OrderedMemoryAwareThreadPoolExecutor (The Netty Project API Reference (3.5.13.Final))

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 &&
           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.

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

protected class OrderedMemoryAwareThreadPoolExecutor.ChildExecutor
- Nested classes/interfaces inherited from class java.util.concurrent.ThreadPoolExecutor
  ThreadPoolExecutor.AbortPolicy, ThreadPoolExecutor.CallerRunsPolicy, ThreadPoolExecutor.DiscardOldestPolicy, ThreadPoolExecutor.DiscardPolicy

Nested Classes
Modifier and Type	Class and Description
`protected class`	`OrderedMemoryAwareThreadPoolExecutor.ChildExecutor`

Field Summary

Fields
Modifier and Type Field and Description

protected ConcurrentMap<Object,Executor> childExecutors

Fields
Modifier and Type	Field and Description
`protected ConcurrentMap<Object,Executor>`	`childExecutors`

Constructor Summary

Constructors
Constructor and Description
`OrderedMemoryAwareThreadPoolExecutor(int corePoolSize, long maxChannelMemorySize, long maxTotalMemorySize)` Creates a new instance.
`OrderedMemoryAwareThreadPoolExecutor(int corePoolSize, long maxChannelMemorySize, long maxTotalMemorySize, long keepAliveTime, TimeUnit unit)` Creates a new instance.
`OrderedMemoryAwareThreadPoolExecutor(int corePoolSize, long maxChannelMemorySize, long maxTotalMemorySize, long keepAliveTime, TimeUnit unit, ObjectSizeEstimator objectSizeEstimator, ThreadFactory threadFactory)` Creates a new instance.
`OrderedMemoryAwareThreadPoolExecutor(int corePoolSize, long maxChannelMemorySize, long maxTotalMemorySize, long keepAliveTime, TimeUnit unit, ThreadFactory threadFactory)` Creates a new instance.

Method Summary

Methods
Modifier and Type	Method and Description
`protected void`	`doExecute(Runnable task)` Executes the specified task concurrently while maintaining the event order.
`protected Executor`	`getChildExecutor(ChannelEvent e)`
`protected Object`	`getChildExecutorKey(ChannelEvent e)`
`protected Set<Object>`	`getChildExecutorKeySet()`
`protected ConcurrentMap<Object,Executor>`	`newChildExecutorMap()`
`protected boolean`	`removeChildExecutor(Object key)`
`protected boolean`	`shouldCount(Runnable task)` Returns `true` if and only if the specified `task` should be counted to limit the global and per-channel memory consumption.

Methods inherited from class org.jboss.netty.handler.execution.MemoryAwareThreadPoolExecutor
beforeExecute, decreaseCounter, doUnorderedExecute, execute, getMaxChannelMemorySize, getMaxTotalMemorySize, getNotifyChannelFuturesOnShutdown, getObjectSizeEstimator, increaseCounter, remove, setMaxChannelMemorySize, setMaxTotalMemorySize, setNotifyChannelFuturesOnShutdown, setObjectSizeEstimator, shutdownNow, shutdownNow, terminated

Methods inherited from class java.util.concurrent.AbstractExecutorService
invokeAll, invokeAll, invokeAny, invokeAny, newTaskFor, newTaskFor, submit, submit, submit

Methods inherited from class java.lang.Object
clone, equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - childExecutors
```
protected final ConcurrentMap<Object,Executor> childExecutors
```
- Constructor Detail
  - 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
    threadFactory - the ThreadFactory of this pool
    objectSizeEstimator - the ObjectSizeEstimator of this pool
- Method Detail
  - newChildExecutorMap
```
protected ConcurrentMap<Object,Executor> newChildExecutorMap()
```
  - getChildExecutorKey
```
protected Object getChildExecutorKey(ChannelEvent e)
```
  - getChildExecutorKeySet
```
protected Set<Object> getChildExecutorKeySet()
```
  - removeChildExecutor
```
protected boolean removeChildExecutor(Object key)
```
  - doExecute
```
protected void doExecute(Runnable task)
```
    Executes the specified task concurrently while maintaining the event order.
    
    Overrides:
    
    doExecute in class MemoryAwareThreadPoolExecutor
  - getChildExecutor
```
protected Executor getChildExecutor(ChannelEvent e)
```
  - shouldCount
```
protected boolean shouldCount(Runnable task)
```
    Description copied from class: MemoryAwareThreadPoolExecutor
    
    Returns true if and only if the specified task should be counted to limit the global and per-channel memory consumption. To override this method, you must call super.shouldCount() to make sure important tasks are not counted.
    
    Overrides:
    
    shouldCount in class MemoryAwareThreadPoolExecutor

Class OrderedMemoryAwareThreadPoolExecutor

Event execution order

Using a different key other than `Channel` to maintain event order

Nested Class Summary

Nested classes/interfaces inherited from class java.util.concurrent.ThreadPoolExecutor

Field Summary

Constructor Summary

Method Summary

Methods inherited from class org.jboss.netty.handler.execution.MemoryAwareThreadPoolExecutor

Methods inherited from class java.util.concurrent.ThreadPoolExecutor

Methods inherited from class java.util.concurrent.AbstractExecutorService

Methods inherited from class java.lang.Object

Field Detail

childExecutors

Constructor Detail

OrderedMemoryAwareThreadPoolExecutor

OrderedMemoryAwareThreadPoolExecutor

OrderedMemoryAwareThreadPoolExecutor

OrderedMemoryAwareThreadPoolExecutor

Method Detail

newChildExecutorMap

getChildExecutorKey

getChildExecutorKeySet

removeChildExecutor

doExecute

getChildExecutor

shouldCount

Class OrderedMemoryAwareThreadPoolExecutor

Event execution order

Using a different key other than Channel to maintain event order

Nested Class Summary

Nested classes/interfaces inherited from class java.util.concurrent.ThreadPoolExecutor

Field Summary

Constructor Summary

Method Summary

Methods inherited from class org.jboss.netty.handler.execution.MemoryAwareThreadPoolExecutor

Methods inherited from class java.util.concurrent.ThreadPoolExecutor

Methods inherited from class java.util.concurrent.AbstractExecutorService

Methods inherited from class java.lang.Object

Field Detail

childExecutors

Constructor Detail

OrderedMemoryAwareThreadPoolExecutor

OrderedMemoryAwareThreadPoolExecutor

OrderedMemoryAwareThreadPoolExecutor

OrderedMemoryAwareThreadPoolExecutor

Method Detail

newChildExecutorMap

getChildExecutorKey

getChildExecutorKeySet

removeChildExecutor

doExecute

getChildExecutor

shouldCount

Using a different key other than `Channel` to maintain event order