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Chapter 2. Configuring the Cluster Observability Operator to monitor a service

You can monitor metrics for a service by configuring monitoring stacks managed by the Cluster Observability Operator (COO).

To test monitoring a service, follow these steps:

  • Deploy a sample service that defines a service endpoint.
  • Create a ServiceMonitor object that specifies how the service is to be monitored by the COO.
  • Create a MonitoringStack object to discover the ServiceMonitor object.

This configuration deploys a sample service named prometheus-coo-example-app in the user-defined ns1-coo project. The service exposes the custom version metric.

Prerequisites

  • You have access to the cluster as a user with the cluster-admin cluster role or as a user with administrative permissions for the namespace.

Procedure

  1. Create a YAML file named prometheus-coo-example-app.yaml that contains the following configuration details for a namespace, deployment, and service: 

    apiVersion: v1
kind: Namespace
metadata:
  name: ns1-coo
---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: prometheus-coo-example-app
  name: prometheus-coo-example-app
  namespace: ns1-coo
spec:
  replicas: 1
  selector:
    matchLabels:
      app: prometheus-coo-example-app
  template:
    metadata:
      labels:
        app: prometheus-coo-example-app
    spec:
      containers:
      - image: ghcr.io/rhobs/prometheus-example-app:0.4.2
        imagePullPolicy: IfNotPresent
        name: prometheus-coo-example-app
---
apiVersion: v1
kind: Service
metadata:
  labels:
    app: prometheus-coo-example-app
  name: prometheus-coo-example-app
  namespace: ns1-coo
spec:
  ports:
  - port: 8080
    protocol: TCP
    targetPort: 8080
    name: web
  selector:
    app: prometheus-coo-example-app
  type: ClusterIP
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  2. Save the file.

  3. Apply the configuration to the cluster by running the following command: 

    $ oc apply -f prometheus-coo-example-app.yaml
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  4. Verify that the pod is running by running the following command and observing the output: 

    $ oc -n ns1-coo get pod
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    Example output

    NAME                                      READY     STATUS    RESTARTS   AGE
prometheus-coo-example-app-0927545cb7-anskj   1/1       Running   0          81m
    Copy to Clipboard Toggle word wrap

To use the metrics exposed by the sample service you created in the "Deploying a sample service for Cluster Observability Operator" section, you must configure monitoring components to scrape metrics from the /metrics endpoint.

You can create this configuration by using a ServiceMonitor object that specifies how the service is to be monitored, or a PodMonitor object that specifies how a pod is to be monitored. The ServiceMonitor object requires a Service object. The PodMonitor object does not, which enables the MonitoringStack object to scrape metrics directly from the metrics endpoint exposed by a pod.

This procedure shows how to create a ServiceMonitor object for a sample service named prometheus-coo-example-app in the ns1-coo namespace.

Prerequisites

  • You have access to the cluster as a user with the cluster-admin cluster role or as a user with administrative permissions for the namespace.
  • You have installed the Cluster Observability Operator.

  • You have deployed the prometheus-coo-example-app sample service in the ns1-coo namespace.

    Note

    The prometheus-coo-example-app sample service does not support TLS authentication.

Procedure

  1. Create a YAML file named example-coo-app-service-monitor.yaml that contains the following ServiceMonitor object configuration details: 

    apiVersion: monitoring.rhobs/v1
kind: ServiceMonitor
metadata:
  labels:
    k8s-app: prometheus-coo-example-monitor
  name: prometheus-coo-example-monitor
  namespace: ns1-coo
spec:
  endpoints:
  - interval: 30s
    port: web
    scheme: http
  selector:
    matchLabels:
      app: prometheus-coo-example-app
    Copy to Clipboard Toggle word wrap

    This configuration defines a ServiceMonitor object that the MonitoringStack object will reference to scrape the metrics data exposed by the prometheus-coo-example-app sample service.

  2. Apply the configuration to the cluster by running the following command: 

    $ oc apply -f example-coo-app-service-monitor.yaml
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  3. Verify that the ServiceMonitor resource is created by running the following command and observing the output: 

    $ oc -n ns1-coo get servicemonitors.monitoring.rhobs
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    Example output

    NAME                         AGE
prometheus-coo-example-monitor   81m
    Copy to Clipboard Toggle word wrap

To scrape the metrics data exposed by the target prometheus-coo-example-app service, create a MonitoringStack object that references the ServiceMonitor object you created in the "Specifying how a service is monitored for Cluster Observability Operator" section. This MonitoringStack object can then discover the service and scrape the exposed metrics data from it.

