Ktor: ClassCastException launching

Created on 1 Jan 2020 · 8Comments · Source: ktorio/ktor

Ktor Version and Engine Used (client or server and name)
kotlin_version=1.3.61
ktor_version=1.3.0-rc2
coroutines_version=1.3.3-native-mt

Describe the bug
Calling testNetworkCall() from ViewController#viewDidLoad in iOS leads to a kotlin.ClassCastException

  GlobalScope.launch {
    HttpClient { }.get {
      url {
        takeFrom("https://api.basebeta.com")
        encodedPath = "/rankings"
      }
    }
  }

Full stacktrace

Uncaught Kotlin exception: kotlinx.coroutines.CoroutinesInternalError: Fatal exception in coroutines machinery for AwaitContinuation(Shareable[used]){HttpResponseData=(statusCode=200 OK)}@cb3ac8. Please read KDoc to 'handleFatalException' method and report this incident to maintainers
        at 0   BaseBetaCommonApi                   0x0000000111c1ac63 kfun:kotlin.Error.<init>(kotlin.String?;kotlin.Throwable?)kotlin.Error + 115
        at 1   BaseBetaCommonApi                   0x0000000111d20703 kfun:kotlinx.coroutines.CoroutinesInternalError.<init>(kotlin.String;kotlin.Throwable)kotlinx.coroutines.CoroutinesInternalError + 115
        at 2   BaseBetaCommonApi                   0x0000000111d86cba kfun:kotlinx.coroutines.DispatchedTask.handleFatalException$kotlinx-coroutines-core(kotlin.Throwable?;kotlin.Throwable?) + 938
        at 3   BaseBetaCommonApi                   0x0000000111d868b0 kfun:kotlinx.coroutines.DispatchedTask.run() + 3568
        at 4   BaseBetaCommonApi                   0x0000000111d1b908 kfun:kotlinx.coroutines.EventLoopImplBase.processNextEvent()ValueType + 792
        at 5   BaseBetaCommonApi                   0x0000000111da26f1 kfun:kotlinx.coroutines.runEventLoop$kotlinx-coroutines-core(kotlinx.coroutines.EventLoop?;kotlin.Function0<kotlin.Boolean>) + 881
        at 6   BaseBetaCommonApi                   0x0000000111da9d12 kfun:kotlinx.coroutines.WorkerCoroutineDispatcherImpl.start$lambda-0#internal + 402
        at 7   BaseBetaCommonApi                   0x0000000111da9efb kfun:kotlinx.coroutines.WorkerCoroutineDispatcherImpl.$start$lambda-0$FUNCTION_REFERENCE$146.invoke#internal + 59
        at 8   BaseBetaCommonApi                   0x0000000111da9f5b kfun:kotlinx.coroutines.WorkerCoroutineDispatcherImpl.$start$lambda-0$FUNCTION_REFERENCE$146.$<bridge-UNN>invoke()#internal + 59
        at 9   BaseBetaCommonApi                   0x0000000111c4fd31 WorkerLaunchpad + 177
        at 10  BaseBetaCommonApi                   0x0000000112052d89 _ZN6Worker19processQueueElementEb + 2569
        at 11  BaseBetaCommonApi                   0x0000000112053336 _ZN12_GLOBAL__N_113workerRoutineEPv + 54
        at 12  libsystem_pthread.dylib             0x00007fff51bfe2eb _pthread_body + 126
        at 13  libsystem_pthread.dylib             0x00007fff51c01249 _pthread_start + 66
        at 14  libsystem_pthread.dylib             0x00007fff51bfd40d thread_start + 13
Caused by: kotlin.ClassCastException: kotlin.coroutines.native.internal.CompletedContinuation cannot be cast to kotlinx.coroutines.DispatchedContinuation
        at 0   BaseBetaCommonApi                   0x0000000111c21227 kfun:kotlin.Throwable.<init>(kotlin.String?)kotlin.Throwable + 87
        at 1   BaseBetaCommonApi                   0x0000000111c1a585 kfun:kotlin.Exception.<init>(kotlin.String?)kotlin.Exception + 85
        at 2   BaseBetaCommonApi                   0x0000000111c1a0c5 kfun:kotlin.RuntimeException.<init>(kotlin.String?)kotlin.RuntimeException + 85
        at 3   BaseBetaCommonApi                   0x0000000111c1ae65 kfun:kotlin.ClassCastException.<init>(kotlin.String?)kotlin.ClassCastException + 85
        at 4   BaseBetaCommonApi                   0x0000000111c6ba5b ThrowClassCastException + 939
