I’m having trouble getting the remote jvm debugger to attach to my ktor application. The applicatio...

# ktor

[Tim Malseed]

I’m having trouble getting the remote jvm debugger to attach to my ktor application.

The application runs in a docker container, via installDist as per the documentation. Running on openjdk 11

JVM args are :

applicationDefaultJvmArgs = listOf(
    "-Dio.ktor.development=true",
    "-Dagentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=*:8081"
)

I’ve exposed the port 8081.

[Tim Malseed]

At this point I think I’ve tried just about everything, but I get

Unable to open debugger port (localhost:8081): java.net.ConnectException “Connection refused (Connection refused)”

Any suggestions?

[Tim Malseed]

Is it possible that there’s some ‘debug’ flag required?

[christophsturm]

i would try debugging with just a simple hello world java app first

[christophsturm]

with the debugging flags that you are setting it should just work and its not really ktor specific

[Tim Malseed]

OK, that’s a good idea

[Tim Malseed]

The issue was the leading D in the jvm args

[Tim Malseed]

"-Dagentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=*:8081"

Should be

"-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=*:8081"

[christophsturm]

ah right. that makes it almost a no-op

[Tim Malseed]

But the first flag

-Dio.ktor.development=true

Does require the ‘D’

[Tim Malseed]

applicationDefaultJvmArgs = listOf(
    "-Dio.ktor.development=true",
    "-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:8081"
)

[christophsturm]

yeah -D just sets an env variable. you can put anything there and will never get an error

[Tim Malseed]

Ohhh! Thanks, I’ve not understood the purpose of ‘D’ in jvm flags for about 10 years

[Tim Malseed]

Thanks so much. This has been causing me pain all day haha