Re: [Qemu-block] [PATCH v4 18/20] iotests: add QMP event waiting queue

[Stefan Hajnoczi]

On Fri, Mar 20, 2015 at 03:17:01PM -0400, John Snow wrote:
> +# Test if 'match' is a recursive subset of 'event'
> +def event_match(event, match = None):

Not worth respinning but PEP8 says there should be no spaces around the
'=' for keyword arguments:
https://www.python.org/dev/peps/pep-0008/#whitespace-in-expressions-and-statements

> +    def event_wait(self, name='BLOCK_JOB_COMPLETED', maxtries=3, match=None):
> +        # Search cached events
> +        for event in self._events:
> +            if (event['event'] == name) and event_match(event, match):
> +                self._events.remove(event)
> +                return event
> +
> +        # Poll for new events
> +        for _ in range(maxtries):
> +            event = self._qmp.pull_event(wait=True)
> +            if (event['event'] == name) and event_match(event, match):
> +                return event
> +            self._events.append(event)
> +
> +        return None

I'm not sure if maxtries is useful.  Why is a particular number of
skipped events useful to the caller and how do they pick the magic
number?

If you added the argument because this is a blocking operation then we
should probably use timeouts instead.  Timeouts will bail out even if
QEMU is unresponsive.

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