Re: timestampField not retrieved using CA provider for pvac::ClientChannel

[Andrew Johnson via Tech-talk <tech-talk at aps.anl.gov>]

The Channel Access network layer can only retrieve specific combinations of metadata corresponding to the DBR types which the native CA code implements, so it's not possible to fetch the timeStamp and alarm data at the same time as other kinds of data such as the display, control or alarm limits. Unfortunately the CA provider doesn't give any errors if you ask for a combination that it can't provide, it just gives you a subset of the metadata — it might be better if it threw an exception, but it doesn't. I think that fully explains your symptoms.

- Andrew

On 5/5/23 2:44 PM, Bisegni, Claudio wrote:

Should be a my mistake because if I use the pvget with the specific parameter it work:

 

developer@e058f4bc2090:/workspace$ pvget -p ca -r "field(field,timeStamp,alarm)" ca:variable:a

ca:variable:a structure

    alarm_t alarm

        int severity 0

        int status 0

        string message

    time_t timeStamp 2023-05-05 19:22:59.521 

        long secondsPastEpoch 1683314579

        int nanoseconds 521323913

        int userTag 0

I am digging into it.

 

Anyway, thank you for point me in the right direction

Claudio

 

From: Bisegni, Claudio <bisegni at slac.stanford.edu>
Date: Friday, 5 May 2023 at 12:24
To: Andrew Johnson <anj at anl.gov>, Veseli, Sinisa <sveseli at anl.gov>, tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: Re: timestampField not retrieved using CA provider for pvac::ClientChannel

I fixed the error reported by Sinisa (the reference to other channel for the sum)

 

I changed the pv name and not I’m trying to get data from ca:variable:a(below) could be some problem on c++ layer of pvData?

 

I done:

caput ca:variable:a.PROC 1

caput ca:variable:a.PROC 1

 

and the I got:

structure

    double value 1

    alarm_t alarm

        int severity 0

        int status 0

        string message

    display_t display

        double limitLow 0

        double limitHigh 0

        string description

        string format F6.0

        string units

    control_t control

        double limitLow 0

        double limitHigh 100

        double minStep 0

    valueAlarm_t valueAlarm

        boolean active false

        double lowAlarmLimit nan

        double lowWarningLimit nan

        double highWarningLimit nan

        double highAlarmLimit nan

        int lowAlarmSeverity 0

        int lowWarningSeverity 0

        int highWarningSeverity 0

        int highAlarmSeverity 0

        byte hysteresis 0

 

 

regards

Claudio

 

 

From: Andrew Johnson <anj at anl.gov>
Date: Friday, 5 May 2023 at 11:46
To: Bisegni, Claudio <bisegni at slac.stanford.edu>, Veseli, Sinisa <sveseli at anl.gov>, tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: Re: timestampField not retrieved using CA provider for pvac::ClientChannel

Hi Claudio,

Please try running the command

caput ca:variable:sum.PROC 1

and then run your client again. I suspect that the timestamp of your CALC record is still undefined i.e. 0,0 and that's why it isn't getting displayed.

- Andrew

On 5/5/23 1:23 PM, Bisegni, Claudio via Tech-talk wrote:

Hi yes sure:

 

This is my code:

 

auto ca_provider  = std::make_unique<pvac::ClientProvider>("ca", epics::pvAccess::ConfigurationBuilder().push_env().build());

auto  channel = std::make_shared<pvac::ClientChannel>(provider.connect(pv_name, opt));

auto op = channel->get(this, pvd::createRequest("field()"));

…

 

 

I need to specify that I connect to a IOCs launched with “sofIOC -d xyz.db” this si the content of the DB:

record(ao, "ca:variable:a")

{

    field(DRVH, "100")

    field(DOL, "0")

    field(PINI, "YES")

}

record(ao, "ca:variable:b")

{

    field(DRVH, "100")

    field(DOL, "0")

    field(PINI, "YES")

}

record(calc, "ca:variable:sum")

{

    field(SCAN, "1 second")

    field(INPA, "variable:a")

    field(INPB, "variable:b")

    field(CALC, "A+B")

}

 

I got this as answer on get operation:

 

structure

    double value 3

    alarm_t alarm

        int severity 0

        int status 0

        string message

    display_t display

        double limitLow 0

        double limitHigh 0

        string description

        string format F6.0

        string units

    control_t control

        double limitLow 0

        double limitHigh 0

        double minStep 0

    valueAlarm_t valueAlarm

        boolean active false

        double lowAlarmLimit nan

        double lowWarningLimit nan

        double highWarningLimit nan

        double highAlarmLimit nan

        int lowAlarmSeverity 0

        int lowWarningSeverity 0

        int highWarningSeverity 0

        int highAlarmSeverity 0

        byte hysteresis 0

 

 

From: Veseli, Sinisa <sveseli at anl.gov>
Date: Friday, 5 May 2023 at 11:05
To: Bisegni, Claudio <bisegni at slac.stanford.edu>, tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: Re: timestampField not retrieved using CA provider for pvac::ClientChannel

Hi,

 

I am not sure I understand what is going on. Perhaps you could include your code so we can see what exactly you are trying to do?

