Antoni S. Puimedon d091f98d29 documentation: fix formatting

It is good practice for those reading on split terminal consoles to
limit the lines to 80 characters for text (not necessarily for
embedded code. All the other documentation of the project follows it,
so I made this one compliant too.

Change-Id: I48be9e542d9c1a94ae8b9f1c081a702b4ba298f4

2015-08-25 10:42:21 +02:00

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Guru Meditation Reports

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

Generating a GMR

A GMR can be generated by sending the USR1 signal to any Magnum process with support (see below). The GMR will then be outputted as standard error for that particular process.

For example, suppose that magnum-api has process id 8675, and was run with 2>/var/log/magnum/magnum-api-err.log. Then, kill -USR1 8675 will trigger the Guru Meditation report to be printed to /var/log/magnum/magnum-api-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 informations.
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.

Adding Support for GMRs to New Executables

Adding support for a GMR to a given executable is fairly easy.

First import the module:

from oslo_reports import guru_meditation_report as gmr
from nova import version

Then, register any additional sections (optional):

TextGuruMeditation.register_section('Some Special Section',
                                    some_section_generator)

Finally (under main), before running the "main loop" of the executable (usually service.server(server) or something similar), register the GMR hook:

TextGuruMeditation.setup_autorun(version)

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 under oslo.reports

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