Experimental Physics and
Industrial Control System

Albert Kagarmanov <[email protected]> · Fri, 11 Mar 2005 16:02:38 +0100 (MET)

	Hi Ken,

   Here at DESY we're also having a small bug with channel access
gateway(v2.0.0b12) but in another area. It's happen with Alarm Handler
(v1.2.13) in global mode:

    For each one new IOC alarm event, alh calculates 2 alh conditions and
creates 2 lines in alarm log file. When I try to debug  alh-C-code I've
found that it's really 2 monitor procedure alCaNewEvent() invoked per one
IOC alh event.

Bug description:

1) This is happen only if alh starts in global mode.

2) This is depend from 2 variables
   LIST=EPICS_CA_ADDR_LIST
   AUTO= EPICS_CA_AUTO_ ADDR_LIST
   This error happen even if LIST contains only one hostname

3) Another application in our environment working with ca_gateway quite OK.
For example
  $> caget PV
returns one answer if  LIST not set  or if it set but AUTO=NO. If LIST is
set and AUTO=YES caget returns value and informs about "Ambiguous channel
host". We can summarize it as a table for a number of caget answers :

    LIST|Empty |"Host"|
 AUTO	|      |      |
---------------|------|
NO      | 0    |    1 |
YES    	| 1    |1+info|

4) ALH also works OK without gateway or if AUTO=YES (in this case alh creates
special warning window in start-time about "Ambiguous channel host").
   But if LIST is not empty and AUTO=NO, alh calculates 2 internal alarm
conditions per one real alarm event and add 2 lines into the alhLogFile.
We can summarize it as a table for a number of additional lines into the
alhLogFiles per 1 ioc-alarm:

  LIST  |Empty |"Host"|
 AUTO	|      |      |
--------|------|------|
NO      | 0    |   2  |
YES    	| 1    |   1  |

Number "2" in the second column is this bug.

Best regards,
Albert Kagarmanov.

On Mon, 7 Mar 2005, Kenneth Evans, Jr. wrote:
> I was able to reproduce this problem with the behavior described by
> Rolf with one combination of systems.  I set DRVH = DRVL =0.0 on a
> test PV to allow the large values.  It then happens for me from an
> MEDM on Windows going to a Gateway on Linux.  The MEDM was using a
> simple ADL file with only a slider.  It does not happen for me for any
> other combination of Solaris, Linux, or Windows MEDMs going to Linux
> or Solaris Gateways.
>
> I was also unable to reproduce the problem (mentioned by Ralph) with
> two simultaneous sliders when going to Solaris Gateways.  That worked
> all right for me.
>
> I was able to set up a test Gateway on a non-standard port on the one
> Linux box with multiple interfaces I have available.  (I cannot debug
> with our Main Gateway on the same machine even though it also
> has the described problem with the Windows MEDM.)
>
> The connection goes:
>
> MEDM -> CAS -> Gateway -> CAC -> IOC
>
> I can verify the MEDM is sending the correct values and CAS is sending
> incorrect values to the test Gateway.  When the Gateway does a CAC
> put, it does a put with callback and does not do any other puts until
> the callback happens.  Any write requests that come in while there is
> a pending write are sent back to CAS as postponed, and CAS handles them
> and resends them later.  Normally things are so fast that there are
> probably no postponements.  With sliders they can happen, and
> apparently there is a problem with the postponed I/O.
>
> I also note the postponed I/O comes back quite some time after it was
> originally sent.  Other new values come in the meantime, so the slider
> values that result in CAC puts are done out of order.  In my tests
> only about 1 in 10 writes was postponed.
>
> The fact that it only happens with Linux may be the speed of our Linux
> box, not the platform itself.  In addition, when I inserted print
> statements in MEDM to check its values, the problem stopped happening
> owing to the slowdown associated with the prints.  It seems to require
> the postponed I/O, which probably rarely happens in the APS Gateways,
> owing their being predominately read only in the first place.
>
> It looks as though it needs to be fixed in CAS.
>
>

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System