tracing module

[davidmarkclements]

So.. this has been removed

I had a play with it in v0.11 and thought it was promising,
the API was not good, and it wasn't immediately clear that it's only for tracing async calls,
but I thought the concept was interesting, you could extend it for javascript level
dtrace tooling, or possibly even use it to feed into kernel level tracing tools

So I've got two questions

1. how come it was removed? (performance? ... philosophy? ... convenience? )

2. will it (or some form of the same idea) make it back into core?

[kenany]

I think nodejs/node-v0.x-archive#8110 is the original PR that removed it?

[AndreasMadsen]

I have read most of the conversation in nodejs/node-v0.x-archive#8110 and from what I can make out:

@trevnorris says: The hooks will remain accessible via process.binding('async_listener'), and
the added functionality will live in an external module.

However there don't appear to be an external module and process.binding('async_listener') throws Error: No such module: async_listener. (This is on io.js latest 804ab7e)

[bnoordhuis]

Outdated comment, maybe. It's called async_wrap now:

$ iojs -p 'process.binding("async_wrap")'
{ setupHooks: [Function: setupHooks],
  Providers: 
   { NONE: 0,
     CARES: 1,
     CONNECTWRAP: 2,
     CRYPTO: 3,
     FSEVENTWRAP: 4,
     FSREQWRAP: 5,
     GETADDRINFOREQWRAP: 6,
     GETNAMEINFOREQWRAP: 7,
     PIPEWRAP: 8,
     PROCESSWRAP: 9,
     QUERYWRAP: 10,
     REQWRAP: 11,
     SHUTDOWNWRAP: 12,
     SIGNALWRAP: 13,
     STATWATCHER: 14,
     TCPWRAP: 15,
     TIMERWRAP: 16,
     TLSWRAP: 17,
     TTYWRAP: 18,
     UDPWRAP: 19,
     WRITEWRAP: 20,
     ZLIB: 21 } }

[davidmarkclements]

thanks everyone

[AndreasMadsen]

@bnoordhuis Thanks. Any information about the external module. I can only see that @tjfontaine have reserved the name on npm.

[Qard]

The code for that lives at http://github.com/joyent/node-tracing now, though it hasn't been getting a lot of attention lately.

[Fishrock123]

probably needs to be sporked into iojs :)

[trevnorris]

@bnoordhuis Thanks for clarifying.

Yes, it's under async_wrap (named after the main class that handles everything under the hood).

The idea was for add-on developers to use and experiment with new APIs so we could come to a conclusion of what the best API would be. Don't want another issue with creating a fundamentally broken API.

[davidmarkclements]

makes sense to me, the tracing API was not ideal.

In my experiments I found combining it with Error.prepareStackTrace to get custom stacks with additional info and then creating a trace on every async op was interesting.

The context object being passed in the async listeners isn't a friendly API