Micro-Locator

A service locator for microservices.

Originally written by Jeremy Likness.

Contact me on Twitter or via my blog.

Reference

Install: npm -i micro-locator --save

import { Locator } from 'micro-locator';

// do this when you bootstrap your app 
let loc = new Locator(); 
loc.configure({...});

// use this throughout your app
let locate = (sig: string) => loc.resolve(sig);

Quick Start

Most front-end web applications either hard-code calls to Web APIs or configure a base URL, something like:

http://localost:1234/someapi

The goal of micro-locator is to make it simple and easy to follow a standard convention for calling APIs throughout your app, and then override the actual end points as needed. For example, consider the following end points:

/api/accounting/func1

/api/accounting/func2

/api/billing/func3

/api/billing/func4

These may be hosted in a local build and the relative syntax is fine. In production, however, a dedicated webserver hosts the end points on a domain:

http://api.myapp.com/api...

With micro-locator, you change a call like this:

$http.get('/api/accounting/func1')

to this:

$http.get(locate('/api/accounting/func1'))

If you do nothing, the endpoint is simply reflected back. For production, just configure the locator like this:

locator.rebase('/', 'http://api.myapp.com/)

Now all urls will resolve like this:

/api/accounting/func1 -> http://api.myapp.com/api/accounting/func1

You can choose to truncate the path you rebase (for example, rebase /api to http://api.myapp.com/ and remove the /api prefix) and replace specific end points. You may configure as many rebases and replacements at any level you like, allowing micro-locator to scale to large applications.

The configure function enables simple, one-pass configuration when you bootstrap your app, and you can simply register the locator function with your dependency injection to hide any implementation details of the micro-services locator itself.

Examples

Based on these test scenarios:

Rebase all calls

loc.rebase('/', 'http://production'); // everything
loc.resolve('/api/accounting/func1'); 
// http://production/api/accounting/func1

Rebase to new path

loc.rebase('/api/billing', 'http://billing.production/');
// everything under /api/billing 
loc.resolve('/api/billing/func3');
// http://billing.production/api/billing/func3

Rebase and truncate the path

loc.rebase('/api/billing', 'http://billing.production').truncate();
// everything under /api/billing 
loc.resolve('/api/billing/func3');
// http://billing.production/func3 

Replace a node

loc.replace('/api/accounting/func2', 'http://experimental/func');
// only for the specific /api/accounting/func2 request
loc.resolve('/api/accounting/func2');
// http://experimental/func 

Configuration syntax for bootstrapping

loc.configure([{
    rebase: ['/', 'http://production']
}, {
    rebase: ['/api/billing', 'http://billing.production/'],
    truncate: true
}, {
    replace: ['/api/accounting/func2', 'http://experimental/func']
}]);