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=======================
Guru Meditation Reports
=======================

Zaqar contains a mechanism whereby developers and system administrators can
generate a report about the state of a running Zaqar executable.
This report is called a *Guru Meditation Report* (*GMR* for short).

Generating a GMR
----------------

For wsgi and websocket mode, a *GMR* can be generated by sending the *USR2*
signal to any Zaqar process with support (see below).
The *GMR* will then be outputted standard error for that particular process.

For example, suppose that ``zaqar-server`` has process id ``8675``, and was
run with ``2>/var/log/zaqar/zaqar-server-err.log``.
Then, ``kill -USR2 8675`` will trigger the Guru Meditation report to be
printed to ``/var/log/zaqar/zaqar-server-err.log``.

For uwsgi mode, user should add a configuration in Zaqar's conf file::

    [oslo_reports]
    file_event_handler=['The path to a file to watch for changes to trigger '
                        'the reports, instead of signals. Setting this option '
                        'disables the signal trigger for the reports.']
    file_event_handler_interval=['How many seconds to wait between polls when '
                                 'file_event_handler is set, default value '
                                 'is 1']

For example, you can specify "file_event_handler=/tmp/guru_report" and
"file_event_handler_interval=1" in Zaqar's conf file.

A *GMR* can be generated by "touch"ing the file which was specified in
file_event_handler. The *GMR* will then output to standard error for
that particular process.

For example, suppose that ``zaqar-server`` was run with
``2>/var/log/zaqar/zaqar-server-err.log``, and the file path is
``/tmp/guru_report``.
Then, ``touch /tmp/guru_report`` will trigger the Guru Meditation report to be
printed to ``/var/log/zaqar/zaqar-server-err.log``.

Structure of a GMR
------------------

The *GMR* is designed to be extensible; any particular executable may add
its own sections.  However, the base *GMR* consists of several sections:

Package
  Shows information about the package to which this process belongs,
  including version information

Threads
  Shows stack traces and thread ids for each of the threads within this process

Green Threads
  Shows stack traces for each of the green threads within this process
  (green threads don't have thread ids)

Configuration
  Lists all the configuration options currently accessible via the CONF object
  for the current process

Extending the GMR
-----------------

As mentioned above, additional sections can be added to the GMR for a
particular executable.  For more information, see the inline documentation
about oslo.reports:
`oslo.reports <http://docs.openstack.org/developer/oslo.reports/>`_
