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package dk.thoerup.curcuitbreaker; |
package dk.thoerup.circuitbreaker; |
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import dk.thoerup.curcuitbreaker.notification.Notifier; |
import java.util.concurrent.ExecutorService; |
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import dk.thoerup.curcuitbreaker.notification.NullNotifier; |
import java.util.concurrent.Executors; |
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import dk.thoerup.circuitbreaker.config.BreakerConfig; |
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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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import dk.thoerup.circuitbreaker.statistics.NullStatistics; |
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import dk.thoerup.circuitbreaker.statistics.Statistics; |
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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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* example of how it can be used |
* example of how it can be used |
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private CircuitBreaker cb = new CircuitBreaker("test", 5, 10000); |
private CircuitBreaker<String> cb = new CircuitBreaker<>("test", 5, 10000); |
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protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { |
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { |
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class TestInvocation implements CircuitInvocation { |
class TestInvocation implements CircuitInvocation<String> { |
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String url; |
String url; |
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public TestInvocation(String url) { |
public TestInvocation(String url) { |
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this.url = url; |
this.url = url; |
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} |
} |
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public Object proceed() throws Exception{ |
public String proceed() throws Exception{ |
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URL u = new URL(url); |
URL u = new URL(url); |
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URLConnection c = u.openConnection(); |
URLConnection c = u.openConnection(); |
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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 = cb.invoke(new TestInvocation("http://rafiki/test")); |
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response.getWriter().print(s); |
response.getWriter().print(s); |
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} catch (Exception e) { |
} catch (Exception e) { |
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logger.warning( e.getMessage() ); |
logger.warning( e.getMessage() ); |
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*/ |
*/ |
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public class CircuitBreaker{ |
public class CircuitBreaker<T>{ |
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private volatile CircuitBreakerState currentState; |
private volatile CircuitBreakerState currentState; |
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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(); |
private Notifier notifier = new NullNotifier(); |
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private Statistics stats = new NullStatistics(); |
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public CircuitBreaker(String name, int threshold, long timeoutMS) { |
public CircuitBreaker(String name, BreakerConfig config) { |
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closed.setThreshold(threshold); |
closed.setThreshold(config); |
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open.setTimeout(timeoutMS); |
open.setTimeout(config); |
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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 Exception |
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public T invoke(CircuitInvocation<T> invocation) throws Exception |
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{ |
{ |
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Object result = null; |
stats.addStatistics(Event.Invocation); |
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T result = null; |
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try |
try |
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{ |
{ |
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getState().preInvoke(this); |
getState().preInvoke(this); |
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getState().postInvoke(this); |
getState().postInvoke(this); |
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} |
} |
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catch(Exception e) |
catch(Exception e) |
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{ |
{ |
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if (e instanceof CircuitBreakerException) { |
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stats.addStatistics(Event.InvocationBlocked); |
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} else { |
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stats.addStatistics(Event.InvocationFailure); |
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} |
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getState().onError(this, e); |
getState().onError(this, e); |
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throw e; |
throw e; |
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} |
} |
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} |
} |
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public void tripBreaker() { |
public void tripBreaker() { |
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synchronized(this) { |
commonTripBreaker(Event.BreakerTripped); |
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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(Event.BreakerRetripped); |
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} |
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private void commonTripBreaker(Event event) { |
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synchronized(this) { |
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if (currentState != open) { // TODO:Is this conditional necessary ?? |
if (currentState != open) { // TODO:Is this conditional necessary ?? |
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open.trip(); |
open.trip(); |
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currentState = open; |
currentState = open; |
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notifier.sendNotification(name, Notifier.Event.BreakerTripped); |
notifier.sendNotification(this, event); |
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stats.addStatistics(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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if (currentState != halfOpen) { // TODO:Is this conditional necessary ?? |
if (currentState != halfOpen) { // TODO:Is this conditional necessary ?? |
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currentState = halfOpen; |
currentState = halfOpen; |
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notifier.sendNotification(name, Notifier.Event.BreakerAttemptReset); |
notifier.sendNotification(this, Event.BreakerAttemptReset); |
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stats.addStatistics(Event.BreakerAttemptReset); |
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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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if (currentState != closed) { // TODO: Is this conditional necessary ?? |
if (currentState != closed) { // TODO: Is this conditional necessary ?? |
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currentState = closed; |
internalReset(); |
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notifier.sendNotification(name, Notifier.Event.BreakerReset); |
notifier.sendNotification(this, Event.BreakerReset); |
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stats.addStatistics(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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} |
} |
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public void setNotifier(Notifier notifier) { |
public void setNotifier(Notifier notifier) { |
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this.notifier = notifier; |
synchronized(this) { |
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this.notifier = notifier; |
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} |
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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 String getNotifierName() { |
public void setStatistics(Statistics newStats) { |
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return notifier.getClass().getName(); |
this.stats = newStats; |
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} |
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public Statistics getStatistics() { |
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return this.stats; |
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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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} |
} |