node-hilo

NHibernate-style hi/lo ID generator for node.js

How to Use It

Requiring & Configuring

node-hilo exports a factory function that takes a configuration object:

/*
	The configuration argument can contain the following:
	{
		hilo: {
			maxLo: 10 // an integer value for maxLo
		},
		// sql is a config object that seriate would understand
		sql: {
			user: "you_me_anyone",
			password: "superseekret",
			server: "some.server.com",
			database: "meh_databass"
		}
	}
*/
var hilo = require( "node-hilo" )( configuration );

How to Use

node-hilo exports three module members: a nextId method, a nextIds method and a read-only property called hival. You will likely never need to care about the hival value - it's there for diagnostics and testing. The nextId method returns a promise, with the newly generated ID being passed to the success callback:

const id = await hilo.nextId();

// block of 100 ids
const ids = await hilo.nextIds( 100 )

The More You Know...

JavaScript doesn't natively support 64 bit integers - we're using a helper lib (big-integer) to allow us to properly represent them. Because of this, the generated IDs are passed back as strings (even though they're long values). You will need to ensure your DB server converts/casts them to long (which SQL will normally implicitly do for you).

If you'd like to learn more about the hi/lo algorithm:

• Look at the NHibernate Source
• ID Generators
• The Hi/Lo Algorithm
• Jon Skeet's answer on SO

Tests, etc

If you plan to run the integration tests, you will need access to an MS SQL server. Create a test database that can be used (the integration tests create two tables), and save a configuration file called intTestDbCfg.json under the spec/integration folder. Your configuration file will look similar to this:

{
	"sql": {
		"user": "dbuser",
		"password": "dbuserpwd",
		"server": "localhost",
		"database": "nhutil"
	},
	"hilo": {
		"maxLo": 100
	},
	"test" : {
		"recordsToCreate" : 15000,
		"startingHiVal" : "314159265"
	}
}