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.server.core.remote;
  
  import java.util.List;
  import org.apache.skywalking.oap.server.core.CoreModule;
  import org.apache.skywalking.oap.server.core.remote.client.RemoteClient;
  import org.apache.skywalking.oap.server.core.remote.client.RemoteClientManager;
  import org.apache.skywalking.oap.server.core.remote.data.StreamData;
  import org.apache.skywalking.oap.server.core.remote.selector.ForeverFirstSelector;
  import org.apache.skywalking.oap.server.core.remote.selector.HashCodeSelector;
  import org.apache.skywalking.oap.server.core.remote.selector.RollingSelector;
  import org.apache.skywalking.oap.server.core.remote.selector.Selector;
  import org.apache.skywalking.oap.server.library.module.ModuleManager;
  import org.apache.skywalking.oap.server.library.module.Service;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * RemoteSenderService represents a gRPC client to send metrics from one OAP node to another through network. It
   * provides several routing mode to select target OAP node.
   */
  public class RemoteSenderService implements Service {
      private static final Logger LOGGER = LoggerFactory.getLogger(RemoteSenderService.class);
  
      private final ModuleManager moduleManager;
      private final HashCodeSelector hashCodeSelector;
      private final ForeverFirstSelector foreverFirstSelector;
      private final RollingSelector rollingSelector;
  
      public RemoteSenderService(ModuleManager moduleManager) {
          this.moduleManager = moduleManager;
          this.hashCodeSelector = new HashCodeSelector();
          this.foreverFirstSelector = new ForeverFirstSelector();
          this.rollingSelector = new RollingSelector();
      }
  
      /**
       * Send data to the target based on the given selector
       *
       * @param nextWorkName points to the worker to process the data when {@link RemoteServiceHandler} received.
       * @param streamData   data to be sent
       * @param selector     strategy implementation to choose suitable OAP node.
       */
      public void send(String nextWorkName, StreamData streamData, Selector selector) {
          RemoteClientManager clientManager = moduleManager.find(CoreModule.NAME)
                                                           .provider()
                                                           .getService(RemoteClientManager.class);
          RemoteClient remoteClient = null;
  
          List<RemoteClient> clientList = clientManager.getRemoteClient();
          if (clientList.size() == 0) {
              LOGGER.warn(
                  "There is no available remote server for now, ignore the streaming data until the cluster metadata initialized.");
              return;
          }
          switch (selector) {
              case HashCode:
                  remoteClient = hashCodeSelector.select(clientList, streamData);
                  break;
              case Rolling:
                  remoteClient = rollingSelector.select(clientList, streamData);
                  break;
              case ForeverFirst:
                  remoteClient = foreverFirstSelector.select(clientList, streamData);
                  break;
          }
          remoteClient.push(nextWorkName, streamData);
      }
  }
  