<!DOCTYPE html><html lang="en"><head><meta charSet="utf-8"/><meta http-equiv="X-UA-Compatible" content="IE=edge"/><title>Logging · Apache Druid</title><meta name="viewport" content="width=device-width"/><link rel="canonical" href="https://druid.apache.org/docs/0.16.1-incubating/configuration/logging.html"/><meta name="generator" content="Docusaurus"/><meta name="description" content="&lt;!--"/><meta name="docsearch:language" content="en"/><meta name="docsearch:version" content="0.16.1-incubating" /><meta property="og:title" content="Logging · 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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class="icon-toc"></i></div></div><div class="navGroups"><div class="navGroup"><h3 class="navGroupCategoryTitle collapsible">Getting started<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/0.16.1-incubating/design/index.html">Introduction to Apache Druid</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/tutorials/index.html">Quickstart</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/operations/single-server.html">Single server deployment</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/tutorials/cluster.html">Clustered deployment</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle collapsible">Tutorials<span class="arrow"><svg width="24" 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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/0.16.1-incubating/ingestion/index.html">Ingestion</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/ingestion/data-formats.html">Data formats</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/ingestion/schema-design.html">Schema design tips</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/ingestion/data-management.html">Data management</a></li><div class="navGroup subNavGroup"><h4 class="navGroupSubcategoryTitle">Stream ingestion</h4><ul><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/development/extensions-core/kafka-ingestion.html">Apache Kafka</a></li><li class="navListItem"><a class="navItem" 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href="/docs/0.16.1-incubating/querying/timeboundaryquery.html">TimeBoundary</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/querying/segmentmetadataquery.html">SegmentMetadata</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/querying/datasourcemetadataquery.html">DatasourceMetadata</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/querying/searchquery.html">Search</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/querying/select-query.html">Select</a></li></ul></div><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/querying/multi-value-dimensions.html">Multi-value dimensions</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/querying/lookups.html">Lookups</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/querying/joins.html">Joins</a></li><li class="navListItem"><a 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support</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/operations/password-provider.html">Password providers</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/operations/dump-segment.html">dump-segment tool</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/operations/reset-cluster.html">reset-cluster tool</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/operations/insert-segment-to-db.html">insert-segment-to-db tool</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/operations/pull-deps.html">pull-deps tool</a></li><div class="navGroup subNavGroup"><h4 class="navGroupSubcategoryTitle">Misc</h4><ul><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/operations/deep-storage-migration.html">Deep storage migration</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/operations/druid-console.html">Web console</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/operations/export-metadata.html">Export Metadata Tool</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/operations/getting-started.html">Getting started with Apache Druid</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/operations/metadata-migration.html">Metadata Migration</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/operations/segment-optimization.html">Segment Size Optimization</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/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 class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/development/overview.html">Developing on Druid</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/development/modules.html">Creating extensions</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/development/javascript.html">JavaScript functionality</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/development/build.html">Build from source</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/development/versioning.html">Versioning</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/development/experimental.html">Experimental features</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle