qa-specs/specs/devstack/counter-inspection.rst

Inspect counters for data collection and gating purposes

Problem description

OpenStack projects vary on their impact to the underlying infrastructure that they rely on greatly. This is hard to measure without going to a full scale deployment, but we should be able to measure the impact by inspecting counters already maintained by the system.

Proposed change

• Create a new "OpenStack QA Tools" repository to house small tools written in python for purposes such as this.
  • Create a tool, os-collect-counters, which collects relevant counters from any backends it can reach using its own configuration and outputs a JSON mapping with all counters. Includes ability to delta with a previous run to allow showing impact on the counters for a given time window.
    • Initial counters will be at a minimum a set of MySQL counters (such as Innodb_bytes_written) and published messages from the RabbitMQ management interface, summarized by scope that can be inferred from each queue name.
• Leverage existing subunit/statsd/graphite infrastructure to record results of several tests in the devstack gate.
  • For each run, the JSON from os-collect-counters will be added as an attachment to the subunit stream.
  • The counters in the attachment will be fed into statsd/graphite to allow establishing trends.
    • This will be facilitated by adding attachment storage plugins to subunit2sql. The plugin used for OpenStack gate jobs will be specific to OpenStack's infrastructure and look for the specifically named attachment to push into statsd/graphite.
• Monitor counters for stable indicators and identify the best predictors of problems.

  • Once stable counters are identified, create an upper bounds for these counters to help prevent new changes in the system from accidentally introducing an inordinate amount of cost into the tested code paths.

    Since there are daunting social issues around failing gate tests on global collisions, warnings and bugs about said warnings are likely the only reasonable outcome we can achieve. It will take a considerable amount of community agreement to make these limits hard.

Implementation

A new python repo, os-performance-tools, has already been created, and will be maintained for the purposes of extracting and pushing counters into statsd/graphite. This will include a subunit2sql attachments plugin and code to output the counters as a subunit attachment.

Assignee(s)

Primary assignee:

• Clint Byrum <clint@fewbar.com>

Milestones

Target Milestone for completion:

Mitaka-2

Work Items

• Create tools to emit counters from a running installation
• Modify devstack gate job output to include counters
• Add subunit2sql attachment plugin to subunit2sql workers to push counters to infra graphite
• Analyze data for stable counters and useful trends
• Add upper bounds check to devstack gate

Dependencies

References