Prerequisites

  • You have access to the cluster as a user with the cluster-admin cluster role or as a user with administrative permissions for the namespace.
  • You have installed the Cluster Observability Operator.
  • You have deployed the prometheus-coo-example-app sample service in the ns1-coo namespace.
  • You have created a ServiceMonitor object named prometheus-coo-example-monitor in the ns1-coo namespace.

Procedure

  1. Create a YAML file for the MonitoringStack object configuration. For this example, name the file example-coo-monitoring-stack.yaml.

  2. Add the following MonitoringStack object configuration details:

    Example MonitoringStack object

    apiVersion: monitoring.rhobs/v1alpha1
kind: MonitoringStack
metadata:
  name: example-coo-monitoring-stack
  namespace: ns1-coo
spec:
  logLevel: debug
  retention: 1d
  resourceSelector:
    matchLabels:
      k8s-app: prometheus-coo-example-monitor
    Copy to Clipboard Toggle word wrap

  3. Apply the MonitoringStack object by running the following command: 

    $ oc apply -f example-coo-monitoring-stack.yaml
    Copy to Clipboard Toggle word wrap

  4. Verify that the MonitoringStack object is available by running the following command and inspecting the output: 

    $ oc -n ns1-coo get monitoringstack
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    Example output

    NAME                         AGE
example-coo-monitoring-stack   81m
    Copy to Clipboard Toggle word wrap

  5. Run the following comand to retrieve information about the active targets from Prometheus and filter the output to list only targets labeled with app=prometheus-coo-example-app. This verifies which targets are discovered and actively monitored by Prometheus with this specific label. 

    $ oc -n ns1-coo exec -c prometheus prometheus-example-coo-monitoring-stack-0 -- curl -s 'http://localhost:9090/api/v1/targets' | jq '.data.activeTargets[].discoveredLabels | select(.__meta_kubernetes_endpoints_label_app=="prometheus-coo-example-app")'
    Copy to Clipboard Toggle word wrap

    Example output

    {
  "__address__": "10.129.2.25:8080",
  "__meta_kubernetes_endpoint_address_target_kind": "Pod",
  "__meta_kubernetes_endpoint_address_target_name": "prometheus-coo-example-app-5d8cd498c7-9j2gj",
  "__meta_kubernetes_endpoint_node_name": "ci-ln-8tt8vxb-72292-6cxjr-worker-a-wdfnz",
  "__meta_kubernetes_endpoint_port_name": "web",
  "__meta_kubernetes_endpoint_port_protocol": "TCP",
  "__meta_kubernetes_endpoint_ready": "true",
  "__meta_kubernetes_endpoints_annotation_endpoints_kubernetes_io_last_change_trigger_time": "2024-11-05T11:24:09Z",
  "__meta_kubernetes_endpoints_annotationpresent_endpoints_kubernetes_io_last_change_trigger_time": "true",
  "__meta_kubernetes_endpoints_label_app": "prometheus-coo-example-app",
  "__meta_kubernetes_endpoints_labelpresent_app": "true",
  "__meta_kubernetes_endpoints_name": "prometheus-coo-example-app",
  "__meta_kubernetes_namespace": "ns1-coo",
  "__meta_kubernetes_pod_annotation_k8s_ovn_org_pod_networks": "{\"default\":{\"ip_addresses\":[\"10.129.2.25/23\"],\"mac_address\":\"0a:58:0a:81:02:19\",\"gateway_ips\":[\"10.129.2.1\"],\"routes\":[{\"dest\":\"10.128.0.0/14\",\"nextHop\":\"10.129.2.1\"},{\"dest\":\"172.30.0.0/16\",\"nextHop\":\"10.129.2.1\"},{\"dest\":\"100.64.0.0/16\",\"nextHop\":\"10.129.2.1\"}],\"ip_address\":\"10.129.2.25/23\",\"gateway_ip\":\"10.129.2.1\",\"role\":\"primary\"}}",
  "__meta_kubernetes_pod_annotation_k8s_v1_cni_cncf_io_network_status": "[{\n    \"name\": \"ovn-kubernetes\",\n    \"interface\": \"eth0\",\n    \"ips\": [\n        \"10.129.2.25\"\n    ],\n    \"mac\": \"0a:58:0a:81:02:19\",\n    \"default\": true,\n    \"dns\": {}\n}]",
  "__meta_kubernetes_pod_annotation_openshift_io_scc": "restricted-v2",
  "__meta_kubernetes_pod_annotation_seccomp_security_alpha_kubernetes_io_pod": "runtime/default",
  "__meta_kubernetes_pod_annotationpresent_k8s_ovn_org_pod_networks": "true",
  "__meta_kubernetes_pod_annotationpresent_k8s_v1_cni_cncf_io_network_status": "true",
  "__meta_kubernetes_pod_annotationpresent_openshift_io_scc": "true",
  "__meta_kubernetes_pod_annotationpresent_seccomp_security_alpha_kubernetes_io_pod": "true",
  "__meta_kubernetes_pod_controller_kind": "ReplicaSet",
  "__meta_kubernetes_pod_controller_name": "prometheus-coo-example-app-5d8cd498c7",
  "__meta_kubernetes_pod_host_ip": "10.0.128.2",
  "__meta_kubernetes_pod_ip": "10.129.2.25",
  "__meta_kubernetes_pod_label_app": "prometheus-coo-example-app",
  "__meta_kubernetes_pod_label_pod_template_hash": "5d8cd498c7",
  "__meta_kubernetes_pod_labelpresent_app": "true",
  "__meta_kubernetes_pod_labelpresent_pod_template_hash": "true",
  "__meta_kubernetes_pod_name": "prometheus-coo-example-app-5d8cd498c7-9j2gj",
  "__meta_kubernetes_pod_node_name": "ci-ln-8tt8vxb-72292-6cxjr-worker-a-wdfnz",
  "__meta_kubernetes_pod_phase": "Running",
  "__meta_kubernetes_pod_ready": "true",
  "__meta_kubernetes_pod_uid": "054c11b6-9a76-4827-a860-47f3a4596871",
  "__meta_kubernetes_service_label_app": "prometheus-coo-example-app",
  "__meta_kubernetes_service_labelpresent_app": "true",
  "__meta_kubernetes_service_name": "prometheus-coo-example-app",
  "__metrics_path__": "/metrics",
  "__scheme__": "http",
  "__scrape_interval__": "30s",
  "__scrape_timeout__": "10s",
  "job": "serviceMonitor/ns1-coo/prometheus-coo-example-monitor/0"
}
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    Note

