The XDS example consists of a Hello World client and a Hello World server capable of being configured with the XDS management protocol. Out-of-the-box the client behaves the same the hello-world version and the server behaves similar to the example-hostname but with a required dependency on xDS.

XDS support is incomplete and experimental, with limited compatibility. It will be very hard to produce a working environment just by this example. Please refer to documentation specific for your XDS management server and environment.

Build the XDS hello-world example client & server. From the grpc-java/examples/examples-xds directory:

$ ../gradlew installDist

This creates the scripts build/install/example-xds/bin/xds-hello-world-client and build/install/example-xds/bin/xds-hello-world-server.

To use XDS, you should first deploy the XDS management server in your deployment environment and know its name. You need to set the GRPC_XDS_BOOTSTRAP environment variable (preferred) or if that is not set then the io.grpc.xds.bootstrap java system property to point to the gRPC XDS bootstrap file (see gRFC A27 for the bootstrap format). This is needed by both build/install/example-xds/bin/xds-hello-world-client and build/install/example-xds/bin/xds-hello-world-server.

1. To start the XDS-enabled example server on its default port of 50051, run:

$ export GRPC_XDS_BOOTSTRAP=/path/to/bootstrap.json
$ ./build/install/example-xds/bin/xds-hello-world-server

2. In a different terminal window, run the XDS-enabled example client:

$ export GRPC_XDS_BOOTSTRAP=/path/to/bootstrap.json
$ ./build/install/example-xds/bin/xds-hello-world-client "xds world" xds:///yourServersName

The first command line argument (xds world) is the name you wish to include in the greeting request to the server and the second argument (xds:///yourServersName) is the target to connect to using the xds: target scheme.

The above example used plaintext (insecure) credentials as explicitly provided by the client and server code. We will now demonstrate how the code can authorize use of xDS provided credentials by using XdsChannelCredentials on the client side and using XdsServerCredentials on the server side. This code is enabled by providing an additional command line argument.

1. On the server side, add --xds-creds on the command line to authorize use of xDS security:

$ export GRPC_XDS_BOOTSTRAP=/path/to/bootstrap.json
$ ./build/install/example-xds/bin/xds-hello-world-server --xds-creds

2. Similarly, add --xds-creds on the command line when you run the xDS client:

$ export GRPC_XDS_BOOTSTRAP=/path/to/bootstrap.json
$ ./build/install/example-xds/bin/xds-hello-world-client --xds-creds "xds world" xds:///yourServersName

In this case, if the xDS management server is configured to provide mTLS credentials (for example) to the client and server, then they will use these credentials to create an mTLS channel to authenticate and encrypt.