@Jeff Hudson Heya, I was just wondering why the

withMdc

function was removed from Kairo in v6, or was it just moved somewhere else? https://github.com/hudson155/kairo/blob/v5.15.1/kairo-mdc/src/main/kotlin/kairo/mdc/withMdc.kt

Hi Team, I am using the following environment for my project: • Kotlin: 2.2.20 • Ktor: 3.3.1 I am generating OpenAPI specifications using

./gradlew buildOpenApi

. I noticed a couple of things: 1. The

@description

annotation in KDoc (as documented here) does not appear in the generated OpenAPI output. It seems the description is ignored, while the first line of the KDoc becomes the summary. 2. The OpenAPI spec currently includes internal endpoints (e.g.,

/json/kotlinx-serialization

). Is there a way/annotation to exclude such endpoints from the generated spec? 3. Is there any support or recommended approach for nested tags? Currently, only flat tag grouping is supported. Thanks in advance for the guidance!

When i run many parallell tests with ktor testApplication i always hit the 10 second timeout on some tests no matter what i configure. I use junit 5, anyone else had this problem?

Hi, I am looking at https://ktor.io/docs/server-request-validation.html and wondering, whether I should install RequestValidation for every route? The Docs just say it can be installed multiple times, but would that be recommended? How should I handle it if I need different validation for e.g.

GET /users/{id}

,

PUT /users/{id}

,

GET /users/

?

Hi everyone, I'm seeing this weird behaviour with ktor-jetty server where when running the code via the commandline, the program log doesn't include any thread name that belong to the jetty server, here is an example:

Nov 02 06:53:48 backend-server java[675013]: Routing resolve result:
Nov 02 06:53:48 backend-server java[675013]:   SUCCESS @ /api/posts/(method:POST)
Nov 02 06:53:48 backend-server java[675013]: This is session null
Nov 02 06:53:48 backend-server java[675013]: 2025-11-02 06:53:48.248 [eventLoopGroupProxy-4-2] TRACE i.k.server.engine.DefaultTransform - Transformed class io.ktor.utils.io.ByteChannel to class io.ktor.http.cio.CIOMultipartDataBase for /api/pos>
Nov 02 06:53:48 backend-server java[675013]: 2025-11-02 06:53:48.249 [eventLoopGroupProxy-4-2] ERROR Application - Unhandled: POST - /api/posts
Nov 02 06:53:48 backend-server java[675013]: java.lang.NullPointerException: null
Nov 02 06:53:48 backend-server java[675013]:         at com.yourart.RoutingKt$configureRouting$1$5.invokeSuspend(Routing.kt:155)
Nov 02 06:53:48 backend-server java[675013]:         at com.yourart.RoutingKt$configureRouting$1$5.invoke(Routing.kt)
Nov 02 06:53:48 backend-server java[675013]:         at com.yourart.RoutingKt$configureRouting$1$5.invoke(Routing.kt)
Nov 02 06:53:48 backend-server java[675013]:         at io.ktor.server.routing.RoutingNode$buildPipeline$1$1.invokeSuspend(RoutingNode.kt:126)
Nov 02 06:53:48 backend-server java[675013]:         at io.ktor.server.routing.RoutingNode$buildPipeline$1$1.invoke(RoutingNode.kt)

This is when I'm running the code locally via Intellij:

Routing resolve result:
  SUCCESS @ /api/posts/(method:POST)
This is session null
2025-11-02 18:29:27.989 [ktor-jetty-8000-1] TRACE i.k.server.engine.DefaultTransform - Transformed class io.ktor.utils.io.ByteChannel to class io.ktor.http.cio.CIOMultipartDataBase for /api/posts
2025-11-02 18:29:28.026 [ktor-jetty-8000-3] TRACE a.s.k.r.h.operation.OperationHandler - operation started
2025-11-02 18:29:28.053 [ktor-jetty-8000-4] DEBUG a.s.k.r.a.c.ProfileCredentialsProvider - Loading credentials from profile `default`
2025-11-02 18:29:28.062 [ktor-jetty-8000-4] DEBUG a.s.k.r.a.c.ProfileCredentialsProvider - Resolving credentials from static credentials

Does anyone know why this is the case? Thanks in advance

Also, I happened to ran into this error as well, does anyone know what the part where it said

Concurrent read attempts

mean? I'm trying to read a file in this function where this error happened.

