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Community Blog Kubernetes Cluster Monitoring Using Prometheus

Kubernetes Cluster Monitoring Using Prometheus

In this article, we will show you how to monitor a Kubernetes cluster using Prometheus Operator on Alibaba Cloud Container Service.

By Anish Nath, Alibaba Cloud Tech Share Author. Tech Share is Alibaba Cloud's incentive program to encourage the sharing of technical knowledge and best practices within the cloud community.

Alibaba Cloud Container Service for Kubernetes is a fully-managed service compatible with Kubernetes to help users focus on their applications rather than managing container infrastructure. There are two ways to deploy Kubernetes on Alibaba Cloud, one through Container Service (built-in) and another through an Elastic Compute Service (ECS) instance (self-built). If you are not sure which installation method suits your needs better, then refer to the documentation Alibaba Cloud Kubernetes vs. self-built Kubernetes.

In case you are new to Alibaba Cloud, you can get $10 worth in credit through my referral link to get started on an ECS instance.

In this article, we will cover the following topics:

  • Kube-prometheus vs Prometheus Operator
  • How to install Prometheus-operator
  • How to Install Kube-prometheus
  • Accessing Promethus Server UI (Grafana/Alert Manager)
  • How to perform Service Monitor Lookup
  • Conclusion

Before You Begin

You only need to have running Kubernetes cluster with deployed Prometheus. Prometheus will use metrics provided by cAdvisor via kubelet service (runs on each node of Kubernetes cluster by default) and via kube-apiserver service only.

Make sure your k8 cluster is up and running

root@kube-master:# kubectl cluster-info
Kubernetes master is running at https://172.16.2.13:6443
KubeDNS is running at https://172.16.2.13:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

Make sure your nodes is up and running

root@kube-master:# kubectl get nodes
NAME  STATUS  ROLES AGE VERSION
kube-master Ready master  1m  v1.11.2
kube-minion Ready <none>  42s v1.11.2

Prometheus-Operator vs. Kube-Prometheus

There are two ways to monitor K8s cluster service

  1. Kube-prometheus collects Kubernetes manifests, Grafana dashboards, and Prometheus rules combined with documentation and scripts to provide easy to operate end-to-end Kubernetes cluster monitoring with Prometheus using the Prometheus Operator.
  2. Prometheus-Operator: The Prometheus Operator for Kubernetes provides easy monitoring definitions for Kubernetes services and deployment and management of Prometheus instances

Prometheus Operator

The Prometheus Operator provides monitoring for k8s services and deployments besides managing the below components.

  1. Prometheus
  2. Alertmanager
  3. Grafana configuration

Operators were introduced by CoreOS as a class of software that operates other software, putting operational knowledge collected by humans into software. The below high reference diagram shows, various service monitor can be created to check various K8 service, the operator lookup to these monitor and reports to Prometheus server

1

Installing Prometheus-Operator

This step uses helm the kubernetes package manager. If you not setup the helm then do the below the configuration, otherwise move to next step.

root@kube-master:# helm init 
root@kube-master:# kubectl create serviceaccount --namespace kube-system tiller
root@kube-master:# kubectl create clusterrolebinding tiller-cluster-rule \
   --clusterrole=cluster-admin --serviceaccount=kube-system:tiller
root@kube-master:# kubectl patch deploy --namespace kube-system tiller-deploy \
   -p '{"spec":{"template":{"spec":{"serviceAccount":"tiller"}}}}'
root@kube-master:# kubectl --namespace monitoring get pods -l "release=prometheus-operator
root@kube-master:# kubectl port-forward -n monitoring prometheus-prometheus-operator-prometheus-0 9090

Once the helm is ready and related titler pods is up and running , use the Prometheus chard from the helm repository

helm install stable/prometheus-operator --name prometheus-operator --namespace monitoring