        at 5   BaseBetaCommonApi                   0x0000000111d14ef8 kfun:kotlinx.coroutines.CoroutineDispatcher.releaseInterceptedContinuation(kotlin.coroutines.Continuation<#STAR>) + 216
        at 6   BaseBetaCommonApi                   0x0000000111c42400 kfun:kotlin.coroutines.native.internal.ContinuationImpl.releaseIntercepted() + 768
        at 7   BaseBetaCommonApi                   0x0000000111c42a62 kfun:kotlin.coroutines.native.internal.BaseContinuationImpl.resumeWith(kotlin.Result<kotlin.Any?>) + 1234
        at 8   BaseBetaCommonApi                   0x0000000111e8cbf2 kfun:io.ktor.util.pipeline.SuspendFunctionGun.resumeRootWith#internal + 930
        at 9   BaseBetaCommonApi                   0x0000000111e8c773 kfun:io.ktor.util.pipeline.SuspendFunctionGun.loop#internal + 1699
        at 10  BaseBetaCommonApi                   0x0000000111e8e651 kfun:io.ktor.util.pipeline.SuspendFunctionGun.object-1.resumeWith#internal + 353
        at 11  BaseBetaCommonApi                   0x0000000111c42b28 kfun:kotlin.coroutines.native.internal.BaseContinuationImpl.resumeWith(kotlin.Result<kotlin.Any?>) + 1432
        at 12  BaseBetaCommonApi                   0x0000000111e8cbf2 kfun:io.ktor.util.pipeline.SuspendFunctionGun.resumeRootWith#internal + 930
        at 13  BaseBetaCommonApi                   0x0000000111e8c773 kfun:io.ktor.util.pipeline.SuspendFunctionGun.loop#internal + 1699
        at 14  BaseBetaCommonApi                   0x0000000111e8e651 kfun:io.ktor.util.pipeline.SuspendFunctionGun.object-1.resumeWith#internal + 353
        at 15  BaseBetaCommonApi                   0x0000000111c42b28 kfun:kotlin.coroutines.native.internal.BaseContinuationImpl.resumeWith(kotlin.Result<kotlin.Any?>) + 1432
        at 16  BaseBetaCommonApi                   0x0000000111e8cbf2 kfun:io.ktor.util.pipeline.SuspendFunctionGun.resumeRootWith#internal + 930
        at 17  BaseBetaCommonApi                   0x0000000111e8c773 kfun:io.ktor.util.pipeline.SuspendFunctionGun.loop#internal + 1699
        at 18  BaseBetaCommonApi                   0x0000000111e8e651 kfun:io.ktor.util.pipeline.SuspendFunctionGun.object-1.resumeWith#internal + 353
        at 19  BaseBetaCommonApi                   0x0000000111c42b28 kfun:kotlin.coroutines.native.internal.BaseContinuationImpl.resumeWith(kotlin.Result<kotlin.Any?>) + 1432
        at 20  BaseBetaCommonApi                   0x0000000111d8659c kfun:kotlinx.coroutines.DispatchedTask.run() + 2780
        at 21  BaseBetaCommonApi                   0x0000000111d1b908 kfun:kotlinx.coroutines.EventLoopImplBase.processNextEvent()ValueType + 792
        at 22  BaseBetaCommonApi                   0x0000000111da26f1 kfun:kotlinx.coroutines.runEventLoop$kotlinx-coroutines-core(kotlinx.coroutines.EventLoop?;kotlin.Function0<kotlin.Boolean>) + 881
        at 23  BaseBetaCommonApi                   0x0000000111da9d12 kfun:kotlinx.coroutines.WorkerCoroutineDispatcherImpl.start$lambda-0#internal + 402
        at 24  BaseBetaCommonApi                   0x0000000111da9efb kfun:kotlinx.coroutines.WorkerCoroutineDispatcherImpl.$start$lambda-0$FUNCTION_REFERENCE$146.invoke#internal + 59
        at 25  BaseBetaCommonApi                   0x0000000111da9f5b kfun:kotlinx.coroutines.WorkerCoroutineDispatcherImpl.$start$lambda-0$FUNCTION_REFERENCE$146.$<bridge-UNN>invoke()#internal + 59
        at 26  BaseBetaCommonApi                   0x0000000111c4fd31 WorkerLaunchpad + 177
        at 27  BaseBetaCommonApi                   0x0000000112052d89 _ZN6Worker19processQueueElementEb + 2569
        at 28  BaseBetaCommonApi                   0x0000000112053336 _ZN12_GLOBAL__N_113workerRoutineEPv + 54
        at 29  libsystem_pthread.dylib             0x00007fff51bfe2eb _pthread_body + 126

