Bugfix/repo 5610 events are not actually sent to activemq (#360)

* Add events tests

* Polished put test: connects to JMS via TCP and validate that the event sent is also received back

* Now the tests provides a simple main() that listens on the topic, useful for quick debug sessions

* Now the user name is collected in the calling thread, so that the sendEvent does not silently fails

* Apply changes following review

* Now using queue system to guarantee events order

* Add license

* Updated logs and corrected comments

* Remove empty methods

* Now catering for spurious events at startup when database is bootstrapped

* Now preserving the txn-id in all events

* Moved up definitions in events2.xml after PR feedback

Co-authored-by: Bruno Bossola <bruno@meterian.com>

repository/src/main/java/org/alfresco/repo/event2/EventGenerator.java

@@ -54,7 +54,6 @@ import org.alfresco.repo.policy.JavaBehaviour;
 import org.alfresco.repo.policy.PolicyComponent;
 import org.alfresco.repo.security.authentication.AuthenticationUtil;
 import org.alfresco.repo.transaction.AlfrescoTransactionSupport;
-import org.alfresco.repo.transaction.RetryingTransactionHelper.RetryingTransactionCallback;
 import org.alfresco.service.cmr.dictionary.DictionaryService;
 import org.alfresco.service.cmr.repository.AssociationRef;
 import org.alfresco.service.cmr.repository.ChildAssociationRef;
@@ -90,11 +89,11 @@ public class EventGenerator extends AbstractLifecycleBean implements Initializin
     protected DictionaryService dictionaryService;
     private DescriptorService descriptorService;
     private EventFilterRegistry eventFilterRegistry;
-    private Event2MessageProducer event2MessageProducer;
     private TransactionService transactionService;
     private PersonService personService;
     protected NodeResourceHelper nodeResourceHelper;
 
+    private EventGeneratorQueue eventGeneratorQueue;
     private NodeTypeFilter nodeTypeFilter;
     private ChildAssociationTypeFilter childAssociationTypeFilter;
     private EventUserFilter userFilter;
@@ -109,10 +108,10 @@ public class EventGenerator extends AbstractLifecycleBean implements Initializin
         PropertyCheck.mandatory(this, "dictionaryService", dictionaryService);
         PropertyCheck.mandatory(this, "descriptorService", descriptorService);
         PropertyCheck.mandatory(this, "eventFilterRegistry", eventFilterRegistry);
-        PropertyCheck.mandatory(this, "event2MessageProducer", event2MessageProducer);
         PropertyCheck.mandatory(this, "transactionService", transactionService);
         PropertyCheck.mandatory(this, "personService", personService);
         PropertyCheck.mandatory(this, "nodeResourceHelper", nodeResourceHelper);
+        PropertyCheck.mandatory(this, "eventGeneratorQueue", eventGeneratorQueue);
 
         this.nodeTypeFilter = eventFilterRegistry.getNodeTypeFilter();
         this.childAssociationTypeFilter = eventFilterRegistry.getChildAssociationTypeFilter();
@@ -177,12 +176,6 @@ public class EventGenerator extends AbstractLifecycleBean implements Initializin
         this.eventFilterRegistry = eventFilterRegistry;
     }
 
-    @SuppressWarnings("unused")
-    public void setEvent2MessageProducer(Event2MessageProducer event2MessageProducer)
-    {
-        this.event2MessageProducer = event2MessageProducer;
-    }
-
     public void setTransactionService(TransactionService transactionService)
     {
         this.transactionService = transactionService;
@@ -198,6 +191,11 @@ public class EventGenerator extends AbstractLifecycleBean implements Initializin
         this.nodeResourceHelper = nodeResourceHelper;
     }
 
+    public void setEventGeneratorQueue(EventGeneratorQueue eventGeneratorQueue)
+    {
+        this.eventGeneratorQueue = eventGeneratorQueue;
+    }
+
     @Override
     public void onCreateNode(ChildAssociationRef childAssocRef)
     {
@@ -428,20 +426,26 @@ public class EventGenerator extends AbstractLifecycleBean implements Initializin
 
         protected void sendEvent(NodeRef nodeRef, EventConsolidator consolidator)
         {
+            EventInfo eventInfo = getEventInfo(AuthenticationUtil.getFullyAuthenticatedUser());
+            eventGeneratorQueue.accept(()-> createEvent(nodeRef, consolidator, eventInfo));
+        }
+
+        private RepoEvent<?> createEvent(NodeRef nodeRef, EventConsolidator consolidator, EventInfo eventInfo)
+        {
+            String user = eventInfo.getPrincipal();
+
             if (consolidator.isTemporaryNode())
             {
                 if (LOGGER.isTraceEnabled())
                 {
                     LOGGER.trace("Ignoring temporary node: " + nodeRef);
                 }
-                return;
+                return null;
             }
 
