org.thales.punch.libraries.storm.util

Class WatchDog

java.lang.Object

org.thales.punch.libraries.storm.util.WatchDog

public class WatchDog
extends Object

This class provides a simple and robust watchdog mechanism. It leverages on the punch LastEventOperator to keep track of a periodic tick. If you stop ticking, the watchdog will exit the entire jvm.

Several LastEventOperators can be registered, the WatchDog use a singleton thread to watch them all. You can cancel a LastEventOperator once done. That is, you can safely create one LastEventOperator per bolt or spout instance.

Here is a typical usage:

 
   LastEventOperator lastEventOp;
         init() {
     // we want to die if not ticked for more than 5 seconds
     lastEventOp = WatchDog.fire(5000, LOG);
     ..
   }
   
   ...  {
       // you must call this regularly, at least once every 5 seconds
       lastEvent.mark();
     
   }
 }
 
 

As an alternative you can also use a watchdog metrics.

Author:

dimi

Constructor Summary

Constructors

Constructor and Description
WatchDog()

Method Summary

Modifier and Type	Method and Description
static void	cancel(org.thales.punch.libraries.punchlang.operator.LastEventOperator le) Stop verifying a watchdog lastEventOperator.
static org.thales.punch.libraries.punchlang.operator.LastEventOperator	fire(long elapsedMs, org.apache.logging.log4j.Logger logger) Return a punch LastEventOperator register into a singleton watchdog.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

WatchDog

public WatchDog()

Method Detail

cancel

public static void cancel(org.thales.punch.libraries.punchlang.operator.LastEventOperator le)

Stop verifying a watchdog lastEventOperator.

Parameters:

le - the LastEventOperator

fire

public static org.thales.punch.libraries.punchlang.operator.LastEventOperator fire(long elapsedMs,
                                                                                   org.apache.logging.log4j.Logger logger)

Return a punch LastEventOperator register into a singleton watchdog. If you do not call LastEventOperator.mark() regularly, the WatchDog will kill the entire jvm.

WATCHOUT: you read correctly : it kills the entire Jvm.

Parameters:

elapsedMs - the watchdog timeout in milliseconds. If that value is less than or equal to zero, you will get an safe without-effect LastEventOperator.

log - a logger to at least have a trace of the owner who fired the watchdog

Returns:

a ready to use LastEventOperator