exec probe in GKE

Question

I'm trying to use exec probes for readiness and liveness in GKE. This is because it is part of Kubernetes' recommended way to do health checks on gRPC back ends. However when I put the exec probe config into my deployment yaml and apply it, it doesn't take effect in GCP. This is my container yaml:

  - name: rev79-uac-sandbox
    image: gcr.io/rev79-232812/uac:latest
    imagePullPolicy: Always
    ports:
    - containerPort: 3011
    readinessProbe:
      exec:
        command: ["bin/grpc_health_probe", "-addr=:3011"]
      initialDelaySeconds: 5
    livenessProbe:
      exec:
        command: ["bin/grpc_health_probe", "-addr=:3011"]
      initialDelaySeconds: 10

But still the health checks fail and when I look at the health check configuration in the GCP console I see a plain HTTP health check directed at '/'

When I edit a health check in GCP console there doesn't seem to be any way to choose an exec type. Also I can't see any mention of liveness checks as contrasted to readiness checks even though these are separate Kubernetes things.

Does Google cloud support using exec for health checks? If so, how do I do it? If not, how can I health check a gRPC server?

Have you taken a look at kubernetes.io/blog/2018/10/01/… ? — Richard Belleville
@Richard Belleville, yes. That's where I learnt about this from. But it doesn't work in GKE — Toby 1 Kenobi
@RichardBelleville the server has to implement the grpc probe protocol — unludo
@Toby1Kenobi..these probes working fine for me 1) downloaded grpc health go utility in my docker image 2) implemented health proto in my grpc server 3) added exec probes in yaml, it shows SERVING status when I do kubect exec -it <POD_NAM> -- /bin/bash — Abhay
Why you're expecting load balancer's health check to use this grpc exec probe? The load balancer will have to do its own health check by querying some end point. Kubernetes health check is done by kubelet and uses the pod IP load balancer IP or ingress IP. Am I missing something here? — Abhay

Suresh Vishnoi Suresh Vishnoi · Accepted Answer · 2019-04-25T15:30:24

TCP probes are useful when we are using gRPC Services rather than using HTTP probes.

    - containerPort: 3011
    readinessProbe:
      tcpSocket:
        port: 3011
      initialDelaySeconds: 5
      periodSeconds: 10
    livenessProbe:
      tcpSocket:
        port: 3011
      initialDelaySeconds: 15
      periodSeconds: 20

the kubelet will attempt to open a socket to your container on the specified port. If it can establish a connection, the container is considered healthy, if it can’t it is considered a failure define-a-tcp-liveness-probe

exec probe in GKE

4 Answers