Package org.apache.storm.policy

Class WaitStrategyProgressive

java.lang.Object

org.apache.storm.policy.WaitStrategyProgressive

All Implemented Interfaces:

IWaitStrategy

public class WaitStrategyProgressive
extends Object
implements IWaitStrategy

A Progressive Wait Strategy.

Has three levels of idling. Stays in each level for a configured number of iterations before entering the next level. Level 1 - No idling. Returns immediately. Stays in this level for `level1Count` iterations. Level 2 - Calls LockSupport.parkNanos(1). Stays in this level for `level2Count` iterations Level 3 - Calls Thread.sleep(). Stays in this level until wait situation changes.

The initial spin can be useful to prevent downstream bolt from repeatedly sleeping/parking when the upstream component is a bit relatively slower. Allows downstream bolt can enter deeper wait states only if the traffic to it appears to have reduced.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.storm.policy.IWaitStrategy

IWaitStrategy.WaitSituation

Constructor Summary

Constructors

Constructor	Description
WaitStrategyProgressive()

Method Summary

Modifier and Type	Method	Description
int	idle(int idleCounter)	Implementations of this method should be thread-safe (preferably no side-effects and lock-free).
void	prepare(Map<String,Object> conf, IWaitStrategy.WaitSituation waitSituation)

Methods inherited from class java.lang.Object

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

Constructor Detail

WaitStrategyProgressive

public WaitStrategyProgressive()

Method Detail

prepare

public void prepare(Map<String,Object> conf,
                    IWaitStrategy.WaitSituation waitSituation)

Specified by:

prepare in interface IWaitStrategy

idle

public int idle(int idleCounter)
         throws InterruptedException

Description copied from interface: IWaitStrategy

Implementations of this method should be thread-safe (preferably no side-effects and lock-free).

Supports static or dynamic backoff. Dynamic backoff relies on idleCounter to estimate how long caller has been idling.

 
  int idleCounter = 0;
  int consumeCount = consumeFromQ();
  while (consumeCount==0) {
     idleCounter = strategy.idle(idleCounter);
     consumeCount = consumeFromQ();
  }
 
 

Specified by:

idle in interface IWaitStrategy

Parameters:

idleCounter - managed by the idle method until reset

Returns:

new counter value to be used on subsequent idle cycle

Throws:

InterruptedException