I just explained it to you for what it's worth.


On Mon, Nov 21, 2011 at 10:53 PM, Hynek Cihlar <hynek.cihlar@gmail.com> wrote:
I really didn't mean to be arrogant. The analogy was just to simplify the communication and express my concerns with the protocol, without the thorough understanding I don't think I can put together a serious esl app.

I guess I will have to dive into the source code now and try to figure out by myself. 

Thank you for your inputs!


Sent from my mobile device

On Nov 22, 2011, at 0:30, Anthony Minessale <anthony.minessale@gmail.com> wrote:

Your tone has changed to be unsatisfactorily arrogant to warrant my attention.  Please refrain from any more disrespectful analogies.
It would be like you came to a free forum to get help on a free software then questioned the response from the guy who designed it..... oh wait that's not an analogy that's what you are doing!


If you sent sendevent with execute to send the playback then sent another one to execute break all (Assuming you did not have event_lock header which will force it to execute each instruction one at a time) it would indeed execute in order.

You asked about using broadcast and uuid_break (broadcast is the same as sendmsg + execute) uuid_break is instant real time call so if you broadcast then uuid_break the break will easily beat the queuing.

BTW I have 3 TV in my house all of which require you to wait for them to come all the way up to shut them back down.




On Mon, Nov 21, 2011 at 1:10 PM, Hynek Cihlar <hynek.cihlar@gmail.com> wrote:
I send execute playback at time t0. I send execute break all also at time t0. Execute playback is queued in the channel queue. Execute break all is also queued in the channel queue. Channel thread picks up the execute playback, posts the execute notification, playback is queued for playback. Channel thread picks up the execute break all command...

Now, what is the particular reason that channel thread cannot stop the initiated playback?

Having to wait for the execute notification to be able to stop the playback makes the esl protocol unnecessary complicated. It's like having to wait for a TV to come up to be able to turn it off. 

Sent from my mobile device

On Nov 21, 2011, at 18:01, Anthony Minessale <anthony.minessale@gmail.com> wrote:

execute over event socket does the same thing as broadcast:

The channel is very busy, its doing I/O in a very critical loop in its own thread.
You cannot simply gain access to it and make it start executing your application because then it would be doing it inside that other thread and possibly stopping it when it's supposed to be doing something else.

Instead the instruction is queued to the channel and the channel does periodic calls to see if it has any tasks to execute when its tolerable to perform such a task and also ensuring its carried out in it's own dedicated session thread.

From the time you send the command there is an expected latency until the command is actually executed.  From your application you should send the command then wait until you receive the channel_execute corresponding to the desired command before continuing and having clearance to send the uuid_break.



On Sun, Nov 20, 2011 at 2:07 AM, Hynek Cihlar <hynek.cihlar@gmail.com> wrote:
So why would the bgapi uuid_break all fail if it queues the same way as execute does?

Hynek



 
On Sun, Nov 20, 2011 at 4:27 AM, Anthony Minessale <anthony.minessale@gmail.com> wrote:
Every way you are discussing does it the same way, doing it over bgapi just wastes an extra thread for no reason.

All of the above queue the command to the session and it will not execute it until the next time its convenient for the session to execute queued instructions.

So any way you slice it, unless you wait for the execute event telling you that the playback you tried to start, has actually started then its not going to help.

You are most likely trying to had implement some convention that is dumbed down to one command already in FS so I suggest you re-evaluate what you are even trying to do.   



On Sat, Nov 19, 2011 at 3:37 AM, Hynek Cihlar <hynek.cihlar@gmail.com> wrote:
So I changed the uuid_X-commands to execute and the use case with stopping tone playback works like a charm now!

Regarding the blocking, you are right. I'm limiting blocking (and context switching) by handling all events and issuing commands always on one (and the same) thread per session. This design also allows me to simplify the programming model, decrease concurrency bugs, simplify debugging, etc. That's why the synthetic delay was giving me troubles since the events and commands must fly through as fast as possible.

Thanks again!

Hynek




On Sat, Nov 19, 2011 at 10:28 AM, Peter Olsson <peter.olsson@visionutveckling.se> wrote:
bgapi can of course be used also, and in some cases you might still need it. But the important thing to keep in mind when doing bgapi is to handle the events correctly. When executing bgapi you will get a job-id back, this job id must then be stored internally, so you can link this to the background job event.

I try to use the sendMsg/execute as much as possible, you will get CHANNEL_EXECUTE/CHANNEL_EXECUTE_COMPLETE events, so you will always know what's going on.

I've only tested my system for about 100 concurrent calls, but that was handled without any problems at all. What's really important is to make really sure you never execute something that will block - since that will cause everything to "hang".

/Peter
________________________________________
Från: freeswitch-users-bounces@lists.freeswitch.org [freeswitch-users-bounces@lists.freeswitch.org] f&#246;r Hynek Cihlar [hynek.cihlar@gmail.com]
Skickat: den 19 november 2011 10:04
Till: FreeSWITCH Users Help
Ämne: Re: [Freeswitch-users] Playback race condition

Peter, thanks for pointing me to the right direction. I will try the execute command, since queueing is exactly what I would need to preserve consistency across commands (I had an impression that bgapi will give me this consistency).