2025-11-02 07:39:59.407 [eventLoopGroupProxy-4-3] ERROR Application - Unhandled exception caught for CoroutineName(call-handler)
Nov 02 07:39:59 backend-server java[675297]: io.ktor.utils.io.ConcurrentIOException: Concurrent read attempts
Nov 02 07:39:59 backend-server java[675297]:         at io.ktor.utils.io.ByteChannel.awaitContent(ByteChannel.kt:272)
Nov 02 07:39:59 backend-server java[675297]:         at io.ktor.utils.io.ByteReadChannel$DefaultImpls.awaitContent$default(ByteReadChannel.kt:30)
Nov 02 07:39:59 backend-server java[675297]:         at io.ktor.utils.io.ByteReadChannelOperationsKt.discard(ByteReadChannelOperations.kt:349)
Nov 02 07:39:59 backend-server java[675297]:         at io.ktor.utils.io.ByteReadChannelOperationsKt.discard$default(ByteReadChannelOperations.kt:344)
Nov 02 07:39:59 backend-server java[675297]:         at io.ktor.server.engine.DefaultEnginePipelineKt$defaultEnginePipeline$1.invokeSuspend(DefaultEnginePipeline.kt:42)
Nov 02 07:39:59 backend-server java[675297]:         at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
Nov 02 07:39:59 backend-server java[675297]:         at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:99)
Nov 02 07:39:59 backend-server java[675297]:         at kotlinx.coroutines.EventLoop.processUnconfinedEvent(EventLoop.common.kt:65)
Nov 02 07:39:59 backend-server java[675297]:         at kotlinx.coroutines.internal.DispatchedContinuation.resumeWith(DispatchedContinuation.kt:327)
Nov 02 07:39:59 backend-server java[675297]:         at io.ktor.util.pipeline.SuspendFunctionGun.resumeRootWith(SuspendFunctionGun.kt:149)
Nov 02 07:39:59 backend-server java[675297]:         at io.ktor.util.pipeline.SuspendFunctionGun.loop(SuspendFunctionGun.kt:134)
Nov 02 07:39:59 backend-server java[675297]:         at io.ktor.util.pipeline.SuspendFunctionGun.proceed(SuspendFunctionGun.kt:89)
Nov 02 07:39:59 backend-server java[675297]:         at io.ktor.util.pipeline.SuspendFunctionGun.execute$ktor_utils(SuspendFunctionGun.kt:109)
Nov 02 07:39:59 backend-server java[675297]:         at io.ktor.util.pipeline.Pipeline.execute(Pipeline.kt:86)
Nov 02 07:39:59 backend-server java[675297]:         at

How can I configure Ktor to use a custom serializers module during content negotiation, specifically for a polymorphic type? Something simple like

val serializerModule = SerializersModule {
    polymorphic(Person::class) {
        subclass(SerializablePerson::class)
    }
}

I am using Ktor 3.3.1 with the

Jetty engine

. Calling

call.request.servletRequestAttributes

from the call interceptor throws the following error. Any idea why it’s not set for the Jetty engine?

Any sample apps using DI yet: https://ktor.io/docs/server-dependency-injection.html?topic=rx?

Was checking out the ktor chat project and just realized, you can do this. Pretty cool. Overall the ktor chat project is very elegant. I have some refactoring to do.

Is there any way to configure multiple connectors in the HOCON file (including the sslConnector) ?

📣 The Ktor Annual Survey is live and we’d love your feedback! Whether you’ve built production systems with it or are just experimenting, your input will help us make Ktor better for everyone. Share your experience with its features, documentation, and tools. ktor new* *Take the survey: https://surveys.jetbrains.com/s3/4c0c162c2785

Hey, i'm getting a strange error with Ktor 3.3.2 and Kotlin 2.2.21 when using the wasmJs HttpClient: ReferenceError: process is not defined at io.ktor.util.logging.getKtorLogLevel This is happening when I try to use the Auth plugin, since it calls the KtorSimpleLogger. When I read the source it says its running catching but apparently I'm still getting the ReferenceError

Hi @Bruce Hamilton Regarding the new OpenAPI spec generation, I’m encountering a few issues:

Here is a silly question.... can Ktor Server be made into a more generic (server) application runtime? I really like the way Ktor is configurable and extendable and a lot of things aren't necessarily HTTP-server related: config management, application parameters, DI, plugins, App lifecycle events. In that sense the http-server can also be a plugin? Out of the box Ktor has some pretty nice ways of setting up and configuring your app. The reason I was thinking about this is that I was adding a simple kafka consumer in my app using a plugin and the plugin system and DI made that very ergonomic:

fun Application.module(myService: MyService) {
    subscribe(topic = "my-topic", autoOffsetReset = Latest) {
         on<UserRegistered> { event ->
            myService.userHasRegistered(event.user)
         }
    }
}

No need for HTTP (although I use it for liveness and readyness probe) but I use al the Ktor app features

Anyone else noticed that the Ktor plugin in Intellij has been broken for ages?

