Cleaned up synchrony start/shutdown. Removed start (it was unnecessary), and shutdown now waits for threads to stop

src/dorkbox/util/messagebus/MessageBus.java

@@ -233,7 +233,6 @@ class MessageBus implements IMessageBus {
     public
     void start() {
         errorHandler.init();
-        asyncPublication.start();
     }
 
     @Override

src/dorkbox/util/messagebus/synchrony/AsyncABQ.java

@@ -22,8 +22,10 @@ import dorkbox.util.messagebus.subscription.Subscription;
 import dorkbox.util.messagebus.synchrony.disruptor.MessageType;
 
 import java.util.ArrayDeque;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.locks.LockSupport;
 
 /**
  * This is similar to the disruptor, however the downside of this implementation is that, while faster than the no-gc version, it
@@ -38,6 +40,7 @@ class AsyncABQ implements Synchrony {
 
     private final ArrayBlockingQueue<MessageHolder> dispatchQueue;
     private final Collection<Thread> threads;
+    private final Collection<Boolean> shutdown;
 
     /**
      * Notifies the consumers during shutdown, that it's on purpose.
@@ -63,14 +66,21 @@ class AsyncABQ implements Synchrony {
                 while (!AsyncABQ.this.shuttingDown) {
                     process(IN_QUEUE, syncPublication1, errorHandler1);
                 }
+
+                synchronized (shutdown) {
+                    shutdown.add(Boolean.TRUE);
+                }
             }
         };
 
         this.threads = new ArrayDeque<Thread>(numberOfThreads);
+        this.shutdown = new ArrayList<Boolean>();
+
         final NamedThreadFactory threadFactory = new NamedThreadFactory("MessageBus");
         for (int i = 0; i < numberOfThreads; i++) {
-            Thread runner = threadFactory.newThread(runnable);
+            Thread thread = threadFactory.newThread(runnable);
-            this.threads.add(runner);
+            this.threads.add(thread);
+            thread.start();
         }
     }
 
@@ -108,7 +118,7 @@ class AsyncABQ implements Synchrony {
                 }
             }
         } catch (Throwable e) {
-            if (event != null) {
+            if (event != null && !this.shuttingDown) {
                 switch (messageType) {
                     case MessageType.ONE: {
                         errorHandler.handlePublicationError(new PublicationError().setMessage("Error during invocation of message handler.")
@@ -134,7 +144,6 @@ class AsyncABQ implements Synchrony {
         }
     }
 
-
     @Override
     public
     void publish(final Subscription[] subscriptions, final Object message1) throws Throwable {
@@ -174,17 +183,14 @@ class AsyncABQ implements Synchrony {
         this.dispatchQueue.put(take);
     }
 
+    @Override
     public
-    void start() {
+    boolean hasPendingMessages() {
-        if (shuttingDown) {
+        return !this.dispatchQueue.isEmpty();
-            throw new Error("Unable to restart the MessageBus");
-        }
-
-        for (Thread t : this.threads) {
-            t.start();
-        }
     }
 
+    @SuppressWarnings("Duplicates")
+    @Override
     public
     void shutdown() {
         this.shuttingDown = true;
@@ -192,10 +198,14 @@ class AsyncABQ implements Synchrony {
         for (Thread t : this.threads) {
             t.interrupt();
         }
-    }
 
-    public
+        while (true) {
-    boolean hasPendingMessages() {
+            synchronized (shutdown) {
-        return !this.dispatchQueue.isEmpty();
+                if (shutdown.size() == threads.size()) {
+                    return;
+                }
+                LockSupport.parkNanos(100L); // wait 100ms for threads to quit
+            }
+        }
     }
 }

src/dorkbox/util/messagebus/synchrony/AsyncABQ_noGc.java

@@ -22,8 +22,10 @@ import dorkbox.util.messagebus.subscription.Subscription;
 import dorkbox.util.messagebus.synchrony.disruptor.MessageType;
 
 import java.util.ArrayDeque;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.locks.LockSupport;
 
 /**
  * This is similar in behavior to the disruptor in that it does not generate garbage, however the downside of this implementation is it is
@@ -42,6 +44,7 @@ class AsyncABQ_noGc implements Synchrony {
     private final ArrayBlockingQueue<MessageHolder> gcQueue;
 
     private final Collection<Thread> threads;
+    private final Collection<Boolean> shutdown;
 
