monitoring-configuring-monitoring-for-an-application.adoc

Configuring monitoring for an application

This procedure shows, on an example, how an application developer can deploy an application and configure monitoring for it.

Prerequisites

• Make sure you configured the cluster for application monitoring. In this example, it is presumed that Prometheus and Alertmanager instances were installed in the default namespace.

Procedure

1. Create a YAML file for your configuration. In this example, it is called deploy.yaml.

2. Add configuration for deploying a sample application:

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: example-app
     namespace: default
   spec:
     selector:
       matchLabels:
         app: example-app
     replicas: 1
     template:
       metadata:
         labels:
           app: example-app
       spec:
         containers:
         - name: example-app
           image: quay.io/brancz/prometheus-example-app:v0.2.0
           ports:
           - name: web
             containerPort: 8080
   ---

3. Add configuration for exposing the sample application as a service:

   kind: Service
   apiVersion: v1
   metadata:
     name: example-app
     namespace: default
     labels:
       tier: frontend
   spec:
     selector:
       app: example-app
     ports:
     - name: web
       port: 8080
   ---

4. Add configuration for creating a service monitor for the sample application. This will add your application as a target for monitoring:

   apiVersion: monitoring.coreos.com/v1
   kind: ServiceMonitor
   metadata:
     name: example-app
     namespace: default
     labels:
       k8s-app: example-app
   spec:
     selector:
       matchLabels:
         tier: frontend
     endpoints:
     - port: web

5. Apply the configuration file to the cluster:

   $ oc apply -f deploy.yaml

6. Forward a port to the Prometheus UI. In this example, port 9090 is used:

   $ oc port-forward -n openshift-user-workload-monitoring svc/prometheus-operated 9090

7. Navigate to the Prometheus UI at http://localhost:9090/targets to see the sample application being monitored.