-            final String user = AuthenticationUtil.getFullyAuthenticatedUser();
             // Get the repo event before the filtering,
             // so we can take the latest node info into account
-            final RepoEvent<?> event = consolidator.getRepoEvent(getEventInfo(user));
+            final RepoEvent<?> event = consolidator.getRepoEvent(eventInfo);
-
 
             final QName nodeType = consolidator.getNodeType();
             if (isFiltered(nodeType, user))
@@ -452,7 +456,7 @@ public class EventGenerator extends AbstractLifecycleBean implements Initializin
                             + ((nodeType == null) ? "Unknown' " : nodeType.toPrefixString())
                             + "' created by: " + user);
                 }
-                return;
+                return null;
             }
 
             if (event.getType().equals(EventType.NODE_UPDATED.getType()) && consolidator.isResourceBeforeAllFieldsNull())
@@ -461,27 +465,34 @@ public class EventGenerator extends AbstractLifecycleBean implements Initializin
                 {
                     LOGGER.trace("Ignoring node updated event as no fields have been updated: " + nodeRef);
                 }
-                return;
+                return null;
             }
 
-            logAndSendEvent(event, consolidator.getEventTypes());
+            logEvent(event, consolidator.getEventTypes());
+            return event;
         }
 
         protected void sendEvent(ChildAssociationRef childAssociationRef, ChildAssociationEventConsolidator consolidator)
         {
+            EventInfo eventInfo = getEventInfo(AuthenticationUtil.getFullyAuthenticatedUser());
+            eventGeneratorQueue.accept(()-> createEvent(eventInfo, childAssociationRef, consolidator));
+        }
+
+        private RepoEvent<?> createEvent(EventInfo eventInfo, ChildAssociationRef childAssociationRef, ChildAssociationEventConsolidator consolidator)
+        {
+            String user = eventInfo.getPrincipal();
             if (consolidator.isTemporaryChildAssociation())
             {
                 if (LOGGER.isTraceEnabled())
                 {
                     LOGGER.trace("Ignoring temporary child association: " + childAssociationRef);
                 }
-                return;
+                return null;
             }
 
-            final String user = AuthenticationUtil.getFullyAuthenticatedUser();
             // Get the repo event before the filtering,
             // so we can take the latest association info into account
-            final RepoEvent<?> event = consolidator.getRepoEvent(getEventInfo(user));
+            final RepoEvent<?> event = consolidator.getRepoEvent(eventInfo);
 
             final QName childAssocType = consolidator.getChildAssocType();
             if (isFilteredChildAssociation(childAssocType, user))
@@ -492,7 +503,7 @@ public class EventGenerator extends AbstractLifecycleBean implements Initializin
                             + ((childAssocType == null) ? "Unknown' " : childAssocType.toPrefixString())
                             + "' created by: " + user);
                 }
-                return;
+                return null;
             } else if (childAssociationRef.isPrimary())
             {
                 if (LOGGER.isTraceEnabled())
@@ -501,13 +512,20 @@ public class EventGenerator extends AbstractLifecycleBean implements Initializin
                             + ((childAssocType == null) ? "Unknown' " : childAssocType.toPrefixString())
                             + "' created by: " + user);
                 }
-                return;
+                return null;
             }
 
-            logAndSendEvent(event, consolidator.getEventTypes());
+            logEvent(event, consolidator.getEventTypes());
+            return event;
         }
 
         protected void sendEvent(AssociationRef peerAssociationRef, PeerAssociationEventConsolidator consolidator)
+        {
+            EventInfo eventInfo = getEventInfo(AuthenticationUtil.getFullyAuthenticatedUser());
+            eventGeneratorQueue.accept(()-> createEvent(eventInfo, peerAssociationRef, consolidator));
+        }
+
+        private RepoEvent<?> createEvent(EventInfo eventInfo, AssociationRef peerAssociationRef, PeerAssociationEventConsolidator consolidator)
         {
             if (consolidator.isTemporaryPeerAssociation())
             {
@@ -515,30 +533,21 @@ public class EventGenerator extends AbstractLifecycleBean implements Initializin
                 {
                     LOGGER.trace("Ignoring temporary peer association: " + peerAssociationRef);
                 }
-                return;
+                return null;
             }
 
-            final String user = AuthenticationUtil.getFullyAuthenticatedUser();
+            RepoEvent<?> event = consolidator.getRepoEvent(eventInfo);
-            // Get the repo event before the filtering,
+            logEvent(event, consolidator.getEventTypes());
-            // so we can take the latest association info into account
+            return event;
-            final RepoEvent<?> event = consolidator.getRepoEvent(getEventInfo(user));
-
-            logAndSendEvent(event, consolidator.getEventTypes());
         }
 
-        protected void logAndSendEvent(RepoEvent<?> event, Deque<EventType> listOfEvents)
+        private void logEvent(RepoEvent<?> event, Deque<EventType> listOfEvents)
         {
             if (LOGGER.isTraceEnabled())
             {
                 LOGGER.trace("List of Events:" + listOfEvents);
                 LOGGER.trace("Sending event:" + event);
             }
-            // Need to execute this in another read txn because Camel expects it
-            transactionService.getRetryingTransactionHelper().doInTransaction((RetryingTransactionCallback<Void>) () -> {
-                event2MessageProducer.send(event);
-
-                return null;
-            }, true, false);
         }
     }
 

