Hot Threads API

The hot threads API gets the current hot threads for Logstash. A hot thread is a Java thread that has high CPU usage and executes for a longer than normal period of time.

curl -XGET 'localhost:9600/_node/hot_threads?pretty'

The output is a JSON document that contains a breakdown of the top hot threads for Logstash.

Example response:

{
  "hot_threads" : {
    "time" : "2017-06-06T18:25:28-07:00",
    "busiest_threads" : 3,
    "threads" : [ {
      "name" : "Ruby-0-Thread-7",
      "percent_of_cpu_time" : 0.0,
      "state" : "timed_waiting",
      "path" : "/path/to/logstash-7.17.26/vendor/bundle/jruby/1.9/gems/puma-2.16.0-java/lib/puma/thread_pool.rb:187",
      "traces" : [ "java.lang.Object.wait(Native Method)", "org.jruby.RubyThread.sleep(RubyThread.java:1002)", "org.jruby.RubyKernel.sleep(RubyKernel.java:803)" ]
    }, {
      "name" : "[test2]>worker3",
      "percent_of_cpu_time" : 0.85,
      "state" : "waiting",
      "traces" : [ "sun.misc.Unsafe.park(Native Method)", "java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)", "java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)" ]
    }, {
      "name" : "[test2]>worker2",
      "percent_of_cpu_time" : 0.85,
      "state" : "runnable",
      "traces" : [ "org.jruby.RubyClass.allocate(RubyClass.java:225)", "org.jruby.RubyClass.newInstance(RubyClass.java:856)", "org.jruby.RubyClass$INVOKER$i$newInstance.call(RubyClass$INVOKER$i$newInstance.gen)" ]
    } ]
  }
}

The parameters allowed are:

`threads`	The number of hot threads to return. The default is 10.
`stacktrace_size`	The depth of the stack trace to report for each thread. The default is 50.
`human`	If true, returns plain text instead of JSON format. The default is false.
`ignore_idle_threads`	If true, does not return idle threads. The default is true.

See Common Options for a list of options that can be applied to all Logstash monitoring APIs.

You can use the ?human parameter to return the document in a human-readable format.

curl -XGET 'localhost:9600/_node/hot_threads?human=true'

Example of a human-readable response:

 ::: {}
 Hot threads at 2017-06-06T18:31:17-07:00, busiestThreads=3:
 ================================================================================
 0.0 % of cpu usage, state: timed_waiting, thread name: 'Ruby-0-Thread-7'
 /path/to/logstash-7.17.26/vendor/bundle/jruby/1.9/gems/puma-2.16.0-java/lib/puma/thread_pool.rb:187
	 java.lang.Object.wait(Native Method)
	 org.jruby.RubyThread.sleep(RubyThread.java:1002)
	 org.jruby.RubyKernel.sleep(RubyKernel.java:803)
 --------------------------------------------------------------------------------
 0.0 % of cpu usage, state: waiting, thread name: 'defaultEventExecutorGroup-5-4'
	 sun.misc.Unsafe.park(Native Method)
	 java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
	 java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
 --------------------------------------------------------------------------------
 0.05 % of cpu usage, state: timed_waiting, thread name: '[test]-pipeline-manager'
	 java.lang.Object.wait(Native Method)
	 java.lang.Thread.join(Thread.java:1253)
	 org.jruby.internal.runtime.NativeThread.join(NativeThread.java:75)

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