Pass dynamic header to federated services

[mxncson]

Hello @jensneuse,

How do you pass a dynamic header to the http handler (engine) ?
I have a simple use case where the client send an auth id that i need to validate(gateway side) then forward others different headers to my services.

I don't see a direct way to interface with the underlying http components in the engine. How can i pass a custom and non-generic headers to services ?

I've read #270 and the other unanswered issue similar to mine, i have tested all of the above and nothing fit this case.

[jensneuse]

In WunderGraph, we do it this way, works also for Federation: https://wundergraph.com/docs/guides/strategies/inject_short_lived_token_to_upstream_requests
That's OSS too, just a level of abstraction to make things easy.
If you want to dig deeper yourself, here's a pointer on how to access headers during execution:

graphql-go-tools/pkg/engine/datasource/graphql_datasource/graphql_datasource_test.go

Line 48 in 9fe3016

Input: `{"method":"POST","url":"https://swapi.com/graphql","header":{"Authorization":["$$1$$"],"Invalid-Template":["{{ request.headers.Authorization }}"]},"body":{"query":"query($id: ID!){droid(id: $id){name aliased: name friends {name} primaryFunction} hero {name} stringList nestedStringList}","variables":{"id":$$0$$}}}`,

Client Request Headers need to be passed to the resolver as part of the execution context to be able to use them during resolving:

graphql-go-tools/pkg/engine/resolve/resolve.go

Line 136 in be7d24d

Header http.Header

[aerfio]

@jensneuse
For me it's not working, I've debugged it quite a bit
Following an examples/federation, you can check that it's broken by applying following patch:

diff --git a/examples/federation/gateway/http/http.go b/examples/federation/gateway/http/http.go
index a29a4091..a90907ad 100644
--- a/examples/federation/gateway/http/http.go
+++ b/examples/federation/gateway/http/http.go
@@ -27,7 +27,9 @@ func (g *GraphQLHTTPRequestHandler) handleHTTP(w http.ResponseWriter, r *http.Re
 
 	buf := bytes.NewBuffer(make([]byte, 0, 4096))
 	resultWriter := graphql.NewEngineResultWriterFromBuffer(buf)
-	if err = g.engine.Execute(r.Context(), &gqlRequest, &resultWriter); err != nil {
+	if err = g.engine.Execute(r.Context(), &gqlRequest, &resultWriter, graphql.WithAdditionalHttpHeaders(http.Header{
+		"X-Request-ID": []string{"123456"},
+	})); err != nil {
 		g.log.Error("engine.Execute", log.Error(err))
 		w.WriteHeader(http.StatusInternalServerError)
 		return
diff --git a/examples/federation/products/server.go b/examples/federation/products/server.go
index 1cf18943..46a3ca7e 100644
--- a/examples/federation/products/server.go
+++ b/examples/federation/products/server.go
@@ -20,7 +20,10 @@ func main() {
 	}
 
 	http.Handle("/", playground.Handler("GraphQL playground", "/query"))
-	http.Handle("/query", graph.GraphQLEndpointHandler(graph.EndpointOptions{EnableDebug: true, EnableRandomness: true}))
+	http.Handle("/query", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		log.Println(r.Header)
+		graph.GraphQLEndpointHandler(graph.EndpointOptions{EnableDebug: true, EnableRandomness: true}).ServeHTTP(w, r)
+	}))
 	http.HandleFunc("/websocket_connections", graph.WebsocketConnectionsHandler)
 
 	log.Printf("connect to http://localhost:%s/ for GraphQL playground", port)

treat X-Request-ID by any user defined header.

If I debugged correctly it's because

graphql-go-tools/pkg/graphql/execution_engine_v2.go

Line 274 in e6e1a13

func (e *ExecutionEngineV2) getCachedPlan(ctx *internalExecutionContext, operation, definition *ast.Document, operationName string, report *operationreport.Report) plan.Plan {

does not take into account any header that is in ctx.Request.Header.

[genesor]

@aerfio there is another step required to have the HTTP Headers passed to the underlying services for the federated gateway.

When creating your schema configuration you need to add the header with a custom syntax that will look for a value in the original HTTP request.

serviceCfg := graphqlSchema.Configuration{
	Fetch: graphqlSchema.FetchConfiguration{
		URL:    url,
		Method: http.MethodPost,
		Header: http.Header{
			// .request.headers.XXX transmits incoming HTTP headers value to the
			// internal sub-requests made
			"X-Request-ID":          []string{"{{ .request.headers.X-Request-ID }}"},
		},
	},
	Federation: graphqlSchema.FederationConfiguration{
		Enabled:    true,
		ServiceSDL: sdl,
	},
}

[reistiago]

Should a similar config work for subscriptions?

I'm trying to propagate headers in the init message by doing something similar to what is here, but the options.Header is always empty.

I've seen this commit, that just landed in master, which does it in a different way, but similar in the end, but I should still have the problem of the headers being empty.

[BenjaminYong]

Bump! Same as @reistiago , I am having difficulty propagating the headers from my subscription request to the federated subgraphs. It works fine for queries and mutations.

Here's my data source config:

dataSourceConfig := graphqlDataSource.Configuration{
	Fetch: graphqlDataSource.FetchConfiguration{
		URL:    serviceConfig.URL,
		Method: http.MethodPost,
		Header: http.Header{
			"Authorization": []string{"{{ .request.headers.Authorization }}"},
		},
	},
	Subscription: graphqlDataSource.SubscriptionConfiguration{
		URL: serviceConfig.WS,
	},
	Federation: graphqlDataSource.FederationConfiguration{
		Enabled:    true,
		ServiceSDL: sdl,
	},
}

I've debugged in my func (g *Gateway) ServeHTTP(w http.ResponseWriter, r *http.Request) HTTP handler and can print the Authorization header in the request. It seems to be lost downstream or not sent to the subgraphs.

[IsabelFreitas-catapult]

Any updates on this? I am using github.com/wundergraph/graphql-go-tools v1.67.2 and the initialPayload is not being propagated to the subgraphs
@reistiago @BenjaminYong did you get this to work with subscriptions?
@genesor