Re: [Quickfix-users] SocketInitiator and SynchronizedApplication vs Application

[Oren M. <or...@qu...>]

First of all, messages on a single Session always come serially, no  
matter which threading model is used.  It is required by the  
specification that messages be processed in sequential order.  So  
while you are processing a message, under no circumstances will you  
receive another message from he same session until you return from  
the callback.  This is true with any model no matter how you  
configure the engine.  So if you are really just running one session,  
there is no need to synchronize anything.

As for the SocketInitiator, all the IO is handled in a single  
thread.  So with this model you will not receive any messages from  
any session managed by that initiator while in the callback.  So  
again, no need to synchronize.  (If you have multiple  
SocketInitiators, than you can continue to receive messages from  
their sessions as they are running on a different thread).  This is  
why while running multiple sessions, messages should either be  
handled quickly, or delegated to another thread or process so  
QuickFIX can continue to receive messages.  (If you are running just  
one session and must process the message sequentially, you can take  
your time in the callbacks).

Since we moved to non-blocking sockets, there probably isn't a great  
case for using the ThreadedSocketInitiator with a  
SynchronizedApplication anymore.  If you are going to do that I would  
just recommend using the SocketInitiator.  You should really only use  
the ThreadedSocketInitiator if a significant portion of your  
processing can be done without shared resources.  Otherwise, you are  
just adding the overhead of mutexes and thread swapping without any  
of the benefits of increased responsiveness or parallelism.

--oren

On Aug 18, 2006, at 8:27 AM, Mark T. Kennedy wrote:

> QuickFIX Documentation: http://www.quickfixengine.org/quickfix/doc/ 
> html/index.html
> QuickFIX Support: http://www.quickfixengine.org/services.html
>
> if i'm using a SocketInitiator (connecting to a single party) with a
> SynchronizedApplication instance, then it is clear that if a callback
> blocks, it will block all other callbacks.
>
> but if i'm using a SocketInitiator with a plain old Application
> instance, what is the model?  if a callback blocks, will it block
> any other callback?  e.g. is a single thread used to receive
> messages and deliver the 'from' callbacks?
>
> /mark
>
>
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