[BUG]: mysql2 instrumentation not supporting promises

[alexpavlov]

Tracer Version(s)

5.80.0

Node.js Version(s)

22.11.0

Bug Report

When using mysql2/promise with dd-trace, the mysql2 instrumentation can return a callback-style Query object instead of a Promise when the appsec abortController.signal.aborted check is true. This causes mysql2's Query.then() safety method to throw an error.

The issue is in packages/datadog-instrumentations/src/mysql2.js lines 167-204. When wrapping Pool.prototype.query, if the abort signal is triggered, the code returns queryCommand (a callback-style object) instead of a Promise:

shimmer.wrap(Pool.prototype, 'query', query => function (sql, values, cb) {
  // ...
  if (abortController.signal.aborted) {
    // ... 
    return queryCommand;  // This is NOT a promise!
  }
  return query.apply(this, arguments)
})

When application code awaits this result, mysql2's Query class has a then() method that throws:
You have tried to call .then(), .catch(), or invoked await on the result of query that is not a promise...

Reproduction Code

1. Use Next.js 15+ with mysql2/promise
2. Enable dd-trace with default settings (appsec enabled)
3. On first request after server restart, when a connection pool is being created, the error appears

// instrumentation.ts
export async function register() {
  if (process.env.NEXT_RUNTIME === 'nodejs') {
    const tracer = await import('dd-trace');
    tracer.default.init({
      runtimeMetrics: true,
    });
  }
}

// lib/db.ts
import mysql from 'mysql2/promise';

const pool = mysql.createPool({ /* config */ });
const [rows] = await pool.query('SELECT * FROM table'); // Throws error

Error Logs

DEBUG: Creating pool for: [schema_id]
You have tried to call .then(), .catch(), or invoked await on the result of query that is not a promise, which is a programming error. Try calling con.promise().query(), or require('mysql2/promise') instead of 'mysql2' for a promise-compatible version of the query interface.
Error: aborted
    at ignore-listed frames {
  code: 'ECONNRESET'
}

Workaround

Disabling appsec resolves the issue:

tracer.default.init({
  appsec: { enabled: false },
});

Suggested Fix

The wrapPool function should properly handle the promise wrapper. When the pool is from mysql2/promise, the wrapped query should return a rejected Promise instead of a callback-style object:

if (abortController.signal.aborted) {
  // Return a rejected promise for promise-based pools
  if (this.promise) {
    return Promise.reject(abortController.signal.reason);
  }
  // ... existing callback handling
}

Operating System

macOS Darwin 24.6.0 (also reproducible on Linux)

Additional Context

• mysql2 version: 3.15.3

Reproduction Environment

The error is triggered when a database connection is severed (ECONNRESET). This is easier to reproduce in the Next.js development environment where:

1. Duplicate requests are common due to React Server Components behavior in dev mode (React's strict mode double-invokes components)
2. Long compilation times on first request can cause client-side request timeouts/aborts
3. Hot module replacement can interrupt in-flight database connections

Error Logs

No response

Tracer Config

No response

Operating System

No response

Bundling

Unsure

[simon-id]

Thank you for reporting this in details. I'm part of the team that own this part of the code, and I will investigate it myself. As we're approaching holiday season, this might take more time than it should. But feel free to ping me again if too much time has passed.

[simon-id]

I'm also taking the liberty to rename this issue, as it looks like it has no title ? Feel free to rename it yourself better if you want to.