Hey does ktor work with grpc? If yes which client does it support?

hey guys, i am having some issue with the CORS plugin, this is my code check 🧵 when i curl the url i do not see the allow methods i’ve added

Thinking of moving from the android ktor-client to the jvm one to use websockets. Would there be a reason I might want to consider a different one?

[Ktor - Android - performances] Hi, we are migrating our REST handling from Retrofit + kotlinx.serizalization JSON to Ktor + kotlinx.serizalization JSON in order to move network layer to KMP and reuse it on iOS. While testing, we noticed significant performance degradation when we executed 10-20 REST calls in parallel (response body size ~2MB each): Ktor + kotlinx.serizalization JSON • Triggering much more Garbage collections with a bunch of following logs in Logcat: ◦ Waiting for a blocking GC Alloc ◦ WaitForGcToComplete blocked Alloc on Background for 868.208ms • Heap spike up to 500MB Retrofit + kotlinx.serizalization JSON • Heap spike up to 250MB • Not triggering GC as mentioned above What could be the reason for this? Is it possible that Ktor + kotlinx.serizalization JSON is creating much more short-lived objects and consumes more memory in order to parse large JSON responses?

@Aleksei Tirman [JB] I started to dig thru the ktor-chat sample app and their are a lot of common reusable models where it almost looks like it is building a ktor/multiplatform-framework. Are there any plans for something like this?

Is netty still not supported in Graalvm? https://youtrack.jetbrains.com/issue/KTOR-2558

Is there a way to set response headers for a websocket route?

Wondering if anybody has encountered anything similar - I am serving a KTOR app as a servlet on a liberty app server. It works okay however there is an issue with the routing in that, every couple of requests to the same path it serves a response from a different path. Access log confirm the correct path is received but KTOR logs that it received a different path. This is not present when run standalone and there is no request filtering.

I think I found a bug with Ktor's Java Client + SSE

suspend fun main() {
    val http = HttpClient(Java) {
        this.expectSuccess = false
        this.followRedirects = false

        install(SSE)
    }

    val sseSession = http.sseSession("<http://127.0.0.1:13004/sse>") {}

    sseSession.cancel()

    delay(100_000)
}

The SSE session does NOT close on the backend, this bug does not happen when using the CIO engine (will create a proper bug report later)

Hello all 👋, I am using Ktor Client in Kotlin Multiplatform app. And theres one use case where i need help/suggestion. ktor Version Details • ktor Ktor 3.1.0 Problem • When I try to inspect the response in a response interceptor, reading

response.body

(or

bodyAsText()

) consumes it so downstream code can’t receive it anymore. • The usual auth callback flow only triggers on network/HTTP 401 — here the HTTP status is 200 so that doesn’t help. eg.

refreshToken

from auth provider Usecase • Server sometimes returns HTTP 200 but the JSON body contains a

"code"

field. If

"code" == 401"

I need to call the refresh-token API, update the auth token, then replay the original request with the new token. So even in HTTPStatus code 200 I need check response and validate about 401 case. So how to intercept response, call the required api in between based on response and Replay the request. ? can anyone please suggest better approach or any document or link ?

For Ktor test framework, when we using testApplication to start up the Ktor application, it is not possible to combine with io.restassured.RestAssured ( We want to to use RestAssured to verify the swagger.yaml ). Is it some other way we can test it without using E2E solution?

For legacy reasons I need to talk to API:s that return both success and error body as http 200. How can i parse/approach that with ktor+kotlinx.serialization? If deserialization fails I get a

JsonConvertException

and not a

ResponseException

with the

HttpResponse

that I can parse into a different structure..

Hey everyone, does anyone know how to unit test SSE on the client side (Android, iOS), I couldn't find any examples

Hi everybody 👋🏼 I'm looking for opensource BE projects that are using Ktor What's your recommandations ?