To Reproduce
Copy and paste the code snippet from above into the common module of a multiplatform project. Run the function from ViewController#viewDidLoad in the iOS app.

Expected behavior
I expect the code to execute without throwing a ClassCastException.

bug

Source

brendanw

👍1

All 8 comments

kotlin.ClassCastException: kotlin.coroutines.native.internal.CompletedContinuation cannot be cast to kotlinx.coroutines.DispatchedContinuation
        at 0   BaseBetaCommonApi                   0x0000000111c21227 kfun:kotlin.Throwable.<init>(kotlin.String?)kotlin.Throwable + 87
        at 1   BaseBetaCommonApi                   0x0000000111c1a585 kfun:kotlin.Exception.<init>(kotlin.String?)kotlin.Exception + 85
        at 2   BaseBetaCommonApi                   0x0000000111c1a0c5 kfun:kotlin.RuntimeException.<init>(kotlin.String?)kotlin.RuntimeException + 85
        at 3   BaseBetaCommonApi                   0x0000000111c1ae65 kfun:kotlin.ClassCastException.<init>(kotlin.String?)kotlin.ClassCastException + 85
        at 4   BaseBetaCommonApi                   0x0000000111c6ba5b ThrowClassCastException + 939
        at 5   BaseBetaCommonApi                   0x0000000111d14ef8 kfun:kotlinx.coroutines.CoroutineDispatcher.releaseInterceptedContinuation(kotlin.coroutines.Continuation<#STAR>) + 216
        at 6   BaseBetaCommonApi                   0x0000000111c42400 kfun:kotlin.coroutines.native.internal.ContinuationImpl.releaseIntercepted() + 768
        at 7   BaseBetaCommonApi                   0x0000000111c42a62 kfun:kotlin.coroutines.native.internal.BaseContinuationImpl.resumeWith(kotlin.Result<kotlin.Any?>) + 1234

cy6erGn0m on 1 Jan 2020

@qwwdfsad any ideas?

cy6erGn0m on 1 Jan 2020

👀1

Looks like a bug in releaseContinuation codegen in K/N backend (especially if it is not reproducible on JVM), meaning that Continuation was resumed twice.
Probably related to reusable continuations in coroutines as well

qwwdfsad on 1 Jan 2020

The stack trace contains AwaitContinuation that is used in *Deferred.await() (CompletableDeferred.await() or async {}.await()). In iOS we have only one place where we invoke such function: HttpClientEngine.executeWithinCallContext (it's async + await).

Also, the code is common that never crashed like this before.

cy6erGn0m on 13 Jan 2020

Please check the following ticket on YouTrack for follow-ups to this issue. GitHub issues will be closed in the coming weeks.

oleg-larshin on 10 Aug 2020

Getting the same crash with ktor 1.4.1 and coroutines 1.3.9-native-mt-2. How can we fix it?

Ornolfr on 9 Oct 2020

👍1

It seems there is an issue with Kotlin 1.4.10, according to this https://github.com/Kotlin/kotlinx.coroutines/issues/2295
I downgraded ktor to 1.3.2, Kotlin back to version 1.3.72 and coroutines to 1.3.7 and only then it worked, not sure if maybe I had something cached somewhere and it was still compiling with Kotlin 1.4