The same is still true... a Channel is pinned to an EventLoop and so it’s IO is
processed by one thread
> Am 16.02.2018 um 00:04 schrieb Sean Bright <sean.bri...@gmail.com>:
>
> Eric,
>
> I don't know what I can add beyond what has already been written in this
> thread. I haven't following Netty development so I don't know if this is
> still the case or not. At the time, a channel was bound to a thread in an
> EventExecutorGroup, so you could run into a situation where a group of
> channels that were all bound to the same thread would be under serviced if
> one of those tasks took a lot of CPU time. If instead you delegate to a
> standard ExecutorService, each task for a given channel might run on a
> separate thread so a single task couldn't starve all of the channels.
>
> Kind regards,
> Sean
>
>> On Friday, February 9, 2018 at 8:40:00 PM UTC-5, Eric Fulton wrote:
>> Hey sorry I know this is a very old thread, but can you explain why in you
>> example you think it would be better to use your own ExecutorService over
>> someEventExecutorGroup? What would be the difference?
>>
>>
>>
>>
>>> On Wednesday, October 9, 2013 at 7:27:06 AM UTC-7, Sean Bright wrote:
>>> Thanks Norman.
>>>
>>> So based on this, it seems that if I have a "typical" pipeline:
>>>
>>> ctx.pipeline().addLast("decoder", new MyProtocolDecoder());
>>> ctx.pipeline().addLast("encoder", new MyProtocolEncoder());
>>> ctx.pipeline().addLast(someEventExecutorGroup, "handler", new
>>> MyProtocolHandler());
>>>
>>> Using an EventExecutorGroup doesn't actually buy me anything. I/O won't be
>>> blocked, but handler execution will.
>>>
>>> I understand the point of doing all of this - if you know your methods will
>>> always be called on the same thread it reduces the synchronization
>>> complexities in the handlers - but in this model when you are dealing with
>>> hundreds of connections, any handler method that causes a delay in
>>> processing will block (num_connections / num_event_executor_threads) - 1
>>> other handlers.
>>>
>>> So it would appear that in order to get the behavior that I want (any one
>>> connection should not affect another), I would eliminate the
>>> EventExecutorGroup and would need to submit tasks to an ExecutorService
>>> that I manage myself, correct?
>>>
>>> I guess I just don't see how an EventExecutorGroup is beneficial.
>>>
>>> In any case, I love Netty. Keep up the good work!
>>>
>>>
>>>> On Tuesday, October 8, 2013 11:40:30 AM UTC-4, Sean Bright wrote:
>>>> Greetings,
>>>>
>>>> I just want to validate my understanding of Netty 4's thread model
>>>> compared to Netty 3's (specifically as it applies to NIO).
>>>>
>>>> With Netty 3, you would specify a boss thread pool and a worker thread
>>>> pool (all/most of the examples use Executors.newCachedThreadPool() with
>>>> the default args). ChannelHandler events would be called on the I/O
>>>> threads from the worker group. Any delay in the handler methods would
>>>> cause a delay in processing I/O for other connections. In order to
>>>> compensate for this, you could add an ExecutionHandler to the pipeline
>>>> which would cause the handler methods to be fired on an executor thread
>>>> and therefore wouldn't affect I/O.
>>>>
>>>> In Netty 4, you specify a boss group and worker group, and as channels
>>>> connect they are registered to specific threads. So channel 1 will always
>>>> have it's handler events fired on thread A, channel 2 will always have
>>>> it's handler events fired on thread B. Again, any delayed processing that
>>>> occurs in the handler method will hurt I/O for other channels registered
>>>> to that worker thread. To compensate, you specify an EventExecutorGroup
>>>> so that I/O is not affected with long running tasks.
>>>>
>>>> Assuming everything above is correct...
>>>>
>>>> Assume that I create a DefaultEventExecutorGroup, passing 4 as the number
>>>> of threads, and assign that to my handler in the pipeline. Now, 8
>>>> channels connect:
>>>>
>>>> Channel A: EventExecutor 1
>>>> Channel B: EventExecutor 2
>>>> Channel C: EventExecutor 3
>>>> Channel D: EventExecutor 4
>>>> Channel E: EventExecutor 1
>>>> Channel F: EventExecutor 2
>>>> Channel G: EventExecutor 3
>>>> Channel H: EventExecutor 4
>>>>
>>>> Each channel is registered to EventExecutor thread. If Channel A in the
>>>> above example performs a long running task (say, in channelRead0), then
>>>> won't Channel E be blocked during this time? Is that correct or am I not
>>>> understanding something? If I am correct, why would I ever want to use an
>>>> EventExecutor? I feel like I would be better off using a shared Executor
>>>> directly from my handler methods (and handling thread synchronization
>>>> myself). At least in that case I wouldn't be blocking other clients.
>>>>
>>>> Thank you,
>>>> Sean
>>>>
>
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