Chapter 4. Managing metrics

Procedure

1. Create a YAML file for the service configuration. In this example, it is called

   prometheus-example-app.yaml

   .

2. 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:0.3.0
           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: ClusterIP

   This configuration deploys a service named

   prometheus-example-app

   in the user-defined

   ns1

   project. This service exposes the custom

   version

   metric.

3. Apply the configuration to the cluster:

   $ oc apply -f prometheus-example-app.yaml

   It takes some time to deploy the service.

4. 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

Procedure

1. Create a YAML file for the

   ServiceMonitor

   resource configuration. In this example, the file is called

   example-app-service-monitor.yaml

   .

2. Add the following

   ServiceMonitor

   resource 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-app

   This defines a

   ServiceMonitor

   resource that scrapes the metrics exposed by the

   prometheus-example-app

   sample service, which includes the

   version

   metric.
   Note

   A

   ServiceMonitor

   resource in a user-defined namespace can only discover services in the same namespace. That is, the

   namespaceSelector

   field of the

   ServiceMonitor

   resource is always ignored.

3. Apply the configuration to the cluster:

   $ oc apply -f example-app-service-monitor.yaml

   It takes some time to deploy the

   ServiceMonitor

   resource.

4. You can check that the

   ServiceMonitor

   resource is running:

   $ oc -n ns1 get servicemonitor

   Example output

   NAME                         AGE
   prometheus-example-monitor   81m

Procedure

1. In the Administrator perspective within the OpenShift Container Platform web console, select Monitoring Metrics.
2. Select Insert Metric at Cursor to view a list of predefined queries.
3. To create a custom query, add your Prometheus Query Language (PromQL) query to the Expression field.
4. To add multiple queries, select Add Query.
5. To delete a query, select next to the query, then choose Delete query.
6. To disable a query from being run, select next to the query and choose Disable query.

7. Select Run Queries to run the queries that you have created. The metrics from the queries are visualized on the plot. If a query is invalid, the UI shows an error message.

   Note

   Queries that operate on large amounts of data might time out or overload the browser when drawing time series graphs. To avoid this, select Hide graph and calibrate your query using only the metrics table. Then, after finding a feasible query, enable the plot to draw the graphs.

8. Optional: The page URL now contains the queries you ran. To use this set of queries again in the future, save this URL.

Procedure

1. From the Developer perspective in the OpenShift Container Platform web console, select Monitoring Metrics.
2. Select the project that you want to view metrics for in the Project: list.

3. Choose a query from the Select Query list, or run a custom PromQL query by selecting Show PromQL.

   Note

   In the Developer perspective, you can only run one query at a time.

1. Initially, all metrics from all enabled queries are shown on the plot. You can select which metrics are shown.

   Note

   By default, the query table shows an expanded view that lists every metric and its current value. You can select ˅ to minimize the expanded view for a query.

   • To hide all metrics from a query, click for the query and click Hide all series.
   • To hide a specific metric, go to the query table and click the colored square near the metric name.

2. To zoom into the plot and change the time range, do one of the following:

   • Visually select the time range by clicking and dragging on the plot horizontally.
   • Use the menu in the left upper corner to select the time range.
3. To reset the time range, select Reset Zoom.
4. To display outputs for all queries at a specific point in time, hold the mouse cursor on the plot at that point. The query outputs will appear in a pop-up box.
5. To hide the plot, select Hide Graph.

1. To zoom into the plot and change the time range, do one of the following:

   • Visually select the time range by clicking and dragging on the plot horizontally.
   • Use the menu in the left upper corner to select the time range.
2. To reset the time range, select Reset Zoom.
3. To display outputs for all queries at a specific point in time, hold the mouse cursor on the plot at that point. The query outputs will appear in a pop-up box.