How to pass RESTDataSource response headers to the ApolloServer response header (express) - graphql

Question

I have ApolloServer running where the frontend makes a query request and the ApolloService fetches the request and then performs a request with RESTDataSource to a third-party service, I receive a response with a header.
Currently, ApolloServer only parses the body through the resolver and sends it back to the client
I wanted to pass also the header received to the client
I don't know how to do that at the RESTDataSource level since I don't have access to the Apollo response
I hope this was clear enough to explain the problem
export abstract class myClass extends RESTDataSource {
getSomething() {
const endpoint = this.endpointPath;
return this.get(endpoint);
}
async didReceiveResponse<T>(response, request): Promise<T | null> {
// these are the response headers desired to have them sent back to the client
console.log(response.headers);
if (response.ok) {
return this.parseBody(response) as any as Promise<T>;
} else {
throw await this.errorFromResponse(response);
}
}
}
In the appolloService initialization i have
const apolloServer = new ApolloServer({
context: async ({ res, req }) => {
// these headers are not the same as received from the getSomething() response above
console.log(res.getHeaders)
}
)}

Answer 1

I solved the issue by passing the res to the context and accessing the response in the didReceiveResponse, then adding the headers needed.
adding a response to context
const apolloServer = new ApolloServer({
context: async ({ res, req }) => {
return {
res: res,
};}
using the response to append the headers to it
async didReceiveResponse<T>(response, request): Promise<T | null> {
// use this.authHeader value in the class anywhere
this.context.res.setHeader(
"x-is-request-cached",
response.headers.get("x-is-request-cached") ?? false
);
this.context.res.setHeader(
"x-request-cached-time",
response.headers.get("x-request-cached-time")
);
if (response.ok) {
return (await this.parseBody(response)) as any as Promise<T>;
} else {
throw await this.errorFromResponse(response);
}}
by doing this you will achieve the desired outcome of passing the headers to the graphQl client