Re: [python API] logging

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On Fri, Sep 14, 2012 at 10:28 PM, Alon Bar-Lev <alonbl@xxxxxxxxxx> wrote:


----- Original Message -----
> From: "tim lauridsen" <tim.lauridsen@xxxxxxxxx>
> To: "Yellowdog Updater, Modified" <yum@xxxxxxxxxxxxxxxxx>
> Sent: Friday, September 14, 2012 8:22:17 AM
> Subject: Re: [python API] logging
>
> On Wed, Sep 12, 2012 at 9:40 PM, Alon Bar-Lev < alonbl@xxxxxxxxxx >
> wrote:
>
>
> Hello All,
>
> I am trying to use yum via python.
>
> It is great apart of one issue I would like to discuss - logging.
>
> Going over the sources I see a lot of logs.
>
> At least:
>
> 'yum', 'yum.Depsolve', 'yum.RepoStorage', 'yum.Repos',
> 'yum.YumBase', 'yum.filelogging',
> 'yum.filelogging.RPMInstallCallback'
> 'yum.plugin', 'yum.verbose',
> 'yum.verbose.Depsolve',
> 'yum.verbose.ProcessTrasactionBaseCallback', 'yum.verbose.Repos',
> 'yum.verbose.YumPlugins', 'yum.verbose.plugin',
> 'yum.verbose.YumBase'
>
> Having so much logs is great, however the yum implementation lazy
> initialize the logs as objects are constructed. This override any
> setting I may have for these logs. Especially the stdout, stderr
> setting.
>
> My mission is to use yum pragmatically an write my own logging, thus
> writing even a single message to stdout/stderr breaks the entire
> application.
>
> Another issue is the large number of logs - as in python the log must
> be explicitly initialized, meaning it is not enough to initialize
> the 'yum' log to have effect on all the other logs.
> So even if explicit logs are properly initialize as application
> evolves it can add new logs, which will break the application.
>
> What I suggest is to add a logging object that will initialize all
> logging for the application at yumbase constructor, then user may
> override the settings as desired.
>
> The logging object will also hold a list of all available logs, so
> implementation can know what logs are available for configuration.
>
> Maybe I missed some feature within the library... I will be happy to
> know.
>
> Thoughts?
> Alon.
>
>
> http://docs.python.org/library/logging.html
>
>
> Take a look at the propagate attribute to Logger class
> setting it to False, will do what you want
>
>
> just use 'yum' as logroot and it will get all yum logging.
>
>
> Check this yumex code for examples for how to create a logger there
> shows output in a gtk.Textview

Hello Tim

Thank you so much for your help!

The propagate is good, but as root loggers set their own handlers there is a need to to setup at least two: 'yum', 'rhsm'... and in future any new one...

However, even if I catch all logs, I still end up with the following in stdout:

---
     for l in ('yum', 'rhsm'):
         log = logging.getLogger(l)
         log.propagate = False
         log.handlers = []
         log.addHandler(miniyum._yumlogger._loghandler(this._output
---

---
Loaded plugins: product-id, rhnplugin
Repository rhel-source is listed more than once in the configuration
Repository rhel-source-beta is listed more than once in the configuration

Freeing read locks for locker 0x1b: 1242/139773667890944
Freeing read locks for locker 0x1d: 1242/139773667890944
Freeing read locks for locker 0x1e: 1242/139773667890944
Freeing read locks for locker 0x1f: 1242/139773667890944
Freeing read locks for locker 0x20: 1242/139773667890944
Freeing read locks for locker 0x21: 1242/139773667890944
Freeing read locks for locker 0x22: 1242/139773667890944

warning: rpmts_HdrFromFdno: Header V3 RSA/SHA256 Signature, key ID fd431d51: NOKEY
Retrieving key from file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release

No package matched to remove: cman
Package qemu-kvm-tools is obsoleted by qemu-kvm-rhev-tools, trying to install 2:qemu-kvm-rhev-tools-0.12.1.2-2.295.el6_3.2.x86_64 instead
---

So I had to put my own Logger class to ignore 'yum', 'rhsm'... Not sure why the propagate does not work correctly.

---
      def addHandler(self, hdlr):
          if self.name.startswith('yum') or self.name.startswith('rhsm'):
              logging.Logger.handlers = []
              logging.Logger.addHandler(
                  self,
                  myhandler
              )
              else:
                  logging.Logger.addHandler(self, hdlr)
---

Now, I left with:
---
Freeing read locks for locker 0x1b: 1242/139773667890944
Freeing read locks for locker 0x1d: 1242/139773667890944
Freeing read locks for locker 0x1e: 1242/139773667890944
Freeing read locks for locker 0x1f: 1242/139773667890944
Freeing read locks for locker 0x20: 1242/139773667890944
Freeing read locks for locker 0x21: 1242/139773667890944
Freeing read locks for locker 0x22: 1242/139773667890944

warning: rpmts_HdrFromFdno: Header V3 RSA/SHA256 Signature, key ID fd431d51: NOKEY
---

So I had to dup /dev/null to stdout, stderr during YumBase.process() to cut the above messages as well, as I could not find where these are coming out from, and almost sure that there are other surprises.

I think that like in Java, an API should not set its own handlers... and make sure there is no output unless explicitly registered.

Thanks,
Alon
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You can silence the build-in yum output by setting errorlevel=0 & debuglevel=0

See.

https://github.com/timlau/yum-daemon/blob/master/yumdaemon/yumdaemon#L1188

The cause that yum has automatic setup of the logger output is to make it easier for API users to use it without having to setup there own loggers, they don't dont normally not have the same
requirement as you have :)

Tim
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