federation: node-fetch in @apollo/gateway doesn't support unix: urls

[lennyburdette]

Version: @apollo/gateway@0.6.6

Description:
We use an envoy sidecar process to manage service-to-service routing. All requests go to the same unix socket and we add headers to tell envoy which service cluster to route to.

const gateway = new ApolloGateway({
  serviceList: [
    { name: 'service-a', url: `unix:/path/to/envoy.sock:/graphql` },
    { name: 'service-b', url: `unix:/path/to/envoy.sock:/graphql` },
  ],
  buildService({ name, url }) {
    return new RemoteGraphQLDataSource({
      url,
      willSendRequest({ request }: any) {
        request.http.headers.set('Host', `${name}.specialenvoyheader`);
      }
    });
  }
});

Currently, this cannot work because getServiceDefinitionsFromRemoteEndpoint in @apollo/gateway uses node-fetch, which throws this error: Only HTTP(S) protocols are supported.

We use unix sockets because we can chown the socket and restrict access to it, unlike a tcp port. If we used TCP we'd have to also use TLS, which is overhead and complexity we'd like to avoid.

Adding support for unix sockets in node-fetch is marked as "wontfix".

I would suggest the got library, which has the same API, but it has 58 transitive dependencies compared to node-fetch's zero. 😬

[lennyburdette]

I might be able to switch to TLS over TCP, but I'll need to be able to pass agent to node-fetch so I can use our self-signed certs.

[jbaxleyiii]

Hey @lennyburdette! We are working on a way to provide the service definitions files instead of having to the do the fetch at startup. That plus providing a custom datasource should be enough for y'all yes?

[lennyburdette]

@jbaxleyiii That would probably do it! I'm blocked on building out a proof-of-concept for now, but it's good to know there's an alternative in the works.

If fetching the _service.sdl field lives on for certain use cases, it might be worth adding an agent: http.Agent option to the ApolloGateway constructor.

[lennyburdette]

closing this as super old! i'm pretty sure i figured it out, and we use make-fetch-happen now anyway.