Apollo Gateway Errors on Subgraphs

[dazlious]

Currently I am experiencing a behaviour I did not expect.

While I instrument all my subgraphs as well as the supergraph, I am seeing an unexpected behaviour in the apollo instrumentation.

on subgraphs and supergraphs we have implemented the following:

import{ tracer, Span } from 'dd-trace';

const BAD_USER_INPUT = 'BAD_USER_INPUT';
const NOT_AUTHORIZED = 'NOT_AUTHORIZED';
const USER_ALREADY_EXISTS = 'USER_ALREADY_EXISTS';

const notLoggableErrors = new Set([
  BAD_USER_INPUT,
  NOT_AUTHORIZED,
  USER_ALREADY_EXISTS,
]);

const isErrorLoggable = error => !notLoggableErrors.has(error?.extensions?.code);

tracer.init({
  plugins: false,
  runtimeMetrics: true,
  service: config.datadog.service,
});

tracer.use('graphql', {
  variables: variables => variables,
  hooks: {
    execute(span, _, res) {
      if (span && res.errors?.length) {
        const isError = res.errors.some(error => isErrorLoggable(error));
        span.setTag('error', isError);
      }
    },
  },
});

Reading about apollo instrumentation it says it is automatically added whenever the condition (Currently this plugin automatically instruments [@apollo/gateway](https://github.com/apollographql/federation) for module versions >= v2.3.0.) is true. Therefore I am able to see the instrumentation on our APM dashboard.

Now the big problem I have is that while I can hook into the graphql instrumentation, I cannot hook into the apollo one. I only see an ability to disable it, which is not what I want.

Am I missing something? How easy would it be to add something similar to apollo? From code perspective it looks like the error is being set based upon the last entry: https://github.com/DataDog/dd-trace-js/blob/master/packages/datadog-plugin-apollo/src/gateway/validate.js#L19

I would also be able to contribute here, if someone would guide me in the right direction.