Re: [Libguestfs] [libnbd PATCH v2 1/5] python: tests: Fix error handling

On 02/03/22 23:49, Nir Soffer wrote: > On Thu, Feb 3, 2022 at 10:26 PM Eric Blake <eblake(a)redhat.com&gt; wrote: >> >> Like a lot of the C examples, the aio copy test ignores read and write >> errors in the completion callback, which can cause silent data >> corruption. The failure in the test is not critical, but this is a bad >> example that may be copied by developers to a real application. >> >> The test dies with an assertion failure now if completion callback >> fails. Tested with the temporary patch of: >> >> | diff --git i/python/t/590-aio-copy.py w/python/t/590-aio-copy.py >> | index 861fa6c8..4cd64d83 100644 >> | --- i/python/t/590-aio-copy.py >> | +++ w/python/t/590-aio-copy.py >> | @@ -117,7 +117,8 @@ src.set_handle_name("src") >> | dst = nbd.NBD() >> | dst.set_handle_name("dst") >> | src.connect_command(["nbdkit", "-s", "--exit-with-parent", "-r", >> | - "pattern", "size=%d" % disk_size]) >> | + "--filter=error", "pattern", "error-pread-rate=1", >> | + "size=%d" % disk_size]) >> | dst.connect_command(["nbdkit", "-s", "--exit-with-parent", >> | "memory", "size=%d" % disk_size]) >> | asynch_copy(src, dst) >> --- >> python/t/590-aio-copy.py | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/python/t/590-aio-copy.py b/python/t/590-aio-copy.py >> index 6cde5934..861fa6c8 100644 >> --- a/python/t/590-aio-copy.py >> +++ b/python/t/590-aio-copy.py >> @@ -1,5 +1,5 @@ >> # libnbd Python bindings >> -# Copyright (C) 2010-2019 Red Hat Inc. >> +# Copyright (C) 2010-2022 Red Hat Inc. >> # >> # This program is free software; you can redistribute it and/or modify >> # it under the terms of the GNU General Public License as published by >> @@ -36,6 +36,7 @@ def asynch_copy(src, dst): >> # This callback is called when any pread from the source >> # has completed. >> def read_completed(buf, offset, error): >> + assert not error > > This works for the test, since the test is not compiled > to pyc file, which removes the asserts (like C -DNODBUG) > by default when building rpms. > > If someone will copy this to a real application they will have no > error checking. I consider this a catastrophic bug in python, to be honest. Eliminating assertions should never be done without an explicit request from whoever builds the package.