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A helful community member rightly pointed out that configuring the adapter was a bit confusing, and a step-by-step example would be useful. This adds such an example, and links to it from relevant places.
85 lines
3.7 KiB
Markdown
85 lines
3.7 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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Quick Links
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-----------
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- [Config walkthrough](docs/config-walkthrough.md) and [config reference](docs/config.md).
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- [End-to-end walkthrough](docs/walkthrough.md)
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- [Deployment info and files](deploy/README.md)
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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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