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Re: [RSPlib-Discusssion] fail-over problems


Chronological Thread 
  • From: Thomas Dreibholz <dreibh AT exp-math.uni-essen.de>
  • To: "Marjan Bozinovski" <marjanb AT cpk.auc.dk>, <rsplib-discussion AT sctp.de>
  • Subject: Re: [RSPlib-Discusssion] fail-over problems
  • Date: Wed Sep 11 17:42:00 2002
  • List-id: RSPlib Discussions <rsplib-discussion.sctp.de>
  • Organization: University of Essen, Institute for Experimental Mathematics

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Am Dienstag, 10. September 2002 23:14 schrieb Marjan Bozinovski:
> Hi,
>
> In my SIP client application I have included a fail-over mechanism. For
> instance, if the application does not receive a response to a particular
> request after a timer expiration, the request has to be resent to another
> active pool element. In principle, my ultimate goal is if the ASAP level
> does the fail-over by using a notification either: a) from the SCTP layer
> that the message could not be delivered to the peer endpoint or b) from the
> ASAP user layer using timer mechanisms as it is at the moment.
>
> Now, the problem is the following. Whenever a timer activated per SIP
> request fires, it is a signal for a failure, and therefore a fail-over is
> made by using the existing function connectToPoolElement() (in
> examplepu.c). Here is what I notice: First, it prints on the screen that
> the connection to the second PE is successfully established and
> connectToPoolElement() is finished. But, when seeing the packets with
> Ethereal I realize that the SCTP association is actually not established.
> On the contrary, the SCTP client side sends an INIT but immediately after
> that it sends an ABORT in which it reports zero error causes with the T bit
> set to 0. Due to the abortion, the SCTP association has never been
> established although connectToPoolElement() notifies successful association
> startup.
>
> I also expected that the SCTP association with the previous SCTP endpoint
> will be shutdown, but that does not happen.
>
> After the connectToPoolElement(), I put sendToPoolElement(), but naturally
> it only says "writing to data socket failed".
>
> I hope that I described this problem clearly.

What do you use to realize your timer, Unix signals (SIGALRM, etc.)? The
socket API is thread-safe but not signal safe. You can not use socket API
functions from a signal handler.

Turn on loglevel 9 for your rsplib program and let it write the output,
including your program's output, to a file, that is "-loglevel=9
- -logcolor=off" (see examplepe and examplepu) and ">logfile 2>&1". Then,
send
me this file with a description what you have done to produce this output.

It would be very helpful if you can reproduce the error in a very simple
program without your SIP library. The simpler the program, the more easily I
can identify the problem.


Best regards
- --
=======================================================================
 Dipl.-Inform. Thomas Dreibholz

 University of Essen,                            Room ES210
 Inst. for Experimental Mathematics              Ellernstraße 29
 Computer Networking Technology Group            D-45326 Essen/Germany
- -----------------------------------------------------------------------
 E-Mail:    
dreibh AT exp-math.uni-essen.de
 Homepage:   http://www.exp-math.uni-essen.de/~dreibh
=======================================================================

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