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luxas has an excellent demo up, tying everything together. This adds a link (with a brief description) to that demo repo.
96 lines
4.2 KiB
Markdown
96 lines
4.2 KiB
Markdown
Kubernetes Custom Metrics Adapter for Prometheus
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================================================
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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.metrics.k8s.io/v1alpha1](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.
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- `--rate-interval=<duration>`: This is the duration used when requesting
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rate metrics from Prometheus. It *must* be larger than your Prometheus
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collection interval.
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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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Presentation
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------------
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The adapter gathers the names of available metrics from Prometheus at the
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specified interval. Only metrics of the following forms are considered:
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- "container" metrics (cAdvisor container metrics): series with a name
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starting with `container_`, as well as non-empty `namespace` and
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`pod_name` labels.
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- "namespaced" metrics (metrics describing namespaced Kubernetes objects):
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series with non-empty namespace labels (which don't start with
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`container_`).
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*Note*: Currently, metrics on non-namespaced objects (besides namespaces
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themselves) are not supported.
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Metrics in Prometheus are converted in the custom-metrics-API metrics as
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follows:
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1. The metric name and type are decided:
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- For container metrics, the `container_` prefix is removed
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- If the metric has the `_total` suffix, it is marked as a counter
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metric, and the suffix is removed
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- If the metric has the `_seconds_total` suffix, it is marked as
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a seconds counter metric, and the suffix is removed.
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- If the metric has none of the above suffixes, is is marked as a gauge
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metric, and the metric name is used as-is
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2. Relevant resources are associated with the metric:
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- container metrics are associated with pods only
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- for non-container metrics, each label on the series is considered. If
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that label represents a resource (without the group) available on the
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server, the metric is associated with that resource. A metric may be
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associated with multiple resources.
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When retrieving counter and seconds-counter metrics, the adapter requests
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the metrics as a rate over the configured amount of time. For metrics
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with multiple associated resources, the adapter requests the metric
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aggregated over all non-requested metrics.
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The adapter does not consider resources consumed by the "POD" container,
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which exists as part of all Kubernetes pods running in Docker simply
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supports the existance of the pod's shared network namespace.
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Example
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-------
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@luxas has an excellent example deployment of Prometheus, this adapter,
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and a demo pod which serves a metric `http_requests_total`, which becomes
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the custom metrics API metric `pods/http_requests`. It also autoscales on
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that metric using the `autoscaling/v2alpha1` HorizontalPodAutoscaler.
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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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