DevStack Logging and Service Names

DevStack Logging and Service Names

NOTE: This spec is still a work in progress, it is being posted to get some early feedback on scope and ordering of steps.

https://blueprints.launchpad.net/tempest/+spec/devstack-logging-and-service-names

DevStack is in need of updates to its log file handling and service naming, both of which were appropriate for the originalscreen-based installs with a handful of services.

This spec contains both the log file reform as well as the service name updates as they are a bit intertwined so some steps will address them both as necessary.

Problem description

DevStack’s logging configuration was initially based on saving screen logs, as part of the development of not using screen the logging was kept compatible and it became obvious that the original special case was not required.

Historically DevStack has used abbreviated service names for identifying services to enable, naming log files and as window names in screen. OpenStack has grown to the point that the abbreviated names are too confusing and non-obvious, especially for the not-so-recently renamed Neutron.

These topics were covered at the Paris summit, notes in the OpenStack Etherpad.

Proposed change

Logging

Update DevStack’s logging configuration to set a logging directory rather than parsing that out of a filename. Ultimately eliminate the use of SCREEN_LOGDIR.

  • Use LOGDIR as the primary setting in local.conf for log locations, default to ${DEST}/logs if LOGFILENAME is not set.
  • Continue to use LOGFILENAME if set, if LOGFILE is not set continue to set it to $(dirname $LOGFILENAME).
  • Deprecate SCREEN_LOGDIR and use LOGDIR instead. For a compatibility period leave symlinks in the old screen log locations.
  • Remove screen- from the beginning of the service log filenames
  • Service log files will implicitly be renamed as the service names change (see above)

Grenade should work seamlessly as it lets both DevStack runs do their thing and devstack-gate contains all of the specifics that need updating fro Grenade jobs.

Service Names

Use fully-formed names for service names (like ceilometer does today): nova-compute, glance-registry, etc. The names will use the project name, as used in devstack/lib/* followed by ‘-‘ and a descriptive name of the service.

Also allow multiple instances of service names, as in running the fake hypervisor has a number of nova-cpu instances. Append an instance counter to the name similar to how n-cpu-N is currently handled. Optionally use a ‘:’ as the separator between the service name and instance number. This will be used in the log file name so it must be shell-safe.

  • There needs to be a mapping of the old abbreviated names to the full names to handle backward compatibility.

  • This will make ENABLED_SERVICES very long by default and harder to scan visually. Is this a real concern? With the recent forced update to using Bash 4 we could use an associative array to do the mapping and the enabled list in a single shot.

    (Note: We just started doing something in Grenade to handle mapping abbreviated service names-> processes (https://review.openstack.org/#/c/113405/5/check-sanity) This would help move that logic into DevStack and also help provide other mappings (ie, service name -> database name))

  • Log filenames will change, but there is more on that front (see below).

  • Grenade will need to be updated before the backward compatibility can be removed.

Implementation

Assignee(s)

Primary assignee:
dtroyer

Work Items

  1. Logging: change the log file names in SCREEN_LOGDIR so the actual files with the timestamp in the names end with the timestamp:

    screen-c-sch.2014-12-10-193405.log becomes  screen-c-sch.log.2014-12-10-193405
    
  2. Logging: change devstack-gate to look for *.log rather than symlinks to select the log files it copies out of screen-logs.

  3. Logging: switch from SCREEN_LOGDIR to LOGDIR for log tests. This will move the log files out of SCREEN_LOGDIR so leave backward-compatibility symlinks in the old locations. (This is the reason for #2 as devstack-gate selects the files top copy by the symlink attribute.)

  4. Logging: follow up in devstack-gate to use LOGDIR directly and copy log files from there.

  5. Logging: after a time, remove the symlinks from SCREEN_LOGDIR.

  6. Services: change how multiple instances of services are handled, currently in lib/nova start_nova_compute() and stop_nova_compute(). If the separator is changed the config filenames will also change, reconsider if parsing is necessary.

  7. Services: build the new service naming structures and compatibility.

  8. Services and Logging: switch logging to use the new service names and ensure nothing gets lost in devstack-gate copies.

Dependencies

The only dependencies are in the order of changes required in multiple projects.

Creative Commons Attribution 3.0 License

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