kube-prometheus: add e.g. of using persistent storage for the prom tsdb

examples/prometheus-pvc.jsonnet

+
+// Reference info: documentation for https://github.com/ksonnet/ksonnet-lib can be found at http://g.bryan.dev.hepti.center
+//
+local k = import 'ksonnet/ksonnet.beta.3/k.libsonnet'; // https://github.com/ksonnet/ksonnet-lib/blob/master/ksonnet.beta.3/k.libsonnet - imports k8s.libsonnet
+// * https://github.com/ksonnet/ksonnet-lib/blob/master/ksonnet.beta.3/k8s.libsonnet defines things such as "persistentVolumeClaim:: {"
+//
+local pvc = k.core.v1.persistentVolumeClaim; // https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.11/#persistentvolumeclaim-v1-core (defines variable named 'spec' of type 'PersistentVolumeClaimSpec')
+
+local kp =
+  (import 'kube-prometheus/kube-prometheus.libsonnet') +
+  (import 'kube-prometheus/kube-prometheus-bootkube.libsonnet') +
+  {
+    _config+:: {
+      namespace: 'monitoring',
+    },
+
+    prometheus+:: {
+      prometheus+: {
+        spec+: { // https://github.com/coreos/prometheus-operator/blob/master/Documentation/api.md#prometheusspec
+          // If a value isn't specified for 'retention', then by default the '--storage.tsdb.retention=24h' arg will be passed to prometheus by prometheus-operator.
+          // The possible values for a prometheus <duration> are:
+          //  * https://github.com/prometheus/common/blob/c7de230/model/time.go#L178 specifies "^([0-9]+)(y|w|d|h|m|s|ms)$" (years weeks days hours minutes seconds milliseconds)
+          retention: "30d",
+
+          // Reference info: https://github.com/coreos/prometheus-operator/blob/master/Documentation/user-guides/storage.md
+          // By default (if the following 'storage.volumeClaimTemplate' isn't created), prometheus will be created with an EmptyDir for the 'prometheus-k8s-db' volume (for the prom tsdb).
+          // This 'storage.volumeClaimTemplate' causes the following to be automatically created (via dynamic provisioning) for each prometheus pod:
+          //  * PersistentVolumeClaim (and a corresponding PersistentVolume)
+          //  * the actual volume (per the StorageClassName specified below)
+          storage: { // https://github.com/coreos/prometheus-operator/blob/master/Documentation/api.md#storagespec
+            volumeClaimTemplate: // (same link as above where the 'pvc' variable is defined)
+              pvc.new() + // http://g.bryan.dev.hepti.center/core/v1/persistentVolumeClaim/#core.v1.persistentVolumeClaim.new
+
+              pvc.mixin.spec.withAccessModes('ReadWriteOnce') +
+
+              // https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.11/#resourcerequirements-v1-core (defines 'requests'),
+              // and https://kubernetes.io/docs/concepts/policy/resource-quotas/#storage-resource-quota (defines 'requests.storage')
+              pvc.mixin.spec.resources.withRequests({ storage: '100Gi' }) +
+
+              // A StorageClass of the following name (which can be seen via `kubectl get storageclass` from a node in the given K8s cluster) must exist prior to kube-prometheus being deployed.
+              pvc.mixin.spec.withStorageClassName('ssd'),
+
+              // The following 'selector' is only needed if you're using manual storage provisioning (https://github.com/coreos/prometheus-operator/blob/master/Documentation/user-guides/storage.md#manual-storage-provisioning).
+              // And note that this is not supported/allowed by AWS - uncommenting the following 'selector' line (when deploying kube-prometheus to a K8s cluster in AWS) will cause the pvc to be stuck in the Pending status and have the following error:
+              //  * 'Failed to provision volume with StorageClass "ssd": claim.Spec.Selector is not supported for dynamic provisioning on AWS'
+              //pvc.mixin.spec.selector.withMatchLabels({}),
+          }, // storage
+        }, // spec
+      }, // prometheus
+    }, // prometheus
+
+  };
+
+{ ['0prometheus-operator-' + name]: kp.prometheusOperator[name] for name in std.objectFields(kp.prometheusOperator) } +
+{ ['node-exporter-' + name]: kp.nodeExporter[name] for name in std.objectFields(kp.nodeExporter) } +
+{ ['kube-state-metrics-' + name]: kp.kubeStateMetrics[name] for name in std.objectFields(kp.kubeStateMetrics) } +
+{ ['alertmanager-' + name]: kp.alertmanager[name] for name in std.objectFields(kp.alertmanager) } +
+{ ['prometheus-' + name]: kp.prometheus[name] for name in std.objectFields(kp.prometheus) } +
+{ ['grafana-' + name]: kp.grafana[name] for name in std.objectFields(kp.grafana) }