Services

To define a service, create a new .proto file in the proto folder next to your source sets:

├── build.gradle.kts
├── settings.gradle.kts
└── src
    ├── main
    │   ├── kotlin
    │   │   ├── Client.kt
    │   │   ├── ImageRecognizer.kt
    │   │   └── Server.kt
    │   └── resources
    │       └── logback.xml
    └── proto
        └── image-recognizer.proto

Inside the .proto file define your service:

syntax = "proto3";

message Image {
  bytes data = 1;
}

message RecogniseResult {
  int32 category = 1;
}

service ImageRecognizer {
  rpc recognize(Image) returns (RecogniseResult);
}

This will generate the necessary code, including the most important interfaces: ImageRecognizer, Image, RecogniseResult:

@Grpc
interface ImageRecognizer {
    suspend fun recognize(image: Image): RecogniseResult
}

interface RecogniseResult {
    val category: Int

    companion object
}

interface Image {
    val data: ByteArray

    companion object
}

You can implement the ImageRecognizer:

class ImageRecognizerImpl : ImageRecognizer {
    override suspend fun recognize(image: Image): RecogniseResult {
        val byte = image.data[0].toInt()
        delay(100) // heavy processing
        val result = RecogniseResult {
            category = if (byte == 0) 0 else 1
        }
        return result
    }
}

Here you can also see the usage of the RecogniseResult interface. To create an instance, use its .invoke() extension function:

RecogniseResult {
    category = 0
}

Services﻿

Limitations﻿

Services

Limitations