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python/aqmp: Disable logging messages by default

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AQMP is a library, and ideally it should not print error diagnostics
unless a user opts into seeing them. By default, Python will print all
WARNING, ERROR or CRITICAL messages to screen if no logging
configuration has been created by a client application.

In AQMP's case, ERROR logging statements are used to report additional
detail about runtime failures that will also eventually be reported to the
client library via an Exception, so these messages should not be
rendered by default.

(Why bother to have them at all, then? In async contexts, there may be
multiple Exceptions and we are only able to report one of them back to
the client application. It is not reasonably easy to predict ahead of
time if one or more of these Exceptions will be squelched. Therefore,
it's useful to log intermediate failures to help make sense of the
ultimate, resulting failure.)

Add a NullHandler that will suppress these messages until a client
application opts into logging via logging.basicConfig or similar. Note
that upon calling basicConfig(), this handler will *not* suppress these
messages from being displayed by the client's configuration.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20210923004938.3999963-8-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
This commit is contained in:
John Snow 2021-09-22 20:49:28 -04:00
parent 3e55dc35b8
commit 3a3d84f5ec
1 changed files with 4 additions and 0 deletions
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4
python/qemu/aqmp/__init__.py
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@ -21,6 +21,7 @@ managing QMP events.
# This work is licensed under the terms of the GNU GPL, version 2. See
# the COPYING file in the top-level directory.
import logging
import warnings
from .error import AQMPError
@ -41,6 +42,9 @@ Proceed with caution!
warnings.warn(_WMSG, FutureWarning)
# Suppress logging unless an application engages it.
logging.getLogger('qemu.aqmp').addHandler(logging.NullHandler())
# The order of these fields impact the Sphinx documentation order.
__all__ = (