in kotlin-native .. what is the correct way to sta...

# ktor

[Nikky]

in kotlin-native ..
what is the correct way to start ktor so that i can shut it down from a signal handler?
seems like doing server.start(wait = true) will just block my application completely when i call server.stop(500, 500)

not sure why.. could it be that joining the jobs is blocking ?

for now i am using this..

server = embeddedServer(...)

server.start(wait = false)

while (true) {
    sleep(1)
}

and in the signal handler i call

server.stop(500, 500)

if anybody knows a cleaner solution.. would like to make this work better

i also noticed.. if i use delay instead of sleep it will also continue to block..?

[hfhbd]

What about using coroutines?

coroutineScope {
  val server = embeddedServer(..)
  server.start(wait = false)

  action()
  server.stop()
}

suspend fun action() = suspendCoroutine { cont ->
  registerSignalHandler(callback = {
    cont.resume()
  })
}

[Nikky]

this works nicely

if i understand this correctly it stops at the end of suspendCoroutine until the signal handler triggers the continuation ?

[hfhbd]

Yes

[ephemient]

IMO it would be safer to use a semaphore,

val stopSignal = Semaphore(1, 1)
registerSignalHandler { stopSignal.release() }
coroutineScope {
    ...
    stopSignal.acquire()
}

note that in both solutions, your program will crash if the signal handler is invoked multiple times. you can use a CompletableDeferred instead if that is a concern

[Nikky]

upon some more experimenting i found this solution..

val completableJob = SupervisorJob()
SignalHandler.onSignal(SIGINT) { _, signalName ->
    logger.warn { "received signal $signalName, stopping server.." }
    // completableJob.complete() // this will cause it to hang
    completableJob.cancel()
}
embeddedServer(
    factory = CIO,
    host = serverOptions.host,
    port = serverOptions.port,
    logger = KtorKLogger(),
    parentCoroutineContext = completableJob
) {
    configureHTTP()
    configureRouting()
}.start(true)

on a sidenote.. ith all these solutions there seems to be the problem that after the interrupt.. any println or logging calls seem to disappear
might be a problem caused by interrupting.. i wonder.. what mistake i am overlooking..
PS: found that using cancel will work..

[Nikky]

but i really like the solution using a CompletableDeferred too