!Seneca

> A [Seneca.js][] transport plugin that provides various client-side
load balancing strategies, and enables dynamic reconfiguration of
client message routing.

seneca-balance-client

[![npm version][npm-badge]][npm-url]
[![Build Status][travis-badge]][travis-url]
[![Coverage Status][coveralls-badge]][coveralls-url]
[![Dependency Status][david-badge]][david-url]
[![Gitter][gitter-badge]][gitter-url]

Description

This module is a plugin for the Seneca framework. It provides a
transport client that load balances outbound messages on a per-pattern basis.

If you're using this module, and need help, you can:

- Post a [github issue][],
- Tweet to [@senecajs][],
- Ask on the [Gitter][gitter-url].

If you are new to Seneca in general, please take a look at
[Senecajs.org][]. We have everything from tutorials to sample apps to
help get you up and running quickly.

$3

Supports Seneca versions 3.x and above.

Install

``sh
npm install seneca-balance-client
`

And in your code:

`js
require('seneca')()
.use('balance-client', { ... options ... })
`

Quick Example

$3

`js
require('seneca')()

.listen( {port: function () { return process.argv[2] }} )

.add('a:1', function (msg, done) {
done( null, {a: 1, x: msg.x} )
})

// run twice:
// $ node server.js 47000 --seneca.log=type:act
// $ node server.js 47001 --seneca.log=type:act
`

$3

`js
require('seneca')()
.use('balance-client')

.client( {type: 'balance'} )
.client( {port: 47000} )
.client( {port: 47001} )

.ready( function () {

for ( var i = 0; i < 4; i++ ) {
this.act( 'a:1,x:1', console.log )
}

})


// $ node client.js --seneca.log=type:act
`

The client will balance requests over both servers using
round-robin. As there is no _pin_ in the .client configuration, this
will apply to all non-local actions. Add a _pin_ to restrict the
action patterns to which this applies - make sure to use the same
_pin_ on both client and server to avoid ambiguity.

Usage

The plugin provides two balancing models:

* consume: messages are sent to individual targets, using a round-robin approach
* observe: messages are duplicated and sent to all targets

You specify the model using the plugin option model:

`js
var Seneca = require('seneca')

var s0 = Seneca({tag: 's0'})
.listen(44440)
.add('a:1', function (msg, done) {
console.log('s0;x='+msg.x);
done()
})

var s1 = Seneca({tag: 's1'})
.listen(44441)
.add('a:1', function (msg, done) {
console.log('s1;x='+msg.x);
done()
})

var c0 = Seneca({tag: 'c0'})
.use('..')
.client({ type: 'balance', pin: 'a:1', model: 'observe' })
.client({ port: 44440, pin: 'a:1' })
.client({ port: 44441, pin: 'a:1' })


s0.ready( s1.ready.bind(s1, c0.ready.bind(c0, function () {
c0.act('a:1,x:y')

// wait a little bit to avoid shutting down in mid flow
setTimeout(
s0.close.bind( s0, s1.close.bind(s1, c0.close.bind(c0))), 111 )
})))
`

You can also provide your own balancing model by providing a function
with signature (seneca, msg, targetstate, done) as the value of the
model setting:

`js
...
.client({
type: 'balance',
pin: 'a:1',
model: function (seneca, msg, targetstate, done) {
if (0 === targetstate.targets.length) {
return done( new Error('No targets') )
}

// select a random target
var index = Math.floor(Math.random() * targetstate.targets.length)
targetstate.targets[index].action.call( seneca, msg, done)
}
})
...
`

The targetstate object provides you with the list of currently
available targets. Review the internal implementations of the
observeModel and the consumeModel in
balance-client.js
for a starting point to write your own model.




Contributing

The [Senecajs org][] encourages open participation. If you feel you
can help in any way, be it with documentation, examples, extra
testing, or new features please get in touch.

Test

To run tests, simply use npm:

`sh
npm run test
``

License

Copyright (c) 2010-2016, Richard Rodger and other contributors.
Licensed under [MIT][].

[MIT]: ./LICENSE
[npm-badge]: https://img.shields.io/npm/v/seneca-balance-client.svg
[npm-url]: https://npmjs.com/package/seneca-balance-client
[coveralls-badge]:https://coveralls.io/repos/senecajs/seneca-balance-client/badge.svg?branch=master&service=github
[coveralls-url]: https://coveralls.io/github/senecajs/seneca-balance-client?branch=master
[david-badge]: https://david-dm.org/senecajs/seneca-balance-client.svg
[david-url]: https://david-dm.org/senecajs/seneca-balance-client
[Senecajs org]: https://github.com/senecajs/
[Seneca.js]: https://www.npmjs.com/package/seneca
[@senecajs]: http://twitter.com/senecajs
[senecajs.org]: http://senecajs.org/
[travis-badge]: https://travis-ci.org/senecajs/seneca-balance-client.svg
[travis-url]: https://travis-ci.org/senecajs/seneca-balance-client
[gitter-badge]: https://badges.gitter.im/Join%20Chat.svg
[gitter-url]: https://gitter.im/senecajs/seneca
[github issue]: https://github.com/senecajs/seneca-balance-client/issues