Enable Log-based Garbage Collection

For applications running in JVMs < 1.7, Garbage Collection monitoring is based on periodically parsing certain Garbage Collection logs.

To set up Garbage Collection logging for your application, use these arguments:

-Xloggc:log-file-path
-XX:+Usecollector-type
-XX:+PrintGCDetails

The log-file-path -XX:+Use

Collector Type Effect

CMS Collector

-XX:+UseConcMarkSweepGC

Good for applications that require low pause times and that can share resources with the garbage collector.

Use the -XX:ParallelCMSThreads=<n> to set the number of threads to use.

Throughput or Parallel Collector

-XX:+UseParallelGC

-XX:+UseParallelOldGC

 Can use multiple CPUs to speed up application throughput; good to use for work-intensive apps that can accept long pauses.

G1 Collector

-XX:+UseG1GC

 Available in Java 7 and designed to be a long term replacement for the CMS collector. This is a parallel, concurrent, and incrementally compacting low-pause collector.

To direct the Controller to display logged information, register the following node properties in the Controller UI:

enable-jmx-visibility=true
enable-log-based-gc=visiblity=true

To change the default log check interval, register the following node property:

logbased-visibility-log-check-interval-in-mills=1000

Specify Regular Expressions for Parsing Garbage Collection Logs

When you enable log-based Garbage Collection metrics, the agent uses built-in regular expressions to accommodate different JDK and Garbage Collection type combinations. If the built-in regular expressions don't return the Garbage Collection metrics for your system, you can register the following node properties to specify custom regular expressions for parsing the logs:

  • young-gc-custom-regex-1
  • young-gc-custom-regex-2
  • young-gc-custom-regex-3
  • full-gc-custom-regex-1
  • full-gc-custom-regex-2
  • full-gc-custom-regex-3

After you set a custom regular expression using a node property, the agent no longer uses any of the built-in regular expressions to parse the logs.