Issues with mysql2/promise

[derN3rd]

Hey there,

We are using the mysql2 module with require('mysql2/promise') which causes the patch to fail:

/home/max/git/my-api/node_modules/dd-trace/src/plugins/mysql2.js:81
  shimmer.wrap(mysql2.Pool.prototype, 'getConnection', createWrapGetConnection(tracer, config))
                          ^

TypeError: Cannot read property 'prototype' of undefined
    at Object.patch (/home/max/git/my-api/node_modules/dd-trace/src/plugins/mysql2.js:81:27)
    at Array.from.filter.filter.forEach.plugin (/home/max/git/my-api/node_modules/dd-trace/src/instrumenter.js:72:16)
    at Array.forEach (<anonymous>)
    at Instrumenter.hookModule (/home/max/git/my-api/node_modules/dd-trace/src/instrumenter.js:67:8)
    at Function.Module._load (/home/max/git/my-api/node_modules/require-in-the-middle/index.js:69:30)
    at Module.require (module.js:517:17)
    at require (internal/module.js:11:18)
    at Object.<anonymous> (/home/max/git/my-api/node_modules/mysql2/lib/pool.js:1:75)
    at Module._compile (module.js:573:30)
    at Object.Module._extensions..js (module.js:584:10)
    at Module.load (module.js:507:32)
    at tryModuleLoad (module.js:470:12)
    at Function.Module._load (module.js:462:3)
    at Function.Module._load (/home/max/git/my-api/node_modules/require-in-the-middle/index.js:25:24)
    at Module.require (module.js:517:17)
    at require (internal/module.js:11:18)

Node version: 8.4.0
dd-trace-js version: ^2.1.0
mysql2 version: ^1.5.2

I'm sure this has something todo with the Promise stuff from mysql2.

Is there any way I can use this module without rewriting my whole code?
Thanks in advance

[rochdev]

@derN3rd This is definitely an oversight as mysql2/promise is not supported at the moment. For now the safest would be to disable plugins and individually enable the plugins you need (except mysql2 until this is fixed). See the API docs for an example.

[derN3rd]

@rochdev Thanks for your quick reply. I already got it to work with mysql2 plugin disabled, but wasn't sure if I did something wrong.

I will wait for mysql2/promise support then 😄

[rochdev]

It seems this bug actually affects even the callback based version. It doesn't happen when mysql2 is required before the plugin however, so that could be a temporary workaround.

For example:

require('mysql2/promise') // require before to work around the bug
const tracer = require('dd-trace').init()
const mysql2 = require('mysql2/promise') // require again to apply patching

[derN3rd]

It doesn't crash now, but I also get no traces of my mysql2 queries.
Can this be because I have all queries in a external module?
If so, how can I patch the dependencies of this module too?

[rochdev]

@derN3rd It should still be instrumented in external modules if the external module is required after the tracer is initialized.

Could you try something like this:

require('mysql2') // require callback version to avoid race condition with promise patch
const tracer = require('dd-trace').init()
const externalModule = require('external-module')

Also make sure you have re-enabled the plugin.

[derN3rd]

@rochdev Thanks man.
Got it to work. I have to do require('mysql2') first, then initialize dd-trace. Afterwards I can use mysql2 OR mysql2/promise without any problems (Like your example).
I tried to require('mysql2/promise') first, but that doesn't work.

Thanks for the help