> Forgive me for reviving this debate about threadlocals.  Before anyone
> loses their heads, I'm not suggesting a need for threads or anything like
> that. However, I've used threadlocal a bit in other languages and and the
> lack of threadlocal(or something with a less contentious name that has
> nothing to do with threads) in node.js makes me wonder how people would
> solve problems like distributed transaction coordination?  In frameworks
> I've used in the past it was common to associate transaction context in
> threadlocal.  That way, if any part of the program needed to interact with
> the transaction coordinator (start, rollback, pause, resume, commit) the
> transaction coordinator could look in thread local for the transaction
> context and  know exactly which transaction was in progress on "this
> thread".  That concept doesn't go away in node.js just because things are
> processed in an event loop, each pass of the event loop could be for
> different transactions.  

> It seems that the only way around this is to always have a direct
> reference to the transaction context, meaning passed to every function that
> might need the transaction context.  This approach seems to require
> transaction api details be litered throughout the code, and makes it nearly
> impossible for a 3rd party to quietly manage transactions.

> I use mongoose, and have created a plugin for tracking some audit
> information for each record change:

> module.exports.auditAttributesPlugin = function(schema, options) {
>   schema.add({
>     createdOn    : {type: Date, default: Date.now, required: true}
>     , changedOn    : {type: Date, default: Date.now, required: true}
>     , createdBy    : {type: Schema.ObjectId}
>     , changedBy    : {type: Schema.ObjectId}
>   });

>   schema.pre('save', function (next) {
>     this.createdOn = this.createdOn || Date.now;
>     this.changedOn = Date.now;
>     this.createdBy = this.createdBy || app.context.userId;
>     this.changedBy = app.context.userId;
>     console.log('orm plugin createdOn: %s, createdBy: %s, updatedOn: %s,
> updatedBy: %s', this.createdOn, this.createdBy, this.changedOn,
> this.changedBy);
>     next()
>   });
> };

> The part where I do app.context.userId, without a threadlocal, I need
> access directly to the request or session that contains the user id.
>  Typically(in threaded languages) I'd use threadlocal to store information
> like the userid executing in this iteration of the event loop.  This
> technique is pretty common, distributed transaction coordination, JAAS,
> etc. all use this technique.

> So far I haven't seen any solutions to this problem, so this post is
> either about to start a flame war, or could just be considered a vote for
> "threadlocal like behavior", or if anyone has any good suggestions, I'd
> like to hear them.

> Thanks, Dave