openstack/cloudkitty-specs
Code Issues Proposed changes
fe84ac27c5
cloudkitty-specs/specs/train/adding_prometheus_fetcher.rst
Justin Ferrieu ad29ece1f9 Spec: Adding Prometheus Fetcher 
This is a spec proposing to add a Prometheus fetcher.

See specs/train/adding_prometheus_fetcher.rst for more
details.

Story: 2005427
Change-Id: I458e2d5a7b06fba25a094ce04cb2050ad51554e8
2019-04-11 13:42:39 +02:00

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Adding Prometheus fetcher

https://storyboard.openstack.org/#!/story/2005427

CloudKitty needs a fetcher describing how to get scopes (formerly tenants) from a Prometheus service. This spec aims at defining what is to be done and why. Everything in this document is open to discussion, equally on the associated storyboard and gerrit.

Problem Description

In the present state, CloudKitty does not implement any method for discovering and fetching scope IDs from a Prometheus service and it needs one.

Proposed Change

The fetcher will be configurable under a [fetcher_prometheus] section in cloudkitty.conf.

The configuration options will be the folllowing :

  • A metric option to provide a metric name from which we can infer the scope ID (default: none).
  • A scope_attribute option to provide the key referring the scope IDs (default: project_id).
  • A filters option as a key-value dictionary to filter out the discovery query response with some metadata (optional).
  • A prometheus_url option to define the HTTP API endpoint URL of a Prometheus service.
  • A prometheus_user and a prometheus_password option to provide credentials for authentication (both defaults: none).
  • A cafile option to allow custom certificate authority file (default: none).
  • An insecure option to explicitly allow insecure HTTPS requests (default: false).

The fetcher will request an aggregation on the specified metric using PromQL query and send it over HTTP to the specified Prometheus service API instant query endpoint. It will also group the result by the specified scope_attribute and filter out the response if some metadata filters have been specified in order to gather the scope_ids.

Example

# cloudkitty.conf

# [...]

[fetcher_prometheus]
metric=container_memory_usage_bytes
scope_attribute=namespace
prometheus_url=https://prometheus-dn.tld/api/v1
prometheus_user=foobar
prometheus_password=foobar
insecure=true
filters=label1:foo,label2:bar

The PromQL request will look the following:

max(container_memory_usage_bytes{label1="foo", label2="bar"}) by (namespace)

The HTTP URL with the url-encoded PromQL will then look the following :

http://prometheus-dn.tld/api/v1/query?query=max%28container_memory_usage_bytes%7Blabel1%3D%22foo%22%2C%20label2%3D%22bar%22%7D%29%20by%20%28namespace%29

Data model impact

None

REST API impact

None

Security impact

None

Notifications Impact

None

Other end user impact

End users will benefit from new Prometheus fetcher to dynamically discover scope IDs.

It will be particularly handy in conjunction with the Prometheus collector.

Performance Impact

None

Other deployer impact

None

Developer impact

None

Implementation

Assignee(s)

Justin Ferrieu is assigned to work on the spec as well as to develop the evoked points.

Primary assignee:

jferrieu

Other contributors:

None

Work Items

  • Implement Prometheus fetcher (with unit tests)
  • Add fetcher documentation

Dependencies

None

Testing

The proposed changes will be tested with unit tests.

Documentation Impact

We will add an entry detailing the Prometheus fetcher configuration in Administration Guide/Configuration Guide/Fetcher/Prometheus.

References