GC logging

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Starting in Elasticsearch 6.2.0, JVM GC logging is enabled out of the box. This lightweight facility gives insight into GC issues. The settings for this are in jvm.options and default to keeping 2 GB worth (rotating every 64 MB) of logs in the default logs directory. If you are upgrading from a previous version of Elasticsearch and preserve your existing jvm.options, you should add the following GC logging settings so that this valuable debugging information is available:

-XX:+PrintGCDetails
-XX:+PrintGCDateStamps
-XX:+PrintTenuringDistribution
-XX:+PrintGCApplicationStoppedTime
-Xloggc:logs/gc.log or /var/log/elasticsearch/gc.log 
-XX:+UseGCLogFileRotation
-XX:NumberOfGCLogFiles=32
-XX:GCLogFileSize=64m

If you have installed Elasticsearch from the RPM or the Debian packaging distributions and use the default logging location use /var/log/elasticsearch otherwise if you have installed from the tar.gz or zip archive distributions and use the default logging location use logs/gc.log; otherwise, set the location to the absolute path to your log files.