <code>Xms</code>, <code>Xmx</code>, and <code>MaxDirectMemorySize</code> parameters in the line above are merely an example. You may use different
values in your specific environment.</p>
<h2><a class="anchor" aria-hidden="true" id="java-17"></a><a href="#java-17" 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>Java 17</h2>
<p>Druid has experimental support for Java 17.</p>
<p>An important change in Java 17 is that <a href="#strong-encapsulation">strong encapsulation</a> is enabled by default. The various
<code>--add-opens</code> and <code>--add-exports</code> parameters listed in the <a href="#strong-encapsulation">strong encapsulation</a> section are
required in all <code>jvm.config</code> files and in <code>druid.indexer.runner.javaOpts</code> or <code>druid.indexer.runner.javaOptsArray</code> on
MiddleManagers. Failure to include these parameters leads to failure of various operations.</p>
<p>In addition, Druid's launch scripts detect Java 17 and log the following message rather than starting up:</p>
<pre><code class="hljs">Druid requires Java <span class="hljs-number">8</span> <span class="hljs-keyword">or</span> <span class="hljs-number">11.</span> Your current version <span class="hljs-keyword">is</span>: <span class="hljs-number">17.</span>X.Y.
</code></pre>
<p>You can skip this check with an environment variable:</p>
<pre><code class="hljs"><span class="hljs-builtin-name">export</span> <span class="hljs-attribute">DRUID_SKIP_JAVA_CHECK</span>=1
</code></pre>
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