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class="menu__link" href="/docs/latest/misc/papers-and-talks">Papers</a></li></ul></nav></div></div></aside><main class="docMainContainer_TBSr"><div class="container padding-top--md padding-bottom--lg"><div class="row"><div class="col docItemCol_VOVn"><div class="docItemContainer_Djhp"><article><nav class="theme-doc-breadcrumbs breadcrumbsContainer_Z_bl" 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 itemscope="" itemprop="itemListElement" itemtype="https://schema.org/ListItem" class="breadcrumbs__item"><a class="breadcrumbs__link" itemprop="item" href="/docs/latest/configuration/"><span itemprop="name">Configuration</span></a><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">Logging</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>Logging</h1></header><p>Apache Druid services emit logs that to help you debug. |
| The same services also emit periodic <a href="/docs/latest/configuration/#metrics-monitors">metrics</a> about their state. |
| To disable metric info logs set the following runtime property: <code>-Ddruid.emitter.logging.logLevel=debug</code>.</p> |
| <p>Druid uses <a href="http://logging.apache.org/log4j/2.x/" target="_blank" rel="noopener noreferrer">log4j2</a> for logging. |
| The default configuration file log4j2.xml ships with Druid at the following path: <code>conf/druid/{config}/_common/log4j2.xml</code>.</p> |
| <p>By default, Druid uses <code>RollingRandomAccessFile</code> for rollover daily, and keeps log files up to 7 days. |
| If that's not suitable in your case, modify the <code>log4j2.xml</code> accordingly.</p> |
| <p>The following example log4j2.xml is based upon the micro quickstart:</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" style="color:#bfc7d5;background-color:#292d3e"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain"><?xml version="1.0" encoding="UTF-8" ?></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"><Configuration status="WARN"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Properties></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <!-- to change log directory, set DRUID_LOG_DIR environment variable to your directory before launching Druid --></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Property name="druid.log.path" value="log" /></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </Properties></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Appenders></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Console name="Console" target="SYSTEM_OUT"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <PatternLayout pattern="%d{ISO8601} %p [%t] %c -%notEmpty{ [%markerSimpleName]} %m%n"/></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </Console></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <!-- Rolling Files--></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <RollingRandomAccessFile name="FileAppender"</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> fileName="${sys:druid.log.path}/${sys:druid.node.type}.log"</span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> filePattern="${sys:druid.log.path}/${sys:druid.node.type}.%d{yyyyMMdd}.log"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <PatternLayout pattern="%d{ISO8601} %p [%t] %c -%notEmpty{ [%markerSimpleName]} %m%n"/></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Policies></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <TimeBasedTriggeringPolicy interval="1" modulate="true"/></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </Policies></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <DefaultRolloverStrategy></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Delete basePath="${sys:druid.log.path}/" maxDepth="1"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <IfFileName glob="*.log" /></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <IfLastModified age="7d" /></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </Delete></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </DefaultRolloverStrategy></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </RollingRandomAccessFile></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </Appenders></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Loggers></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Root level="info"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <AppenderRef ref="FileAppender"/></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </Root></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <!-- Set level="debug" to see stack traces for query errors --></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Logger name="org.apache.druid.server.QueryResource" level="info" additivity="false"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Appender-ref ref="FileAppender"/></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </Logger></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Logger name="org.apache.druid.server.QueryLifecycle" level="info" additivity="false"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Appender-ref ref="FileAppender"/></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </Logger></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <!-- Set level="debug" or "trace" to see more Coordinator details (segment balancing, load/drop rules, etc) --></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Logger name="org.apache.druid.server.coordinator" level="info" additivity="false"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Appender-ref ref="FileAppender"/></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </Logger></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <!-- Set level="debug" to see low-level details about segments and ingestion --></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Logger name="org.apache.druid.segment" level="info" additivity="false"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Appender-ref ref="FileAppender"/></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </Logger></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <!-- Set level="debug" to see more information about extension initialization --></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Logger name="org.apache.druid.initialization" level="info" additivity="false"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Appender-ref ref="FileAppender"/></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </Logger></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <!-- Quieter logging at startup --></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Logger name="com.sun.jersey.guice" level="warn" additivity="false"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Appender-ref ref="FileAppender"/></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </Logger></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </Loggers></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"></Configuration></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>Peons always output logs to standard output. Middle Managers redirect task logs from standard output to |
