Re: gateway enum writes

[Dirk Zimoch <dirk.zimoch@psi.ch>]

This is from the gateway code (gateVc.cc):

caStatus gateVcData::write(const casCtx& ctx, const gdd& dd, gateChan 
&/*chan*/)
{
	int docallback=GATE_DOCALLBACK;

[...]
	switch(at) {
[...]
	case gddAppType_ackt:
	case gddAppType_acks:
		docallback = GATE_NOCALLBACK;
		// Fall through
	default:
[...]
			caStatus stat = pv->put(&dd, docallback);
			if(stat != S_casApp_success) return stat;

			if(docallback) {
				// Start a pending write
#if DEBUG_GDD
				fflush(stderr);
				printf("pending_write\n");
				fflush(stdout);
#endif
				pending_write = new gatePendingWrite(*this,ctx,dd);
				if(!pending_write) return S_casApp_noMemory;
				else return S_casApp_asyncCompletion;
			} else {
				return S_casApp_success;
			}

It seems that ALL puts except alarm handler ackt and acks are done with 
callback. There is no direct flag to write() from the generic CA server 
which indicates writes with or without callback, as far as I can see. 
But the gateway should have look at the CA command in ctx, probably like 
this:

if (ctx.getMsg()->m_cmmd == CA_PROTO_WRITE_NOTIFY) {
  docallback == GATE_DOCALLBACK;
} else {
  docallback == GATE_NOCALLBACK;
}


Dirk


Leicester, PJ (Pete) wrote:
> I can confirm that the problem appears isolated to the scaler record CNT
> field and not enums in general. 
>
> It looks like Tim's ca_put_callback theory may be correct. Is there a
> Gateway expert out there who can confirm this? How are writes done from
> the Gateway. Does it always use ca_put_callback regardless of how the
> put reached the gateway?
>
> Thanks for everyones responses on this.
>
> Pete Leicester
> Diamond
>
> -----Original Message-----
> From: Tim Mooney [mailto:mooney@aps.anl.gov] 
> Sent: 28 March 2006 21:07
> To: Leicester, PJ (Pete)
> Cc: tech-talk@aps.anl.gov
> Subject: Re: gateway enum writes
>
>
> Leicester, PJ (Pete) wrote:
>
> > I am getting some strange behaviour when writing enumerations through
> > the Gateway (version 2.0.0.0 on 3.14.8.2 and RedHat Enterprise 4).
> >
> > The problem first showed itself in edm when pressing a button on a edm
> > screen to send the value resulted in the following error:
> >
> >    CA.Client.Exception...............................................
> >        Warning: "Virtual circuit unresponsive"
> >        Context: "diamrs0005l.diamond.ac.uk:6064"
> >        Source File: ../tcpiiu.cpp line 896
> >        Current Time: Tue Mar 28 2006 16:19:01.334736000
> >    ..................................................................
> >
> > I did some further tests using caput with similar results:
> >
> >    [pjl45@pc0005 pjl45]$ caput  -w15 GDA:scaler2.CNT Count
> >    Old : GDA:scaler2.CNT                Done
> >    Read operation timed out: PV data was not read.
> >    New : GDA:scaler2.CNT
> >    CA.Client.Exception...............................................
> >        Warning: "Virtual circuit disconnect"
> >        Context: "op=0, channel=GDA:scaler2.CNT, type=DBR_TIME_STRING,
> > count=1, ctx="diamrs0005l.diamond.ac.uk:6064""
> >        Source File: ../getCopy.cpp line 82
> >        Current Time: Tue Mar 28 2006 17:04:24.488496000
> > .
> > Despite the above error message the write does actually reach the IOC.
> > However if I now try the change the value back as follows:
> >
> >    [pjl45@pc0005 pjl45]$ caput  -w15 GDA:scaler2.CNT Done
> >    Old : GDA:scaler2.CNT                Count
> >    Read operation timed out: PV data was not read.
> >    New : GDA:scaler2.CNT
> >    CA.Client.Exception...............................................
> >        Warning: "Virtual circuit disconnect"
> >        Context: "op=0, channel=GDA:scaler2.CNT, type=DBR_TIME_STRING,
> > count=1, ctx="diamrs0005l.diamond.ac.uk:6064""
> >        Source File: ../getCopy.cpp line 82
> >        Current Time: Tue Mar 28 2006 17:22:36.167980000
> >    ..................................................................
> >
> > I get an error again however this time the 'Done' value gets written 
> > to
> > the IOC exactly ONE MINUTE after I entered the caput command. This is 
> > long after the caput command has timed out so it appears the gateway
>
> is 
>
> > responsible for the delay?
> >
> > Has anyone any idea what may be happening? Is there a 60 second 
> > timeout
> > in CA or the gateway which may give a clue as to what I am seeing?
> >
> > (For the record this test was done with a very lightly loaded test
> > gateway serving only 20 or so PV's. Also using caput -w70 results in
>
> the 
>
> > same timeouts)
>
>
> Do you get this kind of result with *all* enum fields that you write to
> through the gateway, or only this one?  The scaler record's CNT field is
> different from other enum's in that it starts an operation that may take
> a long time to complete.  I don't know what the gateway is using to do
> put's, but if it should happen to be ca_put_callback(), the gateway may
> be waiting for a callback that will come only after the scaler has
> finished counting.

--
Dr. Dirk Zimoch
Swiss Light Source
Paul Scherrer Institut
Computing and Controls
phone +41 56 310 5182
fax   +41 56 310 4413