content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.security.authentication;
  
  import io.grpc.CallOptions;
  import io.grpc.Channel;
  import io.grpc.ClientCall;
  import io.grpc.ClientInterceptor;
  import io.grpc.ForwardingClientCall;
  import io.grpc.ForwardingClientCallListener;
  import io.grpc.Metadata;
  import io.grpc.MethodDescriptor;
  
  import java.util.UUID;
  import javax.annotation.concurrent.ThreadSafe;
  
  /**
   * Client side interceptor that is used to augment outgoing metadata with the unique id for the
   * channel that the RPC is being called on.
   */
  @ThreadSafe
  public final class ChannelIdInjector implements ClientInterceptor {
  
    /** Metadata key for the channel Id. */
    public static final Metadata.Key<UUID> S_CLIENT_ID_KEY =
        Metadata.Key.of("channel-id", new Metadata.AsciiMarshaller<UUID>() {
          @Override
          public String toAsciiString(UUID value) {
            return value.toString();
          }
  
          @Override
          public UUID parseAsciiString(String serialized) {
            return UUID.fromString(serialized);
          }
        });
  
    // TODO(ggezer) Consider more lightweight Id type.
    private final UUID mChannelId;
  
    /**
     * Creates the injector that augments the outgoing metadata with given Id.
     *
     * @param channelId channel id
     */
    public ChannelIdInjector(UUID channelId) {
      mChannelId = channelId;
    }
  
    @Override
    public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(MethodDescriptor<ReqT, RespT> method,
        CallOptions callOptions, Channel next) {
      return new ForwardingClientCall.SimpleForwardingClientCall<ReqT, RespT>(
          next.newCall(method, callOptions)) {
        @Override
        public void start(Listener<RespT> responseListener, Metadata headers) {
          // Put channel Id to headers.
          headers.put(S_CLIENT_ID_KEY, mChannelId);
          super.start(new ForwardingClientCallListener.SimpleForwardingClientCallListener<RespT>(
              responseListener) {
            @Override
            public void onHeaders(Metadata headers) {
              super.onHeaders(headers);
            }
          }, headers);
        }
      };
    }
  }
  