fix(router): send graphql closing boundary to fit Apollo client

[df-wg]

Motivation and Context

Users noted that our Multipart implementation, while it works and fits the spec (RFC1341), wasn't being correctly parsed by some clients. Specifically, the client wouldn't parse one message until the next message had been pushed, with it's --graphql prefix.

This stems from an issue in their implementation, but we want to ensure that our router is accessible by as many services as possible.

The response now has the --graphql of the next response being sent early, which doesn't seem to impact any other services that I've checked. If necessary, we can hide this behind a feature flag so it's specific for apollo

wget

wget --no-check-certificate --quiet \
--method POST \
--timeout=0 \
--header 'Accept: multipart/mixed;subscriptionSpec="1.0", application/json' \
--header 'Content-Type: application/json' \
--body-data '{"query":"subscription { countEmp2(max: 6, intervalMilliseconds: 1000) }"}' \
-O - 'http://localhost:3003/graphql'

curl

curl -L 'http://localhost:3003/graphql' -H 'Accept: multipart/mixed;subscriptionSpec="1.0", application/json' -H 'Content-Type: application/json' -d '{"query":"subscription { countEmp2(max: 3, intervalMilliseconds: 500) }"}'

Apollo Client

const { ApolloClient, InMemoryCache, HttpLink} = require('@apollo/client');
const gql = require('graphql-tag');

// Define your subscription query
const SUBSCRIPTION_QUERY = `
  subscription Test {
    countEmp2(max: 4, intervalMilliseconds: 1000)
  }
`;

// HTTP link for queries and mutations
const httpLink = new HttpLink({
  uri: 'http://localhost:3003/graphql',
  headers: {
    Accept: 'multipart/mixed;subscriptionSpec="1.0", application/json',
  },
});

// Create the Apollo Client
const client = new ApolloClient({
  link: httpLink,
  cache: new InMemoryCache(),
});

// Execute the subscription
const testSubscription = () => {
  const observable = client.subscribe({
    query: gql(SUBSCRIPTION_QUERY),
  });

  // Listen for incoming data
  observable.subscribe({
    next(data) {
      console.log('Subscription data:', data);
    },
    error(err) {
      if (err?.message === 'internal system error') {
        console.log("system error, ignore")
      } else {
        console.error('Subscription error:', err);
      }
    },
    complete() {
      console.log('Subscription completed');
    },
  });
};

// Start the test
console.log("hello world")
testSubscription();

Checklist

• I have discussed my proposed changes in an issue and have received approval to proceed.
• I have followed the coding standards of the project.
• Tests or benchmarks have been added or updated.
• Documentation has been updated on https://github.com/wundergraph/cosmo-docs.
• I have read the Contributors Guide.

[github-actions]

Router image scan passed

✅ No security vulnerabilities found in image:

ghcr.io/wundergraph/cosmo/router:sha-b6aa8655a8f66759ce46089232b72d6408ab99ef

[Noroth]

I was able to verify locally that this change fixes the error from the apollo client.