Has anyone successfully deployed a Ktor App that uses WebSoc

Question

Has anyone successfully deployed a Ktor App that uses WebSockets to a WAR in Jetty Container While making a simple for Compose for Web I encountered this long standing unresolved issue Ktor tries to use `HttpServletRequest upgrade ` which is not supported in Jetty skull and crossbones This appears to be a complete blocker for deploying WebSockets as a WAR in Jetty Disturbing given that it s a very standard configuration for production usage scream Is anyone able to suggest a fix or workaround Reproduction steps

Chris Miller · Answer

I don t have an answer for you but it seems like upgrade is supported in Jetty since 10 0 1

darkmoon_uk · Answer

< Chris Miller> Thank you This led me to look further into The Ktor neglects to mention which Jetty Netty Tomcat versions are either embedded or tested against this is surely a gap given the variation in compatibility across versions that I m uncovering My original error was seen when hosting a basic websocket example Ktor WAR in a Jetty instance provided by the `docker latest` container It transpires that `latest` is Jetty version `9 x` while `10 x` and `11 x` version streams also exist I tested these `9 x` as already seen doesn t implement the connection `upgrade ` method that Ktor calls internally from its WebSocket implementation `11 x` is plainly unsuitable it represents Jetty project s big bang move to a new Jakarta project servlet standard and doesn t recognise the `javax ` family of Servlet classes at all That leaves `10 x` I hoped this would work but instead I get a new error from the Server when it attempts to open the WebSocket session `ERROR Application 101 Switching Protocols GET web getting started webapp numberUpdates java lang IllegalStateException s=WAITING rs=ASYNC os=OPEN is=IDLE awp=false se=false i=false al=0`

darkmoon_uk · Answer

< e5l> As I can see you are the major author of WebSockets feature in Ktor wondering if you can kindly shine any light on this Jetty WAR deployment situation Maybe there s some gotcha I m missing

darkmoon_uk · Answer

<https youtrack jetbrains com issue KTOR 184> updated

e5l · Answer

Hey sure Will take a look

darkmoon_uk · Answer

Hi < e5l> I understand there may be higher priorities but do you have any more thoughts on using WebSockets from a WAR I ll try to create an even more minimal example tonight next few hours here in Aus and will update the ticket with any findings

darkmoon_uk · Answer

I m working with Ktor code snippets from the documentation repo Notes re the `jetty war` <https github com ktorio ktor documentation tree main codeSnippets snippets jetty war|sample> There s nothing about it that looks Jetty specific could should be called `servlet war` The Gretty plugin version referenced is unmaintained and should be updated to `org gretty` `3 0 4` The sample doesn t work because the main module referenced in `application conf` isn t fully qualified Changing it to `io ktor snippets hello HelloApplicationKt main` makes it work I ll probably raise a PR with these fixes soon

darkmoon_uk · Answer

Confirmed that even minimally adding `install WebSockets ` and `webSocket ws send Frame Text Hello ` to the lightly fixed `jetty war` sample gives rise to ```2021 06 01 14 43 41 914 pool 20 thread 3 ERROR Application 101 Switching Protocols GET jetty war ws java lang IllegalStateException s=WAITING rs=ASYNC os=OPEN is=IDLE awp=false se=false i=false al=0 ```

darkmoon_uk · Answer

when the `war` is deployed in my Dockerised Jetty 10 x Container instance

darkmoon_uk · Answer

In this case the Ktor version is `1 6 0` so WS still broken there disappointed