RE: Problems configuring alarms with PvaPy

[KRL Baker - STFC UKRI via Tech-talk <tech-talk at aps.anl.gov>]

Hi there,

 

Thanks for getting back to me, it definitely helped!

 

However, I’ve implemented this logic in the way you suggested and while it seems to work, I’ve noticed that the alarms seem to trigger when the value is one off the value I set as the limit. I think this is best explained with a Boolean example that I’ve included here:

 

initial_time = time.time()

seconds, nanoseconds = extract_seconds_and_nanoseconds_from_timestamp(initial_time)

timestamp = PvTimeStamp(seconds, nanoseconds, 0)

 

display = PvDisplay(0, 10, 'Test Display', 'Test Format', 'units')

 

alarm = PvAlarm()

 

alarm_values = PvValueAlarm(BOOLEAN)

 

pv_types = {

    'value': BOOLEAN,

    'timeStamp': timestamp,

    'display': display,

    'alarm': alarm,

    'alarm_values': alarm_values

}

pv_values = {

    'timeStamp': timestamp.toDict(),

    'display': display.toDict(),

    'alarm': alarm.toDict(),

    'alarm_values': alarm_values.toDict()

}

 

pv = PvObject(pv_types, pv_values)

pv['alarm_values.highAlarmLimit'] = True # should alarm when the value is True (1)

pv['alarm_values.highAlarmSeverity'] = 2

pv['alarm_values.active'] = True

 

server = PvaServer()

server.addRecord('counter', pv)

 

c = 0

try:

    while True:

        time.sleep(1)

        if c == 2:

            c = 0

        seconds, nanoseconds = extract_seconds_and_nanoseconds_from_timestamp(time.time())

 

        if c == pv['alarm_values.highAlarmLimit']:

            # setting match value to True will raise an alarm when this is false

            # it sets the settings on the right value but propagates through for the wrong value

            (severity, status, message) = (pv['alarm_values.highAlarmSeverity'], 1, 'HIGH ALARM')

        else:

            (severity, status, message) = (0, 0, 'ALL CLEAR')

        print(f'changing match alarm setting for value {c} to: \n severity: {severity}, status: {status}')

 

        epics_message = {

            'value': c,

            'timeStamp': {

                'secondsPastEpoch': seconds,

                'nanoseconds': nanoseconds

            },

            'alarm': {

                'severity': severity,

                'status': status,

                'message': message

            }

        }

        pv.set(epics_message)

        server.update(pv)

        c += 1

finally:

    server.stop()

 

In this case, the settings are set correctly for the value, which I can see with the output of the print statement:

 

changing match alarm setting for value 0 to:

 severity: 0, status: 0

changing match alarm setting for value 1 to:

 severity: 2, status: 1

 

But when I run a pvmonitor on counter in a terminal window, the alarms come through when the value is false:

 

pvmonitor counter

counter 2021-06-09 23:34:46.275  false MAJOR DEVICE HIGH ALARM

counter 2021-06-09 23:34:47.276  true

counter 2021-06-09 23:34:48.277  false MAJOR DEVICE HIGH ALARM

counter 2021-06-09 23:34:49.279  true

counter 2021-06-09 23:34:50.280  false MAJOR DEVICE HIGH ALARM

 

Although I’ve not included an example here, I see a similar pattern with range alarms where the alarm message is still visible on the pvmonitor on value 2 when the lower warning is set to 1 and lower alarm is 0 for example.

 

Again, apologies if I’ve misunderstood how the library works but is this behaviour expected? Is it the case where the alarm message only propagates through to the monitor on the next update?

 

Thanks again for your help,

 

Kathryn

 

 

From: Veseli, Sinisa <sveseli at anl.gov>
Sent: 07 June 2021 18:48
To: tech-talk at aps.anl.gov; Baker, KRL, Kathryn (STFC,RAL,ISIS) <k.baker at stfc.ac.uk>
Subject: Re: Problems configuring alarms with PvaPy

 

Hi,

 

At the moment there is no automated handling of alarm values. You would have to do something like this (compared to your original code example):

 

 

bluegill2> diff s.py s.py.orig

48c48

< server.addRecord('counter', pv.copy())

---

> server.addRecord('counter', pv)

57,66d56

<         (severity, status, message) = (0, 0, 'ALL CLEAR')

<         if c >= pv['alarm_values.highAlarmLimit']:

<             (severity, status, message) = (pv['alarm_values.highAlarmSeverity'], 1, 'HIGH ALARM')

<         elif c >= pv['alarm_values.highWarningLimit']:

<             (severity, status, message) = (pv['alarm_values.highWarningSeverity'], 1, 'HIGH WARNING')

<         elif c <= pv['alarm_values.lowAlarmLimit']:

<             (severity, status, message) = (pv['alarm_values.lowAlarmSeverity'], 1, 'LOW ALARM')

<         elif c <= pv['alarm_values.lowWarningLimit']:

<             (severity, status, message) = (pv['alarm_values.lowWarningSeverity'], 1, 'LOW WARNING')

<

72,76d61

<             },

<             'alarm' : {

<             'severity' : severity,

<             'status' : status,

<             'message' : message

80d64

<         server.update(pv)

bluegill2>

 

I will add better alarm handling in the next release.