repository/src/main/java/org/alfresco/repo/event2/EventGeneratorQueue.java

@@ -0,0 +1,179 @@
+/*
+ * #%L
+ * Alfresco Repository
+ * %%
+ * Copyright (C) 2005 - 2021 Alfresco Software Limited
+ * %%
+ * This file is part of the Alfresco software.
+ * If the software was purchased under a paid Alfresco license, the terms of
+ * the paid license agreement will prevail.  Otherwise, the software is
+ * provided under the following open source license terms:
+ *
+ * Alfresco is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Alfresco is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
+ * #L%
+ */
+package org.alfresco.repo.event2;
+
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.Callable;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.Executor;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.TimeUnit;
+
+import org.alfresco.repo.event.v1.model.RepoEvent;
+import org.alfresco.util.PropertyCheck;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.springframework.beans.factory.InitializingBean;
+
+/*
+ * This queue allows to create asynchronously the RepoEvent offloading the work to a ThreadPool but
+ * at the same time it preserves the order of the events
+ */
+public class EventGeneratorQueue implements InitializingBean
+{
+	protected static final Log LOGGER = LogFactory.getLog(EventGeneratorQueue.class);
+    
+    protected Executor enqueueThreadPoolExecutor;
+    protected Executor dequeueThreadPoolExecutor;
+    protected Event2MessageProducer event2MessageProducer;
+    protected BlockingQueue<EventInMaking> queue = new LinkedBlockingQueue<>();
+    protected Runnable listener = createListener();
+
+    @Override
+    public void afterPropertiesSet() throws Exception
+    {
+        PropertyCheck.mandatory(this, "enqueueThreadPoolExecutor", enqueueThreadPoolExecutor);
+        PropertyCheck.mandatory(this, "dequeueThreadPoolExecutor", dequeueThreadPoolExecutor);
+        PropertyCheck.mandatory(this, "event2MessageProducer", event2MessageProducer);
+    }
+
+    public void setEvent2MessageProducer(Event2MessageProducer event2MessageProducer)
+    {
+        this.event2MessageProducer = event2MessageProducer;
+    }
+    
+    public void setEnqueueThreadPoolExecutor(Executor enqueueThreadPoolExecutor)
+    {
+        this.enqueueThreadPoolExecutor = enqueueThreadPoolExecutor;
+    }
+    
+    public void setDequeueThreadPoolExecutor(Executor dequeueThreadPoolExecutor)
+    {
+        this.dequeueThreadPoolExecutor = dequeueThreadPoolExecutor;
+        dequeueThreadPoolExecutor.execute(listener);
+    }
+
+    /**
+     * Procedure to enqueue the callback functions that creates an event.
+     * @param maker Callback function that creates an event.
+     */
+    public void accept(Callable<RepoEvent<?>> maker)
+    {
+        EventInMaking eventInMaking = new EventInMaking(maker);
+        queue.offer(eventInMaking);
+        enqueueThreadPoolExecutor.execute(() -> {
+            try
+            {
+                eventInMaking.make();
+            }
+            catch (Exception e)
+            {
+                LOGGER.error("Unexpected error while enqueuing maker function for repository event" + e);
+            }
+        });
+    }
+
+    /**
+     * Create listener task in charge of dequeuing and sending events ready to be sent.
+     * @return The task in charge of dequeuing and sending events ready to be sent.
+     */
+    private Runnable createListener()
+    {
+        return new Runnable()
+        {
+            @Override
+            public void run()
+            {
+                try 
+                {
+                    while (!Thread.interrupted())
+                    {
+                        try
+                        {
+                            EventInMaking eventInMaking = queue.take();
+                            RepoEvent<?> event = eventInMaking.getEventWhenReady();
+                            if (event != null)
+                            {
+                                event2MessageProducer.send(event);
+                            }
+                        }
+                        catch (Exception e)
+                        {
+                            LOGGER.error("Unexpected error while dequeuing and sending repository event" + e);
+                        }
+                    }
+                }
+                finally
+                {
+                    LOGGER.warn("Unexpected: rescheduling the listener thread.");
+                    dequeueThreadPoolExecutor.execute(listener);
+                }
+            }
+        };
+
+    }
+
+    /*
+     * Simple class that makes events and allows to retrieve them when ready
+     */
+    private static class EventInMaking
+    {
+        private Callable<RepoEvent<?>> maker;
+        private volatile RepoEvent<?> event;
+        private CountDownLatch latch;
+        
+        public EventInMaking(Callable<RepoEvent<?>> maker)
+        {
+            this.maker = maker;
+            this.latch = new CountDownLatch(1);
+        }
+        
+        public void make() throws Exception
+        {
+            try
+            {
+                event = maker.call();
+            }
+            finally 
+            {
+                latch.countDown();
+            }
+        }
+        
+        public RepoEvent<?> getEventWhenReady() throws InterruptedException
+        {
+            latch.await(30, TimeUnit.SECONDS);
+            return event;
+        }
+        
+        @Override
+        public String toString()
+        {
+            return maker.toString();
+        }
+    }
+
+}

repository/src/main/resources/alfresco/events2-context.xml

@@ -38,9 +38,10 @@
         <property name="dictionaryService" ref="dictionaryService"/>
         <property name="descriptorService" ref="descriptorComponent"/>
         <property name="eventFilterRegistry" ref="event2FilterRegistry"/>
-        <property name="event2MessageProducer" ref="event2MessageProducer"/>
         <property name="transactionService" ref="transactionService"/>
         <property name="personService" ref="personService"/>
+        <property name="nodeResourceHelper" ref="nodeResourceHelper"/>
+        <property name="eventGeneratorQueue" ref="eventGeneratorQueue"/>
     </bean>
 
