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Chapter 7. Scaling the Cluster Monitoring Operator
OpenShift Container Platform exposes metrics that the Cluster Monitoring Operator collects and stores in the Prometheus-based monitoring stack. As an administrator, you can view dashboards for system resources, containers, and components metrics in the OpenShift Container Platform web console by navigating to Observe
7.1. Prometheus database storage requirements
Red Hat performed various tests for different scale sizes.
The Prometheus storage requirements below are not prescriptive and should be used as a reference. Higher resource consumption might be observed in your cluster depending on workload activity and resource density, including the number of pods, containers, routes, or other resources exposing metrics collected by Prometheus.
| Number of Nodes | Number of pods (2 containers per pod) | Prometheus storage growth per day | Prometheus storage growth per 15 days | Network (per tsdb chunk) |
|---|---|---|---|---|
| 50 | 1800 | 6.3 GB | 94 GB | 16 MB |
| 100 | 3600 | 13 GB | 195 GB | 26 MB |
| 150 | 5400 | 19 GB | 283 GB | 36 MB |
| 200 | 7200 | 25 GB | 375 GB | 46 MB |
Approximately 20 percent of the expected size was added as overhead to ensure that the storage requirements do not exceed the calculated value.
The above calculation is for the default OpenShift Container Platform Cluster Monitoring Operator.
CPU utilization has minor impact. The ratio is approximately 1 core out of 40 per 50 nodes and 1800 pods.
Recommendations for OpenShift Container Platform
- Use at least two infrastructure (infra) nodes.
- Use at least three openshift-container-storage nodes with non-volatile memory express (SSD or NVMe) drives.
7.2. Configuring cluster monitoring
You can increase the storage capacity for the Prometheus component in the cluster monitoring stack.
Procedure
To increase the storage capacity for Prometheus:
Create a YAML configuration file,
cluster-monitoring-config.yaml. For example:apiVersion: v1 kind: ConfigMap data: config.yaml: | prometheusK8s: retention: {{PROMETHEUS_RETENTION_PERIOD}}1 nodeSelector: node-role.kubernetes.io/infra: "" volumeClaimTemplate: spec: storageClassName: {{STORAGE_CLASS}}2 resources: requests: storage: {{PROMETHEUS_STORAGE_SIZE}}3 alertmanagerMain: nodeSelector: node-role.kubernetes.io/infra: "" volumeClaimTemplate: spec: storageClassName: {{STORAGE_CLASS}}4 resources: requests: storage: {{ALERTMANAGER_STORAGE_SIZE}}5 metadata: name: cluster-monitoring-config namespace: openshift-monitoring- 1
- The default value of Prometheus retention is
PROMETHEUS_RETENTION_PERIOD=15d. Units are measured in time using one of these suffixes: s, m, h, d. - 2 4
- The storage class for your cluster.
- 3
- A typical value is
PROMETHEUS_STORAGE_SIZE=2000Gi. Storage values can be a plain integer or a fixed-point integer using one of these suffixes: E, P, T, G, M, K. You can also use the power-of-two equivalents: Ei, Pi, Ti, Gi, Mi, Ki. - 5
- A typical value is
ALERTMANAGER_STORAGE_SIZE=20Gi. Storage values can be a plain integer or a fixed-point integer using one of these suffixes: E, P, T, G, M, K. You can also use the power-of-two equivalents: Ei, Pi, Ti, Gi, Mi, Ki.
- Add values for the retention period, storage class, and storage sizes.
- Save the file.
Apply the changes by running:
$ oc create -f cluster-monitoring-config.yaml
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