kora-grpc-client

Kora gRPC Client

Kora sub-skill — obey the kora-v1 meta rules on every task: R0 ensure .kora-agent/ docs+examples are cloned · R1 read this sub-skill before writing code · R2 Kora APIs only — no Spring/Micronaut/Quarkus, no invented annotations or config keys · R3 journal any incorrect Kora usage. Add comments/Javadoc only if asked.

Generate gRPC client stubs from a .proto contract and inject them as components through GrpcClientModule. Kora wires the configured channel and the generated stubs into the application graph; your code just builds protobuf requests and calls stub methods.

Read this first when:

• enabling GrpcClientModule and injecting a generated *BlockingStub/*FutureStub/*Stub,
• configuring a client under grpcClient.<ServiceName>.*,
• adding a ClientInterceptor for metadata headers, auth, or logging,
• making unary or streaming calls.

Key facts (do not get these wrong)

• Stubs are injected directly by type — no @Tag on the constructor parameter. Kora produces one stub per generated *Grpc class. Injecting UserServiceGrpc.UserServiceBlockingStub is enough.
• @Tag(ServiceGrpc.class) belongs on a ClientInterceptor, to scope that interceptor to one service's client. It is not used for stub injection.
• Annotations come from ru.tinkoff.kora.common.* (@Component, @Tag, @KoraApp), not from any annotation.processor.* package.
• Plaintext vs TLS is chosen by the URL scheme (http:// = plaintext, https:///grpc:// per transport). There is no usePlaintext config key.
• The mandatory annotation processor must be present: Java annotationProcessor "ru.tinkoff.kora:annotation-processors", Kotlin ksp "ru.tinkoff.kora:symbol-processors".

Quick Start

1. Dependencies

Pin the BOM (kora-parent); never version individual ru.tinkoff.kora:* artifacts.

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

configurations {
    koraBom
    annotationProcessor.extendsFrom(koraBom)
    implementation.extendsFrom(koraBom)
}

dependencies {
    koraBom platform("ru.tinkoff.kora:kora-parent:1.2.19")
    annotationProcessor "ru.tinkoff.kora:annotation-processors"

    implementation "ru.tinkoff.kora:grpc-client"
    implementation "ru.tinkoff.kora:config-hocon"
    implementation "ru.tinkoff.kora:logging-logback"
    implementation "io.grpc:grpc-protobuf:1.74.0"
    compileOnly "javax.annotation:javax.annotation-api:1.3.2"
}

protobuf {
    protoc { artifact = "com.google.protobuf:protoc:3.25.3" }
    plugins {
        grpc { artifact = "io.grpc:protoc-gen-grpc-java:1.74.0" }
    }
    generateProtoTasks {
        all()*.plugins { grpc {} }
    }
}

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