How to turn on error msgs in the main loop?

[nussfluss]

Hello,

I have recently started using pythonSoftIOC. Is there a way to display Python error msgs once softioc.interactive_ioc(globals()) has been called? softioc.softioc.eltc(1) does not seem to change anything.

cheers
nuss

[Araneidae]

I don't think I understand this question. What error messages are you missing?

All interactive_ioc does is run a Python interactive shell, it is no more than a thin wrapper over code.interact(...). If you don't need this any other blocking operation will do, such as cothread.WaitForQuit() if you're using cothread, I expect there's an aioca equivalent.

[nussfluss]

Thx for the fast reply! I made a minimum code snippet showing my problem from your asyncio example (see script#1). I only added a single line. My issue is that the stack traceback is not printed to stdout when the Exception occurs (see terminal#1). That makes debugging soft IOCs really difficult. When I call the function update() from the interactive console, I get the correct error stack though (see terminal#2).

script#1:

# Import the basic framework components.
from softioc import softioc, builder, asyncio_dispatcher
import asyncio

# Create an asyncio dispatcher, the event loop is now running
dispatcher = asyncio_dispatcher.AsyncioDispatcher()

# Set the record prefix
builder.SetDeviceName("MY-DEVICE-PREFIX")

# Create some records
ai = builder.aIn('AI', initial_value=5)
ao = builder.aOut('AO', initial_value=12.45, always_update=True,
                  on_update=lambda v: ai.set(v))

# Boilerplate get the IOC started
builder.LoadDatabase()
softioc.iocInit(dispatcher)

# Start processes required to be run after iocInit
async def update():
    while True:
        ai.set(ai.get() + 1)
        raise Exception         <---------------------------------------------------------- line added
        await asyncio.sleep(1)

asyncio.run_coroutine_threadsafe(update(), dispatcher.loop)

# Finally leave the IOC running with an interactive shell.
softioc.interactive_ioc(globals())

terminal#1:

[stephan@eg8750 bpm-anomaly-detection]$ python reproduce_problem.py 
Starting iocInit
############################################################################
## EPICS 7.0.6.1
## Rev. 7.0.6.99.2.0
############################################################################
cas warning: Configured TCP port was unavailable.
cas warning: Using dynamically assigned TCP port 36139,
cas warning: but now two or more servers share the same UDP port.
cas warning: Depending on your IP kernel this server may not be
cas warning: reachable with UDP unicast (a host's IP in EPICS_CA_ADDR_LIST)
iocRun: All initialization complete
2022-06-21T10:16:14.067 Using dynamically assigned TCP port 42421.
Python 3.10.5 (main, Jun  6 2022, 18:49:26) [GCC 12.1.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)

terminal#2:

>>> asyncio.run(update())
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/usr/lib/python3.10/asyncio/runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "/usr/lib/python3.10/asyncio/base_events.py", line 646, in run_until_complete
    return future.result()
  File "/home/stephan/programs/python_packages/bpm-anomaly-detection/reproduce_problem.py", line 24, in update
    raise Exception
Exception

[coretl]

This is a failing of the example code. We put some exception handling in the dispatcher, so if an function passed to on_update fails we get the traceback printed, but we don't do anything with the long running update function in the example. We can make use of the same exception handling by scheduling it with the dispatcher:

...
# Start processes required to be run after iocInit
async def update():
    while True:
        ai.set(ai.get() + 1)
        await asyncio.sleep(1)
        raise Exception("Boom")

dispatcher(update)

# Finally leave the IOC running with an interactive shell.
softioc.interactive_ioc(globals())

This now prints

Starting iocInit
############################################################################
## EPICS 7.0.6.1
## Rev. 7.0.6.99.2.0
############################################################################
iocRun: All initialization complete
Python 3.7.2 (default, Jan 20 2020, 11:03:41) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-39)] on linux
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> ERROR:root:Exception when awaiting callback
Traceback (most recent call last):
  File "/dls/science/users/tmc43/common/python/pythonSoftIOC/softioc/asyncio_dispatcher.py", line 35, in async_wrapper
    await ret
  File "example_asyncio_ioc.py", line 26, in update
    raise Exception("Boom")
Exception: Boom

The logging message isn't the best though, I'll make an issue to track this

[nussfluss]

dispatcher(update)

Thank you very much! That works indeed very well!!! 👍 I do not quite understand what the dispatcher call does but I am only getting started with asynchronous coding. So maybe I will get it in the future.

[nussfluss]

future = asyncio.run_coroutine_threadsafe(update(), dispatcher.loop)
print(future.result())

Thanks to you, as well!! That also works! 👍 The previous solution seems simpler though and I will stick with it if there is no catch.

[AlexanderWells-diamond]

future = asyncio.run_coroutine_threadsafe(update(), dispatcher.loop)

Thanks to you, as well!! That also works! +1 The previous solution seems simpler though and I will stick with it if there is no catch.

There's no catch to it, I realised that my suggestion was actually worse than coretl's and so I deleted it.

[nussfluss]

Well it worked and I am glad that you replied!