@opentelemetry/instrumentation-express - incorrect route set to span, if middlewares are being used

[RigoTamas]

What version of OpenTelemetry are you using?

{
    "@opentelemetry/api": "^1.9.0",
    "@opentelemetry/auto-instrumentations-node": "^0.55.3",
    "@opentelemetry/exporter-metrics-otlp-proto": "^0.57.1",
    "@opentelemetry/exporter-trace-otlp-proto": "^0.57.1",
    "@opentelemetry/instrumentation-express": "^0.47.0",
    "@opentelemetry/sdk-metrics": "^1.30.1",
    "@opentelemetry/sdk-node": "^0.57.1",
    "@opentelemetry/sdk-trace-node": "^1.30.1",
    "express": "4.21.1"
  }

What version of Node are you using?

20.15.0

What did you do?

This repository reproduces the bug:
https://github.com/RigoTamas/opentelemetry-express-instrumentation-span-name-bug

// index.ts

import express, { NextFunction, Request, Response, Router } from "express";

const app = express();

const userMiddleware = (req: Request, res: Response, next: NextFunction) => {
  console.log("user middleware running");
  next();
};

const userMiddleware2 = (req: Request, res: Response, next: NextFunction) => {
  console.log("user middleware 2 running");
  next();
};

const userRouter = Router({ mergeParams: true });

userRouter.use(userMiddleware);

userRouter.use(userMiddleware2);

userRouter.get("/", (req: Request, res: Response, next: NextFunction) => {
  res.send({ name: "John" });
});

const v1Router = Router({ mergeParams: true });

v1Router.use("/user", userRouter);

app.use("/v1", v1Router);

app.listen(8000, () => {
  console.log("api listening on 8000");
});

// instrumentation.ts
import { getNodeAutoInstrumentations } from "@opentelemetry/auto-instrumentations-node";
import { OTLPMetricExporter } from "@opentelemetry/exporter-metrics-otlp-http";
import { OTLPTraceExporter } from "@opentelemetry/exporter-trace-otlp-proto";
import { Resource } from "@opentelemetry/resources";
import { PeriodicExportingMetricReader } from "@opentelemetry/sdk-metrics";
import { NodeSDK } from "@opentelemetry/sdk-node";
import { ATTR_SERVICE_NAME } from "@opentelemetry/semantic-conventions";

const sdk = new NodeSDK({
  traceExporter: new OTLPTraceExporter(),
  metricReader: new PeriodicExportingMetricReader({
    exporter: new OTLPMetricExporter(),
  }),
  resource: new Resource({
    [ATTR_SERVICE_NAME]: "test service",
  }),
  instrumentations: [getNodeAutoInstrumentations()],
});
sdk.start();

What did you expect to see?

I expected to see the http.route tag on the root span, and the name of the root span to be set to GET /v1/user

What did you see instead?

Instead I have seen, that the http.route tag on the root span, and also the name of the root span gets set to GET /

Additional Context

This issue arises because I am calling middlewares on a child router.

[dyladan]

@JamieDanielson can you take a look at the associated PR here? You're the listed code owner :)

[dyladan]

Is this a duplicate of #2678?

[RigoTamas]

I don't think that this is a dupicate of #2678. My issue is related to child routers calling middlewares that don't have any associated path (eg.: childRouter.use(someMiddleware)), while that issue does not include such middlewares. Also, I was not able to reproduce #2678, hence why I created this ticket with a standalone PR. The PR clearly demonstrates my issue with a unit test.

[RigoTamas]

Also, my issue is not solved with the PR proposed as a solution for #2678, so I strongly believe they are separate issues.