From: Roman Kagan <rkagan@virtuozzo.com>
To: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Cc: "kwolf@redhat.com" <kwolf@redhat.com>,
Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>,
Denis Lunev <den@virtuozzo.com>,
"qemu-block@nongnu.org" <qemu-block@nongnu.org>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"mreitz@redhat.com" <mreitz@redhat.com>
Subject: Re: [PATCH v3] iotests: Test NBD client reconnection
Date: Mon, 11 Nov 2019 09:48:25 +0000 [thread overview]
Message-ID: <20191111094822.GA126513@rkaganb.sw.ru> (raw)
In-Reply-To: <55df73cb-ffe8-e4c6-b97a-346bdf28f1e2@virtuozzo.com>
On Mon, Nov 11, 2019 at 12:18:48PM +0300, Andrey Shinkevich wrote:
>
>
> On 08/11/2019 17:05, Roman Kagan wrote:
> > On Fri, Nov 08, 2019 at 01:49:50PM +0000, Vladimir Sementsov-Ogievskiy wrote:
> >> 01.11.2019 19:54, Andrey Shinkevich wrote:
> >>> +def check_proc_NBD(proc, connector):
> >>> + try:
> >>> + exitcode = proc.wait(timeout=10)
> >>> +
> >>> + if exitcode < 0:
> >>> + log('NBD {}: EXIT SIGNAL {}\n'.format(connector, -exitcode))
> >>> + log(proc.communicate()[0])
> >>> + else:
> >>> + line = proc.stdout.readline()
> >>
> >>
> >> could we use proc.communicate() for both cases, what is the difference?
> >
> > In fact if proc produces any non-trivial amount of output you are better
> > off using .communicate() otherwise your child may block on output and
> > never exit. See
> > https://docs.python.org/3/library/subprocess.html#subprocess.Popen.communicate
> > for how to express the above logic correctly. The exit code *after*
> > .communicate is available in .returncode.
> >
>
> The pattern by the link above does not work (Python3):
>
> proc = subprocess.Popen(...)
> try:
> outs, errs = proc.communicate(timeout=15)
> except TimeoutExpired:
> proc.kill()
> outs, errs = proc.communicate()
>
> as 'proc' cannot be used for output after being killed. It results in
> another exception being raised.
Of course it can't. You need to use the strings returned by
.communicate().
Roman.
next prev parent reply other threads:[~2019-11-11 9:49 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-01 16:54 [PATCH v3] iotests: Test NBD client reconnection Andrey Shinkevich
2019-11-08 13:49 ` Vladimir Sementsov-Ogievskiy
2019-11-08 14:05 ` Roman Kagan
2019-11-11 9:18 ` Andrey Shinkevich
2019-11-11 9:48 ` Roman Kagan [this message]
2019-11-11 9:07 ` Andrey Shinkevich
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