    The above example uses jq command-line JSON processor to format the output for convenience.

2.4. Validating the monitoring stack
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To validate that the monitoring stack is working correctly, access the example service and then view the gathered metrics.

Prerequisites

  • You have access to the cluster as a user with the cluster-admin cluster role or as a user with administrative permissions for the namespace.
  • You have installed the Cluster Observability Operator.
  • You have deployed the prometheus-coo-example-app sample service in the ns1-coo namespace.
  • You have created a ServiceMonitor object named prometheus-coo-example-monitor in the ns1-coo namespace.
  • You have created a MonitoringStack object named example-coo-monitoring-stack in the ns1-coo namespace.

Procedure

  1. Create a route to expose the example prometheus-coo-example-app service. From your terminal, run the command: 

    $ oc expose svc prometheus-coo-example-app -n ns1-coo
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  2. Access the route from your browser, or command line, to generate metrics.

  3. Execute a query on the Prometheus pod to return the total HTTP requests metric: 

    $ oc -n ns1-coo exec -c prometheus prometheus-example-coo-monitoring-stack-0 -- curl -s 'http://localhost:9090/api/v1/query?query=http_requests_total'
    Copy to Clipboard Toggle word wrap

    Example output (formatted using jq for convenience)

    {
  "status": "success",
  "data": {
    "resultType": "vector",
    "result": [
      {
        "metric": {
          "__name__": "http_requests_total",
          "code": "200",
          "endpoint": "web",
          "instance": "10.129.2.25:8080",
          "job": "prometheus-coo-example-app",
          "method": "get",
          "namespace": "ns1-coo",
          "pod": "prometheus-coo-example-app-5d8cd498c7-9j2gj",
          "service": "prometheus-coo-example-app"
        },
        "value": [
          1730807483.632,
          "3"
        ]
      },
      {
        "metric": {
          "__name__": "http_requests_total",
          "code": "404",
          "endpoint": "web",
          "instance": "10.129.2.25:8080",
          "job": "prometheus-coo-example-app",
          "method": "get",
          "namespace": "ns1-coo",
          "pod": "prometheus-coo-example-app-5d8cd498c7-9j2gj",
          "service": "prometheus-coo-example-app"
        },
        "value": [
          1730807483.632,
          "0"
        ]
      }
    ]
  }
}
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2.5. Scrape targets in multiple namespaces
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To scrape targets in multiple namespaces, set the namespace and resource selector in the MonitoringStack object.

Prerequisites

  • You have access to the cluster as a user with the cluster-admin cluster role or as a user with administrative permissions for the namespace.
  • You have installed the Cluster Observability Operator.

