Passing headers from Gateway to subservices

[tvvignesh]

Hi @gmac - I was wondering what would be the right way to pass the headers from Gateway to subservices when doing typemerging. I am able to get the headers in the gateway but was wondering the right way to pass it on.

Since I am not using Apollo Link like here: apollographql/apollo-server#737 I was wondering how to do the same with a normal fetch executor also since the executor is getting built when the gateway starts up.

Looked up the examples in this repo but that is not discussed so far. Any tips? Thanks.

[gmac]

The headers would pass through the remote executor function (makeRemoteExecutor), you’d add anything you want there. I don’t know all the options that an executor receives in addition to document and variables, but I would assume one is the GraphQL context object. So, you’d setup context however you want it in the gateway server, and then pass those values through as headers in the remote executor call.

[gmac]

Report back on findings: does the exec function indeed receive the context object?

[yaacovCR]

https://www.graphql-tools.com/docs/remote-schemas#using-cross-fetch

See section below that about headers....

Receives context, and also info if you want to do something with that....

[tvvignesh]

@yaacovCR @gmac Thanks for the response on the same. I have got it working now with some minor tweaks with reference from the link @yaacovCR shared and this repo. I had to add context to makeRemoteExecutorWithTimeout function as suggested and.

const makeRemoteExecutorWithTimeout = function(url:string, timeout = 1000) : AsyncExecutor {
  return async ({ document, variables, context }) => {

    const controller = new AbortController();
    const timeoutId = setTimeout(() => controller.abort(), timeout);

    try {
      const query = typeof document === 'string' ? document : print(document);

      let headers = {
        'Content-Type': 'application/json'
      };

      if (context) {
        headers = Object.assign(headers, context['headers']);
      }

      const fetchResult = await fetch(url, {
        method: 'POST',
        headers: headers,
        body: JSON.stringify({
          query, variables
        }),
        signal: controller.signal
      });
      return fetchResult.json();
    } catch (error) {
      return error.name === 'AbortError' ? new Error(`Request exceeded timeout of ${timeout}`) : error;
    } finally {
      clearTimeout(timeoutId);
    }
  };
};

Also add contextFactory from graphql-helix to return the headers as context

contextFactory: () => {
            return {
              headers: req.headers
            };
   },

Thanks.