Lookup all the required pods are up and running

root@kube-master:# kubectl --namespace monitoring get pods -l "release=prometheus-operator"
NAME                                                     READY     STATUS    RESTARTS   AGE
prometheus-operator-grafana-7654f69d89-ztwsk             2/3       Running   0          1m
prometheus-operator-kube-state-metrics-cdf84dd85-229c7   1/1       Running   0          1m
prometheus-operator-operator-66cf889d9f-ngdfq            1/1       Running   0          1m
prometheus-operator-prometheus-node-exporter-68mx2       1/1       Running   0          1m
prometheus-operator-prometheus-node-exporter-x2l68       1/1       Running   0          1m

Installing Kube-Prometheus

To install kube-prometheus, first clone all the required repositories.

root@kube-master:# git clone https://github.com/coreos/prometheus-operator.git
root@kube-master:# git clone https://github.com/mateobur/prometheus-monitoring-guide.git

Apply the default Prometheus manifest

root@kube-master:# kubectl create -f prometheus-operator/contrib/kube-prometheus/manifests/
namespace/monitoring created
customresourcedefinition.apiextensions.k8s.io/alertmanagers.monitoring.coreos.com created
customresourcedefinition.apiextensions.k8s.io/prometheuses.monitoring.coreos.com created
customresourcedefinition.apiextensions.k8s.io/prometheusrules.monitoring.coreos.com created
customresourcedefinition.apiextensions.k8s.io/servicemonitors.monitoring.coreos.com created
clusterrole.rbac.authorization.k8s.io/prometheus-operator created
clusterrolebinding.rbac.authorization.k8s.io/prometheus-operator created
deployment.apps/prometheus-operator created
service/prometheus-operator created
serviceaccount/prometheus-operator created
servicemonitor.monitoring.coreos.com/prometheus-operator created
alertmanager.monitoring.coreos.com/main created
secret/alertmanager-main created
service/alertmanager-main created
serviceaccount/alertmanager-main created
servicemonitor.monitoring.coreos.com/alertmanager created
secret/grafana-datasources created
configmap/grafana-dashboard-k8s-cluster-rsrc-use created
configmap/grafana-dashboard-k8s-node-rsrc-use created
configmap/grafana-dashboard-k8s-resources-cluster created
configmap/grafana-dashboard-k8s-resources-namespace created
configmap/grafana-dashboard-k8s-resources-pod created
configmap/grafana-dashboard-nodes created
configmap/grafana-dashboard-pods created
configmap/grafana-dashboard-statefulset created
configmap/grafana-dashboards created
deployment.apps/grafana created
service/grafana created
serviceaccount/grafana created
clusterrole.rbac.authorization.k8s.io/kube-state-metrics created
clusterrolebinding.rbac.authorization.k8s.io/kube-state-metrics created
deployment.apps/kube-state-metrics created
role.rbac.authorization.k8s.io/kube-state-metrics created
rolebinding.rbac.authorization.k8s.io/kube-state-metrics created
service/kube-state-metrics created
serviceaccount/kube-state-metrics created
servicemonitor.monitoring.coreos.com/kube-state-metrics created
clusterrole.rbac.authorization.k8s.io/node-exporter created
clusterrolebinding.rbac.authorization.k8s.io/node-exporter created
daemonset.apps/node-exporter created
service/node-exporter created
serviceaccount/node-exporter created
servicemonitor.monitoring.coreos.com/node-exporter created
apiservice.apiregistration.k8s.io/v1beta1.metrics.k8s.io created
clusterrole.rbac.authorization.k8s.io/prometheus-adapter created
clusterrolebinding.rbac.authorization.k8s.io/prometheus-adapter created
clusterrolebinding.rbac.authorization.k8s.io/resource-metrics:system:auth-delegator created
clusterrole.rbac.authorization.k8s.io/resource-metrics-server-resources created
configmap/adapter-config created
deployment.apps/prometheus-adapter created
rolebinding.rbac.authorization.k8s.io/resource-metrics-auth-reader created
service/prometheus-adapter created
serviceaccount/prometheus-adapter created
clusterrole.rbac.authorization.k8s.io/prometheus-k8s created
clusterrolebinding.rbac.authorization.k8s.io/prometheus-k8s created
prometheus.monitoring.coreos.com/k8s created
rolebinding.rbac.authorization.k8s.io/prometheus-k8s-config created
rolebinding.rbac.authorization.k8s.io/prometheus-k8s created
rolebinding.rbac.authorization.k8s.io/prometheus-k8s created
rolebinding.rbac.authorization.k8s.io/prometheus-k8s created
role.rbac.authorization.k8s.io/prometheus-k8s-config created
role.rbac.authorization.k8s.io/prometheus-k8s created
role.rbac.authorization.k8s.io/prometheus-k8s created
role.rbac.authorization.k8s.io/prometheus-k8s created
prometheusrule.monitoring.coreos.com/prometheus-k8s-rules created
service/prometheus-k8s created
serviceaccount/prometheus-k8s created
servicemonitor.monitoring.coreos.com/prometheus created
servicemonitor.monitoring.coreos.com/kube-apiserver created
servicemonitor.monitoring.coreos.com/coredns created
servicemonitor.monitoring.coreos.com/kube-controller-manager created
servicemonitor.monitoring.coreos.com/kube-scheduler created
servicemonitor.monitoring.coreos.com/kubelet created

