Hey. Quick question from me surrounding “best-practices”. I have a spring boot application, and I wa...

# graphql-kotlin

[Anders Kirkeby]

Hey. Quick question from me surrounding “best-practices”. I have a spring boot application, and I want to add a sessionId onto each request (for simplicity let’s say i want to a unique id for each query) - what’s the intended way of doing this with contexts/directives, etc? Especially if we’re adding this unique Id onto MDC, where would you thing it natural to put the MDC.put(“session”) and MDC.remove(“session”)?

[Dariusz Kuc]

It is a pretty common use case (especially with something like tracing).

Underlying problem is how to store it so it is available for the whole session. With Spring MVC apps you could use something like ThreadLocals to store it (which MDC relies on). With WebFlux (which we use in graphql-kotlin-spring-server) you have reactor subscriber context (and coroutine context through interop).

[Dariusz Kuc]

Unfortunately though is that since we rely on graphql-java execution logic we jump between reactor/coroutines and CompletableFuture which don't have any contextual information.

One way to solve it is to create your custom GraphQLServer (https://github.com/ExpediaGroup/graphql-kotlin/blob/master/servers/graphql-kotlin-[…]tlin/com/expediagroup/graphql/server/execution/GraphQLServer.kt) which populates MDC (and other contextual data) and then wraps the execution in your coroutine context. You then would also need to create custom DataFetcher (I'd extend https://github.com/ExpediaGroup/graphql-kotlin/blob/master/generator/graphql-kotli[…]expediagroup/graphql/generator/execution/FunctionDataFetcher.kt) that propagates the coroutine context when invoking suspendable functions.

[Dariusz Kuc]

Thats actually what we do internally in our servers.

[Dariusz Kuc]

Personally I'd also store that ID in the GraphQL context object which is bound to the whole GraphQL request and can be retrieved easily from environment (e.g. so you could use it from instrumentations etc)

[Anders Kirkeby]

I see 🤔 Ye, I was curious since it seems like a (very) common use case, but it makes sense when you explain it like that!

Thanks for the pointers! I’ll look into doing something like that 🙂

[Dariusz Kuc]

🤞 one day will have time to rewrite that execution logic to coroutines and drop the completable future dependency

[Anders Kirkeby]

That would indeed be amazing 🙏

[Robert]

Spring WebFlux / Reactor provides some ways to do it: https://piotrminkowski.com/2019/10/15/reactive-logging-with-spring-webflux-and-logstash/