Ktor on Native Image - Doesn't work

[atrianac]

Steps to Reproduce

1. Create a Ktor/Kotlin application using Native Image. The docker file looks like:

FROM oracle/graalvm-ce:20.1.0-java11 as graalvm
RUN gu install native-image

COPY . /home/app/micronaut-api
WORKDIR /home/app/micronaut-api

RUN native-image --verbose --no-server --no-fallback --install-exit-handlers --verbose -J-Xmx8G -J-Xms4G -H:+ReportUnsupportedElementsAtRuntime -H:+ReportExceptionStackTraces -H:+TraceClassInitialization -H:+PrintClassInitialization -H:+RemoveSaturatedTypeFlows -cp build/libs/micronaut-api-*-all.jar

FROM frolvlad/alpine-glibc
RUN apk update && apk add libstdc++
EXPOSE 8080
COPY --from=graalvm /home/app/micronaut-api/micronaut-api /app/micronaut-api
ENTRYPOINT ["/app/micronaut-api"]

2. Create the docker image running:

docker build . -t micronaut-api

3. Launch a container:

 docker run -p 8080:8080 micronaut-api

4. Inspect the docker logs

docker logs {container.id}

The output looks like this:

01:24:18.763 [main] INFO  Application - No ktor.deployment.watch patterns specified, automatic reload is not active
01:24:18.766 [main] INFO  Application - Responding at http://0.0.0.0:8080
01:24:18.768 [main] INFO  io.micronaut.runtime.Micronaut - Startup completed in 4378ms. Server Running: http://0.0.0.0:8080

5. Inspect the response, from any endpoint using curl:

curl http://localhost:8080/{path}

An empty response from the server is returned.

Expected Behaviour

Using the same code project, but on Hotspot runtime, the server returns a response:

FROM amazoncorretto:11.0.8-alpine

COPY ./build/libs/micronaut-api-*-all.jar /home/app/micronaut-api.jar
WORKDIR /home/app

EXPOSE 8080
ENTRYPOINT ["java", "-jar", "micronaut-api.jar"]

Actual Behaviour

An empty response from the server is returned.

Environment Information

• Operating System: MacOS Catalina 10.15.6
• Micronaut Version: 2.0.1
• JDK Version: 11.0.8
• Graal VM: 20.1.0

Example Application

• Gist Example

[atrianac]

I uploaded the complete repository: micronaut-ktor-api

[willbuck]

So @atrianac I was able to reproduce the issue as you describe it, however I think we need to elevate this issue to ktor itself. I was also able to reproduce the issue by replacing the main function of the Application.kt file in your micronaut-ktor-api with the bare-bones "Hello World" example from the ktor docs and see the exact same problem (see below for replaced Application.kt.

So I think likely this is a graal + ktor related issue, and not really related to micronaut.

@atrianac would you feel comfortable filing an issue w/ the ktor folks? I'm afraid I don't have a great deal of ktor experience but I can help with filing the issue if needed, just let me know!

package com.adidas.ys.http
import io.ktor.server.netty.NettyApplicationEngine
import io.ktor.application.*
import io.ktor.http.*
import io.ktor.response.*
import io.ktor.routing.*
import io.ktor.server.engine.*
import io.ktor.server.netty.*

object Application {
    @JvmStatic
    fun main(args: Array<String>) {
        val server = embeddedServer(Netty, port = 8080) {
            routing {
                get("/") {
                    call.respondText("Hello World!", ContentType.Text.Plain)
                }
                get("/demo") {
                    call.respondText("HELLO WORLD!")
                }
            }
        }
        server.start(wait = true)
    }
}

[atrianac]

@willbuck Thanks, I will do!

[atrianac]

The issue in Ktor Project is reported here: https://youtrack.jetbrains.com/issue/KTOR-1307

[atrianac]

@willbuck The Ktor team answered the question. It is necessary to add --initialize-at-build-time=io.ktor,kotlinx,kotlin option to native-image command and this snippet to your `reflection-config.json``

[
  {
    "name": "kotlin.reflect.jvm.internal.ReflectionFactoryImpl",
    "allDeclaredConstructors":true
  },
  {
    "name": "kotlin.KotlinVersion",
    "allPublicMethods": true,
    "allDeclaredFields":true,
    "allDeclaredMethods":true,
    "allDeclaredConstructors":true
  },
  {
    "name": "kotlin.KotlinVersion[]"
  },
  {
    "name": "kotlin.KotlinVersion$Companion"
  },
  {
    "name": "kotlin.KotlinVersion$Companion[]"
  },
  {
    "name": "kotlin.internal.jdk8.JDK8PlatformImplementations",
    "allPublicMethods": true,
    "allDeclaredFields":true,
    "allDeclaredMethods":true,
    "allDeclaredConstructors":true
  }
]

I tested and It is already working. Where do we add those change for the micronaut-kotlinproject?

[willbuck]

@atrianac I will take a look later this week!

[atrianac]

@willbuck thanks. I just updated the original repository with the right changes.

[willbuck]

@atrianac I took a look at this and I think this would actually require a change in https://github.com/micronaut-projects/micronaut-starter/ , probably to the apply method of:

the Ktor feature: https://github.com/micronaut-projects/micronaut-starter/blob/2.3.x/starter-core/src/main/java/io/micronaut/starter/feature/kotlin/Ktor.java#L99

and/or the GraalVM feature (maybe? not sure this is the right spot): https://github.com/micronaut-projects/micronaut-starter/blob/2.3.x/starter-core/src/main/java/io/micronaut/starter/feature/graalvm/GraalVM.java

I'm fairly engaged w/ client work at present so I don't know that I can get to it anytime soon, but contributions would be welcome if you'd like to give it a shot!

[graemerocher]

I don’t believe it needs any of that. The reflection config and native image args can exist in this project in a file in the src/main/resources/META-INF/native-image directory

[graemerocher]

See https://github.com/micronaut-projects/micronaut-r2dbc/blob/master/r2dbc-core/src/main/resources/META-INF/native-image/io.micronaut.r2dbc/micronaut-r2dbc-core/native-image.properties for example

The reflection json needs to be in a file called reflect-config.json in the same directory

[willbuck]

My mistake @atrianac , thanks for correcting me Graeme!

[sdelamo]

@timyates can you verify if this issue is still present?

[timyates]

@sdelamo @graemerocher I believe this issue is still present

At least, I cannot get a native Ktor application to return any content (even with the above changes)