GRPC: simple example of GRPC Health Checking Protocol

HealthCheckerService.kt

package br.com.zup.edu

import io.grpc.health.v1.HealthCheckRequest
import io.grpc.health.v1.HealthCheckResponse
import io.grpc.health.v1.HealthGrpc
import io.grpc.stub.StreamObserver
import javax.inject.Singleton

@Singleton
class HealthCheckerService: HealthGrpc.HealthImplBase() {

    override fun check(request: HealthCheckRequest?, responseObserver: StreamObserver<HealthCheckResponse>?) {

        responseObserver?.onNext(HealthCheckResponse.newBuilder()
                                    .setStatus(HealthCheckResponse.ServingStatus.SERVING)
                                    .build())

        responseObserver?.onCompleted()
    }

    override fun watch(request: HealthCheckRequest?, responseObserver: StreamObserver<HealthCheckResponse>?) {

        for (i in 0 until 10 ) {

            val status = when (i % 2) {
                0 -> HealthCheckResponse.ServingStatus.SERVING
                else -> HealthCheckResponse.ServingStatus.NOT_SERVING
            }

            Thread.sleep(1000)

            responseObserver?.onNext(HealthCheckResponse.newBuilder()
                .setStatus(status)
                .build())
        }

        responseObserver?.onCompleted()
    }
}

• Understanding the GRPC Health Checking Protocol
• The health.proto suggested by Google