     <bean id="baseNodeResourceHelper" abstract="true">
@@ -54,7 +55,45 @@
 
     <bean id="nodeResourceHelper" class="org.alfresco.repo.event2.NodeResourceHelper" parent="baseNodeResourceHelper"/>
 
-    <bean id="eventGeneratorV2" class="org.alfresco.repo.event2.EventGenerator" parent="baseEventGeneratorV2">
+    <bean id="eventGeneratorV2" class="org.alfresco.repo.event2.EventGenerator" parent="baseEventGeneratorV2"/>
-        <property name="nodeResourceHelper" ref="nodeResourceHelper"/>
+
+    <bean id="eventGeneratorQueue" class="org.alfresco.repo.event2.EventGeneratorQueue" >
+        <property name="enqueueThreadPoolExecutor">
+            <ref bean="eventAsyncEnqueueThreadPool" />
+        </property>
+        <property name="dequeueThreadPoolExecutor">
+            <ref bean="eventAsyncDequeueThreadPool" />
+        </property>
+       <property name="event2MessageProducer" ref="event2MessageProducer"/>
+    </bean>
+
+    <bean id="eventAsyncEnqueueThreadPool" class="org.alfresco.util.ThreadPoolExecutorFactoryBean">
+        <property name="poolName">
+            <value>eventAsyncEnqueueThreadPool</value>
+        </property>
+        <property name="corePoolSize">
+            <value>${repo.event2.queue.enqueueThreadPool.coreSize}</value>
+        </property>
+        <property name="maximumPoolSize">
+            <value>${repo.event2.queue.enqueueThreadPool.maximumSize}</value>
+        </property>
+        <property name="threadPriority">
+            <value>${repo.event2.queue.enqueueThreadPool.priority}</value>
+        </property>
+    </bean>
+
+    <bean id="eventAsyncDequeueThreadPool" class="org.alfresco.util.ThreadPoolExecutorFactoryBean">
+        <property name="poolName">
+            <value>eventAsyncDequeueThreadPool</value>
+        </property>
+        <property name="corePoolSize">
+            <value>${repo.event2.queue.dequeueThreadPool.coreSize}</value>
+        </property>
+        <property name="maximumPoolSize">
+            <value>${repo.event2.queue.dequeueThreadPool.maximumSize}</value>
+        </property>
+        <property name="threadPriority">
+            <value>${repo.event2.queue.dequeueThreadPool.priority}</value>
+        </property>
     </bean>
 </beans>

repository/src/main/resources/alfresco/repository.properties

@@ -1211,6 +1211,15 @@ repo.event2.filter.childAssocTypes=rn:rendition
 repo.event2.filter.users=
 # Topic name
 repo.event2.topic.endpoint=amqp:topic:alfresco.repo.event2
+# Thread pool for async enqueue of repo events
+repo.event2.queue.enqueueThreadPool.priority=1
+repo.event2.queue.enqueueThreadPool.coreSize=8
+repo.event2.queue.enqueueThreadPool.maximumSize=10
+# Thread pool for async dequeue and delivery of repo events
+repo.event2.queue.dequeueThreadPool.priority=1
+repo.event2.queue.dequeueThreadPool.coreSize=1
+repo.event2.queue.dequeueThreadPool.maximumSize=1
+
 
 # MNT-21083
 # --DELETE_NOT_EXISTS - default settings

repository/src/test/java/org/alfresco/repo/event2/AbstractContextAwareRepoEvent.java

@@ -30,6 +30,7 @@ import static java.util.concurrent.TimeUnit.SECONDS;
 import static org.awaitility.Awaitility.await;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 import javax.jms.ConnectionFactory;
@@ -77,17 +78,19 @@ import com.fasterxml.jackson.databind.ObjectMapper;
 
 public abstract class AbstractContextAwareRepoEvent extends BaseSpringTest
 {
+    protected static final boolean            DEBUG = false;
+
     protected static final String             TEST_NAMESPACE  = "http://www.alfresco.org/test/ContextAwareRepoEvent";
+    protected static final RepoEventContainer EVENT_CONTAINER = new RepoEventContainer();
 
     private static final   String             BROKER_URL      = "tcp://localhost:61616";
     private static final   String             TOPIC_NAME      = "alfresco.repo.event2";
     private static final   String             CAMEL_ROUTE     = "jms:topic:" + TOPIC_NAME;
-    private static final   RepoEventContainer EVENT_CONTAINER = new RepoEventContainer();
     private static final   CamelContext       CAMEL_CONTEXT   = new DefaultCamelContext();
 
     private static boolean isCamelConfigured;
     private static DataFormat dataFormat;
-
+    
     @Autowired
     protected RetryingTransactionHelper retryingTransactionHelper;
 
