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hobknob-client-nodejs

hobknob-client-nodejs

A node client to retrieve feature toggles stored in Etcd.

Build Status

NPM

Installation

npm install hobknob-client-nodejs

Usage

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));
});

Important Note

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

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

Client(applicationName, [config])

Creates a new feature toggle client

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)

.on(eventName, callback)

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:

client.on('updated-cache', function(toggles){
  console.log(toggles);
});
 
// output 
[
  { name: 'mytoggle', old: false, new: true },
  ...
]

.getOrDefault(toggleName, [secondaryKey], defaultValue)

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

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

.getAll()

Gets the values for all features for the application.

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