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91 lines
3.6 KiB
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91 lines
3.6 KiB
Text
[[advanced-configuration]]
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=== Advanced configuration settings
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The settings below are considered advanced and for expert users only. In
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most cases the {es}-provided default settings should be used. Take caution
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when modifying these settings as this could result in undesired behavior or
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reduced system performance.
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[[setting-jvm-heap-size]]
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==== Setting JVM heap size
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If you need to override the default <<heap-size-settings,heap size settings>>,
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follow the best practices below.
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{es} assigns the entire heap specified in
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<<jvm-options,jvm.options>> via the `Xms` (minimum heap size) and `Xmx` (maximum
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heap size) settings. These two settings must be equal to each other.
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The value for these settings depends on the amount of RAM available on your
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server:
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* Set `Xmx` and `Xms` to no more than 50% of your total system memory. {es} requires
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memory for purposes other than the JVM heap and it is important to leave
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space for this. For instance, {es} uses off-heap buffers for efficient
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network communication, relies on the operating system's filesystem cache for
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efficient access to files, and the JVM itself requires some memory too. It is
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normal to observe the {es} process using more memory than the limit
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configured with the `Xmx` setting.
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* Set `Xmx` and `Xms` to no more than the threshold that the JVM uses for
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compressed object pointers (compressed oops). The exact threshold varies but
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is near 32 GB. You can verify that you are under the threshold by looking for a line in the logs like the following:
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+
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[source,txt]
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----
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heap size [1.9gb], compressed ordinary object pointers [true]
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----
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* Set `Xmx` and `Xms` to no more than the threshold for zero-based
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compressed oops. The exact threshold varies but 26GB is safe on most
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systems and can be as large as 30GB on some systems. You can verify that
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you are under this threshold by starting {es} with the JVM options
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`-XX:+UnlockDiagnosticVMOptions -XX:+PrintCompressedOopsMode` and looking for
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a line like the following:
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+
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[source,txt]
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----
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heap address: 0x000000011be00000, size: 27648 MB, zero based Compressed Oops
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----
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+
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This line shows that zero-based compressed oops are enabled. If zero-based
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compressed oops are not enabled, you'll see a line like the following instead:
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+
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[source,txt]
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----
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heap address: 0x0000000118400000, size: 28672 MB, Compressed Oops with base: 0x00000001183ff000
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----
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The more heap available to {es}, the more memory it can use for its internal
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caches. This leaves less memory for the operating system to use
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for the filesystem cache. Larger heaps can also cause longer garbage
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collection pauses.
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Here is an example of how to set the heap size via a `jvm.options.d/` file:
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[source,txt]
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------------------
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-Xms2g <1>
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-Xmx2g <2>
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------------------
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<1> Set the minimum heap size to 2g.
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<2> Set the maximum heap size to 2g.
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In production, we recommend using `jvm.options.d` to configure heap sizes.
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For testing, you can also set the heap sizes using the `ES_JAVA_OPTS`
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environment variable. The `ES_JAVA_OPTS` variable overrides all other JVM
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options. We do not recommend using `ES_JAVA_OPTS` in production.
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[source,sh]
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------------------
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ES_JAVA_OPTS="-Xms2g -Xmx2g" ./bin/elasticsearch <1>
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ES_JAVA_OPTS="-Xms4000m -Xmx4000m" ./bin/elasticsearch <2>
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------------------
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<1> Set the minimum and maximum heap size to 2 GB.
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<2> Set the minimum and maximum heap size to 4000 MB.
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NOTE: Configuring the heap for the <<windows-service,Windows service>> is
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different than the above. The values initially populated for the Windows
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service can be configured as above but are different after the service has been
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installed. See <<windows-service>>.
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