MySQL Pooled queries have the wrong parent

[fragglebob]

I noticed in DataDog that none of my traces had database calls, except for the first query, which seemed to have them all belong to it.

After loads of debugging I worked out its down to the current span in the query being the span that creates the connection.

My solution for now was to stop using pool.query and use pool.getConnection, however I had to bind the callback to get the correct span for the query.

pool.getConnection(tracer.bind((err, conneciton) => {
    connection.query(sql, values, cb)
}))

The problem happens in pool.acquireConnection, when it enters onOperationComplete the span is changed to that original one.

[rochdev]

I cannot reproduce this issue specifically since the provided snippet gives me the correct span. I was however able to cause a similar issue related to the internal queue of the mysql module.

@fragglebob If I open a PR, would you be able to try it out directly?

[fragglebob]

The snippet I shared produces the correct span. It's the way I've got round the issue for now.

Sure, I can give it a go tomorrow.

[rochdev]

I meant that even without tracer.bind() it still works for me, even if I run multiple queries.

Here's the PR: #178

[fragglebob]

I get ya now.

I think it might have been from using a combination of express, graphql and mysql together. I will give it a go tomorrow. 👍

If I get some time I will figure out how to cause it in a smaller example.

[fragglebob]

Yep, that fixes it completely.