I was recently tasked with modifying an Apollo-based GraphQL endpoint served by a Meteor application to set a field in the resolvers’ context based on a HTTP header pulled out of the incoming GraphQL request.
This should be an easy, well-documented ask.
Unfortunately, Meteor’s Apollo integration seems to exist in an awkward, undocumented state. The createApolloServer
function exposed by the meteor/apollo
package doesn’t seem to have any real documentation anywhere I could find, and the Github repository linked to by the package doesn’t seem to relate to the code in question.
How can I access the current HTTP request when building my resolvers’ context?
With no documentation to guide me, I dove into the package’s source code on my machine to find answers. The source for the package in question lives in ~/.meteor/packages/apollo/<version>/os/src/main-server.js
on my machine. The createApolloServer
function accepts a customOptions
object as its first argument. I quickly learned after digging through the source that if customOptions
is a function, createApolloServer
will call that function with the current request (req
) as its only argument, and use the function call’s result as the value of customOptions
:
const customOptionsObject =
typeof customOptions === 'function'
? customOptions(req)
: customOptions;
This means we need to change our current call to createApolloServer
from something like this:
import { createApolloServer } from "meteor/apollo";
createApolloServer({ schema }, { path });
To something like this:
createApolloServer(
req => ({
context: {
someValue: req.headers['some-value']
},
schema
}),
{ path }
);
This information is probably only pertinent to myself and an ever-shrinking number of people, but if you’re one of those people, I hope this helps.
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