framework: do not double-execute an async job after returning its queue item

In executeQueueItem, when persisting the executing MS id fails (the DB-deadlock
case the catch block exists for), the queue item is returned to the queue so it
can be retried. Execution then fell through to scheduleExecution(job), so the job
was dispatched now AND re-dequeued and dispatched again by the heartbeat, running
the same job (VM start/deploy, volume create, snapshot, etc.) twice concurrently
and defeating the sync queue's serialization. Return after returning the item.

Author: nagaboinaramgopal

framework/jobs/src/main/java/org/apache/cloudstack/framework/jobs/impl/AsyncJobManagerImpl.java

@@ -561,7 +561,7 @@ public String  obfuscatePassword(String result, boolean hidePassword) {
         return StringUtils.obfuscatePasswordInJsonLikeString(result);
     }
 
-    private void scheduleExecution(final AsyncJobVO job) {
+    protected void scheduleExecution(final AsyncJobVO job) {
         scheduleExecution(job, false);
     }
 
@@ -739,7 +739,7 @@ private int getAndResetPendingSignals(AsyncJob job) {
         return signals;
     }
 
-    private void executeQueueItem(SyncQueueItemVO item, boolean fromPreviousSession) {
+    protected void executeQueueItem(SyncQueueItemVO item, boolean fromPreviousSession) {
         AsyncJobVO job = _jobDao.findById(item.getContentId());
         if (job != null) {
             if (logger.isDebugEnabled()) {
@@ -764,6 +764,10 @@ private void executeQueueItem(SyncQueueItemVO item, boolean fromPreviousSession)
                 } catch (Throwable thr) {
                     logger.error("Unexpected exception while returning job-" + item.getContentId() + " to queue", thr);
                 }
+                // The item was returned to the queue for a later retry; do not fall through and also
+                // schedule the job now, or it would execute twice (once here and once when the
+                // returned item is re-dequeued by the heartbeat).
+                return;
             }
 
             try {

framework/jobs/src/test/java/org/apache/cloudstack/framework/jobs/impl/AsyncJobManagerImplExecuteQueueItemTest.java

@@ -0,0 +1,70 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+package org.apache.cloudstack.framework.jobs.impl;
+
+import org.apache.cloudstack.framework.jobs.dao.AsyncJobDao;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.mockito.Spy;
+import org.mockito.junit.MockitoJUnitRunner;
+
+import com.cloud.utils.exception.CloudRuntimeException;
+
+@RunWith(MockitoJUnitRunner.Silent.class)
+public class AsyncJobManagerImplExecuteQueueItemTest {
+
+    @Mock
+    AsyncJobDao _jobDao;
+    @Mock
+    SyncQueueManager _queueMgr;
+
+    @Spy
+    @InjectMocks
+    AsyncJobManagerImpl asyncJobManager = new AsyncJobManagerImpl();
+
+    @Test
+    public void executeQueueItemDoesNotScheduleWhenTheJobUpdateFailsAndItemIsReturned() {
+        long contentId = 10L;
+        long itemId = 20L;
+        long jobId = 1L;
+
+        SyncQueueItemVO item = Mockito.mock(SyncQueueItemVO.class);
+        Mockito.when(item.getContentId()).thenReturn(contentId);
+        Mockito.when(item.getId()).thenReturn(itemId);
+
+        AsyncJobVO job = Mockito.mock(AsyncJobVO.class);
+        Mockito.when(job.getId()).thenReturn(jobId);
+        Mockito.when(_jobDao.findById(contentId)).thenReturn(job);
+
+        // Simulate the DB deadlock the catch block was written to survive.
+        Mockito.doThrow(new CloudRuntimeException("simulated DB deadlock"))
+                .when(_jobDao).update(Mockito.anyLong(), Mockito.any(AsyncJobVO.class));
+
+        // Stub the executor path so we can assert whether it is reached (and avoid the real submit).
+        Mockito.doNothing().when(asyncJobManager).scheduleExecution(Mockito.any(AsyncJobVO.class));
+
+        asyncJobManager.executeQueueItem(item, false);
+
+        // The queue item was returned for a later retry; the job must NOT also be scheduled now, or it
+        // would run twice (once here and once when the heartbeat re-dequeues the returned item).
+        Mockito.verify(_queueMgr).returnItem(itemId);
+        Mockito.verify(asyncJobManager, Mockito.never()).scheduleExecution(Mockito.any(AsyncJobVO.class));
+    }
+}