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package dk.thoerup.curcuitbreaker; |
package dk.thoerup.circuitbreaker; |
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import java.util.logging.Logger; |
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import java.util.concurrent.ExecutorService; |
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import java.util.concurrent.Executors; |
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import dk.thoerup.circuitbreaker.notification.NotiferHelper; |
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import dk.thoerup.circuitbreaker.notification.Notifier; |
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import dk.thoerup.circuitbreaker.notification.NullNotifier; |
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/* Simple CircuitBreaker implementation - snipped from http://www.jroller.com/kenwdelong/entry/circuit_breaker_in_java |
/* Simple CircuitBreaker implementation - snipped from http://www.jroller.com/kenwdelong/entry/circuit_breaker_in_java |
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* |
* |
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try { |
try { |
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String s = (String) cb.invoke(new TestInvocation("http://rafiki/test")); |
String s = (String) cb.invoke(new TestInvocation("http://rafiki/test")); |
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response.getWriter().print(s); |
response.getWriter().print(s); |
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} catch (Throwable e) { |
} catch (Exception e) { |
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logger.warning( e.getMessage() ); |
logger.warning( e.getMessage() ); |
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response.sendError(500); |
response.sendError(500); |
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return; |
return; |
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public class CircuitBreaker{ |
public class CircuitBreaker{ |
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Logger logger = Logger.getLogger(CircuitBreaker.class.getName()); |
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private CircuitBreakerState currentState; |
private volatile CircuitBreakerState currentState; |
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private OpenState open = new OpenState(); |
private final OpenState open = new OpenState(); |
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private HalfOpenState halfOpen = new HalfOpenState(); |
private final HalfOpenState halfOpen = new HalfOpenState(); |
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private ClosedState closed = new ClosedState(); |
private final ClosedState closed = new ClosedState(); |
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private String name; |
private String name; |
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private ExecutorService executor = null; |
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private Notifier notifier = new NullNotifier(); |
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public CircuitBreaker(String name, int threshold, long timeoutMS) { |
public CircuitBreaker(String name, int threshold, long timeoutMS) { |
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closed.setThreshold(threshold); |
closed.setThreshold(threshold); |
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open.setTimeout(timeoutMS); |
open.setTimeout(timeoutMS); |
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this.name = name; |
this.name = name; |
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reset(); |
//set correct intial state |
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internalReset(); |
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} |
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public synchronized void shutdown() { |
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if (executor != null) { |
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executor.shutdown(); |
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} |
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} |
} |
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public Object invoke(CircuitInvocation invocation) throws Throwable |
public Object invoke(CircuitInvocation invocation) throws Exception |
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{ |
{ |
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Object result = null; |
Object result = null; |
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try |
try |
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result = invocation.proceed(); |
result = invocation.proceed(); |
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getState().postInvoke(this); |
getState().postInvoke(this); |
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} |
} |
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catch(Throwable t) |
catch(Exception e) |
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{ |
{ |
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getState().onError(this, t); |
getState().onError(this, e); |
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throw t; |
throw e; |
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} |
} |
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return result; |
return result; |
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} |
} |
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public void tripBreaker() { |
public void tripBreaker() { |
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synchronized(this) { |
commonTripBreaker(Notifier.Event.BreakerTripped); |
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currentState = open; |
} |
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open.trip(); |
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logger.warning("Circuitbreaker tripBreaker - " + name); |
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} |
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//a re-trip should basically do the same as a normal trip, but it is here just to differentiate the two different events |
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public void retripBreaker() { |
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commonTripBreaker(Notifier.Event.BreakerRetripped); |
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} |
} |
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private void commonTripBreaker(Notifier.Event event) { |
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synchronized(this) { |
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if (currentState != open) { // TODO:Is this conditional necessary ?? |
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open.trip(); |
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currentState = open; |
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notifier.sendNotification(this, event); |
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} |
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} |
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} |
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public void attemptReset() { |
public void attemptReset() { |
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synchronized(this) { |
synchronized(this) { |
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currentState = halfOpen; |
if (currentState != halfOpen) { // TODO:Is this conditional necessary ?? |
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currentState = halfOpen; |
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logger.warning("Circuitbreaker attemptReset - " + name); |
notifier.sendNotification(this, Notifier.Event.BreakerAttemptReset); |
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} |
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} |
} |
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} |
} |
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public void reset() { |
public void reset() { |
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synchronized(this) { |
synchronized(this) { |
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currentState = closed; |
if (currentState != closed) { // TODO: Is this conditional necessary ?? |
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internalReset(); |
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logger.warning("Circuitbreaker reset - " + name); |
notifier.sendNotification(this, Notifier.Event.BreakerReset); |
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} |
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} |
} |
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} |
} |
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//This one actually sets the correct closed/reset state |
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private void internalReset() { |
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closed.resetFailureCount(); |
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currentState = closed; |
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} |
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private CircuitBreakerState getState() { |
private CircuitBreakerState getState() { |
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synchronized(this) { |
synchronized(this) { |
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return currentState; |
return currentState; |
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} |
} |
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} |
} |
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public boolean isClosed() { |
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return (getState() == closed); |
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} |
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public boolean isOpen() { |
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return (getState() == open); |
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} |
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public String getName() { |
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return name; |
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} |
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public String getStateName() { |
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return getState().getName(); |
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} |
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public int getThreshold() { |
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return closed.getThreshold(); |
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} |
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public int getTimeout() { |
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return (int)open.getTimeout(); |
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} |
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public int getFailureCount() { |
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if (getState() == closed) { |
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return closed.getFailureCount(); |
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} else { |
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return -1; |
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} |
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} |
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public long getElapsed() { |
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if (getState() == open) { |
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return open.getElapsed(); |
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} else { |
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return -1; |
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} |
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} |
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public void setNotifier(Notifier notifier) { |
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this.notifier = notifier; |
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} |
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public String getNotifierName() { |
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return NotiferHelper.getName(notifier); |
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} |
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public synchronized ExecutorService getExecutor() { |
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if (executor == null) { |
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executor = Executors.newFixedThreadPool(1); |
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} |
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return executor; |
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} |
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} |
} |