code: /*
   * SPDX-License-Identifier: Apache-2.0
   * Copyright 2018-2019 The Feast Authors
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     https://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package feast.serving.service.controller;
  
  import com.google.inject.Inject;
  import feast.proto.serving.ServingAPIProto.GetFeastServingInfoRequest;
  import feast.serving.service.ServingServiceV2;
  import io.grpc.health.v1.HealthGrpc.HealthImplBase;
  import io.grpc.health.v1.HealthProto.HealthCheckRequest;
  import io.grpc.health.v1.HealthProto.HealthCheckResponse;
  import io.grpc.health.v1.HealthProto.ServingStatus;
  import io.grpc.stub.StreamObserver;
  
  // Reference: https://github.com/grpc/grpc/blob/master/doc/health-checking.md
  public class HealthServiceController extends HealthImplBase {
    private final ServingServiceV2 servingService;
  
    @Inject
    public HealthServiceController(final ServingServiceV2 servingService) {
      this.servingService = servingService;
    }
  
    @Override
    public void check(
        HealthCheckRequest request, StreamObserver<HealthCheckResponse> responseObserver) {
      // TODO: Implement proper logic to determine if ServingServiceV2 is healthy e.g.
      // if it's online service check that it the service can retrieve dummy/random
      // feature table.
      // Implement similarly for batch service.
  
      try {
        servingService.getFeastServingInfo(GetFeastServingInfoRequest.getDefaultInstance());
        responseObserver.onNext(
            HealthCheckResponse.newBuilder().setStatus(ServingStatus.SERVING).build());
      } catch (Exception e) {
        responseObserver.onNext(
            HealthCheckResponse.newBuilder().setStatus(ServingStatus.NOT_SERVING).build());
      }
      responseObserver.onCompleted();
    }
  }
  