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Subject: PV's element count differs though CA gateway
From: Carl Schumann <schumann@fnal.gov>
To: tech-talk@aps.anl.gov, Dehong Zhang <dhzhang@fnal.gov>
Cc: Salah J Chaurize <chaurize@fnal.gov>, "Denise S. Finstrom" <dfinstrom@fnal.gov>
Date: Fri, 21 May 2010 14:14:34 -0500
Tech-talk, Dehong Zhang,

We have a client application which attempts to access a PV's elements 0 to 999 . This application is run on two sets of machines. One set must go through an EPICS gateway to access the PV. The other set does not do so. The application does not run properly when going through the gateway because of an out-of-bounds error at element 940. It is able to access elements all they way up to 999 without issue when there is no gateway involved.

We were able to track this issue down to a difference in the element count reported by the originating IOC vs. the gateway using cainfo. For the gateway case cainfo reports element count 940, but for the non-gateway case cainfo reports 1000. Using EPICS_CA_ADDR_LIST we were able to reproduce both element counts on a single machine depending on whether the gateway or the originating IOC responded. The result is attached.

Me and my co-workers find this result unexpected and are not sure how to fix it. Any help would be appreciated please. Thanks for your time.

Sincerely,
Carl Schumann

P.S.: for my co-worker Dehong owner of the hins_ws.py:
The client is hins_ws.py. The PV is PD_LEBT:Inst:WS1.RST1. It is the out-of-bound error that prevents the Save Result button from generating a file. Do have any insight about what might be going on here? Thanks.


clx22$ export EPICS_CA_ADDR_LIST=131.225.143.59
clx22$ cainfo PD_LEBT:Inst:WS1.RST1
CA.Client.Exception...............................................
    Warning: "Identical process variable names on multiple servers"
    Context: "Channel: "PD_LEBT:Inst:WS1.RST1", Connecting to: 131.225.143.59:5064, Ignored: cag-clx-2.fnal.gov:5064"
    Source File: ../cac.cpp line 1209
    Current Time: Fri May 21 2010 13:20:42.301346264
..................................................................
PD_LEBT:Inst:WS1.RST1
    State:         connected
    Host:          hinst1.fnal.gov:5064
    Access:        read, write
    Data type:     DBR_FLOAT (native: DBF_FLOAT)
    Element count: 1000
clx22$ cainfo PD_LEBT:Inst:WS1.RST1
PD_LEBT:Inst:WS1.RST1
    State:         connected
    Host:          cag-clx-2.fnal.gov:5064
    Access:        read, write
    Data type:     DBR_FLOAT (native: DBF_FLOAT)
    Element count: 940
CA.Client.Exception...............................................
    Warning: "Identical process variable names on multiple servers"
    Context: "Channel: "PD_LEBT:Inst:WS1.RST1", Connecting to: 131.225.120.203:5064, Ignored: hinst1.fnal.gov:5064"
    Source File: ../cac.cpp line 1209
    Current Time: Fri May 21 2010 13:25:01.625878952
..................................................................
clx22$

Replies:
RE: PV's element count differs though CA gateway Jeff Hill

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