Added grpc healthcheck by default (#67)

core/build.gradle

@@ -59,6 +59,8 @@ dependencies {
     implementation 'com.github.wnameless:json-flattener:0.6.0'
     implementation 'io.dropwizard.metrics5:metrics-jvm:5.0.0'
     implementation 'io.dropwizard.metrics5:metrics-jmx:5.0.0'
+    implementation rootProject.subprojects.ext.libraries.grpc_stub
+    implementation rootProject.subprojects.ext.libraries.grpc_services
 
     testImplementation libraries.junit4
     testImplementation libraries.assertj

core/src/main/java/com/flipkart/gjex/core/healthcheck/GrpcHealthCheckService.java

@@ -0,0 +1,39 @@
+package com.flipkart.gjex.core.healthcheck;
+
+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.Inject;
+import javax.inject.Named;
+import javax.inject.Singleton;
+
+/**
+ * Default GRPC HealthCheck Service
+ * @author ajay.jalgaonkar
+ */
+
+@Singleton
+@Named("GrpcHealthCheckService")
+public class GrpcHealthCheckService extends HealthGrpc.HealthImplBase {
+  private RotationManagementBasedHealthCheck rotationManagementBasedHealthCheck;
+
+  @Inject
+  public GrpcHealthCheckService(RotationManagementBasedHealthCheck rotationManagementBasedHealthCheck){
+    this.rotationManagementBasedHealthCheck = rotationManagementBasedHealthCheck;
+  }
+
+  @Override
+  public void check(HealthCheckRequest request,
+                    StreamObserver<HealthCheckResponse> responseObserver) {
+    HealthCheckResponse.Builder builder = HealthCheckResponse.newBuilder();
+    if (rotationManagementBasedHealthCheck.inRotation()) {
+      builder.setStatus(HealthCheckResponse.ServingStatus.SERVING);
+    } else {
+      builder.setStatus(HealthCheckResponse.ServingStatus.NOT_SERVING);
+    }
+    responseObserver.onNext(builder.build());
+    responseObserver.onCompleted();
+  }
+}

guice/src/main/java/com/flipkart/gjex/guice/GuiceBundle.java

@@ -22,6 +22,7 @@
 
 import com.flipkart.gjex.core.job.ScheduledJob;
 import com.flipkart.gjex.grpc.service.ScheduledJobManager;
+import io.grpc.health.v1.HealthGrpc;
 import org.glassfish.jersey.server.ResourceConfig;
 
 import io.dropwizard.metrics5.health.HealthCheck;
@@ -138,8 +139,13 @@ public void run(T configuration, U configMap, Environment environment) {
 		setEnvironment(configuration, environment); // NOTE
 		GrpcServer grpcServer = baseInjector.getInstance(GrpcServer.class);
 
+		List<BindableService> bindableServices = new ArrayList<>();
 		// Add all Grpc Services to the Grpc Server
-		List<BindableService> bindableServices = getInstances(baseInjector, BindableService.class);
+		bindableServices.addAll(getInstances(baseInjector, BindableService.class));
+
+		// Add all Grpc Health Check Services to the Grpc Server
+		bindableServices.addAll(getInstances(baseInjector, HealthGrpc.HealthImplBase.class));
+
 		grpcServer.registerServices(bindableServices);
 
 		// Add all Grpc Filters to the Grpc Server

guice/src/main/java/com/flipkart/gjex/guice/module/ServerModule.java

@@ -16,6 +16,7 @@
 
 package com.flipkart.gjex.guice.module;
 
+import com.flipkart.gjex.core.healthcheck.GrpcHealthCheckService;
 import com.flipkart.gjex.core.service.Service;
 import com.flipkart.gjex.grpc.interceptor.FilterInterceptor;
 import com.flipkart.gjex.grpc.interceptor.StatusMetricInterceptor;
@@ -26,6 +27,8 @@
 import com.flipkart.gjex.grpc.service.ScheduledJobManager;
 import com.google.inject.AbstractModule;
 import com.google.inject.name.Names;
+import io.grpc.BindableService;
+import io.grpc.health.v1.HealthGrpc;
 
 /**
  * <code>ServerModule</code> is a Guice {@link AbstractModule} implementation used for configuring the Grpc Server and Dashboard server.
@@ -41,6 +44,7 @@ protected void configure() {
 		bind(TracingInterceptor.class).annotatedWith(Names.named("TracingInterceptor")).to(TracingInterceptor.class);
 		bind(StatusMetricInterceptor.class).annotatedWith(Names.named("StatusMetricInterceptor")).to(StatusMetricInterceptor.class);
 		bind(Service.class).annotatedWith(Names.named("GrpcServer")).to(GrpcServer.class);
+		bind(HealthGrpc.HealthImplBase.class).annotatedWith(Names.named("GrpcHealthCheckService")).to(GrpcHealthCheckService.class);
 		bind(Service.class).annotatedWith(Names.named("DashboardServer")).to(DashboardServer.class);
 		bind(Service.class).annotatedWith(Names.named("APIServer")).to(ApiServer.class);
 		bind(Service.class).annotatedWith(Names.named("ScheduleJobManager")).to(ScheduledJobManager.class);