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']
}]);