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.webapp;
  
  import static java.util.stream.Collectors.toList;
  import java.net.URI;
  import java.util.List;
  import java.util.stream.Stream;
  import com.linecorp.armeria.client.Endpoint;
  import com.linecorp.armeria.client.WebClient;
  import com.linecorp.armeria.client.endpoint.EndpointGroup;
  import com.linecorp.armeria.client.endpoint.EndpointSelectionStrategy;
  import com.linecorp.armeria.client.logging.LoggingClient;
  import com.linecorp.armeria.common.HttpRequest;
  import com.linecorp.armeria.common.HttpResponse;
  import com.linecorp.armeria.common.SessionProtocol;
  import com.linecorp.armeria.server.AbstractHttpService;
  import com.linecorp.armeria.server.ServiceRequestContext;
  import lombok.SneakyThrows;
  
  public final class ZipkinProxyService extends AbstractHttpService {
      private final WebClient loadBalancingClient;
  
      public ZipkinProxyService(String[] zipkinServices) throws Exception {
          final List<Endpoint> endpoints =
              Stream
                  .of(zipkinServices)
                  .map(URI::create)
                  .map(URI::getAuthority)
                  .map(Endpoint::parse)
                  .collect(toList());
          loadBalancingClient = newLoadBalancingClient(
              EndpointGroup.of(
                  EndpointSelectionStrategy.roundRobin(),
                  endpoints));
      }
  
      @SneakyThrows
      private static WebClient newLoadBalancingClient(EndpointGroup zipkinGroup) {
          return WebClient
              .builder(SessionProtocol.HTTP, zipkinGroup)
              .decorator(LoggingClient.newDecorator())
              .build();
      }
  
      @Override
      protected HttpResponse doGet(ServiceRequestContext ctx, HttpRequest req) throws Exception {
          return loadBalancingClient.execute(req);
      }
  }
  