hi
I have some question related to the threading model used by MINA.
I've read the FAQ entry titled "Do I need to make my IoHandler thread-
safe?", but was still a bit confused. So I've built a simple sample
application.
The server checks how many threads are executing the code of the
messageReceived method of the IoHandler. The client sends a lot of
messages to the server. To simulate a long running task, the
messageReceived method of the server contains a Thread.sleep.
Without adding any filter (in particular the ThreadPoolFilter, of
course), the messageReceived method of the server IoHandler is
executed by just one thread at a time (in fact, always the same
thread). The overall throughput of the server is low (the server was
sleeping most of the time...).
After adding a ThreadPool filter the situation changed. The IoHandler
messageReceived method is called by more than one thread at a time
(server-side). However, the method is called by only one thread at a
time for a particular session.
What I find a bit strange is that on the server-side, there is only
one IoHandler for all the sessions. Therefore it is unsafe to use any
instance variables inside handlers (that is, without proper
synchronization). I guess that's what is meant with "shared resource"
in the FAQ. To achieve thread safety, the state should be stored as
session attributes (correct?) or the access would have to be properly
synchronized.
On the client side, it is possible to specify a separate IoHandler
for each session. Wouldn't it be more natural to have the possibility
to store state in the handler itself? On the server, this would
require to have a separate IoHandler for each session. What do you
think?
Simon
