Provide basic notification if the JVM is unable to keep its threads running for extended periods of time e.g. because of GC, lack of CPU time.

The alarm has very basic configuration available:

• Check interval -- how long to wait between each time check
• Alarm time -- minimum pause to report
• Action on pause -- user-supplied callback when a pause alarms
• Clock -- replace the system clock for testing purposes

public class MyCoolApp {
  public static void main(String[] args) {
    try (new JvmPauseAlarm(100, 400).start()) {
      runMyCoolApp();
    }
  }
}

This will set up the pause alarm to check every 100ms for pauses of at least 400ms.

Example output:

[jvm-pause-alarm] INFO com.opentable.pausedetector.JvmPauseAlarm - Watching JVM for GC pausing.  Checking every 10ms for pauses of at least 400ms.
[jvm-pause-alarm] WARN com.opentable.pausedetector.JvmPauseAlarm - Detected pause of 1000ms!

For Spring, you can import JvmPauseAlarmConfiguration and starting / stopping the alarm is taken care of for you. You then use the following properties to configure it:

ot.jvm-pause.enabled=true
ot.jvm-pause.check-time=PT0.05s
ot.jvm-pause.pause-time=PT0.2s

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