Anonymous namespaces

[binki]

Hi, I’m looking into using Sequelize’s continuation-local-storage support. I don’t want to have to decide on a name for the namespace because I don’t like coming up with names and I would probably choose something stupid and generic which might conflict with code which I haven’t written.

I have no need to ever call getNamespace(). I can access the return value of createNamespace() from all code where the README would suggest I should call getNamespace(), so what’s the point of that function when I have an object reference available?

I would like to be able to something like the following to get automatic transaction binding through Promise chains whenever I use the sequelize object:

var clsNamespace = require('continuation-local-storage').createNamespace();
var Sequelize = require('sequelize');
Sequelize.cls = clsNamespace;
var sequelize = new Sequelize('sqlite:file.sqlite');

but this fails with AssertionError: namespace must be given a name! thrown by [email protected]. I don’t get it—what insurmountable technical obstacle to supporting anonymous namespaces requires me to use a name here? Could that be documented along with a workaround (i.e., a way reliably generate unique namespace names) if it isn’t going to be fixed?

[othiym23]

Since the point of CLS is to communicate across components in the same way that thread-local storage does (where the lookup is based on the thread itself), because it's not safe to assume that you're the only user of CLS within a given application, and because some applications of CLS do fancy things with the namespaces they create, the API requires that you give each namespace a name. It doesn't require it to be a good name – I've seen a lot of people simply using 'ns' or 'namespace' – but it does have to be there.

I'd be happy to land a patch that documents the motivation for the requirement, but I think adding a namespace name generator is superfluous, given that it's very rare that any application would need to generate more than a small handful of namespaces (which is good, because each one gets its own async-listener wrapping, which can pile up into some pretty significant overhead if you're not careful).

[binki]

adding a namespace name generator is superfluous

That would be the wrong approach. The intention would be to be able to treat a CLS as anonymous/unnamed. You would only be able to access a particular CLS pool if you had a reference to its defining object. See the following behavior for comparing object references. I am able to determine if two handles are the same or not without having to name them. I’d like the same behavior from continuation-local-storage:

> var x = {};
undefined
> var y = {}
undefined
> x == y
false
> var z = x;
undefined
> z == x
true

Why must I come up with a string to identify a namespace? Naming things should only be necessary when trying to do something like IPC or when defining an interface that needs to be decoupled (such as look for a JSON key named X or pass a GET parameter Y). It shouldn’t be necessary when all parties needing to cooperate can exchange object references…

[binki]

Just to clarify, I would implement this with Symbol or, if backwards compatibility is required, I would use something like a counter and a field such as anonymousId instead of name to distinguish named namespaces from anonymous ones.