Merge pull request #1621 from mattrjacobs/stuck-circuit-breaker

Fixed bug where an unsubscription of a command in half-open state leaves circuit  permanently open

Author: mattrjacobs

hystrix-core/src/main/java/com/netflix/hystrix/AbstractCommand.java

@@ -382,6 +382,7 @@ public void call() {
         final Action0 unsubscribeCommandCleanup = new Action0() {
             @Override
             public void call() {
+                circuitBreaker.markNonSuccess();
                 if (_cmd.commandState.compareAndSet(CommandState.OBSERVABLE_CHAIN_CREATED, CommandState.UNSUBSCRIBED)) {
                     if (!_cmd.executionResult.containsTerminalEvent()) {
                         _cmd.eventNotifier.markEvent(HystrixEventType.CANCELLED, _cmd.commandKey);

hystrix-core/src/main/java/com/netflix/hystrix/HystrixCircuitBreaker.java

@@ -272,8 +272,11 @@ public boolean attemptExecution() {
                 return true;
             } else {
                 if (isAfterSleepWindow()) {
+                    //only the first request after sleep window should execute
+                    //if the executing command succeeds, the status will transition to CLOSED
+                    //if the executing command fails, the status will transition to OPEN
+                    //if the executing command gets unsubscribed, the status will transition to OPEN
                     if (status.compareAndSet(Status.OPEN, Status.HALF_OPEN)) {
-                        //only the first request after sleep window should execute
                         return true;
                     } else {
                         return false;

hystrix-core/src/test/java/com/netflix/hystrix/HystrixCircuitBreakerTest.java

@@ -32,6 +32,7 @@
 import com.netflix.hystrix.strategy.HystrixPlugins;
 import com.netflix.hystrix.strategy.executionhook.HystrixCommandExecutionHook;
 import rx.Observable;
+import rx.Subscription;
 
 /**
  * These tests each use a different command key to ensure that running them in parallel doesn't allow the state
@@ -565,6 +566,56 @@ public void testLowVolumeDoesNotTripCircuit() {
         }
     }
 
+    @Test
+    public void testUnsubscriptionDoesNotLeaveCircuitStuckHalfOpen() {
+        String key = "cmd-J";
+        try {
+            int sleepWindow = 200;
+
+            // fail
+            HystrixCommand<Boolean> cmd1 = new FailureCommand(key, 1, sleepWindow);
+            HystrixCommand<Boolean> cmd2 = new FailureCommand(key, 1, sleepWindow);
+            HystrixCommand<Boolean> cmd3 = new FailureCommand(key, 1, sleepWindow);
+            HystrixCommand<Boolean> cmd4 = new FailureCommand(key, 1, sleepWindow);
+            cmd1.execute();
+            cmd2.execute();
+            cmd3.execute();
+            cmd4.execute();
+
+            HystrixCircuitBreaker cb = cmd1.circuitBreaker;
+
+            // everything has failed in the test window so we should return false now
+            Thread.sleep(100);
+            assertFalse(cb.allowRequest());
+            assertTrue(cb.isOpen());
+
+            //this should occur after the sleep window, so get executed
+            //however, it is unsubscribed, so never updates state on the circuit-breaker
+            HystrixCommand<Boolean> cmd5 = new SuccessCommand(key, 5000, sleepWindow);
+
+            //wait for sleep window to pass
+            Thread.sleep(sleepWindow + 50);
+
+            Observable<Boolean> o = cmd5.observe();
+            Subscription s = o.subscribe();
+            s.unsubscribe();
+
+            //wait for 10 sleep windows, then try a successful command.  this should return the circuit to CLOSED
+
+            Thread.sleep(10 * sleepWindow);
+            HystrixCommand<Boolean> cmd6 = new SuccessCommand(key, 1, sleepWindow);
+            cmd6.execute();
+
+            Thread.sleep(100);
+            assertTrue(cb.allowRequest());
+            assertFalse(cb.isOpen());
+
+        } catch (Exception e) {
+            e.printStackTrace();
+            fail("Error occurred: " + e.getMessage());
+        }
+    }
+
     /**
      * Utility method for creating {@link HystrixCommandMetrics} for unit tests.
      */