zenx-lb
A tiny http(s)/ws(s) load balancer.
Last updated 2 years ago by raelgor .
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zenx-lb

A tiny load balancer used by the ZenX project.

Manual

Installation

Depending on your Node version, you may need --harmony or --es_staging to use this package.

Quick example

const lib = require('zenx-lb');
const co = require('co');

var lbOptions = {
    protocol: 'http',
    port: 10001,
    host: 'localhost',
    numOfClusters: 3,
    ws: true,
    ssl: null
}

var lb = new lib.LoadBalancer(lbOptions);

var tgOptions = {
    id: 'group-1',
    method: 'random',
    targets: [
        { port: 8182, host: 'localhost', protocol: 'http' },
        { port: 8183, host: 'localhost', protocol: 'http' }
    ]
}

var tg = new lib.TargetGroup(tgOptions);

lb.on('listening', () => co(function*(){

    yield lb.addTargetGroup(tg);

    yield lb.addRule({ host: 'mysite.com', targets: ['group-1'] });
    yield lb.addRule({ host: 'mysite2.com', path: '/images/*', targets: ['group-1'] });

    tg.addTarget({ port: 8184, host: 'localhost', protocol: 'http' });
    tg.removeTarget(0);

}));

Class: lib.LoadBalancer(options)

Creates a LoadBalancer object that is an EventEmitter and wraps clustered subprocesses that host an http/s server which balances load between servers based on Rules.

Options:

  • protocol (Default: 'http'): Protocol used by the load balancer server.
  • port: Port to be used by the load balancer.
  • host: Host address to bind load balancer to.
  • numOfClusters: The number of clusters to be used. Usually as many as the available processors.
  • ws (Default: true): Whether or not to proxy WebSockets.
  • ssl: The ssl object will be passed directly as ssl settings to Node's require('https').createServer(ssl, handler).

Event: 'listening'

function() { }

Emitted when all clusters are created and each cluster's server handle has emitted a 'listening' event.

Event: 'close'

function() { }

Emitted when all clusters are dead.

Event: 'error'

function(error) { }

Emitted when an error occurs.

lb.addTargetGroup(targetGroup)

Returns a Promise that is resolved when the targetGroup has been successfully introduced to all clusters.

lb.removeTargetGroup(targetGroup)

Returns a Promise that is resolved when the targetGroup has been successfully removed from all clusters. targetGroup can either be the object itself or it's id.

lb.addRule(rule)

Returns a Promise that is resolved when the rule has been successfully introduced to all clusters.

lb.removeRule(rule)

Returns a Promise that is resolved when the rule has been successfully removed from all clusters. targetGroup can either be the object itself or it's id.

lb.close()

Returns undefined. Sends a SIGTERM signal to all clusters.

Class: lib.TargetGroup(options)

Creates an object that stores a group of target server addresses.

Options:

  • id: The group's id or a unique friendly name line 'group-1'.
  • method (Default: 'serial'): The method used to balance the load. Can be 'random', 'serial' or function() { } called by the targetGroup object. Only provide a function if you know what you're doing.
  • targets (Default: []): An Array that stores target information. Can be filled later with the tg.addTarget(options) method.

tg.addTarget(options)

Adds a target server to a group. That group will emit an update event so that listening LoadBalancers will update themselves.

Example:

tg.addTarget({ port: 8080, protocol: 'http', host: 'localhost' });

tg.removeTarget(target)

Removes a target by object reference or index number. That group will emit an update event so that listening LoadBalancers will update themselves.

Class: lib.Rule(options)

Creates a proxying rule. Rules work in the order they are introduced.

Example:

new Rule({ host: 'mysite.com', targets: ['group-1'] }});

rule.update()

Makes the rule emit an update event so that listening LoadBalancers will update themselves.

Example:

var mainRule = new Rule({ host: 'mysite.com', targets: ['group-1'] });

lb.addRule(mainRule);

mainRule.targets.push('group-2');
mainRule.update();

License

(The MIT License)

Copyright (c) 2015 Kosmas Papadatos <kosmas.papadatos@gmail.com>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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