Fastify instrumentation incorrectly sets middleware span as parent span to route handler with sync hooks

[drewcorlin1]

What version of OpenTelemetry are you using?

  "dependencies": {
   "@opentelemetry/auto-instrumentations-node": "^0.55.0",
    "@opentelemetry/exporter-trace-otlp-proto": "^0.57.0",
    "@opentelemetry/sdk-node": "^0.57.0",
    "@opentelemetry/sdk-trace-base": "^1.30.0"
  }

What version of Node are you using?

20.18

What did you do?

Repo to reproduce with steps in the README: https://github.com/drewcorlin1/fastify-otel-bug-example

What did you expect to see?

The route handler as a child span of the GET /example from @opentelemetry/instrumentation-http (and thus, jaeger correctly identifying the critical path of the request)

What did you see instead?

The route handler has a child span of the first middleware span middleware - fastify -> @fastify/request-context from @opentelemetry/instrumentation-fastify (and thus jaeger incorrectly identifying the critical path of my trace)

Additional context

Screenshot of what I'm seeing and full JSON of the trace downloaded from jaeger attached

fastify-trace.json

[drewcorlin1]

More context: If I update my onRequest hook to be an async callback

app.addHook('onRequest', async (_req, _res) => {
  await new Promise((r) => setTimeout(r, 100));
});

instead of

app.addHook('onRequest', (_req, _res, done) => {
  new Promise((r) => setTimeout(r, 100)).then(done);
});

then I get the correct behavior as far as parent spans go, but the duration of the span is incorrect