org.apache.commons.lang3.concurrent

Class ThresholdCircuitBreaker

java.lang.Object

org.apache.commons.lang3.concurrent.AbstractCircuitBreaker<java.lang.Long>

org.apache.commons.lang3.concurrent.ThresholdCircuitBreaker

All Implemented Interfaces:

CircuitBreaker<java.lang.Long>

public class ThresholdCircuitBreaker
extends AbstractCircuitBreaker<java.lang.Long>

A simple implementation of the Circuit Breaker pattern that opens if the requested increment amount is greater than a given threshold.

It contains an internal counter that starts in zero, and each call increments the counter by a given amount. If the threshold is zero, the circuit breaker will be in a permanent open state.

An example of use case could be a memory circuit breaker.

 long threshold = 10L;
 ThresholdCircuitBreaker breaker = new ThresholdCircuitBreaker(10L);
 ...
 public void handleRequest(Request request) {
     long memoryUsed = estimateMemoryUsage(request);
     if (breaker.incrementAndCheckState(memoryUsed)) {
         // actually handle this request
     } else {
         // do something else, e.g. send an error code
     }
 }
 

#Thread safe#

Since:

3.5

Field Summary

Fields inherited from class org.apache.commons.lang3.concurrent.AbstractCircuitBreaker

PROPERTY_NAME

Constructor Summary

Constructors

Constructor and Description
ThresholdCircuitBreaker(long threshold) Creates a new instance of ThresholdCircuitBreaker and initializes the threshold.

Method Summary

Modifier and Type	Method and Description
boolean	checkState() Checks the state of this circuit breaker and changes it if necessary.
void	close() Closes this circuit breaker.
long	getThreshold() Gets the threshold.
boolean	incrementAndCheckState(java.lang.Long increment) Increments the monitored value and performs a check of the current state of this circuit breaker.

Methods inherited from class org.apache.commons.lang3.concurrent.AbstractCircuitBreaker

addChangeListener, isClosed, isOpen, open, removeChangeListener

Methods inherited from class java.lang.Object

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

Constructor Detail

ThresholdCircuitBreaker

public ThresholdCircuitBreaker(long threshold)

Creates a new instance of ThresholdCircuitBreaker and initializes the threshold.

Parameters:

threshold - the threshold.

Method Detail

getThreshold

public long getThreshold()

Gets the threshold.

Returns:

the threshold

checkState

public boolean checkState()

Checks the state of this circuit breaker and changes it if necessary. The return value indicates whether the circuit breaker is now in state closed; a value of true typically means that the current operation can continue.

Specified by:

checkState in interface CircuitBreaker<java.lang.Long>

Specified by:

checkState in class AbstractCircuitBreaker<java.lang.Long>

Returns:

true if the circuit breaker is now closed; false otherwise

close

public void close()

Closes this circuit breaker. Its state is changed to closed. If this circuit breaker is already closed, this method has no effect.

Resets the internal counter back to its initial value (zero).

Specified by:

close in interface CircuitBreaker<java.lang.Long>

Overrides:

close in class AbstractCircuitBreaker<java.lang.Long>

incrementAndCheckState

public boolean incrementAndCheckState(java.lang.Long increment)

Increments the monitored value and performs a check of the current state of this circuit breaker. This method works like CircuitBreaker.checkState(), but the monitored value is incremented before the state check is performed.

If the threshold is zero, the circuit breaker will be in a permanent open state.

Specified by:

incrementAndCheckState in interface CircuitBreaker<java.lang.Long>

Specified by:

incrementAndCheckState in class AbstractCircuitBreaker<java.lang.Long>

Parameters:

increment - value to increment in the monitored value of the circuit breaker

Returns:

true if the circuit breaker is now closed; false otherwise