Also, if you'd like to get all fields, the string 'field()' or just empty string '' should work:

 

>>> print(c.get('field()'))

epics:nt/NTEnum:1.0

    enum_t value

        int index 0

        string[] choices [Off, On]

    alarm_t alarm

        int severity 0

        int status 0

        string message

    time_t timeStamp

        long secondsPastEpoch 1683129086

        int nanoseconds 834120910

        int userTag 0

 

 

--

Siniša Veseli

Scientific Software Engineering & Data Management

Advanced Photon Source

Argonne National Laboratory

sveseli at anl.gov

(630)252-9182

---

From: Bisegni, Claudio <bisegni at slac.stanford.edu>
Sent: Friday, May 5, 2023 12:56 PM
To: Veseli, Sinisa <sveseli at anl.gov>; tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: Re: timestampField not retrieved using CA provider for pvac::ClientChannel

 

I tried to set request field as:

pvd::createRequest("field(value, timeStamp, alarm, display, control, valueAlarm)

but I didn’t get the timeStamp Field in PVStructure. The request field work well for all other (for CA provider) for the PVA provider, instead, I always got every field also if I put only “filed(value)” in the request.

 

I’m wrong somenting….

 

Claudio

 

From: Bisegni, Claudio <bisegni at slac.stanford.edu>
Date: Friday, 5 May 2023 at 10:44
To: Veseli, Sinisa <sveseli at anl.gov>, tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: Re: timestampField not retrieved using CA provider for pvac::ClientChannel

Hi,

Thank you for yor help, is effect on get operation I use the default request, so Iat this point I need to use pvd::createRequest("field(value, timeStamp, alarm, display, control, valueAlarm)")); to retrieve all field

 

I’ll give a try!

 

Thank you very much.

 

Claudio

From: Veseli, Sinisa <sveseli at anl.gov>
Date: Friday, 5 May 2023 at 09:55
To: tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>, Bisegni, Claudio <bisegni at slac.stanford.edu>
Subject: Re: timestampField not retrieved using CA provider for pvac::ClientChannel

Hi,

 

I am not sure exactly why is there a difference in behavior between caget and pvget, but you should be able to get timestamps if you request them explicitly:

 

$ caget -a S01-DAQTBT:Strm:DataCaptureC

S01-DAQTBT:Strm:DataCaptureC   2023-05-03 10:51:26.834121 Off 

 

PV request string like field(value,timeStamp) should work from C++:

 

>>> from pvapy import *

>>> c = Channel('S01-DAQTBT:Strm:DataCaptureC', CA)

>>> print(c.get('field(value,timeStamp)'))

epics:nt/NTEnum:1.0

    enum_t value

        int index 0

        string[] choices [Off, On]

    time_t timeStamp

        long secondsPastEpoch 1683129086

        int nanoseconds 834120910

        int userTag 0

 

Hope this helps,

 

Sinisa

 

--

Siniša Veseli

Scientific Software Engineering & Data Management

Advanced Photon Source

Argonne National Laboratory

sveseli at anl.gov

(630)252-9182

---

From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Bisegni, Claudio via Tech-talk <tech-talk at aps.anl.gov>
Sent: Friday, May 5, 2023 11:39 AM
To: tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: timestampField not retrieved using CA provider for pvac::ClientChannel

 

Hello EPICS tech,

I'm working with last epics release and I have notice that making a get operation for an IOC using a CA provider for crete a pvac::ClientChannel I don't receive the timestamp field:

 

I noticed that also the official caget has the problem:

 

developer@e058f4bc2090:/workspace$ pvget variable:sum

variable:sum 2023-05-05 16:34:54.607 3

developer@e058f4bc2090:/workspace$ caget variable:sum

variable:sum 3

 

so is a client library problem or a server or something else?

 

Thank

 

you in advance.

Claudio

-- 

Complexity is free, it's Simplicity that takes work.

-- 
Complexity is free, it's Simplicity that takes work.