Firebase functions--how to handle needing to wait for an async process to end before the express app is ready to be exported

user_2996555 0
Viewed 8869

I'm trying to get apollo gateway to run in google's cloud functions (particularly through firebase). Running apollo server is super easy on cloud functions with the following code

const functions = require("firebase-functions");
const { ApolloServer } = require("apollo-server-express");
var app = require("express")();

const server = new ApolloServer({
schema: buildFederatedSchema([{ typeDefs, resolvers }])
});

server.applyMiddleware({ app });

exports.apollo = functions.https.onRequest(app);

That all works nice and dandy because there's no async functions to wait on. But with apollo gateway, we do have an async function to wait on before the server can start listening.

The way it works with just expressjs is this:

const { ApolloServer } = require("apollo-server-express");
var app = require("express")();

const gateway = new ApolloGateway({
     serviceList: [{ name: "clients", url:"http://localhost:5000/apollo/graphql" }]
});

(async () => {
  const { schema, executor } = await gateway.load();

  const server = new ApolloServer({ schema, executor });

  server.listen().then(({ url }) => {
    console.log(` Server ready at ${url}`);
  });
})();

So now the question becomes how do I execute that in a cloud function? One idea I had was to pass the express app to the firebase functions, and THEN do all the async stuff to initialize the listening for federation. But that doesnt work :(. Any ideas?

const functions = require("firebase-functions");
const { ApolloServer } = require("apollo-server-express");
var app = require("express")();

const gateway = new ApolloGateway({
    serviceList: [{ name: "clients", url: "http://localhost:5000/apollo/graphql" }]
});

exports.apollo = functions.https.onRequest(app);

(async () => {
   const { schema, executor } = await gateway.load();
   const server = new ApolloServer({ schema, executor });
   server.applyMiddleware({ app });
})()
apollo google-cloud-functions firebase
1 Answers

I got it to work! So the trick was to put the logic of setting up the federation INSIDE the onRequest piece.

Here's the solution:

var app = require("express")();
var server;
var start_gateway = async () => {
     if (server !== undefined) return;
     const gateway = new ApolloGateway({
         serviceList: [{ name: "clients", url: "http://localhost:4000/graphql" 
                  }]
     });

     const { schema, executor } = await gateway.load();
     server = new ApolloServer({ schema, executor });
     server.applyMiddleware({ app });
     console.log("Made FEDERATED GRAPH");

     return;
};

exports.apollo = functions.https.onRequest(async (req, res) => {
        await start_gateway();
        return await app(req, res);
})
user_29965550
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