Hi I run a Ktor server on Android 5+ and I m trying to upgra

Question

Hi I run a Ktor server on Android 5+ and I m trying to upgrade Ktor from 1 4 to 1 6 Unfortunately some of the changes in ktor uses `java nio file FileSystems` which breaks on Android 5 8 but works in newer versions <https github com ktorio ktor blob b519016210d5ced5f63b6da9a3489e3a799903b1 ktor server ktor server host common jvm src io ktor server engine ApplicationEngineEnvironmentReloading kt L71|This line in >`ApplicationEngineEnvironmentReloading` is the culprit but I don t think that class should be used in production right So how can I disable that behaviour so that that class won t be loaded I m not running the server in development mode so it shouldn t be trying to reload the server

Gus · Answer

<https youtrack jetbrains com issue KTOR 2916|I just reported this bug> but if anyone can think of a workaround I d really appreciate it

Aleksei Tirman [JB] · Answer

As a workaround you can explicitly pass empty list for watch paths ```val server = embeddedServer CIO port = 8082 watchPaths = emptyList routing get ```

Gus · Answer

Thanks I ll try it now But I just realised autoreload isn t used anyway according to the logs which I ve just enabled `INFO ktor application Autoreload is disabled because the development mode is off `

Gus · Answer

So that code using `java nio file FileSystems` must be executed anyway regardless of development mode

Aleksei Tirman [JB] · Answer

That s why I suggested passing an empty list for watch paths There are guards like `watchPatterns isEmpty ` before usage of `watcher`

Gus · Answer

Oh cool I m going to try it in a moment and I ll let you know how it goes

Gus · Answer

I get a different error on Android 5 7 if I make the change you suggested ```java lang NoSuchMethodError No virtual method getParameterCount I in class Ljava lang reflect Constructor or its super classes declaration of java lang reflect Constructor appears in system framework core libart jar FATAL EXCEPTION main Process tech relaycorp gateway PID 6740 java lang NoSuchMethodError No virtual method getParameterCount I in class Ljava lang reflect Constructor or its super classes declaration of java lang reflect Constructor appears in system framework core libart jar at io ktor server engine internal CallableUtilsKt executeModuleFunction CallableUtils kt 43 at io ktor server engine ApplicationEngineEnvironmentReloading$launchModuleByName$1 invoke ApplicationEngineEnvironmentReloading kt 317 at io ktor server engine ApplicationEngineEnvironmentReloading$launchModuleByName$1 invoke ApplicationEngineEnvironmentReloading kt 316 at io ktor server engine ApplicationEngineEnvironmentReloading avoidingDoubleStartupFor ApplicationEngineEnvironmentReloading kt 341 at io ktor server engine ApplicationEngineEnvironmentReloading launchModuleByName ApplicationEngineEnvironmentReloading kt 316 at io ktor server engine ApplicationEngineEnvironmentReloading access$launchModuleByName ApplicationEngineEnvironmentReloading kt 30 at io ktor server engine ApplicationEngineEnvironmentReloading$instantiateAndConfigureApplication$1 invoke ApplicationEngineEnvironmentReloading kt 304 at io ktor server engine ApplicationEngineEnvironmentReloading$instantiateAndConfigureApplication$1 invoke ApplicationEngineEnvironmentReloading kt 295 at io ktor server engine ApplicationEngineEnvironmentReloading avoidingDoubleStartup ApplicationEngineEnvironmentReloading kt 323 at io ktor server engine ApplicationEngineEnvironmentReloading instantiateAndConfigureApplication ApplicationEngineEnvironmentReloading kt 295 at io ktor server engine ApplicationEngineEnvironmentReloading createApplication ApplicationEngineEnvironmentReloading kt 136 at io ktor server engine ApplicationEngineEnvironmentReloading start ApplicationEngineEnvironmentReloading kt 268 at io ktor server netty NettyApplicationEngine start NettyApplicationEngine kt 174 at tech relaycorp gateway pdc local PDCServer$start$2 invokeSuspend PDCServer kt 41 at kotlin coroutines jvm internal BaseContinuationImpl resumeWith ContinuationImpl kt 33 at kotlinx coroutines DispatchedTask run DispatchedTask kt 106 at kotlinx coroutines scheduling CoroutineScheduler runSafely CoroutineScheduler kt 571 at kotlinx coroutines scheduling CoroutineScheduler$Worker executeTask CoroutineScheduler kt 750 at kotlinx coroutines scheduling CoroutineScheduler$Worker runWorker CoroutineScheduler kt 678 at kotlinx coroutines scheduling CoroutineScheduler$Worker run CoroutineScheduler kt 665 ``` The server continues to work on Android 8+

Aleksei Tirman [JB] · Answer

That s something in the code of a module most likely not related to Ktor

Gus · Answer

I ve just created a from scratch and I get the same behaviour when I

Gus · Answer

Also unless I m misreading it the stack trace suggests the exception is thrown at `io ktor server engine internal CallableUtilsKt executeModuleFunction CallableUtils kt 43 `

Aleksei Tirman [JB] · Answer

Sorry I misread the stack trace Indeed the `getParameterCount` method was added in Android API 26

Aleksei Tirman [JB] · Answer

Here is the <https youtrack jetbrains com issue KTOR 2924|issue>

Gus · Answer

Thanks