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0d220eafef
The wording on the relist interval confused a couple of people, so this should clarify it a bit.
78 lines
3.5 KiB
Markdown
78 lines
3.5 KiB
Markdown
Kubernetes Custom Metrics Adapter for Prometheus
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================================================
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[](https://travis-ci.org/DirectXMan12/k8s-prometheus-adapter)
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This repository contains an implementation of the Kubernetes custom
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metrics API
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([custom.metrics.k8s.io/v1beta1](https://github.com/kubernetes/metrics/tree/master/pkg/apis/custom_metrics)),
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suitable for use with the autoscaling/v2 Horizontal Pod Autoscaler in
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Kubernetes 1.6+.
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Configuration
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-------------
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The adapter takes the standard Kubernetes generic API server arguments
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(including those for authentication and authorization). By default, it
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will attempt to using [Kubernetes in-cluster
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config](https://kubernetes.io/docs/tasks/access-application-cluster/access-cluster/#accessing-the-api-from-a-pod)
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to connect to the cluster.
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It takes the following addition arguments specific to configuring how the
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adapter talks to Prometheus and the main Kubernetes cluster:
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- `--lister-kubeconfig=<path-to-kubeconfig>`: This configures
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how the adapter talks to a Kubernetes API server in order to list
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objects when operating with label selectors. By default, it will use
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in-cluster config.
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- `--metrics-relist-interval=<duration>`: This is the interval at which to
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update the cache of available metrics from Prometheus. Since the adapter
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only lists metrics during discovery that exist between the current time and
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the last discovery query, your relist interval should be equal to or larger
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than your Prometheus scrape interval, otherwise your metrics will
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occaisonally disappear from the adapter.
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- `--prometheus-url=<url>`: This is the URL used to connect to Prometheus.
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It will eventually contain query parameters to configure the connection.
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- `--config=<yaml-file>` (`-c`): This configures how the adapter discovers available
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Prometheus metrics and the associated Kubernetes resources, and how it presents those
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metrics in the custom metrics API. More information about this file can be found in
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[docs/config.md](docs/config.md).
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Presentation
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------------
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The adapter gathers the names of available metrics from Prometheus
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a regular interval (see [Configuration](#configuration) above), and then
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only exposes metrics that follow specific forms.
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The rules governing this discovery are specified in a [configuration file](docs/config.md).
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If you were relying on the implicit rules from the previous version of the adapter,
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you can use the included `config-gen` tool to generate a configuration that matches
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the old implicit ruleset:
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```shell
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$ go run cmd/config-gen main.go [--rate-interval=<duration>] [--label-prefix=<prefix>]
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```
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Example
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-------
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A brief walkthrough exists in [docs/walkthrough.md](docs/walkthrough.md).
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Additionally, [@luxas](https://github.com/luxas) has an excellent example
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deployment of Prometheus, this adapter, and a demo pod which serves
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a metric `http_requests_total`, which becomes the custom metrics API
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metric `pods/http_requests`. It also autoscales on that metric using the
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`autoscaling/v2beta1` HorizontalPodAutoscaler. Note that @luxas's tutorial
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uses a slightly older version of the adapter.
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It can be found at https://github.com/luxas/kubeadm-workshop. Pay special
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attention to:
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- [Deploying the Prometheus
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Operator](https://github.com/luxas/kubeadm-workshop#deploying-the-prometheus-operator-for-monitoring-services-in-the-cluster)
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- [Setting up the custom metrics adapter and sample
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app](https://github.com/luxas/kubeadm-workshop#deploying-a-custom-metrics-api-server-and-a-sample-app)
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