collapsible">Misc<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/0.16.1-incubating/misc/math-expr.html">Expressions</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/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/0.16.1-incubating/comparisons/druid-vs-elasticsearch.html">Apache Druid vs Elasticsearch</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/comparisons/druid-vs-key-value.html">Apache Druid vs. Key/Value Stores (HBase/Cassandra/OpenTSDB)</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/comparisons/druid-vs-kudu.html">Apache Druid vs Kudu</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/comparisons/druid-vs-redshift.html">Apache Druid vs Redshift</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/comparisons/druid-vs-spark.html">Apache Druid vs Spark</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/comparisons/druid-vs-sql-on-hadoop.html">Apache Druid vs SQL-on-Hadoop</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/design/auth.html">Authentication and Authorization</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/design/broker.html">Broker</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/design/coordinator.html">Coordinator Process</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/design/historical.html">Historical Process</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/design/indexer.html">Indexer Process</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/design/indexing-service.html">Indexing Service</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/design/middlemanager.html">MiddleManager Process</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/design/overlord.html">Overlord Process</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/design/router.html">Router Process</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/design/peons.html">Peons</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/development/extensions-core/approximate-histograms.html">Approximate Histogram aggregators</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/development/extensions-core/avro.html">Apache Avro</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/development/extensions-core/bloom-filter.html">Bloom Filter</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/development/extensions-core/datasketches-extension.html">DataSketches extension</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/development/extensions-core/datasketches-hll.html">DataSketches HLL Sketch module</a></li><li class="navListItem"><a class="navItem" href="/docs/0.16.1-incubating/development/extensions-core/datasketches-quantiles.html">DataSketches Quantiles Sketch module</a></li><li class="navListItem"><a class="navItem" 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<p>Apache Druid (incubating) processes will emit logs that are useful for debugging to the console. Druid processes also emit periodic metrics about their state. For more about metrics, see <a href="../configuration/index.html#enabling-metrics">Configuration</a>. Metric logs are printed to the console by default, and can be disabled with <code>-Ddruid.emitter.logging.logLevel=debug</code>.</p>
<p>Druid uses <a href="http://logging.apache.org/log4j/2.x/">log4j2</a> for logging. Logging can be configured with a log4j2.xml file. Add the path to the directory containing the log4j2.xml file (e.g. the _common/ dir) to your classpath if you want to override default Druid log configuration. Note that this directory should be earlier in the classpath than the druid jars. The easiest way to do this is to prefix the classpath with the config dir.</p>
<p>To enable java logging to go through log4j2, set the <code>-Djava.util.logging.manager=org.apache.logging.log4j.jul.LogManager</code> server parameter.</p>
<p>An example log4j2.xml ships with Druid under config/_common/log4j2.xml, and a sample file is also shown below:</p>
<pre><code class="hljs"><span class="xml"><span class="hljs-meta">&lt;?xml version="1.0" encoding="UTF-8" ?&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">Configuration</span> <span class="hljs-attr">status</span>=<span class="hljs-string">"WARN"</span>&gt;</span>
  <span class="hljs-tag">&lt;<span class="hljs-name">Appenders</span>&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">Console</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"Console"</span> <span class="hljs-attr">target</span>=<span class="hljs-string">"SYSTEM_OUT"</span>&gt;</span>
      <span class="hljs-tag">&lt;<span class="hljs-name">PatternLayout</span> <span class="hljs-attr">pattern</span>=<span class="hljs-string">"%d</span></span></span><span class="hljs-template-variable">{ISO8601}</span><span class="xml"><span class="hljs-tag"><span class="hljs-string"> %p [%t] %c - %m%n"</span>/&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">Console</span>&gt;</span>
  <span class="hljs-tag">&lt;/<span class="hljs-name">Appenders</span>&gt;</span>
  <span class="hljs-tag">&lt;<span class="hljs-name">Loggers</span>&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">Root</span> <span class="hljs-attr">level</span>=<span class="hljs-string">"info"</span>&gt;</span>
      <span class="hljs-tag">&lt;<span class="hljs-name">AppenderRef</span> <span class="hljs-attr">ref</span>=<span class="hljs-string">"Console"</span>/&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">Root</span>&gt;</span>

