grpc-gcp provides gRPC support for Google Cloud Clients.

This module is currently used by the Google Cloud Spanner client library to provide gRPC-GCP channel pooling and related transport behavior. It is published separately as com.google.cloud:grpc-gcp because Spanner exposes grpc-gcp types in its public API.

Use Spanner API as an example.

First, Create a json file defining API configuration, with ChannelPoolConfig and MethodConfig.

{
  "channelPool": {
    "maxSize": 3,
    "maxConcurrentStreamsLowWatermark": 0
  },
  "method": [
    {
      "name": [ "google.spanner.v1.Spanner/CreateSession" ],
      "affinity": {
        "command": "BIND",
        "affinityKey": "name"
      }
    },
    {
      "name": [ "google.spanner.v1.Spanner/GetSession" ],
      "affinity": {
        "command": "BOUND",
        "affinityKey": "name"
      }
    },
    {
      "name": [ "google.spanner.v1.Spanner/DeleteSession" ],
      "affinity": {
        "command": "UNBIND",
        "affinityKey": "name"
      }
    }
  ]
}

Initialize GcpManagedChannel based on this API config file.

String API_CONFIG_FILE = "api_config_file.json"
String SPANNER_TARGET = "spanner.googleapis.com";
...

ManagedChannelBuilder delegateChannelBuilder = ManagedChannelBuilder.forAddress(SPANNER_TARGET, 443);
GcpManagedChannelBuilder gcpBuilder = 
  GcpManagedChannelBuilder.forDelegateBuilder(delegateChannelBuilder)
                          .withApiConfigJsonFile(jsonApiConfig);
ManagedChannel gcpChannel = gcpBuilder.build();

Create Cloud API stub using GcpManagedChannel.

GoogleCredentials creds = getCreds();
SpannerBlockingStub stub =
    SpannerGrpc.newBlockingStub(gcpChannel)
               .withCallCredentials(MoreCallCredentials.from(creds));

Download source.

git clone https://github.com/googleapis/google-cloud-java.git && cd google-cloud-java/grpc-gcp-java

Build project with unit tests.

mvn verify

Install the jar to your local Maven repository.

mvn install

Setup credentials. See Getting Started With Authentication for more details.

export GOOGLE_APPLICATION_CREDENTIALS=path/to/key.json

export GCP_PROJECT_ID=project_id

Run unit tests.

mvn test

Integration tests are kept as source references but are not wired into the default monorepo Maven lifecycle.

This artifact is released by the google-cloud-java monorepo release pipeline.

Run google-java-format

mvn fmt:format