Also I like to hear that it is possible to use a single connection since I have designed the communication with one connection also. May I ask how many concurrent sessions can your system handle?

Hynek



On Sat, Nov 19, 2011 at 9:35 AM, Peter Olsson <peter.olsson@visionutveckling.se<mailto:peter.olsson@visionutveckling.se>> wrote:
If you think about performance I would say it's better to handle this without spawning lots of extra threads.

First of all, most common commands can be queued into the the channel thread using the execute method (http://wiki.freeswitch.org/wiki/Mod_event_socket#execute), this makes it possible to queue commands directly to the channel's thread, and the ESL session will never wait for the result, it returns immediately.

I've never used uuid_broadcast myself, so I'm not really sure how it's handled, but by looking quickly in the code it looks like it shouldn't block either, since it's actually just queuing a playback command to the channel's thread.

So basically, keep away from uuid_X-commands, and use execute method as much as possible, and when using uuid_x-methods, make sure that won't block - but if they do, make sure to handle handle the events for the bgapi correctly.

I've built a complete IVR system using these methods, with a single ESL connection, and I've never had any performace issues.

/Peter

________________________________________
Skickat: den 19 november 2011 09:12
Till: FreeSWITCH Users Help
Ämne: Re: [Freeswitch-users] Playback race condition

Two reasons I am not using api in this case.

1. Performance
2. Doesn't seem to work

1. Blocking issuing the command will eventually reduce the system throughput. Agree this is only a potential theoretical problem and I haven't gotten into production where I could get the actual results.

2. When issuing api uuid_playback and api uuid_break right after, I'm always getting an error response from the uuid_break. The ESL message body is "-ERR no reply". Nothing in the logs (no idea which log type/level will could generate other useful info).

Hynek



On Sat, Nov 19, 2011 at 8:48 AM, Peter Olsson <peter.olsson@visionutveckling.se<mailto:peter.olsson@visionutveckling.se><mailto:peter.olsson@visionutveckling.se<mailto:peter.olsson@visionutveckling.se>>> wrote:
Since you're using bgapi, it's impossible to guarantee that uuid_broadcast has actually executed before you exeute uuid_break (they will be executed in two different threads). You will have to do this in a more controlled way (wait for events to show up etc.). And also, do you really need to use bgapi all the time? I'm not sure how uuid_broadcast is handled, but uuid_break is totally safe to use without bgapi, since it will just update a flag and then return immediately. I think uuid_broadcast will do the same thing - so getting rid of bgapi should be a good ebnough solution.

/Peter
________________________________________
Från: freeswitch-users-bounces@lists.freeswitch.org<mailto:freeswitch-users-bounces@lists.freeswitch.org><mailto:freeswitch-users-bounces@lists.freeswitch.org<mailto:freeswitch-users-bounces@lists.freeswitch.org>> [freeswitch-users-bounces@lists.freeswitch.org<mailto:freeswitch-users-bounces@lists.freeswitch.org><mailto:freeswitch-users-bounces@lists.freeswitch.org<mailto:freeswitch-users-bounces@lists.freeswitch.org>>] f&#246;r Hynek Cihlar [hynek.cihlar@gmail.com<mailto:hynek.cihlar@gmail.com><mailto:hynek.cihlar@gmail.com<mailto:hynek.cihlar@gmail.com>>]
Skickat: den 19 november 2011 08:31
Till: FreeSWITCH Users Help
Ämne: Re: [Freeswitch-users] Playback race condition

As a workaround I put a synthetic a delay between the start and stop of the playback. I wouldn't want to keep this solution however since it blocks one of the worker threads (decreasing overall system throughput) and second, I really don't know what the synthetic delay should be or whether it could differ during different conditions like during a high load.

Was anybody facing similar problem? How did you solve it? Am I using the API wrong and is there another way to invoke playback/stop?

Thanks!
Hynek



On Fri, Nov 18, 2011 at 6:46 PM, Hynek Cihlar <hynek.cihlar@gmail.com<mailto:hynek.cihlar@gmail.com><mailto:hynek.cihlar@gmail.com<mailto:hynek.cihlar@gmail.com>><mailto:hynek.cihlar@gmail.com<mailto:hynek.cihlar@gmail.com><mailto:hynek.cihlar@gmail.com<mailto:hynek.cihlar@gmail.com>>>> wrote:
Hello all,

I got on shaky grounds issuing commands to Freeswitch over ESL.

For example, issuing the following commands close enough (on my system at around 100 ms and less) causes troubles.

bgapi uuid_broadcast 71f8f250-8ad6-4ab3-855a-3cbc71075fe2 playback::tone_stream://%(150,4000,425);loops=-1
<100ms appart
bgapi uuid_break 71f8f250-8ad6-4ab3-855a-3cbc71075fe2 all
previous playback is not stopped, the following is queued (not played)
bgapi uuid_broadcast 71f8f250-8ad6-4ab3-855a-3cbc71075fe2 playback::tone_stream://%(1000,4000,425);loops=-1

It looks like the first tone playback is not properly initialized when the break arrives. Waiting for the start of the first tone playback (waiting for the right event) is not a solution, I don't want the tone to be played at all if the events come this close.

Any ideas?


Hynek




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