add plugin mysql

[zijin-m]

In addition, use the resolve package to read package.json because mysql2 does not add package.json in the exports field of the package.json file

[tom-pytel]

Question about this, the current form (module.constructor as any)._resolveFilename(request, topModule); ensures that the resolution is done from the point of view of the topmost module (the main app). This is necessary because if for example you have skwalking npm linked into a project instead of installed alongside all its dependancies then normal resolve will get the wrong path, one that sits in the skywalking node_modules path instead of the applicatiuon. Does the resolve package do this?

[zijin-m]

Sorry, I missed this point. According to the documentation resolve, this can be done by
private readonly resolve = (request: string) => resolve.sync(request, {basedir: path.dirname(topModule.id) });
if You agree i will update later

[tom-pytel]

Ok, well I checked your fix and it seems to work, so I am ok with this.

[tom-pytel]

In addition, use the resolve package to read package.json because mysql2 does not export the file package.json

What do you mean by "does not export"? It HAS a package.json.

[zijin-m]

In addition, use the resolve package to read package.json because mysql2 does not export the file package.json

What do you mean by "does not export"? It HAS a package.json.

I'm sorry my description is not clear enough, I have updated it.
According to the node documentation modules

Bare specifiers like 'some-package' or 'some-package/shuffle'. They can refer to the main entry point of a package by the package name, or a specific feature module within a package prefixed by the package name as per the examples respectively. Including the file extension is only necessary for packages without an "exports" field.

while mysql2 defines the exports field in its package.json file, similar to issue

[tom-pytel]

Some ideas for your plugin:

• Wrap entire section after newExitSpan() with try / catch so that you can catch any exception from _query.apply() or even your own code and span.error() that and then span.stop() cleanly.
• Put static init stuff like span.component = Component.MYSQL before the query call so that if there is an exception the span will have as much information as possible.
• Does mysql2 do row streaming like mysql? If so it should be handled.
• And a really silly detail, you don't need span.errored = true before span.error(err), that is set by the .error() function.

@kezhenxu94 asked me to review this because I also recently added a mysql plugin, just the first one, not mysql2, so you can look at that for some ideas of what I am talking about, its in master.

[tom-pytel]

Actually, better look at #31, master had some errors.

[tom-pytel]

Hey @zijin-m, going back to #27 where you said:

After testing, if two requests are repeatedly sent in a short time, the subsequent requests may use the AsyncState initialized by the previous request. It is temporarily unclear why store.enterWith(undefined as unknown as AsyncState) in the clear method not work(The store cannot be reset), I tried to add an invalid flag, which works normally, I hope to discuss the feasibility of this implementation with you, thx

I realize some time has passed, but is there any chance you can provide a short snippet case of this happening before the invalid flag fix? I am looking at some other things regarding async plugins living together peacefully.

[kezhenxu94]

Closing in favor of #54