Learning - Prometheus Exporter

Steps to monitor MongoDB metrics

• Deploy MongoDB App
• Deploy MongoDB Exporter
• Deploy ServiceMonitor

Deployment

minikube start --cpus 4 --memory 8192 --vm-driver hyperkit
helm ls
kubectl get pod
kubectl get svc
kubectl port-forward prometheus-kube-prometheus-prometheus 9090
kubectl port-forward prometheus-grafana 80

servicemonitor

ServiceMonitor is a custom Kubernetes component

kubectl get servicemonitor
kubectl get servicemonitor prometheus-kube-prometheus-grafana -oyaml
...
metadata:
  labels:
    release: prometheus

spec:
  endpoints:
    - path: /metrics
      port: service
  selector:
    matchLabels:
      app.kubernetes.io/instance: prometheus
      app.kubernetes.io/name: grafana

CRD configuration

$ kubectl get crd
...
prometheuses.monitoring.coreos.com ...
...
$ kubectl get prometheuses.monitoring.coreos.com -oyaml
...
spec:
  serviceMonitorSelector:
    matchLabels:
      release: prometheus
...

Deploy MongoDB

mongodb-without-exporter.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: mongodb-deployment
  labels:
    app: mongodb
spec:
  replicas: 1
  selector:
    matchLabels:
      app: mongodb
  template:
    metadata:
      labels:
        app: mongodb
    spec:
      containers:
      - name: mongodb
        image: mongo
        ports:
        - containerPort: 27017
---
apiVersion: v1
kind: Service
metadata:
  name: mongodb-service
spec:
  selector:
    app: mongodb
  ports:
    - protocol: TCP
      port: 27017
      targetPort: 27017

kubectl apply -f mongodb-without-exporter.yaml
kubectl get pod

Deploy MongoDB Exporter

Translator between apps data to Prometheus understandable metrics

Target (MongoDB App) <= fetches metrics <= converts to correct format <= expose /metrics <= Prometheus Server

• Separate deployment - No need to change config files

MongoDB exporter (mongodb-exporter) can be downloaded from exporter site or dockerhub.

Exporter Site

Exporters can be downloaded from https://prometheus.io/docs/instrumenting/exporters

Nodes exporter - translates metrics of cluster Nodes, exposes /metrics

prometheus-prometheus-node-exporter-8qvwn

Components for exporter

• Exporter application - exposes /metrics endpoint
• Service - for connnecting to the exporter
• ServiceMonitor - to be discovered

Helm chart for exporter

Search for mongodb-exporter helm chart

https://github.com/prometheus-community/helm-charts

Override values using chart parameters

helm show values <chart-name>

Add Helm repo

helm repo add prometheus-community https://prometheus-community.github.io/helm-charts
helm show values prometheus-community/prometheus-mongodb-exporter > values.yaml

Override values in values.yaml

mongodb:
  uri: "mongodb://mongodb-service:27017"

serviceMonitor:
  additionalLabels:
    release: prometheus

with the label Prometheus automatically discovers a new ServiceMonitor in the cluster

$ helm install mongodb-exporter prometheus-community/prometheus-mongodb-exporter -f values.yaml
...
$ helm ls
mongodb-exporter
...
$ kubectl get pod
...
mongodb-exporter-prometheus-mongodb-exporter-75...
...
$ kubectl get svc
...
mongodb-exporter-prometheus-mongodb-exporter
...
$ kubectl get servicemonitor
...
mongodb-exporter-prometheus-mongodb-exporter
...
$ kubectl get servicemonitor mongodb-exporter-prometheus-mongodb-exporter -o yaml
...
metadata:
  labels:
    release: prometheus
...

Check endpoint /metrics

$ kubectl get svc
...
mongodb-exporter-prometheus-mongodb-exporter
...
kubectl port-forward service/mongodb-exporter-prometheus-mongodb-exporter 9216

Access https://127.0.0.1:9216/metrics

The mongodb-exporter is added as targets in prometheus, because the label release: prometheus is set and auto discovered.

MongoDB metrics data in Grafana UI

kubectl get deployment
kubectl port-forward deployment/prometheus-grafana 3000

References

Prometheus Monitoring - Steps to monitor third-party apps using Prometheus Exporter | Part 2