Adopt Oslo Guru reports

https://blueprints.launchpad.net/neutron/+spec/guru-meditation-report

This spec proposes adoption for Oslo Guru reports in Neutron. The new feature will enhance debugging capabilities of all official Neutron services, by providing an easy way to gather runtime data about current threads and configuration, among other things, to developers, operators, and tech support.

Problem Description

Currently Neutron does not have a way to gather runtime data from active service processes. The only information that is available to deployers, developers, and tech support to analyze is what was actually logged by the service in question. Additional data could be usefully used to debug and solve problems that occur during Neutron operation. Among other things, we could be interested in stack traces of all (both green and real) threads, pid/ppid info, package version, configuration as seen by the service, etc.

Oslo Guru reports provide an easy way to add support for gathering this kind of information to any service. Report generation is triggered by sending a special (USR1) signal to a service. Reports are generated on stderr, that can be piped into system log, if needed.

Guru reports are extensible, meaning that we will be able to add more information to those reports in case we see it needed. For example, we could add a new report section for L2 Open vSwitch agent to dump flows and other relevant networking data to the report. Note that this spec does not cover any of possible extensions and just lays the foundation for them.

Guru reports are supported by Nova.

Proposed Change

First, a new oslo-incubator module (reports.*) should be synchronized into neutron tree. Then, each service entry point should be extended to register reporting functionality before proceeding to its real main(). This may be achieved through utilizing neutron/cmd/__init__.py or a similar way that would automatically expose the functionality to all services.

After neutron core repository adopts the feature, advanced services’ repositories will be similarly updated to utilize the module.

Data Model Impact

None.

REST API Impact

None.

Security Impact

In theory, the change could expose service internals to someone who is able to send the needed signal to a service. That said, we can probably assume that the user is already authorized to achieve a lot more than just having an access to stack traces and configuration used. Also, if deployers are afraid of the information leak for some reason, they could also make sure their stderr output is channeled into safe place.

Notifications Impact

None.

Other End User Impact

None.

Performance Impact

The feature does not require any additional resources until it’s triggered by the user. Default report generation is not expected to take too long. Report extensions will need to be assessed on case by case basis. In any case, reports are not expected to be generated too often and are assumed to be debugging capability, not something to trigger once per minute just in case.

IPv6 Impact

None.

Other Deployer Impact

Deployers may be interested in making sure those reports are collected somewhere (e.g. stderr should be captured by syslog).

Developer Impact

None.

Community Impact

None.

Alternatives

We could reimplement the wheel, but we hopefully won’t.

Implementation

Assignee(s)

ihrachyshka

Work Items

  • sync reports.* module from oslo-incubator
  • adopt it in all neutron services using a wrapper located under neutron/cmd/...

Note: the feature was once proposed for inclusion but was later abandoned: https://review.openstack.org/#/q/project:openstack/neutron+topic:bp/guru-meditation-report,n,z

Dependencies

reports.* module is currently going thru graduation consideration. In case it’s graduated into oslo.reports library before neutron switches to it, we won’t actually need to sync any code from oslo-incubator but instead add a new external oslo dependency. If Neutron switches to the module before graduation is complete, then we’ll need to adopt oslo.reports later as part of usual oslo liaison effort.

Testing

Ideally, the feature would be tested using full stack testing framework that was expected to enter the tree in Kilo but was postponed to Liberty. Note that the framework is not yet reproposed for Liberty.

Tempest Tests

None.

Functional Tests

None.

API Tests

None.

Documentation Impact

User Documentation

Documentation should be extended to describe the new feature.

Developer Documentation

Developer documentation should be updated to include information on how to add support for the reporting feature. Special attention should be made on those who implement Neutron extensions out of tree.