 

I 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 KRL Baker - STFC UKRI via Tech-talk <tech-talk at aps.anl.gov>
Sent: Monday, June 7, 2021 8:20 AM
To: tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: Problems configuring alarms with PvaPy

 

Hello Tech-Talk,

 

I am working with PvaPy to create and update some PVs and am trying to work out how to configure the alarms for the pv.

 

I have created the object using the code below, which creates the ‘counter’ pv and updates the values (which I can see with a pvmonitor or a pvinfo).

 

         initial_time = time.time()

    seconds, nanoseconds = extract_seconds_and_nanoseconds_from_timestamp(initial_time)

    timestamp = PvTimeStamp(seconds, nanoseconds, 0)

 

    # configure display values

    display = PvDisplay(0, 10, 'Test Display', 'Test Format', 'units')

 

    # set up alarm - severity (0=NO_ALARM, 1=MINOR, 2=MAJOR, 3=INVALID, 4=UNDEFINED), status, message

    alarm = PvAlarm()

    alarm.setSeverity(0)

    alarm.setMessage('test alarm message')

 

    alarm_values = PvValueAlarm(FLOAT)

 

    alarm_values.setHighAlarmLimit(9)

    alarm_values.setLowAlarmLimit(2)

    alarm_values.setHighWarningLimit(8)

    alarm_values.setLowWarningLimit(3)

 

    alarm_values.setHighAlarmSeverity(2)

    alarm_values.setLowAlarmSeverity(2)

    alarm_values.setHighWarningSeverity(1)

    alarm_values.setLowWarningSeverity(1)

    alarm_values.setActive(True)

 

    pv = PvObject({

        'value': FLOAT,

        'timeStamp': timestamp,

        'display': display,

        'alarm': alarm,

        'alarm_values': alarm_values

    }, {

        'timeStamp': timestamp.toDict(),

        'display': display.toDict(),

        'alarm': alarm.toDict(),

        'alarm_values': alarm_values.toDict()

    })

 

    server = PvaServer()

    server.addRecord('counter', pv)

    c = 0

    startTime = time.time()

    try:

        while True:

            time.sleep(1)

            if c == 11:

                c = 0

            seconds, nanoseconds = extract_seconds_and_nanoseconds_from_timestamp(time.time())

            epics_message = {

                'value': c,

                'timeStamp': {

                    'secondsPastEpoch': seconds,

                    'nanoseconds': nanoseconds

                }

            }

            pv.set(epics_message)

            c += 0.5

    finally:

        server.stop()

 

 

This creates a PV with the following structure:

    float value 10.5

    time_t timeStamp 2021-06-07 13:31:45.733

        long secondsPastEpoch 1623069105

        int nanoseconds 732768297

        int userTag 0

    display_t display

        double limitLow 0

        double limitHigh 10

        string description "Test Display"

        string format "Test Format"

        string units units

    alarm_t alarm

        int severity 0

        int status 0

        string message "test alarm message"

    valueAlarm_t alarm_values

       boolean active true

        float lowAlarmLimit 2

        float lowWarningLimit 3

        float highWarningLimit 8

        float highAlarmLimit 9

        int lowAlarmSeverity 2

        int lowWarningSeverity 1

        int highWarningSeverity 1

        int highAlarmSeverity 2

        byte hysteresis 0

 

As you can hopefully see from the code, I have set up the alarms with severity 0 (NO_ALARM) to begin with and set the severity of the warnings and limits to be MINOR and MAJOR (2 and 3).

 

However, using this set-up I would expect to see the alarm messages raised when the value of the PV approaches 0 or 10, but no alarm messages are displayed. The only time I am able to see messages is if I set the severity of the alarm object to be something other than 0, but this then raises alarm messages for all value states which is not the desired behaviour.

 

Is there something that I’m missing in the configuration of the alarms? Is there something that I need to set to ‘activate’ the logic behind the alarms?

 

Kathryn Baker (she/her)

Software Development for Accelerator Control Systems Graduate

Science and Technology Facilities Council

k.baker at stfc.ac.uk

 

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