Debugging Prometheus ServiceMonitors
The way that Prometheus uses
ServiceMonitors to scrape metrics from your pods might not be so straight
forward for various reasons (you are new to this or like me, I don’t deal with this everyday and I just
Here is a Doc about it that is a must read:
The following also walks you through a concrete example of the usage and how everything is linked together.
The final output is being able to go to the Prometheus WebUI and to the
Status->Targets page and see your
endpoints being scraped per your config.
How does Prometheus know which ServiceMonitor to use?
The Prometheus Operator is configured pick up
ServiceMonitors via a config. Here is how to
find out what that label is. Get the prometheus CRD:
kubectl -n monitoring get prometheus NAME AGE prometheus-operator-prometheus 23d
Describe the CRD to output it’s config:
kubectl -n monitoring describe prometheus prometheus-operator-prometheus Name: prometheus-operator-prometheus Namespace: monitoring Labels: app=prometheus-operator-prometheus chart=prometheus-operator-6.11.0 heritage=Tiller release=prometheus-operator Annotations: <none> API Version: monitoring.coreos.com/v1 Kind: Prometheus Metadata: Creation Timestamp: 2019-10-15T00:45:15Z Generation: 1 Resource Version: 87788471 Self Link: /apis/monitoring.coreos.com/v1/namespaces/monitoring/prometheuses/prometheus-operator-prometheus UID: 0dd57ecf-eee5-11e9-a08f-02d13237d5b2 Spec: Alerting: Alertmanagers: Name: prometheus-operator-alertmanager Namespace: monitoring Path Prefix: / Port: web Base Image: quay.io/prometheus/prometheus Enable Admin API: false Listen Local: false Log Format: logfmt Log Level: info Paused: false ... .... ... ... Resources: Requests: Memory: 1000Mi Retention: 10d Route Prefix: / Rule Namespace Selector: Rule Selector: Match Labels: App: prometheus-operator Release: prometheus-operator Security Context: Fs Group: 2000 Run As Non Root: true Run As User: 1000 Service Account Name: prometheus-operator-prometheus Service Monitor Namespace Selector: Service Monitor Selector: Match Labels: Release: prometheus-operator <---- We are interested in this Storage: Volume Claim Template: Selector: Spec: Access Modes: ReadWriteOnce Resources: Requests: Storage: 10Gi Version: v2.12.0 Events: <none>
The section we are interested in that output is:
Service Monitor Selector: Match Labels: Release: prometheus-operator
This is the label that has to be matched in the
ServiceMonitor MUST have this label:
kubectl -n myapp-gar describe servicemonitors myapp-api-svc-live Name: myapp-api-svc-live Namespace: myapp-gar Labels: app.kubernetes.io/instance=myapp-gar-api-svc-live app.kubernetes.io/managed-by=Tiller app.kubernetes.io/name=myapp-api-svc-live app.selector=myapp-api-svc-live helm.sh/chart=master-service-1-0.1.3 release=prometheus-operator <------- It has the label Annotations: <none> API Version: monitoring.coreos.com/v1 Kind: ServiceMonitor Metadata: Creation Timestamp: 2019-11-07T18:47:26Z Generation: 1 Resource Version: 95279034 Self Link: /apis/monitoring.coreos.com/v1/namespaces/myapp-gar/servicemonitors/myapp-api-svc-live UID: 0b020a96-018f-11ea-9ce4-024e93ab8437 Spec: Endpoints: Interval: 30s Path: /foo Port: prometheus Scheme: http Namespace Selector: Match Name: myapp-gar Selector: Match Labels: app.selector: myapp-api-v1.1.1 Events: <none>
When this Prometheus (because you can have multiple instances of Prometheus running) sees a
with this label, it will add it into the list of
ServiceMonitors it monitors.
ServiceMonitor configuration also has label selectors and it uses these selectors to find the endpoints
to monitor. From our previous
ServiceMonitor describe output we saw this section:
Selector: Match Labels: app.selector: myapp-api-v1.1.1
This section is configuring a label to select from a Kuberenetes Service on which endpoint to include in.
This means that the Kubernetes Service needs to have this label for the Prometheus
ServiceMonitor to find
the endpoints to monitor.
kubectl -n myall-gar describe svc myapp-api-svc-live Name: myapp-api-svc-live Namespace: myapp-gar Labels: app.kubernetes.io/instance=myapp-gar-api-svc-live app.kubernetes.io/managed-by=Tiller app.kubernetes.io/name=myapp-api-svc-live app.selector=myapp-api-v1.1.1 <------ Needs this lable in the Kube Service helm.sh/chart=master-service-1-0.1.3
You should now be able to go to
Status->Targets in the Prometheus WebGUI and see your targets being scraped.
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Prometheus | Operator | ServiceMonitor | Troubleshooting