Sean McGinnis a77335012f Update docs to generate Guru Meditation Report

Guru Meditation Reports (GMR) code in oslo.reports was recently updated
to expect SIGUSR2 as opposed to SIGUSR1, because it is reserved by
Apache 'mod_wsgi' for its own use.

Signal was changed and merged in change:
I9d3b6079ba2cca41fe4723723a6f80b2c3c0b9c0

Change-Id: Id58dd3c32b095f4c6b14caf650d36f2fc7dfb12c

2015-10-21 17:41:06 -05:00

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Guru Meditation Reports

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

Generating a GMR

A GMR can be generated by sending the USR2 signal to any Cinder process with support (see below). The GMR will then be outputted standard error for that particular process.

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

Adding Support for GMRs to New Executables

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

First import the module (currently residing in oslo-incubator), as well as the Cinder version module:

from oslo_reports import guru_meditation_report as gmr
from cinder 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 about oslo.reports: oslo.reports

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