gRPC health probe on Kine deployment does not work

[yelshall]

It seems that the gRPC server is not working, as when I try to query the server I get back nothing:

> grpcurl -plaintext -d '{"service": "kine"}' localhost:2379 grpc.health.v1.Health/Check
Failed to dial target host "localhost:2379": context deadline exceeded

This is in the new version (0.11.1) where it seems the HTTP server was removed. However, querying the HTTP server in version 0.10.3 seems to be fine.

[brandond]

As discussed at kubernetes/kubernetes#118460 the HTTP endpoint is no longer used by Kubernetes for health checking, so we don't need to support it here in Kine.

The "context deadline exceeded" error doesn't seem to have anything to do with that change though, it sounds to me like kine isn't actually running on that port. Here's what I get:

brandond@dev01:~$ ./grpcurl -plaintext -d '{"service": "kine"}' 172.17.0.7:2379 grpc.health.v1.Health/Check
Error invoking method "grpc.health.v1.Health/Check": failed to query for service descriptor "grpc.health.v1.Health": server does not support the reflection API

[brandond]

I guess this can be left open as a feature request, but I do want to confirm that I don't believe this is necessary to support health checks from clients that already have the grpc.health.v1.Health protobuf descriptors available - which would include Kubernetes.

[brandond]

I will also note that kine doesn't really do health checks, it will always just respond with healthpb.HealthCheckResponse_SERVING. This is consistent with etcd though, which also responds with a fixed response.

[brandond]

Also, I'm not sure where you got the '{"service": "kine"}' bit from, but it does not appear to work with etcd OR kine. Where did you get that from?

With the change from my linked PR, things seem to work properly if you just query health:

brandond@dev01:~$ ./grpcurl -plaintext 172.17.0.7:2379 list
etcdserverpb.Cluster
etcdserverpb.KV
etcdserverpb.Lease
etcdserverpb.Maintenance
etcdserverpb.Watch
grpc.health.v1.Health
grpc.reflection.v1alpha.ServerReflection

brandond@dev01:~$ ./grpcurl -plaintext 172.17.0.7:2379 grpc.health.v1.Health/Check
{
  "status": "SERVING"
}