Procedure

  1. Deploy the following namespace object and MonitoringStack YAML file:

    Example MonitoringStack

    apiVersion: v1
kind: Namespace
metadata:
  name: ns1-coo
  labels:
    monitoring.rhobs/stack: multi-ns
---
apiVersion: monitoring.rhobs/v1alpha1
kind: MonitoringStack
metadata:
  name: example-coo-monitoring-stack
  namespace: ns1-coo
spec:
  logLevel: debug
  retention: 1d
  resourceSelector:
      matchLabels:
        k8s-app: prometheus-coo-example-monitor
  namespaceSelector:
      matchLabels:
        monitoring.rhobs/stack: multi-ns
    Copy to Clipboard Toggle word wrap

  2. Deploy a sample application in the namespace ns1-coo, with an alert that is always firing: 

    apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: prometheus-coo-example-app
  name: prometheus-coo-example-app
  namespace: ns1-coo
spec:
  replicas: 1
  selector:
    matchLabels:
      app: prometheus-coo-example-app
  template:
    metadata:
      labels:
        app: prometheus-coo-example-app
    spec:
      containers:
      - image: ghcr.io/rhobs/prometheus-example-app:0.4.2
        imagePullPolicy: IfNotPresent
        name: prometheus-coo-example-app
---
apiVersion: v1
kind: Service
metadata:
  labels:
    app: prometheus-coo-example-app
  name: prometheus-coo-example-app
  namespace: ns1-coo
spec:
  ports:
  - port: 8080
    protocol: TCP
    targetPort: 8080
    name: web
  selector:
    app: prometheus-coo-example-app
  type: ClusterIP
---
apiVersion: monitoring.rhobs/v1
kind: ServiceMonitor
metadata:
  labels:
    k8s-app: prometheus-coo-example-monitor
  name: prometheus-coo-example-monitor
  namespace: ns1-coo
spec:
  endpoints:
  - interval: 30s
    port: web
    scheme: http
  selector:
    matchLabels:
      app: prometheus-coo-example-app
---
apiVersion: monitoring.rhobs/v1
kind: PrometheusRule
metadata:
  name: example-alert
  namespace: ns1-coo
  labels:
    k8s-app: prometheus-coo-example-monitor
spec:
  groups:
  - name: example
    rules:
    - alert: VersionAlert
      for: 1m
      expr: version{job="prometheus-coo-example-app"} > 0
      labels:
        severity: warning
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  3. Deploy the same example application in another namespace labeled with monitoring.rhobs/stack: multi-ns: 

    apiVersion: v1
kind: Namespace
metadata:
  name: ns2-coo
  labels:
    monitoring.rhobs/stack: multi-ns
---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: prometheus-coo-example-app
  name: prometheus-coo-example-app
  namespace: ns2-coo
spec:
  replicas: 1
  selector:
    matchLabels:
      app: prometheus-coo-example-app
  template:
    metadata:
      labels:
        app: prometheus-coo-example-app
    spec:
      containers:
      - image: ghcr.io/rhobs/prometheus-example-app:0.4.2
        imagePullPolicy: IfNotPresent
        name: prometheus-coo-example-app
---
apiVersion: v1
kind: Service
metadata:
  labels:
    app: prometheus-coo-example-app
  name: prometheus-coo-example-app
  namespace: ns2-coo
spec:
  ports:
  - port: 8080
    protocol: TCP
    targetPort: 8080
    name: web
  selector:
    app: prometheus-coo-example-app
  type: ClusterIP
---
apiVersion: monitoring.rhobs/v1
kind: ServiceMonitor
metadata:
  labels:
    k8s-app: prometheus-coo-example-monitor
  name: prometheus-coo-example-monitor
  namespace: ns2-coo
spec:
  endpoints:
  - interval: 30s
    port: web
    scheme: http
  selector:
    matchLabels:
      app: prometheus-coo-example-app
    Copy to Clipboard Toggle word wrap

Verification

  1. Verify that the Prometheus instance adds new targets and that the alert are firing. Use a port-forward command to expose the Prometheus or the Alertmanager user interface that has been deployed by the Monitoringstack instance.

    Prometheus

    $ oc port-forward -n ns1-coo pod/prometheus-example-coo-monitoring-stack-0 9090
    Copy to Clipboard Toggle word wrap

    Alertmanager

    $ oc port-forward -n ns1-coo pod/alertmanager-example-coo-monitoring-stack-0 9093
    Copy to Clipboard Toggle word wrap

  2. Verify that the targets are being scraped and that the alerts are firing by browsing to http://localhost:9090/targets or http://localhost:9093/#/alerts.
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