org.camunda.bpm.engine.impl.jobexecutor
Class BackoffJobAcquisitionStrategy

java.lang.Object
  org.camunda.bpm.engine.impl.jobexecutor.BackoffJobAcquisitionStrategy

All Implemented Interfaces:

JobAcquisitionStrategy

public class BackoffJobAcquisitionStrategy
extends Object
implements JobAcquisitionStrategy

Determines the number of jobs to acquire and the time to wait between acquisition cycles by an exponential backoff strategy.

Manages two kinds of backoff times:

• idle time: Wait for a certain amount of time when no jobs are available
• backoff time: Wait for a certain amount of time when jobs are available but could not successfully be acquired

Both times are calculated by applying an exponential backoff. This means, when the respective conditions repeatedly hold, the time increases exponentially from one acquisition cycle to the next.

This implementation manages idle and backoff time in terms of levels. The initial backoff level is 0, meaning that no backoff is applied. In case the condition for increasing backoff applies, the backoff level is incremented. The actual time to wait is then computed as follows

timeToWait = baseBackoffTime * (backoffFactor ^ (backoffLevel - 1))

Accordingly, the maximum possible backoff level is

maximumLevel = floor( log( backoffFactor, maximumBackoffTime / baseBackoffTime) ) + 1

(where log(a, b) is the logarithm of b to the base of a)

Author:

Thorben Lindhauer

Field Summary

protected boolean	applyJitter
protected int	backoffDecreaseThreshold
protected float	backoffIncreaseFactor
protected int	backoffLevel
protected long	baseBackoffWaitTime
protected long	baseIdleWaitTime
protected int	baseNumJobsToAcquire
static long	DEFAULT_EXECUTION_SATURATION_WAIT_TIME
protected boolean	executionSaturated
protected long	executionSaturationWaitTime
protected float	idleIncreaseFactor
protected int	idleLevel
protected Map<String,Integer>	jobsToAcquire
protected int	maxBackoffLevel
protected long	maxBackoffWaitTime
protected int	maxIdleLevel
protected long	maxIdleWaitTime
protected int	numAcquisitionsWithoutLockingFailure

Constructor Summary

BackoffJobAcquisitionStrategy(JobExecutor jobExecutor)

BackoffJobAcquisitionStrategy(long baseIdleWaitTime, float idleIncreaseFactor, long maxIdleTime, long baseBackoffWaitTime, float backoffIncreaseFactor, long maxBackoffTime, int backoffDecreaseThreshold, int baseNumJobsToAcquire)

Method Summary

protected boolean	allSubmittedJobsRejected(JobAcquisitionContext context)
protected long	calculateBackoffTime()
protected long	calculateIdleTime()
int	getNumJobsToAcquire(String processEngine)
long	getWaitTime()
protected void	initializeMaxLevels()
protected double	log(double base, double value)
void	reconfigure(JobAcquisitionContext context)
protected void	reconfigureBackoffLevel(JobAcquisitionContext context)
protected void	reconfigureIdleLevel(JobAcquisitionContext context)
protected void	reconfigureNumberOfJobsToAcquire(JobAcquisitionContext context)

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_EXECUTION_SATURATION_WAIT_TIME

public static long DEFAULT_EXECUTION_SATURATION_WAIT_TIME

baseIdleWaitTime

protected long baseIdleWaitTime

idleIncreaseFactor

protected float idleIncreaseFactor

idleLevel

protected int idleLevel

maxIdleLevel

protected int maxIdleLevel

maxIdleWaitTime

protected long maxIdleWaitTime

baseBackoffWaitTime

protected long baseBackoffWaitTime

backoffIncreaseFactor

protected float backoffIncreaseFactor

backoffLevel

protected int backoffLevel

maxBackoffLevel

protected int maxBackoffLevel

maxBackoffWaitTime

protected long maxBackoffWaitTime

applyJitter

protected boolean applyJitter

numAcquisitionsWithoutLockingFailure

protected int numAcquisitionsWithoutLockingFailure

backoffDecreaseThreshold

protected int backoffDecreaseThreshold

baseNumJobsToAcquire

protected int baseNumJobsToAcquire

jobsToAcquire

protected Map<String,Integer> jobsToAcquire

executionSaturated

protected boolean executionSaturated

executionSaturationWaitTime

protected long executionSaturationWaitTime

Constructor Detail

BackoffJobAcquisitionStrategy

public BackoffJobAcquisitionStrategy(long baseIdleWaitTime,
                                     float idleIncreaseFactor,
                                     long maxIdleTime,
                                     long baseBackoffWaitTime,
                                     float backoffIncreaseFactor,
                                     long maxBackoffTime,
                                     int backoffDecreaseThreshold,
                                     int baseNumJobsToAcquire)

BackoffJobAcquisitionStrategy

public BackoffJobAcquisitionStrategy(JobExecutor jobExecutor)

Method Detail

initializeMaxLevels

protected void initializeMaxLevels()

log

protected double log(double base,
                     double value)

reconfigure

public void reconfigure(JobAcquisitionContext context)

Specified by:

reconfigure in interface JobAcquisitionStrategy

allSubmittedJobsRejected

protected boolean allSubmittedJobsRejected(JobAcquisitionContext context)

Returns:

true, if all acquired jobs (spanning all engines) were rejected for execution

reconfigureIdleLevel

protected void reconfigureIdleLevel(JobAcquisitionContext context)

reconfigureBackoffLevel

protected void reconfigureBackoffLevel(JobAcquisitionContext context)

reconfigureNumberOfJobsToAcquire

protected void reconfigureNumberOfJobsToAcquire(JobAcquisitionContext context)

getWaitTime

public long getWaitTime()

Specified by:

getWaitTime in interface JobAcquisitionStrategy

calculateIdleTime

protected long calculateIdleTime()

calculateBackoffTime

protected long calculateBackoffTime()

getNumJobsToAcquire

public int getNumJobsToAcquire(String processEngine)

Specified by:

getNumJobsToAcquire in interface JobAcquisitionStrategy