@@ -104,6 +107,13 @@ public abstract class AbstractContextAwareRepoEvent extends BaseSpringTest
     @Autowired
     protected ObjectMapper event2ObjectMapper;
 
+    @Autowired @Qualifier("eventGeneratorV2")
+    protected EventGenerator eventGenerator;
+
+    @Autowired
+    @Qualifier("eventGeneratorQueue")
+    protected EventGeneratorQueue eventQueue;
+
     protected NodeRef rootNodeRef;
 
     @BeforeClass
@@ -141,8 +151,35 @@ public abstract class AbstractContextAwareRepoEvent extends BaseSpringTest
             }
             return nodeService.getRootNode(storeRef);
         });
+
+        flushSpuriousEvents();
     }
 
+    /*
+     * When running with an empty database some events related to the creation may
+     * creep up here making the test fails. After attempting several other
+     * strategies, a smart sleep seems to do the work.
+     */
+    protected void flushSpuriousEvents() throws InterruptedException
+    {
+        int maxloops = 5;
+        
+        int count = maxloops;
+        do
+        {
+            Thread.sleep(165l);
+            if (EVENT_CONTAINER.isEmpty())
+            {
+                count--;
+            } else 
+            {
+                EVENT_CONTAINER.reset();
+                count = maxloops;
+            }
+
+        } while (count > 0);
+    }
+    
     @After
     public void tearDown()
     {
@@ -179,6 +216,16 @@ public abstract class AbstractContextAwareRepoEvent extends BaseSpringTest
             propertyMap).getChildRef());
     }
 
+    protected NodeRef updateNodeName(NodeRef nodeRef, String newName)
+    {
+        PropertyMap propertyMap = new PropertyMap();
+        propertyMap.put(ContentModel.PROP_NAME, newName);
+        return retryingTransactionHelper.doInTransaction(() -> {
+            nodeService.addProperties(nodeRef, propertyMap);
+            return null;
+        });
+    }
+
     protected void deleteNode(NodeRef nodeRef)
     {
         retryingTransactionHelper.doInTransaction(() -> {
@@ -376,13 +423,18 @@ public abstract class AbstractContextAwareRepoEvent extends BaseSpringTest
 
     public static class RepoEventContainer implements Processor
     {
-        private final List<RepoEvent<?>> events = new ArrayList<>();
+        private final List<RepoEvent<?>> events = Collections.synchronizedList(new ArrayList<>());
 
         @Override
         public void process(Exchange exchange)
         {
             Object object = exchange.getIn().getBody();
             events.add((RepoEvent<?>) object);
+
+            if (DEBUG)
+            {
+                System.err.println("XX: "+object);
+            }
         }
 
         public List<RepoEvent<?>> getEvents()
@@ -404,6 +456,12 @@ public abstract class AbstractContextAwareRepoEvent extends BaseSpringTest
         {
             events.clear();
         }
+
+        public boolean isEmpty()
+        {
+            return events.isEmpty();
+        }
+
     }
 
     @SuppressWarnings("unchecked")

repository/src/test/java/org/alfresco/repo/event2/EventGeneratorQueueUnitTest.java

