An unexpected error occured in promise module

[larsewi]

I'm trying to write a custom RSS promise type using python.

When running a policy using mu custom promise type, I get the following error:
error: An unexpected error occured in promise module (rss promise, promiser: '/tmp/ISS-oldest.txt' module: '/var/cfengine/masterfiles/services/../modules/promises/rss.py
The error happens right after calling return Result in the evaluate_promise function in my promise module.

Not the most descriptive error message, thus not quite sure what I'm doing wrong. Any ideas to what might be the issue?

[olehermanse]

Thanks for posting the question @larsewi . Could you try running in debug mode and attaching the log messages that come before the error message?

cf-agent -K --debug -f test.cf

[olehermanse]

@larsewi Yep, that looks good and is what I meant. The advantage now is that you can debug the module more easily. (You can run it in the python debugger or start adding print statements). The problem is definitely in the library, cfengine.py.

Here is the code which is supposed to log the exception:

core/docs/custom_promise_types/cfengine.py

Lines 168 to 174 in 3e1a39b

	def _log(self, level, message):
	# Message can be str or an object which implements __str__()
	# for example an exception:
	message = str(message).replace("\n", r"\n")
	assert "\n" not in message
	self._out.write(f"log_{level}={message}\n")
	self._out.flush()

@vpodzime do you see the problem?

[vpodzime]

@vpodzime do you see the problem?

No, it looks weird. Like if message was really an empty string or just a newline. Which is weird because it's supposed to be str(e) where e is an Exception, right?

[olehermanse]

Which is weird because it's supposed to be str(e) where e is an Exception, right?

Yes, exactly. message is supposed to be an exception here, and it looks like str(message) just returns empty string.

[vpodzime]

We have found a problem in the cfengine.py library that was fixed in #4498. It was causing an AssertionError to be raised and str(AssertionError()) is just an empty string (:open_mouth:).

[larsewi]

Thank you @vpodzime @olehermanse . My promise module works now !