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...
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).
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
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: 80Then 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 15mAfter 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 35mResult:
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-containerLet me know if that answer your question.