Re: [PATCH v10 14/14] iotests: use python logging for iotests.log()

[Kevin Wolf]

Am 31.03.2020 um 02:00 hat John Snow geschrieben:
> We can turn logging on/off globally instead of per-function.
> 
> Remove use_log from run_job, and use python logging to turn on
> diffable output when we run through a script entry point.
> 
> iotest 245 changes output order due to buffering reasons.
> 
> 
> An extended note on python logging:
> 
> A NullHandler is added to `qemu.iotests` to stop output from being
> generated if this code is used as a library without configuring logging.
> A NullHandler is only needed at the root, so a duplicate handler is not
> needed for `qemu.iotests.diff_io`.
> 
> When logging is not configured, messages at the 'WARNING' levels or
> above are printed with default settings. The NullHandler stops this from
> occurring, which is considered good hygiene for code used as a library.
> 
> See https://docs.python.org/3/howto/logging.html#library-config
> 
> When logging is actually enabled (always at the behest of an explicit
> call by a client script), a root logger is implicitly created at the
> root, which allows messages to propagate upwards and be handled/emitted
> from the root logger with default settings.
> 
> When we want iotest logging, we attach a handler to the
> qemu.iotests.diff_io logger and disable propagation to avoid possible
> double-printing.
> 
> For more information on python logging infrastructure, I highly
> recommend downloading the pip package `logging_tree`, which provides
> convenient visualizations of the hierarchical logging configuration
> under different circumstances.
> 
> See https://pypi.org/project/logging_tree/ for more information.
> 
> Signed-off-by: John Snow <address@hidden>
> Reviewed-by: Max Reitz <address@hidden>

Should we enable logger if -d is given?

Previously we had:

$ ./check -d -T -raw 281
[...]
281 not run: not suitable for this image format: raw
281      not run    [15:39:03] [15:39:04]                    not suitable for 
this image format: raw
Not run: 281

After this series, the first line of output from notrun() is missing.
Not that I think it's important to have the line, but as long as we
bother to call logger.warning(), I thought that maybe we want to be able
to actually see the effect of it somehwere?

Kevin