Important

Hobknob is deprecated and no longer actively supported.

If you are a contributor willing to take this project over then please get in touch via search-experience@opentable.com

hobknob-client-nodejs

A node client to retrieve feature toggles stored in Etcd.

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"
});