Experimental Physics and
Industrial Control System

Today I found a “solution” to this that does not make sense: if I start the softioc (the call to softioc.iotInit()) in the first thread, and not in the main process, everything works as expected.

Our engineers are unable to explain this behavior.  I hope there’s someone here on the list that might know why!

Example code that demonstrates the failure:

--------------------

import os

import time

import threading

os.environ['EPICS_CA_SERVER_PORT'] = '5100'

os.environ['EPICS_CA_ADDR_LIST'] = 'localhost:5100'

os.environ['EPICS_CA_AUTO_ADDR_LIST'] = 'NO'

try:

    import epicscorelibs.path.pyepics

except ImportError:

    pass

import epics

from softioc import softioc, builder

# Create a long record for this demo

long = builder.longOut('prefix:long', initial_value=1)

builder.LoadDatabase()

softioc.iocInit()

def thread1():

    while True:

        val = long.get()

        long.set(val + 1)

        print(f'thread1: {val}')

        time.sleep(1)

def thread2():

    pv = epics.PV('prefix:long')

    while True:

        val = pv.get()

        print(f'thread2: {val}')

        time.sleep(1)

t1 = threading.Thread(target=thread1, daemon=True)

t2 = threading.Thread(target=thread2, daemon=True)

t1.start()

t2.start()

time.sleep(10)

Example that works; note the only change is the movement of the .iocInit() line down into thread1:

--------------------

import os

import time

import threading

os.environ['EPICS_CA_SERVER_PORT'] = '5100'

os.environ['EPICS_CA_ADDR_LIST'] = 'localhost:5100'

os.environ['EPICS_CA_AUTO_ADDR_LIST'] = 'NO'

try:

    import epicscorelibs.path.pyepics

except ImportError:

    pass

import epics

from softioc import softioc, builder

# Create a long record for this demo

long = builder.longOut('prefix:long', initial_value=1)

builder.LoadDatabase()

def thread1():

    softioc.iocInit()

    while True:

        val = long.get()

        long.set(val + 1)

        print(f'thread1: {val}')

        time.sleep(1)

def thread2():

   pv = epics.PV('prefix:long')

    while True:

        val = pv.get()

        print(f'thread2: {val}')

        time.sleep(1)

t1 = threading.Thread(target=thread1, daemon=True)

t2 = threading.Thread(target=thread2, daemon=True)

t1.start()

t2.start()

time.sleep(10)

The output when it fails:

$ python3 ./demoFailingDaemon.py

Starting iocInit

############################################################################

## EPICS 7.0.6.0

## Rev. 7.0.6.99.1.0

############################################################################

iocRun: All initialization complete

thread1: 1

thread1: 2

thread1: 3

thread2: None

thread1: 4

thread1: 5

thread2: None

thread1: 6

thread1: 7

thread1: 8

thread2: None

thread1: 9

thread1: 10

thread1: 11

The output when it works:

$ python3 ./demoWorkingDaemon.py

Starting iocInit

############################################################################

## EPICS 7.0.6.0

## Rev. 7.0.6.99.1.0

############################################################################

iocRun: All initialization complete

thread1: 1

thread2: 2

thread1: 2

thread2: 3

thread1: 3

thread2: 4

thread1: 4

thread2: 5

thread1: 5

thread2: 6

thread1: 6

thread2: 7

thread1: 7

thread2: 8

thread1: 8

thread2: 9

thread1: 9

thread2: 10

thread1: 10

thread2: 11

Paul