hobknob-client-nodejs

> A node client to retrieve feature toggles stored in Etcd.



Installation

``
npm install hobknob-client-nodejs
`

Usage

`javascript
var Client = require('hobknob-client-nodejs');

var client = new Client("application-name", {
etcdHost: "127.0.0.1",
etcdPort: 4001,
cacheIntervalMs: 60000
});

client.on("error", function(err) {
console.log(err);
});

client.on("updated-cache", function(togglesChanged){
console.log('updated-cache' + JSON.stringify(togglesChanged)); // contains an array of toggles that changed in the last update
});

client.initialise(function(err) {

if(err){
throw err;
}

console.log(client.getOrDefault("toggle2", true));
});
`

$3

The "error" event must be subscribed to, otherwise errors will cause the application to exit

`javascript
client.on("error", function(err) { });
`

Etcd

Feature toggles are stored in Etcd using the following convention:
http://host:port/v2/keys/v1/toggles/applicationName/toggleName

API

$3

Creates a new feature toggle client

`javascript
var Client = require("hobknob-client-nodejs");
var client = new Client("application-name", { etcdHost: "127.0.0.1" });
`

- applicationName the name of the application used to find feature toggles
- config (optional)
- etcdHost (default: "127.0.0.1")
- etcdPort (default: 4001)
- cacheIntervalMs interval for the cache update, which loads all the applications toggles into memory (default: 60000)

$3

Subscribes to events emitted by the client.

- eventName - name of the event to listen to (see below for possible event names)
- callback - callback that is called with different arguments per event when the event is fired (see below for event callbacks)

Events:
- error - function(err){ } // required, will return a javascript error object
- updated-cache - function(togglesChanged){ } // optional, will return a list of toggles that changed in the last update

example:
`javascript
client.on('updated-cache', function(toggles){
console.log(toggles);
});

// output
[
{ name: 'mytoggle', old: false, new: true },
...
]
`

$3

Gets the value of a feature toggle (true or false) if exists, otherwise return the default value (true or false)

`javascript
var isFeatureToggle1Enabled = client.getOrDefault('featureToggle1', false);
`

- toggleName - the name of the toggle, used with the application name to get the feature toggle value
- secondaryKey - [optional] used when accessing a multi feature-toggle (e.g. client.getOrDefault('domainFeature', 'com', false))
- defaultValue - the value to return if the toggle value is not found or if there is an error

$3

Gets the values for all features for the application.

`javascript
var features = client.getAll();

features.should.be.eql({
"feature1": "true",
"feature2": "false",
"domFeature/com": "true",
"domFeature/couk": "false"
});

``