Package org.jboss.netty.handler.execution

Class OrderedMemoryAwareThreadPoolExecutor

java.lang.Object
java.util.concurrent.AbstractExecutorService
java.util.concurrent.ThreadPoolExecutor
org.jboss.netty.handler.execution.MemoryAwareThreadPoolExecutor
org.jboss.netty.handler.execution.OrderedMemoryAwareThreadPoolExecutor
All Implemented Interfaces:
Executor, ExecutorService
Direct Known Subclasses:
OrderedDownstreamThreadPoolExecutor
public class OrderedMemoryAwareThreadPoolExecutor extends MemoryAwareThreadPoolExecutor
A MemoryAwareThreadPoolExecutor which makes sure the events from the same Channel are executed sequentially.

NOTE: This thread pool inherits most characteristics of its super type, so please make sure to refer to MemoryAwareThreadPoolExecutor to understand how it works basically.

Event execution order

For example, let's say there are two executor threads that handle the events from the two channels: 
           -------------------------------------> Timeline ------------------------------------>

 Thread X: --- Channel A (Event A1) --.   .-- Channel B (Event B2) --- Channel B (Event B3) --->
                                      \ /
                                       X
                                      / \
 Thread Y: --- Channel B (Event B1) --'   '-- Channel A (Event A2) --- Channel A (Event A3) --->
As you see, the events from different channels are independent from each other. That is, an event of Channel B will not be blocked by an event of Channel A and vice versa, unless the thread pool is exhausted.

Also, it is guaranteed that the invocation will be made sequentially for the events from the same channel. For example, the event A2 is never executed before the event A1 is finished. (Although not recommended, if you want the events from the same channel to be executed simultaneously, please use MemoryAwareThreadPoolExecutor instead.)

However, it is not guaranteed that the invocation will be made by the same thread for the same channel. The events from the same channel can be executed by different threads. For example, the Event A2 is executed by the thread Y while the event A1 was executed by the thread X.

Using a different key other than Channel to maintain event order

OrderedMemoryAwareThreadPoolExecutor uses a Channel as a key that is used for maintaining the event execution order, as explained in the previous section. Alternatively, you can extend it to change its behavior. For example, you can change the key to the remote IP of the peer: 

 public class RemoteAddressBasedOMATPE extends OrderedMemoryAwareThreadPoolExecutor {

     ... Constructors ...

     @Override
     protected ConcurrentMap<Object, Executor> newChildExecutorMap() {
         // The default implementation returns a special ConcurrentMap that
         // uses identity comparison only (see IdentityHashMap).
         // Because SocketAddress does not work with identity comparison,
         // we need to employ more generic implementation.
         return new ConcurrentHashMap<Object, Executor>
     }

     protected Object getChildExecutorKey(ChannelEvent e) {
         // Use the IP of the remote peer as a key.
         return ((InetSocketAddress) e.getChannel().getRemoteAddress()).getAddress();
     }

     // Make public so that you can call from anywhere.
     public boolean removeChildExecutor(Object key) {
         super.removeChildExecutor(key);
     }
 }
Please be very careful of memory leak of the child executor map. You must call removeChildExecutor(Object) when the life cycle of the key ends (e.g. all connections from the same IP were closed.) Also, please keep in mind that the key can appear again after calling removeChildExecutor(Object) (e.g. a new connection could come in from the same old IP after removal.) If in doubt, prune the old unused or stall keys from the child executor map periodically: 
 RemoteAddressBasedOMATPE executor = ...;

 on every 3 seconds:

   for (Iterator<Object> i = executor.getChildExecutorKeySet().iterator; i.hasNext();) {
       InetAddress ip = (InetAddress) i.next();
       if (there is no active connection from 'ip' now invalid input: '&'invalid input: '&'
           there has been no incoming connection from 'ip' for last 10 minutes) {
           i.remove();
       }
   }
If the expected maximum number of keys is small and deterministic, you could use a weak key map such as ConcurrentWeakHashMap or synchronized WeakHashMap instead of managing the life cycle of the keys by yourself.

  • Field Details

  • Constructor Details

    • OrderedMemoryAwareThreadPoolExecutor

      public OrderedMemoryAwareThreadPoolExecutor(int corePoolSize, long maxChannelMemorySize, long maxTotalMemorySize)
      Creates a new instance.
      Parameters:
      corePoolSize - the maximum number of active threads
      maxChannelMemorySize - the maximum total size of the queued events per channel. Specify 0 to disable.
      maxTotalMemorySize - the maximum total size of the queued events for this pool Specify 0 to disable.

    • OrderedMemoryAwareThreadPoolExecutor

      public OrderedMemoryAwareThreadPoolExecutor(int corePoolSize, long maxChannelMemorySize, long maxTotalMemorySize, long keepAliveTime, TimeUnit unit)
      Creates a new instance.
      Parameters:
      corePoolSize - the maximum number of active threads
      maxChannelMemorySize - the maximum total size of the queued events per channel. Specify 0 to disable.
      maxTotalMemorySize - the maximum total size of the queued events for this pool Specify 0 to disable.
      keepAliveTime - the amount of time for an inactive thread to shut itself down
      unit - the TimeUnit of keepAliveTime

    • OrderedMemoryAwareThreadPoolExecutor

      public OrderedMemoryAwareThreadPoolExecutor(int corePoolSize, long maxChannelMemorySize, long maxTotalMemorySize, long keepAliveTime, TimeUnit unit, ThreadFactory threadFactory)
      Creates a new instance.
      Parameters:
      corePoolSize - the maximum number of active threads
      maxChannelMemorySize - the maximum total size of the queued events per channel. Specify 0 to disable.
      maxTotalMemorySize - the maximum total size of the queued events for this pool Specify 0 to disable.
      keepAliveTime - the amount of time for an inactive thread to shut itself down
      unit - the TimeUnit of keepAliveTime
      threadFactory - the ThreadFactory of this pool

    • OrderedMemoryAwareThreadPoolExecutor

      public OrderedMemoryAwareThreadPoolExecutor(int corePoolSize, long maxChannelMemorySize, long maxTotalMemorySize, long keepAliveTime, TimeUnit unit, ObjectSizeEstimator objectSizeEstimator, ThreadFactory threadFactory)
      Creates a new instance.
      Parameters:
      corePoolSize - the maximum number of active threads
      maxChannelMemorySize - the maximum total size of the queued events per channel. Specify 0 to disable.
      maxTotalMemorySize - the maximum total size of the queued events for this pool Specify 0 to disable.
      keepAliveTime - the amount of time for an inactive thread to shut itself down
      unit - the TimeUnit of keepAliveTime
      objectSizeEstimator - the ObjectSizeEstimator of this pool
      threadFactory - the ThreadFactory of this pool

  • Method Details