fix multithreaded problem with orphaned timeouts that appears in highly concurrent non-atomic sequence cancel() -> schedule()

src/main/java/com/corundumstudio/socketio/SocketIOChannelInitializer.java

@@ -15,6 +15,7 @@
  */
 package com.corundumstudio.socketio;
 
+import com.corundumstudio.socketio.scheduler.HashedWheelTimeoutScheduler;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.ChannelInitializer;
@@ -82,7 +83,7 @@ public class SocketIOChannelInitializer extends ChannelInitializer<Channel> impl
     private EncoderHandler encoderHandler;
     private WrongUrlHandler wrongUrlHandler;
 
-    private CancelableScheduler scheduler = new HashedWheelScheduler();
+    private CancelableScheduler scheduler = new HashedWheelTimeoutScheduler();
 
     private InPacketHandler packetHandler;
     private SSLContext sslContext;

src/main/java/com/corundumstudio/socketio/handler/ClientHead.java

@@ -120,7 +120,6 @@ public class ClientHead {
     }
 
     public void schedulePingTimeout() {
-        cancelPingTimeout();
         SchedulerKey key = new SchedulerKey(Type.PING_TIMEOUT, sessionId);
         disconnectScheduler.schedule(key, new Runnable() {
             @Override

src/main/java/com/corundumstudio/socketio/scheduler/HashedWheelTimeoutScheduler.java

@@ -0,0 +1,120 @@
+/**
+ * Modified version of HashedWheelScheduler specially for timeouts handling.
+ * Difference:
+ * - handling old timeout with same key after adding new one
+ *   fixes multithreaded problem that appears in highly concurrent non-atomic sequence cancel() -> schedule()
+ *
+ * (c) Alim Akbashev, 2015-02-11
+ */
+
+/**
+ * Copyright 2012 Nikita Koksharov
+ *
+ * Licensed 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 com.corundumstudio.socketio.scheduler;
+
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.util.HashedWheelTimer;
+import io.netty.util.Timeout;
+import io.netty.util.TimerTask;
+import io.netty.util.internal.PlatformDependent;
+
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.TimeUnit;
+
+public class HashedWheelTimeoutScheduler implements CancelableScheduler {
+
+    private final ConcurrentMap<SchedulerKey, Timeout> scheduledFutures = PlatformDependent.newConcurrentHashMap();
+    private final HashedWheelTimer executorService = new HashedWheelTimer();
+
+    private volatile ChannelHandlerContext ctx;
+
+    @Override
+    public void update(ChannelHandlerContext ctx) {
+        this.ctx = ctx;
+    }
+
+    public void cancel(SchedulerKey key) {
+        Timeout timeout = scheduledFutures.remove(key);
+        if (timeout != null) {
+            timeout.cancel();
+        }
+    }
+
+    public void schedule(final Runnable runnable, long delay, TimeUnit unit) {
+        executorService.newTimeout(new TimerTask() {
+            @Override
+            public void run(Timeout timeout) throws Exception {
+                runnable.run();
+            }
+        }, delay, unit);
+    }
+
+    public void scheduleCallback(final SchedulerKey key, final Runnable runnable, long delay, TimeUnit unit) {
+        Timeout timeout = executorService.newTimeout(new TimerTask() {
+            @Override
+            public void run(Timeout timeout) throws Exception {
+                ctx.executor().execute(new Runnable() {
+                    @Override
+                    public void run() {
+                        try {
+                            runnable.run();
+                        } finally {
+                            scheduledFutures.remove(key);
+                        }
+                    }
+                });
+            }
+        }, delay, unit);
+
+        replaceScheduledFuture(key, timeout);
+    }
+
+    public void schedule(final SchedulerKey key, final Runnable runnable, long delay, TimeUnit unit) {
+        Timeout timeout = executorService.newTimeout(new TimerTask() {
+            @Override
+            public void run(Timeout timeout) throws Exception {
+                try {
+                    runnable.run();
+                } finally {
+                    scheduledFutures.remove(key);
+                }
+            }
+        }, delay, unit);
+
+        replaceScheduledFuture(key, timeout);
+    }
+
+    public void shutdown() {
+        executorService.stop();
+    }
+
+    private void replaceScheduledFuture(final SchedulerKey key, final Timeout newTimeout) {
+        final Timeout oldTimeout;
+
+        if (newTimeout.isExpired()) {
+            // no need to put already expired timeout to scheduledFutures map.
+            // simply remove old timeout
+            oldTimeout = scheduledFutures.remove(key);
+        } else {
+            oldTimeout = scheduledFutures.put(key, newTimeout);
+        }
+
+        // if there was old timeout, cancel it
+        if (oldTimeout != null) {
+            oldTimeout.cancel();
+        }
+    }
+}