gRPC client

Module for gRPC client service support based on grpc.io functionality.

Dependency

Java Kotlin

Dependency build.gradle:

implementation "ru.tinkoff.kora:grpc-client"
implementation "io.grpc:grpc-protobuf:1.62.2"
implementation "javax.annotation:javax.annotation-api:1.3.2"

Module:

@KoraApp
public interface Application extends GrpcClientModule { }

Dependency build.gradle.kts:

implementation("ru.tinkoff.kora:grpc-client")
implementation("io.grpc:grpc-protobuf:1.62.2")
implementation("javax.annotation:javax.annotation-api:1.3.2")

Module:

@KoraApp
interface Application : GrpcClientModule

Plugin

The code for the gRPC client is created with protobuf gradle plugin.

Java Kotlin

Plugin build.gradle:

plugins {
    id "com.google.protobuf" version "0.9.4"
}

protobuf {
    protoc { artifact = "com.google.protobuf:protoc:3.25.3" }
    plugins {
        grpc { artifact = "io.grpc:protoc-gen-grpc-java:1.62.2" }
    }
    generateProtoTasks {
        all()*.plugins { grpc {} }
    }
}

sourceSets {
    main.java {
        srcDirs "build/generated/source/proto/main/grpc"
        srcDirs "build/generated/source/proto/main/java"
    }
}

Plugin build.gradle.kts:

import com.google.protobuf.gradle.id

plugins {
    id("com.google.protobuf") version ("0.9.4")
}

protobuf {
    protoc { artifact = "com.google.protobuf:protoc:3.25.3" }
    plugins {
        id("grpc") { artifact = "io.grpc:protoc-gen-grpc-java:1.62.2" }
    }
    generateProtoTasks {
        ofSourceSet("main").forEach { it.plugins { id("grpc") { } } }
    }
}

kotlin {
    sourceSets.main {
        kotlin.srcDir("build/generated/source/proto/main/grpc")
        kotlin.srcDir("build/generated/source/proto/main/java")
    }
}

Configuration

gRPC service named SimpleService, will have configuration with path of grpcClient.SimpleService.

Example of the complete configuration described in the GrpcClientConfig class (default or example values are specified):

Hocon YAML

grpcClient {
    SimpleService {
        url = "grpc://localhost:8090" //(1)!
        timeout = "10s"  //(2)!
        keepAliveTime = "0s" //(3)!
        keepAliveTimeout = "0s" //(4)!
        loadBalancingPolicy = "pick_first" //(5)!
        telemetry {
            logging {
                enabled = false //(6)!
            }
            metrics {
                enabled = true //(7)!
                slo = [ 1, 10, 50, 100, 200, 500, 1000, 2000, 5000, 10000, 20000, 30000, 60000, 90000 ] //(8)!
            }
            tracing {
                enabled = true //(9)!
            }
        }
    }
}

1. URL of the server where to make requests (required)
2. Maximum request time (optional)
3. Sets the interval in milliseconds between PING frames
4. Sets the timeout in milliseconds for a PING frame to be acknowledged. If sender does not receive an acknowledgment within this time, it will close the connection
5. Sets the load balancing policy
6. Enables module logging (default false)
7. Enables module metrics (default true)
8. Configures SLO for DistributionSummary metrics
9. Enables module tracing (default true)

grpcClient:
  SimpleService:
    url: "grpc://localhost:8090" //(1)!
    timeout: "10s" //(2)!
    keepAliveTime: "0s" //(3)!
    keepAliveTimeout: "0s" //(4)!
    loadBalancingPolicy: "pick_first" //(5)!
    telemetry:
      logging:
        enabled: false #(6)!
      metrics:
        enabled: true #(7)!
        slo: [ 1, 10, 50, 100, 200, 500, 1000, 2000, 5000, 10000, 20000, 30000, 60000, 90000 ] #(8)!
      telemetry:
        enabled: true #(9)!

1. URL of the server where to make requests (required)
2. Maximum request time (optional)
3. Sets the interval in milliseconds between PING frames
4. Sets the timeout in milliseconds for a PING frame to be acknowledged. If sender does not receive an acknowledgment within this time, it will close the connection
5. Sets the load balancing policy
6. Enables module logging (default false)
7. Enables module metrics (default true)
8. Configures SLO for DistributionSummary metrics
9. Enables module tracing (default true)

You can also configure Netty transport.

Service

Created gRPC services can be injected as dependency:

Java Kotlin

@KoraApp
public interface Application extends HoconConfigModule, GrpcClientModule {

    default SomeService(SimpleServiceGrpc.SimpleServiceBlockingStub grpcService) {
        return new SomeService(grpcService);
    }
}

@KoraApp
interface Application : HoconConfigModule, GrpcClientModule {
    fun SomeService(grpcService: SimpleServiceGrpc.SimpleServiceBlockingStub?) {
        return SomeService(grpcService)
    }
}

Interceptors

Interceptors allow you to intercept requests before they are passed to services.

Default

The following interceptors are used at client startup by default:

• GrpcClientConfigInterceptor.

Custom

In order to add your custom interceptor, you need to register the interceptor as a component with the service tag:

Java Kotlin

@Tag(SimpleServiceGrpc.class)
@Component
public final class MyClientInterceptor implements ClientInterceptor {
    @Override
    public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(MethodDescriptor<ReqT, RespT> method, CallOptions callOptions, Channel next) {
        LoggerFactory.getLogger(Application.class).info("INTERCEPTED");
        return next.newCall(method, callOptions);
    }
}

@Tag(SimpleServiceGrpc::class)
@Component
class MyClientInterceptor : ClientInterceptor {
    fun <ReqT, RespT> interceptCall(
        method: MethodDescriptor<ReqT, RespT>,
        callOptions: CallOptions,
        next: Channel
    ): ClientCall<ReqT, RespT> {
        return next.newCall(method, callOptions)
    }
}

Alternatively you can modify the gRPC service with GraphInterceptor.