mmm / charm-node

juju formula to deploy a user-defined node.js app

This is an example juju formula to deploy a user-defined node app directly from revision control.

This formula will be maintained with a general set of hooks for various services that can be used with node apps (like mongodb).

Using this formula

First, edit config.yaml to add info about your app.

Then deploy some basic services

$ juju deploy --repository ~/formulas node-app myapp
$ juju deploy --repository ~/formulas mongodb
$ juju deploy --repository ~/formulas haproxy

relate them

$ juju add-relation mongodb myapp
$ juju add-relation myapp haproxy

scale up your app

$ for i in {1..10}; do
$   juju add-unit myapp
$ done

open it up to the outside world

$ juju expose haproxy

Find the haproxy instance's public URL from

$ juju status

(or attach it to an elastic IP via the aws console) and open it up in a browser.

What the formula does

During the install hook,

• installs node/npm
• clones your node app from the repo specified in app_repo
• runs npm if your app contains package.json
• configures networking if your app contains config/config.js
• waits to be joined to a mongodb service

when related to a mongodb service, the formula

• configures db access if your app contains config/config.js
• starts your node app as a service

Formula configuration

Configurable aspects of the formula are listed in config.yaml and can be set by either editing the default values directly in the yaml file or passing a myapp.yaml configuration file during deployment

$ juju deploy --repository ~/formulas --config ~/myapp.yaml node-app myapp

Some of these parameters are used directly by the formula, and some are passed through to the node app using config/config.js.

Application configuration

The formula looks for config/config.js in your app which starts off looking something like this

module.exports = config = {
  "name" : "mynodeapp"
  ,"listen_port" : 8000
  ,"mongo_host" : "localhost"
  ,"mongo_port" : 27017
}

and gets modified with contextually correct configuration information during either deployment (via the install hook) or relation to another service (relation-changed hook).

This config can be used from within your application using snippets like

...
var config = require('./config/config')
...
  new mongo.Server(config.mongo_host, config.mongo_port, {}),
...
server.listen(config.listen_port);
...

Network access

This formula does not open any public ports itself. The intention is to relate it to a proxy service like haproxy, which will in turn open port 80 to the outside world. This allows for instant horizontal scalability.

If your node app is itself a proxy and you want it directly exposed, this can easily be done by adding

open-port $app_port

to the bottom of the install hook, and then once your stack is started, you expose

$ juju expose myapp

it to the outside world.

By default, juju services within the same environment can talk to each other on any port over internal network interfaces.

Making this work with your node.js app

This formula makes some strong assumptions about the structure of the node application (config/config.js) that might not apply to your app. Please treat this formula as a template that you can fork and modify to suit your needs.

The biggest difference between how the formula behaves for different kind of apps is application startup. A simple application will want to start upon install (startup code goes in the install hook), whereas some applications will not want to start up until a database has be associated (startup code goes in the db-relation-joined hooks).

Mirrored

lp:charm/node-app

charm-node's Issues

Previous Blog links want to point here

See: http://markmims.com/page2/
The old links for 'node-app charm' want to point here, I think.
Sorry if not appropriate place to post.