Use ChannelGroups for shutdowns. This cleans up the code and makes the PeerGroup shutdown futures work correctly.

core/src/main/java/com/google/bitcoin/core/PeerGroup.java

@@ -26,6 +26,8 @@ import com.google.common.collect.Sets;
 import com.google.common.util.concurrent.*;
 import org.jboss.netty.bootstrap.ClientBootstrap;
 import org.jboss.netty.channel.*;
+import org.jboss.netty.channel.group.ChannelGroup;
+import org.jboss.netty.channel.group.DefaultChannelGroup;
 import org.jboss.netty.channel.socket.nio.NioClientSocketChannelFactory;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -74,7 +76,7 @@ public class PeerGroup extends AbstractIdleService {
     private List<Peer> peers;
     // Currently connecting peers.
     private List<Peer> pendingPeers;
-    private Map<Peer, ChannelFuture> channelFutures;
+    private ChannelGroup channels;
 
     // The peer that has been selected for the purposes of downloading announced data.
     private Peer downloadPeer;
@@ -117,9 +119,9 @@ public class PeerGroup extends AbstractIdleService {
         }
 
         public void onPeerDisconnected(Peer peer) {
+            // The channel will be automatically removed from channels.
             pendingPeers.remove(peer);
             peers.remove(peer);
-            channelFutures.remove(peer);
             handlePeerDeath(peer);
         }
     }
@@ -193,7 +195,7 @@ public class PeerGroup extends AbstractIdleService {
         inactives = Collections.synchronizedList(new ArrayList<PeerAddress>());
         peers = Collections.synchronizedList(new ArrayList<Peer>());
         pendingPeers = Collections.synchronizedList(new ArrayList<Peer>());
-        channelFutures = Collections.synchronizedMap(new HashMap<Peer, ChannelFuture>());
+        channels = new DefaultChannelGroup();
         peerDiscoverers = new CopyOnWriteArraySet<PeerDiscovery>(); 
         peerEventListeners = new ArrayList<PeerEventListener>();
         // This event listener is added to every peer. It's here so when we announce transactions via an "inv", every
@@ -256,8 +258,8 @@ public class PeerGroup extends AbstractIdleService {
             this.maxConnections = maxConnections;
             if (!isRunning()) return;
         }
-        // We may now have too many or too few open connections. Adding the sizes together here is a race condition.
+        // We may now have too many or too few open connections. Add more or drop some to get to the right amount.
-        adjustment = maxConnections - (peers.size() + pendingPeers.size());
+        adjustment = maxConnections - channels.size();
         while (adjustment > 0) {
             try {
                 connectToAnyPeer();
@@ -267,11 +269,7 @@ public class PeerGroup extends AbstractIdleService {
             adjustment--;
         }
         while (adjustment < 0) {
-            Channel channel;
+            channels.iterator().next().close();
-            synchronized (peers) {
-                channel = channelFutures.get(peers.remove(peers.size() - 1)).getChannel();
-            }
-            channel.close();
             adjustment++;
         }
     }
@@ -486,15 +484,10 @@ public class PeerGroup extends AbstractIdleService {
         synchronized (this) {
             pingTimer.cancel();
         }
-        // TODO: Make this shutdown process use a ChannelGroup.
+        // Blocking close of all sockets. TODO: there is a race condition here, for the solution see:
-        LinkedList<ChannelFuture> futures;
+        // http://biasedbit.com/netty-releaseexternalresources-hangs/
-        synchronized (channelFutures) {
+        channels.close().await();
-            // Copy the list here because the act of closing the channel modifies the channelFutures map.
+        // All thread pools should be stopped by this call.
-            futures = new LinkedList<ChannelFuture>(channelFutures.values());
-        }
-        for (ChannelFuture future : futures) {
-            future.getChannel().close();
-        }
         bootstrap.releaseExternalResources();
         for (PeerDiscovery peerDiscovery : peerDiscoverers) {
             peerDiscovery.shutdown();
@@ -573,6 +566,14 @@ public class PeerGroup extends AbstractIdleService {
     // Internal version. Do not call whilst holding the PeerGroup lock.
     protected ChannelFuture connectTo(SocketAddress address, boolean incrementMaxConnections) {
         ChannelFuture future = bootstrap.connect(address);
+        // Make sure that the channel group gets access to the channel only if it connects successfully (otherwise
+        // it cannot be closed and trying to do so will cause problems).
+        future.addListener(new ChannelFutureListener() {
+            public void operationComplete(ChannelFuture future) throws Exception {
+                if (future.isSuccess())
+                    channels.add(future.getChannel());
+            }
+        });
         // When the channel has connected and version negotiated successfully, handleNewPeer will end up being called on
         // a worker thread.
 
@@ -585,8 +586,6 @@ public class PeerGroup extends AbstractIdleService {
             networkHandler.getOwnerObject().setRemoteAddress(address);
         }
         synchronized (this) {
-            Peer peer = peerFromChannelFuture(future);
-            channelFutures.put(peer, future);
             if (incrementMaxConnections) {
                 // We don't use setMaxConnections here as that would trigger a recursive attempt to establish a new
                 // outbound connection.

core/src/test/java/com/google/bitcoin/core/FakeChannel.java

@@ -53,4 +53,9 @@ public class FakeChannel extends AbstractChannel {
     public ChannelEvent nextEventBlocking() throws InterruptedException {
         return events.take();
     }
+
+    @Override
+    public boolean setClosed() {
+        return super.setClosed();
+    }
 }

core/src/test/java/com/google/bitcoin/core/FakeChannelSink.java

@@ -20,7 +20,7 @@ public class FakeChannelSink extends AbstractChannelSink {
             switch (state) {
             case OPEN:
                 if (Boolean.FALSE.equals(value)) {
-                    // Close
+                    channel.setClosed();
                 }
                 break;
             case BOUND:

core/src/test/java/com/google/bitcoin/core/PeerGroupTest.java

@@ -111,7 +111,6 @@ public class PeerGroupTest extends TestWithNetworkConnections {
         // Check that we did indeed throw an exception. If we got here it means we threw and then PeerGroup tried
         // again a bit later.
         assertTrue(result[0]);
-        peerGroup.stop();
     }
 
     @Test