The default stack deploys the components like :

root@kube-master:# kubectl get pods -n monitoring
NAME                                   READY     STATUS    RESTARTS   AGE
alertmanager-main-0                    2/2       Running   0          1m
alertmanager-main-1                    2/2       Running   0          1m
alertmanager-main-2                    2/2       Running   0          40s
grafana-7b9578fb4-dqskm                1/1       Running   0          2m
kube-state-metrics-7f4478ff68-zdbgk    4/4       Running   0          47s
node-exporter-4p5nm                    2/2       Running   0          2m
node-exporter-6dxt9                    2/2       Running   0          2m
prometheus-adapter-69bd74fc7-m4jl5     1/1       Running   0          2m
prometheus-k8s-0                       3/3       Running   1          1m
prometheus-k8s-1                       3/3       Running   1          48s
prometheus-operator-6db8dbb7dd-s2tbz   1/1       Running   0          2m

We have defined the following configurations:

  • Every things are built under the namespace of monitoring
  • 2 replica of Prometheus server deployment prometheus-k8s
  • 3 replica of Alertmanager deployment alertmanager-main
  • 1 replica of grafana
  • node-exporter pod per physical host
  • kube-state-metrics exporter
  • prometheus-operator pod, the core of the stack,

Note: The default configuration is not production ready, the TLS setting needs to applied and to re-work on which API needs to be exposed.

Accessing Grafana

Grafana dashboard has a datasource ready to query on Prometheus

root@kube-master:# kubectl port-forward grafana-7b9578fb4-dqskm -n monitoring 3000:3000
Forwarding from 127.0.0.1:3000 -> 3000
Forwarding from [::1]:3000 -> 3000

Open web browser to http://localhost:300 , you will access the Grafana interface, which is already populated with some useful dashboards related to kubernetes (k8)
By default, Grafana will be listening on http://localhost:3000. The default login is "admin" / "admin".

Grafana Login

2

The Grafana interface already populated with some useful dashboards.

3

The K8s / Compute Resources / Cluster Dashboard.

4

The K8s / Compute Resources / Namespaces Dashboard

5

The K8s / Compute Resources / Pods Dashboard

6

Data Sources / Prometheus: Service lookup is achieved through kube-dns lookup URL http://prometheus-k8s.monitoring.svc:9090

7

Prometheus Server UI

Create the service pods which will expose the endpoint address

root@kube-master:# kubectl create -f prometheus-monitoring-guide/operator/service-prometheus.yaml
prometheus.monitoring.coreos.com/service-prometheus created

