continuation-local-storage support for bluebird promises

Patch bluebird for continuation-local-storage support.

Current Status

Compatible with bluebird v2.x and v3.x. Tests cover both versions.

Usage

clsBluebird( ns [, Promise] )

var cls = require('continuation-local-storage');
var ns = cls.createNamespace('myNamespace');

var Promise = require('bluebird');
var clsBluebird = require('cls-bluebird');

clsBluebird( ns );
// Promise is now patched to maintain CLS context

The above patches the "global" instance of bluebird. So anywhere else in the same app that calls require('bluebird') will get the patched version (assuming npm resolves to the same file).

Patching a particular instance of Bluebird

To patch a particular instance of bluebird:

var Promise = require('bluebird');
var clsBluebird = require('cls-bluebird');

clsBluebird( ns, Promise );

This is a more robust approach.

Nature of patching

Combining CLS and promises is a slightly tricky business. There are 3 different conventions one could use (see this issue for more detail).

cls-bluebird follows the convention of binding .then() callbacks to the context in which .then() is called.

var promise;
ns.run(function() {
    ns.set('foo', 123);
    promise = Promise.resolve();
});

ns.run(function() {
    ns.set('foo', 456);
    promise.then(print);
});

function print() {
    console.log(ns.get('foo'));
}

// this outputs '456' (the value of `foo` at the time `.then()` was called)

Global error handlers

Promise.onPossiblyUnhandledRejection() and Promise.onUnhandledRejectionHandled() allow you to attach global handlers to intercept unhandled rejections.

The CLS context in which callbacks are called is unknown. It's probably unwise to rely on the CLS context in the callback being that when the rejection occurred - use .catch() on the end of the promise chain that's created within namespace.run() instead.

Tests

Use npm test to run the tests. Use npm run cover to check coverage.

Changelog

See changelog.md

Issues

If you discover a bug, please raise an issue on Github. https://github.com/TimBeyer/cls-bluebird/issues

Contribution

Pull requests are very welcome. Please:

• ensure all tests pass before submitting PR
• add an entry to changelog
• add tests for new features
• document new functionality/API additions in README