Are Bus Messages Queued?

[Nastooh Avessta]

Hi Tim
Thank you for your reply. Here is my use case:
1-	Application solicits plugins for messages, in a serialized ordered manner 
2-	Plugins reply in an asynchronous manner
3-	Upon receiving messages from all targeted plugins, an action is taken
Part 3, is coded inside the bus message handler:
…
case GST_MESSAGE_ELEMENT:
	    g_print("Got message from %s\n",gst_object_get_name (GST_MESSAGE_SRC(msg)));
     int i;
	        for(i=0;i<messageCnt;i++){
	            if(!strcmp(messagePlug[i],gst_object_get_name (GST_MESSAGE_SRC(msg)))){
	                noMessage++;
	                if(noMessages==messageCnt){
	                    g_print("Life is good\n");
	                    
	                }
	            }
	        }
	    break;
…
(Here, messageCnt is the expected number of messages to be received, and messagePlug is a pointer array containing the names of the plugins.)
What I was wondering is that while processing the current message, i.e., somewhere in that for loop, could I miss an incoming message? And if I understand you correctly, that should not be the case, as I am not popping any messages or going to NULL state. Am I correct in my understanding?
I should mention that this gstreamer 1.4.5.
Cheers,

-----Original Message-----
From: gstreamer-devel [mailto:gstreamer-devel-bounces at lists.freedesktop.org] On Behalf Of Tim Müller
Sent: Friday, November 04, 2016 1:47 AM
To: gstreamer-devel at lists.freedesktop.org
Subject: Re: Are Bus Messages Queued?

On Thu, 2016-11-03 at 17:42 -0700, Nastooh Avessta wrote:

Hi Nastooh,

> Got an application that would take an action, upon receiving messages 
> from multiple plugins , through a watch on the app bus: (Note that 
> these messages are asynchronous and may arrive at the ~ same time.) …
>  
> What I am seeing is that on different runs not all messages make it to    
> “case GST_MESSAGE_ELEMENT”, and am wondering if I need to queue 
> messages myself, start a new processing thread per message, etc.?

No, GstBus is a message queue itself. All messages should make it through to your handler. No messages should be lost unless you pop them off the bus yourself.

Two exceptions:

If you set a pipeline to NULL state the bus is 'flushed' in the NULL-
>READY state change transition. You can disable that behaviour though.

If you pop messages off the bus e.g. with gst_bus_*_pop_filtered() in another thread whist at the same time having a bus watch set up that might interact in weird ways.

Check the GST_DEBUG=GST_BUS:6 log to see whether those messages make it to the bus in the first place.

Cheers
 -Tim
--
Tim Müller, Centricular Ltd - http://www.centricular.com _______________________________________________
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