private ChannelAndRequestCounter buildManagedChannel() {
  ActiveRequestCounter counter = new ActiveRequestCounter();
  ManagedChannel channel =
      GoogleDefaultChannelBuilder.forTarget(
              isNullOrEmpty(readOptions.getGrpcServerAddress())
                  ? DEFAULT_GCS_GRPC_SERVER_ADDRESS
                  : readOptions.getGrpcServerAddress())
          .enableRetry()
          .defaultServiceConfig(getGrpcServiceConfig())
          .intercept(counter)
          .build();
  return new ChannelAndRequestCounter(channel, counter);
}
 

/**
 * Creates a channel to the first server in the given list.
 */
@Override
ManagedChannel createChannel(List<ServerInfo> servers) {
  checkArgument(!servers.isEmpty(), "No management server provided.");
  XdsLogger logger = XdsLogger.withPrefix("xds-client-channel-factory");
  ServerInfo serverInfo = servers.get(0);
  String serverUri = serverInfo.getServerUri();
  logger.log(XdsLogLevel.INFO, "Creating channel to {0}", serverUri);
  List<ChannelCreds> channelCredsList = serverInfo.getChannelCredentials();
  ManagedChannelBuilder<?> channelBuilder = null;
  // Use the first supported channel credentials configuration.
  // Currently, only "google_default" is supported.
  for (ChannelCreds creds : channelCredsList) {
    if (creds.getType().equals("google_default")) {
      logger.log(XdsLogLevel.INFO, "Using channel credentials: google_default");
      channelBuilder = GoogleDefaultChannelBuilder.forTarget(serverUri);
      break;
    }
  }
  if (channelBuilder == null) {
    logger.log(XdsLogLevel.INFO, "Using default channel credentials");
    channelBuilder = ManagedChannelBuilder.forTarget(serverUri);
  }

  return channelBuilder
      .keepAliveTime(5, TimeUnit.MINUTES)
      .build();
}
 

@Override
protected ManagedChannel createChannel() {
  if (customCredentialsType != null
      && customCredentialsType.equals("google_default_credentials")) {
    return GoogleDefaultChannelBuilder.forAddress(serverHost, serverPort).build();
  }
  if (useAlts) {
    return AltsChannelBuilder.forAddress(serverHost, serverPort).build();
  }
  AbstractManagedChannelImplBuilder<?> builder;
  if (!useOkHttp) {
    SslContext sslContext = null;
    if (useTestCa) {
      try {
        sslContext = GrpcSslContexts.forClient().trustManager(
                TestUtils.loadCert("ca.pem")).build();
      } catch (Exception ex) {
        throw new RuntimeException(ex);
      }
    }
    NettyChannelBuilder nettyBuilder =
        NettyChannelBuilder.forAddress(serverHost, serverPort)
            .flowControlWindow(65 * 1024)
            .negotiationType(useTls ? NegotiationType.TLS : NegotiationType.PLAINTEXT)
            .sslContext(sslContext);
    if (serverHostOverride != null) {
      nettyBuilder.overrideAuthority(serverHostOverride);
    }
    if (fullStreamDecompression) {
      nettyBuilder.enableFullStreamDecompression();
    }
    builder = nettyBuilder;
  } else {
    OkHttpChannelBuilder okBuilder = OkHttpChannelBuilder.forAddress(serverHost, serverPort);
    if (serverHostOverride != null) {
      // Force the hostname to match the cert the server uses.
      okBuilder.overrideAuthority(
          GrpcUtil.authorityFromHostAndPort(serverHostOverride, serverPort));
    }
    if (useTls) {
      try {
        SSLSocketFactory factory = useTestCa
            ? TestUtils.newSslSocketFactoryForCa(Platform.get().getProvider(),
                TestUtils.loadCert("ca.pem"))
            : (SSLSocketFactory) SSLSocketFactory.getDefault();
        okBuilder.sslSocketFactory(factory);
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
    } else {
      okBuilder.usePlaintext();
    }
    if (fullStreamDecompression) {
      okBuilder.enableFullStreamDecompression();
    }
    builder = okBuilder;
  }
  io.grpc.internal.TestingAccessor.setStatsImplementation(
      builder, createClientCensusStatsModule());
  return builder.build();
}
 

@Override
protected ManagedChannel createChannel() {
  if (customCredentialsType != null
      && customCredentialsType.equals("google_default_credentials")) {
    return GoogleDefaultChannelBuilder.forAddress(serverHost, serverPort).build();
  }
  if (customCredentialsType != null
      && customCredentialsType.equals("compute_engine_channel_creds")) {
    return ComputeEngineChannelBuilder.forAddress(serverHost, serverPort).build();
  }
  if (useAlts) {
    return AltsChannelBuilder.forAddress(serverHost, serverPort).build();
  }
  AbstractManagedChannelImplBuilder<?> builder;
  if (!useOkHttp) {
    SslContext sslContext = null;
    if (useTestCa) {
      try {
        sslContext = GrpcSslContexts.forClient().trustManager(
                TestUtils.loadCert("ca.pem")).build();
      } catch (Exception ex) {
        throw new RuntimeException(ex);
      }
    }
    NettyChannelBuilder nettyBuilder =
        NettyChannelBuilder.forAddress(serverHost, serverPort)
            .flowControlWindow(65 * 1024)
            .negotiationType(useTls ? NegotiationType.TLS :
              (useH2cUpgrade ? NegotiationType.PLAINTEXT_UPGRADE : NegotiationType.PLAINTEXT))
            .sslContext(sslContext);
    if (serverHostOverride != null) {
      nettyBuilder.overrideAuthority(serverHostOverride);
    }
    if (fullStreamDecompression) {
      nettyBuilder.enableFullStreamDecompression();
    }
    builder = nettyBuilder;
  } else {
    OkHttpChannelBuilder okBuilder = OkHttpChannelBuilder.forAddress(serverHost, serverPort);
    if (serverHostOverride != null) {
      // Force the hostname to match the cert the server uses.
      okBuilder.overrideAuthority(
          GrpcUtil.authorityFromHostAndPort(serverHostOverride, serverPort));
    }
    if (useTls) {
      if (useTestCa) {
        try {
          SSLSocketFactory factory = TestUtils.newSslSocketFactoryForCa(
              Platform.get().getProvider(), TestUtils.loadCert("ca.pem"));
          okBuilder.sslSocketFactory(factory);
        } catch (Exception e) {
          throw new RuntimeException(e);
        }
      }
    } else {
      okBuilder.usePlaintext();
    }
    if (fullStreamDecompression) {
      okBuilder.enableFullStreamDecompression();
    }
    builder = okBuilder;
  }
  // Disable the default census stats interceptor, use testing interceptor instead.
  io.grpc.internal.TestingAccessor.setStatsEnabled(builder, false);
  return builder.intercept(createCensusStatsClientInterceptor()).build();
}