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Re: [PATCH 12/15] iotests: Disable AQMP logging under non-debug modes


From: John Snow
Subject: Re: [PATCH 12/15] iotests: Disable AQMP logging under non-debug modes
Date: Fri, 17 Sep 2021 22:14:00 -0400



On Fri, Sep 17, 2021 at 8:58 PM John Snow <jsnow@redhat.com> wrote:


On Fri, Sep 17, 2021 at 10:30 AM Hanna Reitz <hreitz@redhat.com> wrote:
On 17.09.21 07:40, John Snow wrote:
> Disable the aqmp logger, which likes to (at the moment) print out
> intermediate warnings and errors that cause session termination; disable
> them so they don't interfere with the job output.
>
> Leave any "CRITICAL" warnings enabled though, those are ones that we
> should never see, no matter what.

I mean, looks OK to me, but from what I understand (i.e. little),
qmp_client doesn’t log CRITICAL messages, at least I can’t see any. Only
ERRORs.


There's *one* critical message in protocol.py, used for a circumstance that I *think* should be impossible. I do not think I currently use any WARNING level statements.
 
I guess I’m missing some CRITICAL messages in external functions called
from qmp_client.py, but shouldn’t we still keep ERRORs?

...Mayyyyyybe?

The errors logged by AQMP are *almost always* raised as Exceptions somewhere else, eventually. Sometimes when we encounter them in one context, we need to save them and then re-raise them in a different execution context. There's one good exception to this: My pal, EOFError.

If the reader context encounters EOF, it raises EOFError and this causes a disconnect to be scheduled asynchronously. *Any* Exception that causes a disconnect to be scheduled asynchronously is dutifully logged as an ERROR. At this point in the code, we don't really know if the user of the library considers this an "error" yet or not. I've waffled a lot on how exactly to treat this circumstance. ...Hm, I guess that's really the only case where I have an error that really ought to be suppressed. I suppose what I will do here is: if the exception happens to be an EOFError I will drop the severity of the log message down to INFO. I don't know why it takes being challenged on this stuff to start thinking clearly about it, but here we are. Thank you for your feedback :~)

--js

Oh, CI testing reminds me of why I am a liar here.

the mirror-top-perms test intentionally expects not to be able to connect, but we're treated to these two additional lines of output:

+ERROR:qemu.aqmp.qmp_client.qemub-2536319:Negotiation failed: EOFError
+ERROR:qemu.aqmp.qmp_client.qemub-2536319:Failed to establish session: EOFError

Uh. I guess a temporary suppression in mirror-top-perms, then ...? In most other cases I rather imagine we do want to see this kind of output to help give more information about how things have failed -- they ARE errors. We just happen to not care about them right here. The only thing I don't exactly like about this is that it requires some knowledge by the caller to know to disable it. It makes writing negative tests a bit more annoying because the library leans so heavily on yelling loudly when it encounters problems.

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