@@ -0,0 +1,290 @@
+/*
+ * #%L
+ * Alfresco Repository
+ * %%
+ * Copyright (C) 2005 - 2021 Alfresco Software Limited
+ * %%
+ * This file is part of the Alfresco software.
+ * If the software was purchased under a paid Alfresco license, the terms of
+ * the paid license agreement will prevail.  Otherwise, the software is
+ * provided under the following open source license terms:
+ *
+ * Alfresco is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Alfresco is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
+ * #L%
+ */
+package org.alfresco.repo.event2;
+
+import static java.lang.Thread.sleep;
+import static org.junit.Assert.assertEquals;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.Callable;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.Executor;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.SynchronousQueue;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+
+import org.alfresco.repo.event.v1.model.RepoEvent;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mockito;
+import org.mockito.invocation.InvocationOnMock;
+import org.mockito.stubbing.Answer;
+
+public class EventGeneratorQueueUnitTest
+{
+    private EventGeneratorQueue queue;
+
+    private Event2MessageProducer bus;
+    private ExecutorService enqueuePool;
+    private ExecutorService dequeuePool;
+    private List<RepoEvent<?>> recordedEvents;
+    private Map<String, RepoEvent<?>> events;
+
+    @Before
+    public void setup() 
+    {
+        queue = new EventGeneratorQueue();
+
+        enqueuePool = newThreadPool();
+        queue.setEnqueueThreadPoolExecutor(enqueuePool);
+        dequeuePool = newThreadPool();
+        queue.setDequeueThreadPoolExecutor(dequeuePool);
+
+        bus = mock(Event2MessageProducer.class);
+        queue.setEvent2MessageProducer(bus);
+
+        events = new HashMap<>();
+
+        setupEventsRecorder();
+    }
+
+    @After
+    public void teardown() 
+    {
+        enqueuePool.shutdown();
+    }
+
+    private void setupEventsRecorder()
+    {
+        recordedEvents = new CopyOnWriteArrayList<>();
+
+        Mockito.doAnswer(new Answer<Void>()
+        {
+            @Override
+            public Void answer(InvocationOnMock invocation) throws Throwable
+            {
+                RepoEvent<?> event = invocation.getArgument(0, RepoEvent.class);
+                recordedEvents.add(event);
+                return null;
+            }
+        }).when(bus).send(any());
+    }
+
+    @Test
+    public void shouldReceiveSingleQuickMessage() throws Exception 
+    {
+        queue.accept(messageWithDelay("A", 55l));
+
+        sleep(150l);
+
+        assertEquals(1, recordedEvents.size());
+        assertEquals("A", recordedEvents.get(0).getId());
+    }
+
+    @Test
+    public void shouldNotReceiveEventsWhenMessageIsNull() throws Exception 
+    {
+        queue.accept(() -> { return null; });
+
+        sleep(150l);
+
+        assertEquals(0, recordedEvents.size());
+    }
+
+    @Test
+    public void shouldReceiveMultipleMessagesPreservingOrderScenarioOne() throws Exception {
+        queue.accept(messageWithDelay("A", 0l));
+        queue.accept(messageWithDelay("B", 100l));
+        queue.accept(messageWithDelay("C", 200l));
+
+        sleep(450l);
+
+        assertEquals(3, recordedEvents.size());
+        assertEquals("A", recordedEvents.get(0).getId());
+        assertEquals("B", recordedEvents.get(1).getId());
+        assertEquals("C", recordedEvents.get(2).getId());
+    }
+
+    @Test
+    public void shouldReceiveMultipleMessagesPreservingOrderScenarioTwo() throws Exception
+    {
+        queue.accept(messageWithDelay("A", 300l));
+        queue.accept(messageWithDelay("B", 150l));
+        queue.accept(messageWithDelay("C", 0l));
+
+        sleep(950l);
+
+        assertEquals(3, recordedEvents.size());
+        assertEquals("A", recordedEvents.get(0).getId());
+        assertEquals("B", recordedEvents.get(1).getId());
+        assertEquals("C", recordedEvents.get(2).getId());
+    }
+
+    @Test
+    public void shouldReceiveMultipleMessagesPreservingOrderEvenWhenMakerPoisoned() throws Exception
+    {
+        queue.accept(messageWithDelay("A", 300l));
+        queue.accept(() -> {throw new RuntimeException("Boom! (not to worry, this is a test)");});
