Federation Tracing

graphql-kotlin-federation module relies on apollographql/federation-jvm package to provide support for Apollo Federation tracing. Tracing is turned on by including FederatedTracingInstrumentation in your GraphQL instance. In order for the FederatedTracingInstrumentation to know whether incoming request should be traced, we need to provide it a apollo-federation-include-trace header value.

val schema = toFederatedSchema(myFederatedConfig, listOf(TopLevelObject(MyFederatedQuery())))
val graphQL = GraphQL.newGraphQL(schema)
    .instrumentation(FederatedTracingInstrumentation())
    .build()

GraphQL Context Map

note

Default GraphQLContextFactory provided by graphql-kotlin-spring-server populates this header information automatically.

Tracing header information can be provided by populating info directly on the GraphQL context map.

val contextMap = mutableMapOf<Any, Any>()
    .also { map ->
        request.headers().firstHeader(FEDERATED_TRACING_HEADER_NAME)?.let { headerValue ->
            map[FEDERATED_TRACING_HEADER_NAME] = headerValue
        }
    }

val executionInput = ExecutionInput.newExecutionInput()
    .graphQLContext(contextMap)
    .query(queryString)
    .build()
graphql.executeAsync(executionInput)

FederatedGraphQLContext (Deprecated)

danger

Support for custom GraphQL context object is deprecated and will be removed in future releases. Please migrate to use generic GraphQL context map.

To best support tracing, the context must implement a specific method to get the HTTP headers from the request. This is done by implementing the FederatedGraphQLContext interface instead of just the GraphQLContext interface from graphql-kotlin-schema-generator.

class MyFederatedGraphQLContext(private val request: ServerRequest) : FederatedGraphQLContext {
    override fun getHTTPRequestHeader(caseInsensitiveHeaderName: String): String? =
        request.headers().firstHeader(caseInsensitiveHeaderName)
}

val executionInput = ExecutionInput.newExecutionInput()
    .context(MyFederatedGraphQLContext(httpRequest))
    .query(queryString)
    .build()
graphql.executeAsync(executionInput)