org.springframework.batch.retry.backoff
Class ExponentialBackOffPolicy

java.lang.Object
  org.springframework.batch.retry.backoff.ExponentialBackOffPolicy

All Implemented Interfaces:

BackOffPolicy

public class ExponentialBackOffPolicy
extends Object
implements BackOffPolicy

Implementation of BackOffPolicy that increases the back off period for each retry attempt in a given set using the exponential function.

This implementation is thread-safe and suitable for concurrent access. Modifications to the configuration do not affect any retry sets that are already in progress.

The setInitialInterval(long) property controls the initial value passed to Math.exp(double) and the setMultiplier(double) property controls by how much this value is increased for each subsequent attempt.

Author:

Rob Harrop, Dave Syer

Field Summary

static long	DEFAULT_INITIAL_INTERVAL The default 'initialInterval' value - 100 millisecs.
static long	DEFAULT_MAX_INTERVAL The default maximum backoff time (30 seconds).
static double	DEFAULT_MULTIPLIER The default 'multiplier' value - value 2 (100% increase per backoff).

Constructor Summary

ExponentialBackOffPolicy()

Method Summary

void	backOff(BackOffContext backOffContext) Pause for a length of time equal to ' exp(backOffContext.expSeed)'.
long	getInitialInterval() The initial period to sleep on the first backoff.
long	getMaxInterval() The maximum interval to sleep for.
double	getMultiplier() The multiplier to use to generate the next backoff interval from the last.
void	setInitialInterval(long initialInterval) Set the initial sleep interval value.
void	setMaxInterval(long maxInterval) Setter for maximum back off period.
void	setMultiplier(double multiplier) Set the multiplier value.
void	setSleeper(Sleeper sleeper) Public setter for the Sleeper strategy.
BackOffContext	start(RetryContext context) Returns a new instance of BackOffContext configured with the 'expSeed' and 'increment' values.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_INITIAL_INTERVAL

public static final long DEFAULT_INITIAL_INTERVAL

The default 'initialInterval' value - 100 millisecs. Coupled with the default 'multiplier' value this gives a useful initial spread of pauses for 1-5 retries.

See Also:

Constant Field Values

DEFAULT_MAX_INTERVAL

public static final long DEFAULT_MAX_INTERVAL

The default maximum backoff time (30 seconds).

See Also:

Constant Field Values

DEFAULT_MULTIPLIER

public static final double DEFAULT_MULTIPLIER

The default 'multiplier' value - value 2 (100% increase per backoff).

See Also:

Constant Field Values

Constructor Detail

ExponentialBackOffPolicy

public ExponentialBackOffPolicy()

Method Detail

setSleeper

public void setSleeper(Sleeper sleeper)

Public setter for the Sleeper strategy.

Parameters:

sleeper - the sleeper to set defaults to ObjectWaitSleeper.

setInitialInterval

public void setInitialInterval(long initialInterval)

Set the initial sleep interval value. Default is 100 millisecond. Cannot be set to a value less than one.

setMultiplier

public void setMultiplier(double multiplier)

Set the multiplier value. Default is '2.0'. Hint: do not use values much in excess of 1.0 (or the backoff will get very long very fast).

setMaxInterval

public void setMaxInterval(long maxInterval)

Setter for maximum back off period. Default is 30000 (30 seconds). the value will be reset to 1 if this method is called with a value less than 1. Set this to avoid infinite waits if backing off a large number of times (or if the multiplier is set too high).

Parameters:

maxInterval - in milliseconds.

getInitialInterval

public long getInitialInterval()

The initial period to sleep on the first backoff.

Returns:

the initial interval

getMaxInterval

public long getMaxInterval()

The maximum interval to sleep for. Defaults to 30 seconds.

Returns:

the maximum interval.

getMultiplier

public double getMultiplier()

The multiplier to use to generate the next backoff interval from the last.

Returns:

the multiplier in use

start

public BackOffContext start(RetryContext context)

Returns a new instance of BackOffContext configured with the 'expSeed' and 'increment' values.

Specified by:

start in interface BackOffPolicy

Parameters:

context - the current retry context, which might contain information that we can use to decide how to proceed.

Returns:

the implementation-specific BackOffContext or 'null'.

backOff

public void backOff(BackOffContext backOffContext)
             throws BackOffInterruptedException

Pause for a length of time equal to ' exp(backOffContext.expSeed)'.

Specified by:

backOff in interface BackOffPolicy

Throws:

BackOffInterruptedException - if the attempt at back off is interrupted.

toString

public String toString()

Overrides:

toString in class Object