    <span class="hljs-comment">&lt;!-- Uncomment to enable logging of all HTTP requests
    &lt;Logger name="org.apache.druid.jetty.RequestLog" additivity="false" level="DEBUG"&gt;
        &lt;AppenderRef ref="Console"/&gt;
    &lt;/Logger&gt;
    --&gt;</span>
  <span class="hljs-tag">&lt;/<span class="hljs-name">Loggers</span>&gt;</span>
<span class="hljs-tag">&lt;/<span class="hljs-name">Configuration</span>&gt;</span>
</span></code></pre>
<h2><a class="anchor" aria-hidden="true" id="my-logs-are-really-chatty-can-i-set-them-to-asynchronously-write"></a><a href="#my-logs-are-really-chatty-can-i-set-them-to-asynchronously-write" 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>My logs are really chatty, can I set them to asynchronously write?</h2>
<p>Yes, using a <code>log4j2.xml</code> similar to the following causes some of the more chatty classes to write asynchronously:</p>
<pre><code class="hljs"><span class="xml"><span class="hljs-meta">&lt;?xml version="1.0" encoding="UTF-8" ?&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">Configuration</span> <span class="hljs-attr">status</span>=<span class="hljs-string">"WARN"</span>&gt;</span>
  <span class="hljs-tag">&lt;<span class="hljs-name">Appenders</span>&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">Console</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"Console"</span> <span class="hljs-attr">target</span>=<span class="hljs-string">"SYSTEM_OUT"</span>&gt;</span>
      <span class="hljs-tag">&lt;<span class="hljs-name">PatternLayout</span> <span class="hljs-attr">pattern</span>=<span class="hljs-string">"%d</span></span></span><span class="hljs-template-variable">{ISO8601}</span><span class="xml"><span class="hljs-tag"><span class="hljs-string"> %p [%t] %c - %m%n"</span>/&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">Console</span>&gt;</span>
  <span class="hljs-tag">&lt;/<span class="hljs-name">Appenders</span>&gt;</span>
  <span class="hljs-tag">&lt;<span class="hljs-name">Loggers</span>&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">AsyncLogger</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"org.apache.druid.curator.inventory.CuratorInventoryManager"</span> <span class="hljs-attr">level</span>=<span class="hljs-string">"debug"</span> <span class="hljs-attr">additivity</span>=<span class="hljs-string">"false"</span>&gt;</span>
      <span class="hljs-tag">&lt;<span class="hljs-name">AppenderRef</span> <span class="hljs-attr">ref</span>=<span class="hljs-string">"Console"</span>/&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">AsyncLogger</span>&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">AsyncLogger</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"org.apache.druid.client.BatchServerInventoryView"</span> <span class="hljs-attr">level</span>=<span class="hljs-string">"debug"</span> <span class="hljs-attr">additivity</span>=<span class="hljs-string">"false"</span>&gt;</span>
      <span class="hljs-tag">&lt;<span class="hljs-name">AppenderRef</span> <span class="hljs-attr">ref</span>=<span class="hljs-string">"Console"</span>/&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">AsyncLogger</span>&gt;</span>
    <span class="hljs-comment">&lt;!-- Make extra sure nobody adds logs in a bad way that can hurt performance --&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">AsyncLogger</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"org.apache.druid.client.ServerInventoryView"</span> <span class="hljs-attr">level</span>=<span class="hljs-string">"debug"</span> <span class="hljs-attr">additivity</span>=<span class="hljs-string">"false"</span>&gt;</span>
      <span class="hljs-tag">&lt;<span class="hljs-name">AppenderRef</span> <span class="hljs-attr">ref</span>=<span class="hljs-string">"Console"</span>/&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">AsyncLogger</span>&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">AsyncLogger</span> <span class="hljs-attr">name</span> =<span class="hljs-string">"org.apache.druid.java.util.http.client.pool.ChannelResourceFactory"</span> <span class="hljs-attr">level</span>=<span class="hljs-string">"info"</span> <span class="hljs-attr">additivity</span>=<span class="hljs-string">"false"</span>&gt;</span>
      <span class="hljs-tag">&lt;<span class="hljs-name">AppenderRef</span> <span class="hljs-attr">ref</span>=<span class="hljs-string">"Console"</span>/&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">AsyncLogger</span>&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">Root</span> <span class="hljs-attr">level</span>=<span class="hljs-string">"info"</span>&gt;</span>
      <span class="hljs-tag">&lt;<span class="hljs-name">AppenderRef</span> <span class="hljs-attr">ref</span>=<span class="hljs-string">"Console"</span>/&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">Root</span>&gt;</span>
  <span class="hljs-tag">&lt;/<span class="hljs-name">Loggers</span>&gt;</span>
<span class="hljs-tag">&lt;/<span class="hljs-name">Configuration</span>&gt;</span>
</span></code></pre>
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