Extension Points

ClientInterceptor

io.grpc.ClientInterceptor is an interceptor to intercept the lifecycle of a gRPC call on the client side.

Register a ClientInterceptor for all gRPC stubs:

@Component
public class LoggingClientInterceptor implements ClientInterceptor {
    private static final Logger log = LoggerFactory.getLogger(LoggingClientInterceptor.class);

    @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 sendMessage(ReqT message) {
                log.info("Sending message: {}", message);
                super.sendMessage(message);
            }
        };
    }
}

Multiple ClientInterceptor will be called in the order defined by the Spring Bean's order, from smallest to largest.

GrpcChannelCustomizer

GrpcChannelCustomizer customize the Channel before it is created.

Register a GrpcChannelCustomizer to set the retry attempts for the gRPC channels:

@Component
public class RetryGrpcChannelCustomizer implements GrpcChannelCustomizer {
    @Override
    public void customize(GrpcClientProperties.Channel channelConfig, ManagedChannelBuilder<?> channelBuilder) {
        channelBuilder.enableRetry().maxRetryAttempts(3);
    }
}

Multiple GrpcChannelCustomizer will be called in the order defined by the Spring Bean's order, from smallest to largest.

GrpcClientBeanDefinitionHandler

Starting from 3.4.3.1, GrpcClientBeanDefinitionHandler is used to post-process BeanDefinition before the gRPC client bean is registered.

You can set beanDefinitionHandler by @EnableGrpcClient or configuring grpc.client.bean-definition-handler. If both are set, the one set by @EnableGrpcClient will be used.

If you want only blocking stub to be registered:

@EnableGrpcClients(beanDefinitionHandler = GrpcClientBeanDefinitionHandler.Blocking.class)

The framework provides some built-in GrpcClientBeanDefinitionHandler implementations:

• GrpcClientBeanDefinitionHandler.Default: Register all stubs.
• GrpcClientBeanDefinitionHandler.Blocking: Only register blocking stub.
• GrpcClientBeanDefinitionHandler.Future: Only register future stub.
• GrpcClientBeanDefinitionHandler.Async: Only register async stub.

Deep Customization

Manual Bean Creation

If you're not happy with the autoconfigured gRPC client bean, you can configure it using the Spring original approach (@Bean).

If you manually create the gRPC client bean, the autoconfigured gRPC client bean will not be created.

@Configuration
class GrpcClientConfiguration {
    @Bean
    public SimpleServiceGrpc.SimpleServiceBlockingStub simpleServiceBlockingStub() {
        var channel = ManagedChannelBuilder.forAddress("localhost", 9090)
                .usePlaintext()
                .build();
        return SimpleServiceGrpc.newBlockingStub(channel);
    }
}

ManagedChannels API

Starting from 3.5.3, you can use ManagedChannels to access configured gRPC channels by name.

Configure multiple named channels:

grpc:
  client:
    channels:
      - name: "service-a"
        authority: "localhost:9090"
      - name: "service-b"
        authority: "localhost:9091"

Use ManagedChannels to create custom stub beans:

@Configuration
class CustomStubConfiguration {

    @Bean
    public HealthGrpc.HealthBlockingStub customHealthStub(ManagedChannels channels) {
        ManagedChannel channel = channels.getChannel("service-a");
        return HealthGrpc.newBlockingStub(channel);
    }
}