I'm migrating our Ktor app to Docker Compose for local development, but I'm struggling to get watch ...

# ktor

[Matt]

I'm migrating our Ktor app to Docker Compose for local development, but I'm struggling to get watch mode working inside the container. It works if I run it directly on my machine, but inside the container I get:
No ktor.deployment.watch patterns match classpath entries, automatic reload is not active
Any ideas on what might be the issue? (It's running OpenJDK 1.8 in the container)

[cy]

How do you run your app in a docker container? is it a fatjar or you are compiling it via gradle inside of the container?

[Matt]

Yeah, compiling it inside the container:

CMD ["../gradlew", "run"]

[cy]

How does your watch pattern look like?

[cy]

And what is your main class? Is it DevelopmentEngine or your own class?

[cy]

Are you sure that you use Java 8 (not 9) in your container?

[Matt]

ktor {
  deployment {
    port = 8080
    watch = [gems]
  }

(All code is beneath gems.* namespace)

[Matt]

Main class is:

fun main(args: Array<String>) {
    val environment = commandLineEnvironment(args)
    val server = embeddedServer(Netty, environment)
    server.start()
}

[Matt]

$ docker exec -it backend java -version
openjdk version "1.8.0_162"
OpenJDK Runtime Environment (build 1.8.0_162-8u162-b12-1~deb9u1-b12)
OpenJDK 64-Bit Server VM (build 25.162-b12, mixed mode)

[cy]

With debug loglevel it should be a full classloader urls list logged

[cy]

something like [DEBUG] Class Loader:

[Matt]

https://gist.githubusercontent.com/mdr/5bf6a5fd7ec70a043c9dae2773f04d47/raw/849d0e31f0418971e7a4c6e4b56bc5fb74302705/gistfile1.txt

[cy]

Ah I see..

[cy]

adding backend to watches list should fix it

[cy]

this is so disappointing problem

[Matt]

ah, OK, I see...apologies, I somehow got the impression the watch had to be a substring of the package, rather than the classloader URL, my bad 🤦

[cy]

Yes, I don't know why it makes such impressioin

[cy]

It's quite common

[Matt]

Well, thanks for helping me discover my stupidity 😉 Cheers!