Config global datasource preference

Config global datasource preference

https://blueprints.launchpad.net/watcher/+spec/global-datasource-preference

Currently, datasources need to be configured on a per strategy basis. Configuring the datasources per strategy is error prone and time consuming. By being able to configure a global datasource preference the time to configure Watcher is reduced and there is a single point for configuring the datasources used by Watcher.

Problem description

The datasources available to Watcher differs per OpenStack deployment so there can not be a standard preference that will work for all deployments. Configuring which datasources are preferred is essential to correctly deploying Watcher, however, the datasource preference needs to be defined per strategy. As a result the datasource preference will have to be configured many times which can lead to errors and costs more time.

Use Cases

As a user of Watcher, I want to configure the datasources only once.

As a user of Watcher, I want to configure the datasources only once but have specific exceptions for some strategies.

Proposed change

Allow specifying of global datasource order by exposing new configuration parameter. This parameter will be part of a new group labeled watcher_datasource. The datasource parameter for strategies remains available and overrides the globally configured datasources.

[watcher_datasource]
datasources = ceilometer, gnocchi, monasca

Alternatives

Try datasources but ensure that if they are not properly configured an error is raised and an alternative datasource is tried. Major downside of this approach is that it will create a lot of errors in some scenarios.

Data model impact

None

REST API impact

None

Security impact

None

Notifications impact

None

Other end user impact

None

Performance Impact

None

Other deployer impact

None

Developer impact

None

Implementation

Assignee(s)

Primary assignee:

<dantalion>

Work Items

  • Add configuration parameter to specify an order of preferred datasources.

  • Read global datasource preference from config on selecting backend.

  • Allow specific strategy datasource configurations to preference.

  • On error attempt the next datasource.

Dependencies

None

Testing

  • Determine if global preference is used correctly.

  • Determine if strategies can override the global preference.

Documentation Impact

Documentation on configuration parameters will need to be updated to reflect the new parameter.

History

None

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