Re: libezca and EPICS-3.14

[Till Straumann <strauman@SLAC.Stanford.EDU>]

Having Stephanie next door pays off :-)

My application behaves like this:

   ezcaGet();

   /* user works; this can take minutes, hours, days */

   ezcaGet();
   /* second ezcaGet() fails if more than ~80sec expire
    * between the ezca calls
    */

Steph pointed out that the CA library still needs to handle
beacons even when idle and recommended to initialize the
application's CA context with ca_enable_preemptive_callback.
As a (undocumented) side effect, this would result in beacons
being handled by one of the CA background threads.
(At least, this is what I recall from our conversation - if
not completely accurate, I'm to blame for misquoting)

Anyways, this helped, the disconnects are gone and I'm  happy
because I no longer need 3.13 around :-)

-- Till

PS: the app now does

    ca_context_create(ca_enable_preemptive_callback);

    ...
    ezcaGet();

    /* user works for hours */

    ezcaGet();
    /* SUCCESS */


Jeff Hill wrote:
> > CA.Client.Exception............................................
> > ...
> >     Warning: "Virtual circuit disconnect"
> >     Context: "134.79.35.35:5064"
> >     Source File: ../cac.cpp line 1809
> >     Current Time: Wed Dec 04 2002 13:48:18.219267000
> > ...............................................................
>
>
> Do you know for certain that the "read command" is failing or are you
> encountering the following situation?
>
> In R3.14 beta 1 and beta 2 the ca client library will print the above
> message if a connected channel still exists when you call
> ca_task_exit(). To remain strictly backwards compatibility this message
> is suppressed, only for this specific situation, in the latest version
> of R3.14.
>
> Does ezca block in ca_pend_io() when it is waiting for the "read
> command" to complete? If so, then how long is the timeout which is
> provided to ca_pend_io()?
>
> Jeff 
>
>
> > -----Original Message-----
> > From: Till Straumann [mailto:strauman@SLAC.Stanford.EDU]
> > Sent: Wednesday, December 04, 2002 3:12 PM
> > To: Tech-talk
> > Subject: libezca and EPICS-3.14
> >
> > Hi.
> >
> > I discussed this briefly with Marty at JLAB. He suggested
> > I should post to the list. I was not sure whether the
> > EZCA library is supported under 3.14.
> >
> > Here's my problem:
> >
> > I have put together a CA interface for SCILAB (a nice open
> > source tool a la matlab) who builds on top of libezca. Works
> > fine with 3.13.
> > Using 3.14_beta1, I can access (e.g. read using ezcaget) a PV
> > into SCILAB without problem. An attempt to access the same PV
> > a couple of minutes later fails, however, giving the following
> > error:
> >
> > CA.Client.Exception............................................
> > ...
> >     Warning: "Virtual circuit disconnect"
> >     Context: "134.79.35.35:5064"
> >     Source File: ../cac.cpp line 1809
> >     Current Time: Wed Dec 04 2002 13:48:18.219267000
> > ...............................................................
> > .....
> >
> > Strange enough, if I repeat the read command for a couple
> > of times, it works again. Let some time expire and it again
> > fails.
> > And so on.
> >
> > Does somebody have an explanation or, yet better, a fix?
> >
> > -- Till