+        queue.accept(messageWithDelay("B", 55l));
+        queue.accept(messageWithDelay("C", 0l));
+
+        sleep(950l);
+
+        assertEquals(3, recordedEvents.size());
+        assertEquals("A", recordedEvents.get(0).getId());
+        assertEquals("B", recordedEvents.get(1).getId());
+        assertEquals("C", recordedEvents.get(2).getId());
+    }
+    
+    @Test
+    public void shouldReceiveMultipleMessagesPreservingOrderEvenWhenSenderPoisoned() throws Exception
+    {
+        Callable<RepoEvent<?>> makerB = messageWithDelay("B", 55l);
+        RepoEvent<?> messageB = makerB.call();
+        doThrow(new RuntimeException("Boom! (not to worry, this is a test)")).when(bus).send(messageB);
+        queue.accept(messageWithDelay("A", 300l));
+        queue.accept(makerB);
+        queue.accept(messageWithDelay("C", 0l));
+
+        sleep(950l);
+
+        assertEquals(2, recordedEvents.size());
+        assertEquals("A", recordedEvents.get(0).getId());
+        assertEquals("C", recordedEvents.get(1).getId());
+    }
+
+    @Test
+    public void shouldReceiveMultipleMessagesPreservingOrderEvenWhenMakerPoisonedWithError() throws Exception
+    {
+        queue.accept(messageWithDelay("A", 300l));
+        queue.accept(() -> {throw new OutOfMemoryError("Boom! (not to worry, this is a test)");});
+        queue.accept(messageWithDelay("B", 55l));
+        queue.accept(messageWithDelay("C", 0l));
+
+        sleep(950l);
+
+        assertEquals(3, recordedEvents.size());
+        assertEquals("A", recordedEvents.get(0).getId());
+        assertEquals("B", recordedEvents.get(1).getId());
+        assertEquals("C", recordedEvents.get(2).getId());
+    }
+    
+    @Test
+    public void shouldReceiveMultipleMessagesPreservingOrderEvenWhenSenderPoisonedWithError() throws Exception
+    {
+        Callable<RepoEvent<?>> makerB = messageWithDelay("B", 55l);
+        RepoEvent<?> messageB = makerB.call();
+        doThrow(new OutOfMemoryError("Boom! (not to worry, this is a test)")).when(bus).send(messageB);
+        queue.accept(messageWithDelay("A", 300l));
+        queue.accept(makerB);
+        queue.accept(messageWithDelay("C", 0l));
+
+        sleep(950l);
+
+        assertEquals(2, recordedEvents.size());
+        assertEquals("A", recordedEvents.get(0).getId());
+        assertEquals("C", recordedEvents.get(1).getId());
+    }
+
+    private Callable<RepoEvent<?>> messageWithDelay(String id, long delay)
+    {
+        Callable<RepoEvent<?>> res = new Callable<RepoEvent<?>>() {
+
+            @Override
+            public RepoEvent<?> call() throws Exception
+            {
+                if(delay != 0)
+                {
+                    sleep(delay); 
+                }
+                return newRepoEvent(id);
+            } 
+            
+            @Override
+            public String toString()
+            {
+                return id;
+            }
+        };
+        return res;
+    }
+    
+    private RepoEvent<?> newRepoEvent(String id)
+    {
+        RepoEvent<?> ev = events.get(id);
+        if (ev!=null)
+            return ev;
+        
+        ev = mock(RepoEvent.class);
+        when(ev.getId()).thenReturn(id);
+        when(ev.toString()).thenReturn(id);
+        events.put(id, ev);
+
+        return ev;
+    }
+
+    public static ExecutorService newThreadPool() 
+    {
+        return new ThreadPoolExecutor(2, Integer.MAX_VALUE,
+                                      60L, TimeUnit.SECONDS,
+                                      new SynchronousQueue<Runnable>());
+    }
+
+    public static final Executor SYNC_EXECUTOR_SAME_THREAD = new Executor()
+    {
+        @Override
+        public void execute(Runnable command)
+        {
+            command.run();
+        }
+    };
+
+    public static final Executor SYNC_EXECUTOR_NEW_THREAD = new Executor()
+    {
+        @Override
+        public void execute(Runnable command)
+        {
+            Thread t = new Thread(command);
+            t.start();
+            try
+            {
+                t.join();
+            }
+            catch (InterruptedException e)
+            {
+                Thread.currentThread().interrupt();
+            }
+        }
+    };
+}

