Chapter 7. Managing metrics
You can collect metrics to monitor how cluster components and your own workloads are performing.
7.1. Understanding metrics
In OpenShift Container Platform 4.11, cluster components are monitored by scraping metrics exposed through service endpoints. You can also configure metrics collection for user-defined projects.
You can define the metrics that you want to provide for your own workloads by using Prometheus client libraries at the application level.
In OpenShift Container Platform, metrics are exposed through an HTTP service endpoint under the /metrics canonical name. You can list all available metrics for a service by running a curl query against http://<endpoint>/metrics. For instance, you can expose a route to the prometheus-example-app example service and then run the following to view all of its available metrics:
$ curl http://<example_app_endpoint>/metrics
Example output
# HELP http_requests_total Count of all HTTP requests
# TYPE http_requests_total counter
http_requests_total{code="200",method="get"} 4
http_requests_total{code="404",method="get"} 2
# HELP version Version information about this binary
# TYPE version gauge
version{version="v0.1.0"} 1
Additional resources
7.2. Setting up metrics collection for user-defined projects
You can create a ServiceMonitor resource to scrape metrics from a service endpoint in a user-defined project. This assumes that your application uses a Prometheus client library to expose metrics to the /metrics canonical name.
This section describes how to deploy a sample service in a user-defined project and then create a ServiceMonitor resource that defines how that service should be monitored.
7.2.1. Deploying a sample service
To test monitoring of a service in a user-defined project, you can deploy a sample service.
Procedure
-
Create a YAML file for the service configuration. In this example, it is called
prometheus-example-app.yaml. Add the following deployment and service configuration details to the file:
apiVersion: v1 kind: Namespace metadata: name: ns1 --- apiVersion: apps/v1 kind: Deployment metadata: labels: app: prometheus-example-app name: prometheus-example-app namespace: ns1 spec: replicas: 1 selector: matchLabels: app: prometheus-example-app template: metadata: labels: app: prometheus-example-app spec: containers: - image: ghcr.io/rhobs/prometheus-example-app:0.4.2 imagePullPolicy: IfNotPresent name: prometheus-example-app --- apiVersion: v1 kind: Service metadata: labels: app: prometheus-example-app name: prometheus-example-app namespace: ns1 spec: ports: - port: 8080 protocol: TCP targetPort: 8080 name: web selector: app: prometheus-example-app type: ClusterIPThis configuration deploys a service named
prometheus-example-appin the user-definedns1project. This service exposes the customversionmetric.Apply the configuration to the cluster:
$ oc apply -f prometheus-example-app.yaml
It takes some time to deploy the service.
You can check that the pod is running:
$ oc -n ns1 get pod
Example output
NAME READY STATUS RESTARTS AGE prometheus-example-app-7857545cb7-sbgwq 1/1 Running 0 81m
7.2.2. Specifying how a service is monitored
To use the metrics exposed by your service, you must configure OpenShift Container Platform monitoring to scrape metrics from the /metrics endpoint. You can do this using a ServiceMonitor custom resource definition (CRD) that specifies how a service should be monitored, or a PodMonitor CRD that specifies how a pod should be monitored. The former requires a Service object, while the latter does not, allowing Prometheus to directly scrape metrics from the metrics endpoint exposed by a pod.
This procedure shows you how to create a ServiceMonitor resource for a service in a user-defined project.
Prerequisites
-
You have access to the cluster as a user with the
cluster-admincluster role or themonitoring-editcluster role. - You have enabled monitoring for user-defined projects.
For this example, you have deployed the
prometheus-example-appsample service in thens1project.NoteThe
prometheus-example-appsample service does not support TLS authentication.
Procedure
-
Create a YAML file for the
ServiceMonitorresource configuration. In this example, the file is calledexample-app-service-monitor.yaml. Add the following
ServiceMonitorresource configuration details:apiVersion: monitoring.coreos.com/v1 kind: ServiceMonitor metadata: labels: k8s-app: prometheus-example-monitor name: prometheus-example-monitor namespace: ns1 spec: endpoints: - interval: 30s port: web scheme: http selector: matchLabels: app: prometheus-example-appThis defines a
ServiceMonitorresource that scrapes the metrics exposed by theprometheus-example-appsample service, which includes theversionmetric.NoteA
ServiceMonitorresource in a user-defined namespace can only discover services in the same namespace. That is, thenamespaceSelectorfield of theServiceMonitorresource is always ignored.Apply the configuration to the cluster:
$ oc apply -f example-app-service-monitor.yaml
It takes some time to deploy the
ServiceMonitorresource.You can check that the
ServiceMonitorresource is running:$ oc -n ns1 get servicemonitor
Example output
NAME AGE prometheus-example-monitor 81m