     /**
      * Notifies the consumers during shutdown, that it's on purpose.
@@ -75,14 +78,21 @@ class AsyncABQ_noGc implements Synchrony {
                 while (!AsyncABQ_noGc.this.shuttingDown) {
                     process(IN_QUEUE, OUT_QUEUE, syncPublication1, errorHandler1);
                 }
+
+                synchronized (shutdown) {
+                    shutdown.add(Boolean.TRUE);
+                }
             }
         };
 
         this.threads = new ArrayDeque<Thread>(numberOfThreads);
+        this.shutdown = new ArrayList<Boolean>();
+
         final NamedThreadFactory threadFactory = new NamedThreadFactory("MessageBus");
         for (int i = 0; i < numberOfThreads; i++) {
-            Thread runner = threadFactory.newThread(runnable);
+            Thread thread = threadFactory.newThread(runnable);
-            this.threads.add(runner);
+            this.threads.add(thread);
+            thread.start();
         }
     }
 
@@ -126,7 +136,7 @@ class AsyncABQ_noGc implements Synchrony {
                 }
             }
         } catch (Throwable e) {
-            if (event != null) {
+            if (event != null && !this.shuttingDown) {
                 switch (messageType) {
                     case MessageType.ONE: {
                         errorHandler.handlePublicationError(new PublicationError().setMessage("Error during invocation of message handler.")
@@ -191,17 +201,14 @@ class AsyncABQ_noGc implements Synchrony {
         this.dispatchQueue.put(take);
     }
 
+    @Override
     public
-    void start() {
+    boolean hasPendingMessages() {
-        if (shuttingDown) {
+        return !this.dispatchQueue.isEmpty();
-            throw new Error("Unable to restart the MessageBus");
-        }
-
-        for (Thread t : this.threads) {
-            t.start();
-        }
     }
 
+    @SuppressWarnings("Duplicates")
+    @Override
     public
     void shutdown() {
         this.shuttingDown = true;
@@ -209,10 +216,14 @@ class AsyncABQ_noGc implements Synchrony {
         for (Thread t : this.threads) {
             t.interrupt();
         }
-    }
 
-    public
+        while (true) {
-    boolean hasPendingMessages() {
+            synchronized (shutdown) {
-        return !this.dispatchQueue.isEmpty();
+                if (shutdown.size() == threads.size()) {
+                    return;
+                }
+                LockSupport.parkNanos(100L); // wait 100ms for threads to quit
+            }
+        }
     }
 }

src/dorkbox/util/messagebus/synchrony/AsyncDisruptor.java

@@ -166,23 +166,7 @@ class AsyncDisruptor implements Synchrony {
     }
 
 
-    public
+    @Override
-    void start() {
-    }
-
-    public
-    void shutdown() {
-        for (WorkProcessor<?> processor : workProcessors) {
-            processor.halt();
-        }
-
-        for (MessageHandler handler : handlers) {
-            while (!handler.isShutdown()) {
-                LockSupport.parkNanos(100L); // wait 100ms for handlers to quit
-            }
-        }
-    }
-
     public
     boolean hasPendingMessages() {
         // from workerPool.drainAndHalt()
@@ -196,4 +180,18 @@ class AsyncDisruptor implements Synchrony {
 
         return false;
     }
+
+    @Override
+    public
+    void shutdown() {
+        for (WorkProcessor<?> processor : workProcessors) {
+            processor.halt();
+        }
+
+        for (MessageHandler handler : handlers) {
+            while (!handler.isShutdown()) {
+                LockSupport.parkNanos(100L); // wait 100ms for handlers to quit
+            }
+        }
+    }
 }

src/dorkbox/util/messagebus/synchrony/Sync.java

@@ -51,11 +51,6 @@ class Sync implements Synchrony {
         }
     }
 
-    @Override
-    public
-    void start() {
-    }
-
     @Override
     public
     void shutdown() {

src/dorkbox/util/messagebus/synchrony/Synchrony.java

@@ -26,7 +26,6 @@ interface Synchrony {
     void publish(final Subscription[] subscriptions, Object message1, Object message2) throws Throwable ;
     void publish(final Subscription[] subscriptions, Object message1, Object message2, Object message3) throws Throwable ;
 
-    void start();
     void shutdown();
     boolean hasPendingMessages();
 }