repository/src/test/java/org/alfresco/repo/event2/EventGeneratorTest.java

@@ -0,0 +1,249 @@
+/*
+ * #%L
+ * Alfresco Repository
+ * %%
+ * Copyright (C) 2005 - 2020 Alfresco Software Limited
+ * %%
+ * This file is part of the Alfresco software.
+ * If the software was purchased under a paid Alfresco license, the terms of
+ * the paid license agreement will prevail.  Otherwise, the software is
+ * provided under the following open source license terms:
+ *
+ * Alfresco is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Alfresco is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
+ * #L%
+ */
+package org.alfresco.repo.event2;
+
+import java.util.Collections;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+
+import javax.jms.Destination;
+import javax.jms.JMSException;
+import javax.jms.Message;
+import javax.jms.MessageConsumer;
+import javax.jms.MessageListener;
+import javax.jms.Session;
+
+import org.alfresco.model.ContentModel;
+import org.alfresco.repo.event.databind.ObjectMapperFactory;
+import org.alfresco.repo.event.v1.model.RepoEvent;
+import org.alfresco.service.cmr.repository.NodeRef;
+import org.apache.activemq.ActiveMQConnection;
+import org.apache.activemq.ActiveMQConnectionFactory;
+import org.apache.activemq.advisory.DestinationSource;
+import org.apache.activemq.command.ActiveMQQueue;
+import org.apache.activemq.command.ActiveMQTextMessage;
+import org.apache.activemq.command.ActiveMQTopic;
+import org.awaitility.Awaitility;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Qualifier;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+public class EventGeneratorTest extends AbstractContextAwareRepoEvent
+{
+    private static final String EVENT2_TOPIC_NAME = "alfresco.repo.event2";
+
+    private static final long DUMP_BROKER_TIMEOUT = 50000000l;
+
+    @Autowired @Qualifier("event2ObjectMapper")
+    private ObjectMapper objectMapper;
+
+    private ActiveMQConnection connection;
+    protected List<RepoEvent<?>> receivedEvents;
+
+    @Before
+    public void startupTopicListener() throws Exception
+    {
+        ActiveMQConnectionFactory connectionFactory = new ActiveMQConnectionFactory("tcp://localhost:61616");
+        connection = (ActiveMQConnection) connectionFactory.createConnection();
+        connection.start();
+
+        Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
+        Destination destination = session.createTopic(EVENT2_TOPIC_NAME);
+        MessageConsumer consumer = session.createConsumer(destination);
+
+        receivedEvents = Collections.synchronizedList(new LinkedList<>());
+        consumer.setMessageListener(new MessageListener()
+        {
+            @Override
+            public void onMessage(Message message)
+            {
+                String text = getText(message);
+                RepoEvent<?> event = toRepoEvent(text);
+
+                if (DEBUG)
+                {
+                    System.err.println("RX: " + event);
+                }
+
+                receivedEvents.add(event);
+            }
+
+            private RepoEvent<?> toRepoEvent(String json)
+            {
+                try
+                {
+                    return objectMapper.readValue(json, RepoEvent.class);
+                } catch (Exception e)
+                {
+                    e.printStackTrace();
+                    return null;
+                }
+            }
+        });
+
+        if (DEBUG)
+        {
+            System.err.println("Now actively listening on topic " + EVENT2_TOPIC_NAME);
+        }
+    }
+
+    protected ObjectMapper createObjectMapper()
+    {
+        return ObjectMapperFactory.createInstance();
+    }
+
+    @After
+    public void shutdownTopicListener() throws Exception
+    {
+        connection.close();
+        connection = null;
+    }
+
+    @Test
+    public void shouldReceiveEvent2EventsOnNodeCreation() throws Exception
+    {
+        createNode(ContentModel.TYPE_CONTENT);
+
+        Awaitility.await().atMost(6, TimeUnit.SECONDS).until(() -> receivedEvents.size() == 1);
+
+        RepoEvent<?> sent = getRepoEvent(1);
+        RepoEvent<?> received = receivedEvents.get(0);
+        assertEventsEquals("Events are different!", sent, received);
+    }
+
+    private void assertEventsEquals(String message, RepoEvent<?> expected, RepoEvent<?> current)
+    {
+        if (DEBUG)
+        {
+            System.err.println("XP: " + expected);
+            System.err.println("CU: " + current);
+        }
+        
+        assertEquals(message, expected, current);
+    }
+
+    @Test
+    public void shouldReceiveEvent2EventsInOrder() throws Exception
+    {
+        NodeRef nodeRef = createNode(ContentModel.TYPE_CONTENT);
+        updateNodeName(nodeRef, "TestFile-" + System.currentTimeMillis() + ".txt");
+        deleteNode(nodeRef);
+
+        Awaitility.await().atMost(6, TimeUnit.SECONDS).until(() -> receivedEvents.size() == 3);
+
+        RepoEvent<?> sentCreation = getRepoEvent(1);
+        RepoEvent<?> sentUpdate = getRepoEvent(2);
+        RepoEvent<?> sentDeletion = getRepoEvent(3);
+        assertEquals("Expected create event!", sentCreation, (RepoEvent<?>) receivedEvents.get(0));
+        assertEquals("Expected update event!", sentUpdate, (RepoEvent<?>) receivedEvents.get(1));
+        assertEquals("Expected delete event!", sentDeletion, (RepoEvent<?>) receivedEvents.get(2));
+    }
+
+    private static String getText(Message message)
+    {
+        try
+        {
+            ActiveMQTextMessage am = (ActiveMQTextMessage) message;
+            return am.getText();
+        } catch (JMSException e)
+        {
+            return null;
+        }
+    }
+
+    // a simple main to investigate the contents of the local broker
+    public static void main(String[] args) throws Exception
+    {
+        dumpBroker("tcp://localhost:61616", DUMP_BROKER_TIMEOUT);
+        System.exit(0);
+    }
+
+    private static void dumpBroker(String url, long timeout) throws Exception
+    {
+        System.out.println("Broker at url: '" + url + "'");
+
+        ActiveMQConnectionFactory connectionFactory = new ActiveMQConnectionFactory(url);
+        ActiveMQConnection connection = (ActiveMQConnection) connectionFactory.createConnection();
+        try
+        {
+            connection.start();
+
+            DestinationSource ds = connection.getDestinationSource();
+
+            Set<ActiveMQQueue> queues = ds.getQueues();
+            System.out.println("\nFound " + queues.size() + " queues:");
+            for (ActiveMQQueue queue : queues)
+            {
+                try
+                {
+                    System.out.println("- " + queue.getQueueName());
+                } catch (JMSException e)
+                {
+                    e.printStackTrace();
+                }
+            }
+
+            Set<ActiveMQTopic> topics = ds.getTopics();
+            System.out.println("\nFound " + topics.size() + " topics:");
+            for (ActiveMQTopic topic : topics)
+            {
+                try
+                {
+                    System.out.println("- " + topic.getTopicName());
+                } catch (JMSException e)
+                {
+                    e.printStackTrace();
+                }
+            }
+
+            Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
+            Destination destination = session.createTopic(EVENT2_TOPIC_NAME);
+            MessageConsumer consumer = session.createConsumer(destination);
+
+            System.out.println("\nListening to topic " + EVENT2_TOPIC_NAME + "...");
+            consumer.setMessageListener(new MessageListener()
+            {
+                @Override
+                public void onMessage(Message message)
+                {
+                    String text = getText(message);
+                    System.out.println("Received message " + message + "\n" + text + "\n");
+                }
+            });
+
+            Thread.sleep(timeout);
+        } finally
+        {
+            connection.close();
+        }
+    }
+}

repository/src/test/java/org/alfresco/repo/event2/RepoEvent2ITSuite.java

@@ -34,7 +34,8 @@ import org.junit.runners.Suite.SuiteClasses;
                 UpdateRepoEventIT.class,
                 DeleteRepoEventIT.class,
                 ChildAssociationRepoEventIT.class,
-                PeerAssociationRepoEventIT.class
+                PeerAssociationRepoEventIT.class,
+                EventGeneratorTest.class
 })
 public class RepoEvent2ITSuite
 {

repository/src/test/java/org/alfresco/repo/event2/RepoEvent2UnitSuite.java

@@ -33,7 +33,8 @@ import org.junit.runners.Suite.SuiteClasses;
 @RunWith(Suite.class)
 @SuiteClasses({ EventFilterUnitTest.class,
                 EventConsolidatorUnitTest.class,
-                EventJSONSchemaUnitTest.class
+                EventJSONSchemaUnitTest.class,
+                EventGeneratorQueueUnitTest.class
 })
 public class RepoEvent2UnitSuite
 {