| <a href="/docs/latest/configuration/#log-long-term-storage">long-term storage</a>.</p> |
| <div class="theme-admonition theme-admonition-info admonition_xJq3 alert alert--info"><div class="admonitionHeading_Gvgb"><span class="admonitionIcon_Rf37"><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_BuS1"><p>Druid shares the log4j configuration file among all services, including task peon processes. |
| However, you must define a console appender in the logger for your peon processes. |
| If you don't define a console appender, Druid creates and configures a new console appender |
| that retains the log level, such as <code>info</code> or <code>warn</code>, but does not retain any other appender |
| configuration, including non-console ones.</p></div></div> |
| <h2 class="anchor anchorWithStickyNavbar_LWe7" id="log-directory">Log directory<a href="#log-directory" class="hash-link" aria-label="Direct link to Log directory" title="Direct link to Log directory"></a></h2> |
| <p>The included log4j2.xml configuration for Druid and ZooKeeper writes logs to the <code>log</code> directory at the root of the distribution.</p> |
| <p>If you want to change the log directory, set the environment variable <code>DRUID_LOG_DIR</code> to the right directory before you start Druid.</p> |
| <h2 class="anchor anchorWithStickyNavbar_LWe7" id="all-in-one-start-commands">All-in-one start commands<a href="#all-in-one-start-commands" class="hash-link" aria-label="Direct link to All-in-one start commands" title="Direct link to All-in-one start commands"></a></h2> |
| <p>If you use one of the all-in-one start commands, such as <code>bin/start-micro-quickstart</code>, the default configuration for each service has two kinds of log files. |
| Log4j2 writes the main log file and rotates it periodically. |
| For example, <code>log/historical.log</code>.</p> |
| <p>The secondary log file contains anything that is written by the component |
| directly to standard output or standard error without going through log4j2. |
| For example, <code>log/historical.stdout.log</code>. |
| This consists mainly of messages from the |
| Java runtime itself. |
| This file is not rotated, but it is generally small due to the low volume of messages. |
| If necessary, you can truncate it using the Linux command <code>truncate --size 0 log/historical.stdout.log</code>.</p> |
| <h2 class="anchor anchorWithStickyNavbar_LWe7" id="set-the-logs-to-asynchronously-write">Set the logs to asynchronously write<a href="#set-the-logs-to-asynchronously-write" class="hash-link" aria-label="Direct link to Set the logs to asynchronously write" title="Direct link to Set the logs to asynchronously write"></a></h2> |
| <p>If your logs are really chatty, you can set them to write asynchronously. |
| The following example shows a <code>log4j2.xml</code> that configures some of the more chatty classes to write asynchronously:</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" style="color:#bfc7d5;background-color:#292d3e"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token plain"><?xml version="1.0" encoding="UTF-8" ?></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"><Configuration status="WARN"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Appenders></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Console name="Console" target="SYSTEM_OUT"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <PatternLayout pattern="%d{ISO8601} %p [%t] %c -%notEmpty{ [%markerSimpleName]} %m%n"/></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </Console></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </Appenders></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"><Loggers></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <!-- AsyncLogger instead of Logger --></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <AsyncLogger name="org.apache.druid.curator.inventory.CuratorInventoryManager" level="debug" additivity="false"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <AppenderRef ref="Console"/></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </AsyncLogger></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <AsyncLogger name="org.apache.druid.client.BatchServerInventoryView" level="debug" additivity="false"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <AppenderRef ref="Console"/></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </AsyncLogger></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <!-- Make extra sure nobody adds logs in a bad way that can hurt performance --></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <AsyncLogger name="org.apache.druid.client.ServerInventoryView" level="debug" additivity="false"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <AppenderRef ref="Console"/></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </AsyncLogger></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <AsyncLogger name ="org.apache.druid.java.util.http.client.pool.ChannelResourceFactory" level="info" additivity="false"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <AppenderRef ref="Console"/></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </AsyncLogger></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <Root level="info"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> <AppenderRef ref="Console"/></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </Root></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </Loggers></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"></Configuration></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></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/configuration/extensions"><div class="pagination-nav__sublabel">Previous</div><div class="pagination-nav__label">Extensions</div></a><a class="pagination-nav__link pagination-nav__link--next" href="/docs/latest/api-reference/automatic-compaction-api"><div class="pagination-nav__sublabel">Next</div><div class="pagination-nav__label">Automatic compaction</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="#log-directory" class="table-of-contents__link toc-highlight">Log directory</a></li><li><a href="#all-in-one-start-commands" class="table-of-contents__link toc-highlight">All-in-one start commands</a></li><li><a href="#set-the-logs-to-asynchronously-write" class="table-of-contents__link toc-highlight">Set the logs to asynchronously write</a></li></ul></div></div></div></div></main></div></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="footer__logo themedComponent_mlkZ themedComponent--light_NVdE"><img src="/img/favicon.png" class="footer__logo themedComponent_mlkZ 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