CODEWITHSUNDEEP
kuberneteskubernetes-servicekubernetes-deployment
Borhink
Borhink

Reputation: 367

Kubernetes check readinessProbe at Service/Deployment level

Is there a way to request the status of a readinessProbe by using a service name linked to a deployment ? In an initContainer for example ?

Imagine we have a deployment X, using a readinessProbe, a service linked to it so we can request for example http://service-X:8080. Now we create a deployment Y, in the initContainer we want to know if deployment X is ready. Is there a way to ask something likedeployment-X.ready or service-X.ready ?

I know that the correct way to handle dependencies is to let kubernetes do it for us, but i have a container which doesn't crash and I have no hand on it...

Upvotes: 0

Views: 509

Answers (3)

Borhink
Borhink

Reputation: 367

I finaly found a solution by following this link : https://blog.giantswarm.io/wait-for-it-using-readiness-probes-for-service-dependencies-in-kubernetes/

We first need to create a ServiceAccount in Kubernetes to allow listing endpoints from an initContainer. After this, we ask for the available endpoints, if there is at least one, dependency is ready (in my case).

Upvotes: 0

Jakub
Jakub

Reputation: 8840

Instead of readinessProbe You can use just InitContainer.

You create a pod/deployment X, make service X, and create a initContainer which is searching for the service X.

If he find it -> he will make the pod.

If he won't find it -> he will keep looking until service X will be created.

Just a simple example, we create nginx deployment by using kubectl apply -f nginx.yaml.

nginx.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-nginx
spec:
  selector:
    matchLabels:
      run: my-nginx
  replicas: 2
  template:
    metadata:
      labels:
        run: my-nginx
    spec:
      containers:
      - name: my-nginx
        image: nginx
        ports:
        - containerPort: 80

Then we create initContainer

initContainer.yaml

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
  - name: myapp-container
    image: busybox:1.28
    command: ['sh', '-c', 'echo The app is running! && sleep 3600']
  initContainers:
  - name: init-myservice
    image: busybox:1.28
    command: ['sh', '-c', 'until nslookup my-nginx; do echo waiting for myapp-pod2; sleep 2; done;']

initContainer will look for service my-nginx, until You create it ,it will be in Init:0/1 status.

NAME                        READY   STATUS     RESTARTS   AGE
myapp-pod                   0/1     Init:0/1   0          15m

After You add service for example by using kubectl expose deployment/my-nginx and initContainer will find my-nginx service, he will be created.

NAME                        READY   STATUS     RESTARTS   AGE
myapp-pod                   1/1     Running    0          35m

Result:

Events:
  Type    Reason     Age        From               Message
  ----    ------     ----       ----               -------
  Normal  Scheduled  <unknown>  default-scheduler  Successfully assigned default/myapp-pod to kubeadm2
  Normal  Pulled     20s        kubelet, kubeadm2  Container image "busybox:1.28" already present on machine
  Normal  Created    20s        kubelet, kubeadm2  Created container init-myservice
  Normal  Started    20s        kubelet, kubeadm2  Started container init-myservice
  Normal  Pulled     20s        kubelet, kubeadm2  Container image "busybox:1.28" already present on machine
  Normal  Created    20s        kubelet, kubeadm2  Created container myapp-container
  Normal  Started    20s        kubelet, kubeadm2  Started container myapp-container

Let me know if that answer your question.

Upvotes: 1

Yang
Yang

Reputation: 888

You can add a ngnix proxy sidecar on deployment Y. Set the deploymentY.initContainer.readynessProbe to a port on nginx and that port is proxied to deploymentY.readynessProbe

Upvotes: 1

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