[asterisk-dev] [Code Review]: Hangup handlers - Dialplan subroutines that run when the channel hangs up.

[rmudgett]

> On June 25, 2012, 4:27 p.m., Mark Michelson wrote:
> > /trunk/main/channel.c, lines 1187-1189
> > <https://reviewboard.asterisk.org/r/2002/diff/1/?file=29143#file29143line1187>
> >
> >     I can't think of a good reason to manage hangup handlers on dummy channels. I think they should be left off of dummy channels completely if possible.

Dummy channels are used internally to evaluate expressions if you don't have a channel available.
You could potentially evaluate:
${SET(CHANNEL(hangup_handler_push)=hangup,s,1)}
which would push a hangup handler onto the dummy channel.
The dummy channel would never run the handler, but there would subsequently be a memory leak.


> On June 25, 2012, 4:27 p.m., Mark Michelson wrote:
> > /trunk/main/features.c, lines 4692-4695
> > <https://reviewboard.asterisk.org/r/2002/diff/1/?file=29145#file29145line4692>
> >
> >     You could simplify this to
> >     
> >     hangup_run = ast_pbx_hangup_handler_run(chan);

This would introduce a bug.  The h-exten is executed above and sets the hangup_run flag.


- rmudgett


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On June 25, 2012, 11:30 a.m., rmudgett wrote:
> 
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> 
> (Updated June 25, 2012, 11:30 a.m.)
> 
> 
> Review request for Asterisk Developers and kobaz.
> 
> 
> Summary
> -------
> 
> This feature originated with https://reviewboard.asterisk.org/r/1230/ by kobaz.
> 
> See
> https://wiki.asterisk.org/wiki/display/AST/Asterisk+11+Projects
> https://wiki.asterisk.org/wiki/display/AST/Hangup+handlers
> 
> Hangup handlers are an alternative to the h extension.  They can be used 
> in addition to the h extension.  The idea is to attach a Gosub routine to 
> a channel that will execute when the call hangs up.  Whereas which h 
> extension gets executed depends on the location of dialplan execution when 
> the call hangs up, hangup handlers are attached to the call channel.  You 
> can attach multiple handlers that will execute in the order of most 
> recently added first.  
> 
> Call transfers, call pickup, and call parking can result in channels on 
> both sides of a bridge containing hangup handlers.  
> 
> Hangup handlers can also be attached to any call leg because of pre-dial 
> routines.  
> 
> 
> When hangup handlers are executed
> 
> Any hangup handlers associated with a channel are always executed when the 
> channel is hung up.  
> 
> 
> Manipulating hangup handlers on a channel
> 
> Hangup handlers pass the saved handler string to the Gosub application to 
> execute.  The syntax is intentionally the same as the Gosub application.  
> If context or exten are not supplied then the current values from the 
> channel pushing the hangup handler are inserted before storing on the 
> hangup handler stack.  
> 
> Push a hangup handler onto a channel:
> same => n,Set(CHANNEL(hangup_handler_push)=[[context,]exten,]priority[(arg1[,...][,argN])]);
> 
> Pop a hangup handler off a channel and optionally push a replacement:
> same => n,Set(CHANNEL(hangup_handler_pop)=[[[context,]exten,]priority[(arg1[,...][,argN])]]);
> 
> Pop all hangup handlers off a channel and optionally push a replacement:
> same => n,Set(CHANNEL(hangup_handler_replace)=[[[context,]exten,]priority[(arg1[,...][,argN])]]);
> 
> Cascading hangup handlers
> same => n,Set(CHANNEL(hangup_handler_push)=hdlr3,s,1(args));
> same => n,Set(CHANNEL(hangup_handler_push)=hdlr2,s,1(args));
> same => n,Set(CHANNEL(hangup_handler_push)=hdlr1,s,1(args));
> 
> 
> AMI events
> 
> The hangup handler AMI events are output as part of the AMI dialplan 
> permission class.  
> 
> * The AMI event HangupHandlerPush is generated whenever a hangup handler 
> is pushed on the stack by the CHANNEL() function.  
> 
> * The AMI event HangupHandlerPop is generated whenever a hangup handler is 
> popped off the stack by the CHANNEL() function.  
> 
> * The AMI event HangupHandlerRun is generated as a hangup handler is about 
> to be executed.  
> 
> 
> CLI commands
> 
> Single channel:
> core show hanguphandlers <chan>
> 
> Output:
> Channel       Handler
> <chan-name>   <first handler to execute>
>               <second handler to execute>
>               <third handler to execute>
> 
> All channels:
> core show hanguphandlers all
> 
> Output:
> Channel       Handler
> <chan1-name>  <first handler to execute>
>               <second handler to execute>
>               <third handler to execute>
> <chan2-name>  <first handler to execute>
> <chan3-name>  <first handler to execute>
>               <second handler to execute>
> 
> 
> This addresses bug ASTERISK-19549.
>     https://issues.asterisk.org/jira/browse/ASTERISK-19549
> 
> 
> Diffs
> -----
> 
>   /trunk/.cleancount 369297 
>   /trunk/apps/app_dial.c 369297 
>   /trunk/apps/app_followme.c 369297 
>   /trunk/apps/app_queue.c 369297 
>   /trunk/channels/chan_local.c 369297 
>   /trunk/configs/cdr.conf.sample 369297 
>   /trunk/funcs/func_channel.c 369297 
>   /trunk/include/asterisk/channel.h 369297 
>   /trunk/include/asterisk/pbx.h 369297 
>   /trunk/main/autoservice.c 369297 
>   /trunk/main/channel.c 369297 
>   /trunk/main/channel_internal_api.c 369297 
>   /trunk/main/features.c 369297 
>   /trunk/main/pbx.c 369297 
> 
> Diff: https://reviewboard.asterisk.org/r/2002/diff
> 
> 
> Testing
> -------
> 
> Attached hangup handlers to channels and done the following kinds of calls:
> Simple A to B call.
> DTMF attended transfer
> DTMF blind transfer
> 
> Hangup handlers were executed when expected.
> 
> 
> Thanks,
> 
> rmudgett
> 
>

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