GRPC health check

[steven-sheehy]

Problem
Ops requested a health check API to monitor the new GRPC component

Solution
Add a GRPC endpoint that provides health status of the component

Alternatives

• Monitor logs
• Add to monitor service
• Add a REST endpoint to GRPC process

Additional Context

[steven-sheehy]

Turns out this is already implemented by Spring Boot GRPC and using standard GRPC health check API:

$ grpcurl -plaintext -d '{"service":"com.hedera.mirror.api.proto.ConsensusService"}' localhost:5600 grpc.health.v1.Health/Check
{
  "status": "SERVING"
}

To watch for changes instead of polling:

$ grpcurl -plaintext -d '{"service":"com.hedera.mirror.api.proto.ConsensusService"}' localhost:5600 grpc.health.v1.Health/Watch
{
  "status": "SERVING"
}

[steven-sheehy]

Reopening as Ops' pingdom is unable to take advantage of the GRPC or HTTP/2 based health check endpoint. We will have to implement a REST based health check for this component