Changed BulkheadImpl.releasePermit to ensure that it claims a permit …

…when running a task from the pending queue (#366)

* Changed BulkheadImpl.releasePermit to ensure that it claims a permit when running a task from the pending queue

Before this change, releasePermit would check the queue but not modify the permit field. This could eventually
result in permits being equal to maxPermits and would erroneously report the bulkhead as being full

This should fix issue #365

---------

Co-authored-by: Nick Merlo <nick.merlo@aligntrac.com>

core/src/main/java/dev/failsafe/internal/BulkheadImpl.java

@@ -99,8 +99,10 @@ public synchronized void releasePermit() {
     if (permits < maxPermits) {
       permits += 1;
       CompletableFuture<Void> future = futures.pollFirst();
-      if (future != null)
+      if (future != null){
+        permits -= 1;
         future.complete(null);
+      }
     }
   }
 

core/src/test/java/dev/failsafe/functional/BulkheadTest.java

@@ -18,10 +18,15 @@
 import dev.failsafe.Bulkhead;
 import dev.failsafe.BulkheadFullException;
 import dev.failsafe.Failsafe;
+import dev.failsafe.FailsafeExecutor;
+import dev.failsafe.function.CheckedRunnable;
 import dev.failsafe.testing.Testing;
+import org.testng.Assert;
 import org.testng.annotations.Test;
 
 import java.time.Duration;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.TimeUnit;
 
 /**
  * Tests various Bulkhead scenarios.
@@ -46,6 +51,27 @@ public void testPermitAcquiredAfterWait() {
     }, "test");
   }
 
+  public void testPermitAcquiredAfterWaitWithLargeQueue(){
+    Bulkhead<Object> bulkhead = Bulkhead.builder(1).withMaxWaitTime(Duration.ofSeconds(15)).build();
+    FailsafeExecutor<Object> exec = Failsafe.with(bulkhead);
+    CompletableFuture<Void>[] tasks = new CompletableFuture[10];
+    for(int i = 0; i < tasks.length; i++){
+      int index = i;
+      CheckedRunnable sleep = () -> {
+        ignoreExceptions(() ->{
+          System.out.println("Running sleep task " + (index + 1));
+          TimeUnit.MILLISECONDS.sleep(10);
+          System.out.println("Finished sleep task " + (index + 1));
+        });
+      };
+      CompletableFuture<Void> task = exec.runAsync(sleep);
+      task.whenComplete((r, ex) -> Assert.assertNull(ex));
+      tasks[i] = task;
+    }
+
+    CompletableFuture.allOf(tasks).join();
+  }
+
   public void shouldThrowBulkheadFullExceptionAfterPermitsExceeded() {
     // Given
     Bulkhead<Object> bulkhead = Bulkhead.of(2);