I have a query and a response object - is there way - for logging purposes - to retrieve request hea...

# apollo-kotlin

[Jan Skrasek]

I have a query and a response object - is there way - for logging purposes - to retrieve request headers that were added automatically by custom Apollo's HttpInterceptor? Thank you.

[mbonnin]

I don't think you can retrieve x-apollo-operation-name from the query neither the response. You could write your own interceptor to get them though and store them in a custom ExecutionContext

[mbonnin]

That being said, the headers that ApolloClient is adding automatically are very few: https://github.com/apollographql/apollo-kotlin/blob/782f7ebbc155471ca8b15bbeaa78ec[…]om/apollographql/apollo3/api/http/DefaultHttpRequestComposer.kt

[mbonnin]

So you can use query.name() and query.id() to retrieve the same values

[Jan Skrasek]

ExecutionContext seems great! I'm just looking for my custom headers.

[mbonnin]

Right 👍

[Jan Skrasek]

I struggle a bit to find a way to add it there in my interceptor - is there a doc for execution context? Or where should I do this?

internal class NetworkAuthorizationInterceptor(
  private val ...
) :
  HttpInterceptor {

  override suspend fun intercept(request: HttpRequest, chain: HttpInterceptorChain): HttpResponse {
    return chain.proceed(
      request
        .newBuilder()
        .addHeader("Authorization", ...)
        .build()
    )
  }
}

[mbonnin]

ExecutionContext is not documented a lot, it's mostly used internally. It works the same as CoroutineContext , it's a type-safe map-like API

[mbonnin]

You might have to wrap the DefaultNetorkTransport to transfer that information from the HTTP layer to the GraphQL layer. 2min, I'll try to make an example

[mbonnin]

I think something like this would do it:

class RequestHeaders(
      val headers: List<HttpHeader>
  ): ExecutionContext.Element {
    override val key: ExecutionContext.Key<*>
      get() = Key

    companion object Key : ExecutionContext.Key<RequestHeaders>
  }
  
  class MyNetworkTransport(serverUrl: String): NetworkTransport {
    private val httpRequestComposer = DefaultHttpRequestComposer(serverUrl)
    private val delegate = HttpNetworkTransport.Builder()
        .serverUrl(serverUrl)
        .httpEngine(DefaultHttpEngine())
        .build()
    
    override fun <D : Operation.Data> execute(request: ApolloRequest<D>): Flow<ApolloResponse<D>> {
      val customScalarAdapters = request.executionContext[CustomScalarAdapters]!!
      val httpRequest = httpRequestComposer.compose(request)

      return delegate.execute(request, httpRequest, customScalarAdapters).map { 
        it.newBuilder()
            .addExecutionContext(RequestHeaders(httpRequest.headers))
            .build()
      }
    }

    override fun dispose() {
      delegate.dispose()
    }

  }
  
  @Test
  fun executionContext() = runTest {
    val mockServer = MockServer()
    val apolloClient = ApolloClient.Builder()
        .networkTransport(MyNetworkTransport(mockServer.url()))
        .build()

    apolloClient.query(EpisodeHeroNameQuery(Episode.EMPIRE))
  }

[mbonnin]

This reminds me of https://github.com/apollographql/apollo-kotlin/issues/3890

[Jan Skrasek]

Thank you! I'm thinking about exposing whole httpRequest - could be there any issue?

[mbonnin]

You'd be holding HttpRequest.body longer than needed. This is a non-trivial object (contains an Okio source, etc...) so it might take some memory

[mbonnin]

Not the end of the world but I wouldn't recommend exposing it

[Jan Skrasek]

Thank you very much! :)
I see. I'm debugging some backend issue and need an extensive conditional logging. Maybe - is there a way to convert query to actual string to be able to log it later (and not being forced to expose httpRequest for all requests)?

[mbonnin]

I mean if it's only for debug you can certainly leak all the memory you want 😄

[mbonnin]

Just disable it in production builds 😅

[Jan Skrasek]

Well, I'm using my users to debug it for me 😄

[mbonnin]

ahah

[mbonnin]

Then if you need the data for logging then there's no real way around

[mbonnin]

You could convert to a String but not sure how much you'd save

[mbonnin]

Most of the data is the actual bytes

[Jan Skrasek]

The point is my toString() would be just for single query, instead of leaking all graphql requests.

[mbonnin]

And it's not huge, just not required in a typical application but if you need it then I guess you can expose httpRequest completely

[Jan Skrasek]

Anyway, thank you! I have options now 🙂

[mbonnin]

Sure thing!