Re: [Cppcms-users] Consumer producer problem

[Artyom B. <art...@ya...>]

----- Original Message -----

> From: Christian Gmeiner <chr...@gm...>
> To: cpp...@li...
> Cc: 
> Sent: Wednesday, March 13, 2013 10:39 AM
> Subject: [Cppcms-users] Consumer producer problem
> 
> Hi all.
> 
> I am using a QProcess to run an external bash script. There I am
> reading back stdout and stderr and
> send these information back to the client via SSE.
> Now I run into the problem that QProcess produces messages a lot
> faster then they got send via SSE.
> The result is that the used ring-buffer has overwritten elements and
> not all "messages" got send.
> At the moment I am using the sse::bounded_event_queue.
> 
> Is there anything I need to take of when using condition_variable?

> What is the best approach to get
> this handled in a clean way?
> 
> thanks

> --
> Christian Gmeiner, MSc
> 

First of all how they are generated, synchronously, asynchronously?
how many client do you have?

In general it is not a producer consumer problem
but rather message broker problem.

if you have 1 client and 1 source you don't really need an
asynchronous SSE... you can do it easily synchronously as 
in any case process itself is synchronous.

However if you have many clients and one source it is 
a different problem.

What happens if somebody requests the date after the process
started do you send it from the begging or from the last
event? What happens on reconnect you need to start from the
last point but how long do you want to keep the data?

In general you can keep all events - all the output

and send it from the beginning, in such case you can either
make the ring buffer with a big ring or just alter
the class

http://sourceforge.net/p/cppcms/code/2238/tree/framework/trunk/contrib/server_side/sse/server_sent_events.h


With the policy you need. You can derive the event_source
class and provide the policy of keeping and throwing messages
the way you need.



Artyom Beilis
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