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
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Justin Ferrieu
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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======================================
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Adding Prometheus fetcher
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======================================
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https://storyboard.openstack.org/#!/story/2005427
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CloudKitty needs a fetcher describing how to get scopes (formerly tenants) from
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a Prometheus service.
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This spec aims at defining what is to be done and why.
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Everything in this document is open to discussion, equally on the associated
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storyboard and gerrit.
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Problem Description
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===================
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In the present state, CloudKitty does not implement any method for discovering
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and fetching scope IDs from a Prometheus service and it needs one.
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Proposed Change
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===============
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The fetcher will be configurable under a ``[fetcher_prometheus]`` section
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in ``cloudkitty.conf``.
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The configuration options will be the folllowing :
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* A ``metric`` option to provide a metric name from which we can infer
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the scope ID (default: none).
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* A ``scope_attribute`` option to provide the key referring the scope IDs
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(default: ``project_id``).
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* A ``filters`` option as a key-value dictionary to filter out the discovery
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query response with some metadata (optional).
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* A ``prometheus_url`` option to define the HTTP API endpoint URL of a
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Prometheus service.
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* A ``prometheus_user`` and a ``prometheus_password`` option
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to provide credentials for authentication (both defaults: none).
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* A ``cafile`` option to allow custom certificate authority
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file (default: none).
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* An ``insecure`` option to explicitly allow insecure HTTPS requests
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(default: false).
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The fetcher will request an aggregation on the specified ``metric``
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using PromQL query and send it over HTTP to the specified
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Prometheus service API instant query endpoint.
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It will also group the result by the specified ``scope_attribute`` and
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filter out the response if some metadata ``filters`` have been specified
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in order to gather the scope_ids.
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Example
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-------
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.. code-block:: ini
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# cloudkitty.conf
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# [...]
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[fetcher_prometheus]
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metric=container_memory_usage_bytes
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scope_attribute=namespace
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prometheus_url=https://prometheus-dn.tld/api/v1
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prometheus_user=foobar
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prometheus_password=foobar
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insecure=true
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filters=label1:foo,label2:bar
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The PromQL request will look the following:
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``max(container_memory_usage_bytes{label1="foo", label2="bar"}) by (namespace)``
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The HTTP URL with the url-encoded PromQL will then look the following :
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``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``
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Data model impact
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-----------------
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None
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REST API impact
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---------------
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None
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Security impact
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---------------
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None
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Notifications Impact
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--------------------
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None
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Other end user impact
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---------------------
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End users will benefit from new Prometheus fetcher to dynamically discover
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scope IDs.
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It will be particularly handy in conjunction with the Prometheus collector.
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Performance Impact
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------------------
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None
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Other deployer impact
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---------------------
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None
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Developer impact
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----------------
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None
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Implementation
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==============
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Assignee(s)
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-----------
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Justin Ferrieu is assigned to work on the spec as well as to develop
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the evoked points.
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Primary assignee:
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jferrieu
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Other contributors:
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None
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Work Items
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----------
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* Implement Prometheus fetcher (with unit tests)
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* Add fetcher documentation
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Dependencies
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============
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None
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Testing
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=======
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The proposed changes will be tested with unit tests.
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Documentation Impact
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====================
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We will add an entry detailing the Prometheus fetcher configuration
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in ``Administration Guide/Configuration Guide/Fetcher/Prometheus``.
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References
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==========
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* Prometheus documentation: https://prometheus.io/docs/
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@ -1,31 +0,0 @@
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..
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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==================
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(Placeholder Spec)
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==================
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This file is just a placeholder for Train specs directory.
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It will be removed soon after some spec for Train is merged.
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The latest spec template is found at ``specs/template.rst``
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in the ``cloudkitty-specs`` repository.
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Problem Description
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===================
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Sphinx toctree complains if no file exists in a directory
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specified in toctree glob.
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Proposed Change
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===============
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Add this file.
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References
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==========
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None.
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