Wait for the prometheus-service-prometheus-0 to be up and running

root@kube-master:# kubectl get pods -n monitoring
NAME                                   READY     STATUS    RESTARTS   AGE
alertmanager-main-0                    2/2       Running   0          2h
alertmanager-main-1                    2/2       Running   0          2h
alertmanager-main-2                    2/2       Running   0          2h
grafana-7b9578fb4-dqskm                1/1       Running   0          2h
kube-state-metrics-7f4478ff68-zdbgk    4/4       Running   0          2h
node-exporter-4p5nm                    2/2       Running   0          2h
node-exporter-6dxt9                    2/2       Running   0          2h
prometheus-adapter-69bd74fc7-m4jl5     1/1       Running   0          2h
prometheus-k8s-0                       3/3       Running   1          2h
prometheus-k8s-1                       3/3       Running   1          2h
prometheus-operator-6db8dbb7dd-s2tbz   1/1       Running   0          2h
prometheus-service-prometheus-0        3/3       Running   1          21s

Then Enable port forward configuration to access Prometheus server UI

root@kube-master:# kubectl port-forward -n monitoring prometheus-service-prometheus-0   9090
Forwarding from 127.0.0.1:9090 -> 9090
Forwarding from [::1]:9090 -> 9090

Open web browser to http://localhost:9090, you will access the Prometheus interface.

8

These are the standard ports which will be helpful while dealing with Prometheus server and its associated service.

  • 9090 - Prometheus server
  • 9091 - Pushgateway
  • 9092 - UNALLOCATED (to avoid collision with Kafka)
  • 9093 - Alertmanager
  • 9094 - Alertmanager clustering

Performing ServiceMonitor Lookups

Until now, we have worked out with the example of monitoring the K8 cluster with prometheus-operator, what about the application which is loaded externally, well for that we have ServiceMonitor Lookups but before jumping to it, let's revisit

  • CRD (CustomResourceDefinitions), API resource allows you to define custom resources. Defining a CRD object creates a new custom resource with a name and schema that you specify.
  • ServiceMonitor defines monitoring for a set of services.
  • Prometheus-operator uses a Custom Resource Definition (CRD), named ServiceMonitor, to abstract the configuration to target.

For example the below YAML configuration will select and monitor the nginx pod using the matchLabels selector. i.e app=nginx

apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  name: nginx
spec:
  selector:
    matchLabels:
      app: nginx
  namespaceSelector:
    matchNames:
    - default
  endpoints:
  - port: web
    interval: 30s

serviceMonitorSelector which defines a selection of ServiceMonitors to be used.

Here's another example of using ServiceMonitor. Let's first deploy three instances of a simple example application, which listens and exposes metrics on port 8080

root@kube-master:# kubectl apply -f https://raw.githubusercontent.com/coreos/prometheus-operator/master/contrib/kube-prometheus/examples/example-app/example-app.yaml
example-app.yaml
service/example-app created
deployment.extensions/example-app created
root@kube-master:# kubectl get pods 
NAME                                READY     STATUS    RESTARTS   AGE
example-app-5d644dbfc6-4t4gn        1/1       Running   0          33s
example-app-5d644dbfc6-dsxzq        1/1       Running   0          33s
example-app-5d644dbfc6-sb8xd        1/1       Running   0          33s
example-app-5d644dbfc6-v7l89        1/1       Running   0          33s

This serviceobject is discovered and monitor by a ServiceMonitor where app=example-app

apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  name: example-app
  labels:
    team: frontend
spec:
  selector:
    matchLabels:
      app: example-app
  endpoints:
  - port: web
root@kube-master:/home/ansible# kubectl create -f  example-app.yaml 
servicemonitor.monitoring.coreos.com/example-app created

Conclusion

That's it! It is fairly easy to deploy Prometheus Operator and now I hope it's easy to monitor all your services even if they are exist outside from your Kubernetes cluster. While running up this exercise, you might end-up with troubleshooting, as this is the beauty of kubernetes, In order to debug it correctly, you must have a good understanding of kubernetes deployment and related k8 services then proceed with Prometheus setup. There are many other thing Prometheus offer like third party integration and it's not an event logging system, and attempting to use it that way will result in low performance and other issues.

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