code: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You 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
   *
   *     http://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 org.apache.skywalking.oap.query.graphql.resolver;
  
  import graphql.kickstart.tools.GraphQLQueryResolver;
  import java.util.Optional;
  import lombok.RequiredArgsConstructor;
  import org.apache.skywalking.oap.server.core.query.type.HealthStatus;
  import org.apache.skywalking.oap.server.health.checker.module.HealthCheckerModule;
  import org.apache.skywalking.oap.server.health.checker.provider.HealthQueryService;
  import org.apache.skywalking.oap.server.library.module.ModuleManager;
  
  @RequiredArgsConstructor
  public class HealthQuery implements GraphQLQueryResolver {
  
      private final ModuleManager moduleManager;
  
      private HealthQueryService service;
  
      private HealthQueryService getService() {
          return Optional.ofNullable(service)
              .orElseGet(() -> {
                  service = moduleManager.find(HealthCheckerModule.NAME).provider().getService(HealthQueryService.class);
                  return service;
              });
      }
  
      public HealthStatus checkHealth() {
          return getService().checkHealth();
      }
  }
  