butter npm

Popcorn Authoring Library


An SDK for authoring Popcorn projects.

Supported Platforms

We’re writing Butter so that it runs in modern, HTML5 compatible browsers. For version 1.0, we’re targeting modern HTML5 desktop browsers. In the current version we are supporting:


  • Chrome stable
  • Firefox stable
  • Internet Explorer 9+
  • Safari stable


  • node v0.8 or higher
  • npm (comes with node v0.8 installer)
  • A working build environment:
    • Mac OS X - Xcode or Command Line Tools package
    • Windows - Python 2.5+ and Visual Studio 2010; specifically:
    • uninstall any and all “Microsoft Visual C++ 2010 x86/64 Redistributable” copies
    • install Microsoft Visual C++ 2010 (Express edition is fine)
    • install Microsoft Visual Studio 2010 SP1
    • install Microsoft Windows SDK v7.1
    • install Microsoft Visual C++ 2010 SP1 Compiler Update for Windows SDK v7.1
    • Linux - build-essential package on Debian/Ubuntu, or the equivalent for your distro

Environment Setup

  1. git clone --recursive https://github.com/mozilla/butter.git
  2. cd butter
  3. npm install

Running Butter in development mode

  1. Run node make server.
  2. Navigate to http://localhost:8888/ in your favourite browser.

If you want to change the bind IP or port check the Configuration section below.

Packaging and Distributing Butter

Running node make deploy will compile all the necessary files into the dist/ folder. Run NODE_ENV=production node app.js in the dist/cornfield directory in order to run the server in production mode.


Cornfield is PopcornMaker’s back-end server system, designed to serve content to users, store their ongoing work, and publish what they’ve done.


There are two types of storage Cornfield needs to run:

  • A database: To store user project data, a database is required. Cornfield uses the Sequelize middleware, so multiple database options are available. You are responsible for setting up and maintaining a PostgreSQL or MySQL database enrivonment if you choose to use either, so make sure a user has access to a database called popcorn for cornfield to run correctly.

  • A data-blob store: To store published projects, Cornfield can use the filesystem, or Amazon’s S3. See the configuration options below for setting up this feature for your environment.


There are several configuration files in cornfield/config/ that control how cornfield works. They are applied in order from most general to most specific to present one configuration to the server:

  1. default.json
  2. hostname.json
  3. environment.json
  4. hostname-environment.json
  5. runtime.json

hostname and environment are variable:

  • hostname - The hostname of the machine. Defaults to the output of hostname on the cli.
  • environment - The value of the NODE_ENV environment variable. Defaults to development.

To change the cornfield configuration for your deployment of Butter, it’s best to create a new file called hostname-environment.json that overrides the cornfield defaults.

Configuration Options

  • server settings for the cornfield server

    • bindIP the IP or hostname to use for the server (e.g., localhost).
    • bindPort the Port number to use for the server (e.g., 8888). If using a port number lower than 1024, the server will have to be run as root.
  • sentry settings for sentry error reporting

    • dsn the DSN to send events to. Look at your sentry client configuration page for this value.
    • options pass any additional options to raven
  • logger settings for server logging

    • format the logging format to use. Possible values include: default, short, tiny, dev.
  • session settings for user sessions

    • secret the sessions secret (i.e., some long string)
    • duration the session’s duration (e.g., 2419200000)
  • staticMiddleware settings for cornfield Connect middleware

    • maxAge the max age of static assests
  • dirs settings for various directories, paths, hostnames

    • wwwRoot the server’s WWW root directory (e.g., ../)
    • templates the location of templates (e.g., ../templates)
    • appHostname the hostname URL for the application, usually the same as server.bindIP and server.bindPort (e.g., http://localhost:8888)
    • embedHostname [optional] the hostname URL where published embed documents are stored, if different from dirs.appHostname (e.g., http://s3.amazonaws.com/your-bucket)
  • templates list of templates to serve. The format is as follows: <template-name>: {{templateBase}}<path/to/template/config.json>. The {{templateBase}} string will be replaced by the value in dirs.templates (e.g., “basic”: “{{templateBase}}basic/config.json”)

  • exportedAssets list of scripts to include in exported assets. These are things like popcorn.js or other scripts that your exported projects depend upon in order to run.

  • additionalStaticRoots list of additional roots to use.

  • database database configuration options

    • database the database name. Used by mysql and postgresql
    • username the username to use when connecting to the database. Used by mysql and postgresql
    • password the password for the username. Used by mysql and postgresql
    • options additional sequelize options. Please see the sequelize manual for the complete listing.
      • dialect the sql dialect of the database. Default is mysql, must be one of mysql, sqlite, or postgresql
      • storage the storage engine for sqlite. Default is :memory:, an in-memory db, must be a string representing a file path or :memory:
      • logging function to print sql queries to console. Default is console.log, must be a function or false
      • host hostname of the mysql or postgresql server. Default is localhost
      • port port of the mysql or postgresql server. Default is 3306
      • pool connection pooling options for mysql and postgresql. Default is none
      • maxConnections - maximum number of connections open in the pool
      • maxIdleTime - maximum time in seconds to leave an idle connection open in the pool
  • publishStore a fileStore used to publish project HTML files (see fileStore below for details)

  • feedbackStore a fileStore used to publish feedback from the user as JSON (see fileStore below for details)

  • crashStore a fileStore used to publish crash reports from the user as JSON (see fileStore below for details)

  • imageStore a fileStore used to retain converted data-uri images for published projects (see the ImageStore section below for details)

The fileStore type is used to setup a backend for storing data:

  • type the type of file store to use. Possible values include local (i.e., local file system) and s3 (i.e., Amazon S3)
  • options options for the file store, which depends on the type chosen.
    • hostname the hostname to use for constructing urls if different than embedHostname
    • local options
      • root the root directory under which all exported files are placed (e.g., ./view)
      • namePrefix [optional] the path prefix to add to any filenames passed to the local file store. For example, if using “v” all filenames will become “v/
      • nameSuffix [optional] the filename suffix to use for all filenames (e.g., “.html”)
    • s3 options
      • key the AWS S3 key to use for authentication
      • secret the AWS S3 secret to use for authentication
      • bucket the AWS S3 bucket name to use for storing key/value pairs
      • namePrefix [optional] the prefix to add to any key names passed to the s3 file store. For example, if using “v” all keys will become “v/
      • nameSuffix [optional] the suffix to add to any key names passed to the s3 file store. For example, if using “.json” all keys will end in “.json”
      • contentType [optional] the mime type to use for data written to S3. If none given text/plain is used.
      • headers [optional] any additional headers to use for data written to S3. For example, setting cache control headers with { 'Cache-Control': 'max-age=1800' }.


As part of the configuration, an imageStore should be specified to store converted data-uri images for published projects. When a project is saved, the project data is scanned for data-uris which are converted into binary blobs and stored on the server in the imageStore. Currently, there are no special checks or functionality for image store content-types. However, the only images which will be converted are jpegs and pngs. Everything else is ignored. See below for an example imageStore configuration.

Sample production config


This sample config uses a mix of the local file system as well as Amazon S3 for storage.

  "server" : {
    "bindIP" : "",
    "bindPort" : "80"
  "logger" : {
    "format" : "default"
  "session" : {
    "secret": "1721f7a15316469fa4a9-5117d0d20e9f"
  "staticMiddleware": {
    "maxAge": "3600000"
  "dirs": {
    "appHostname": "http://example.org",
    "embedHostname": "http://s3.amazonaws.com/my-bucket"
  "publishStore": {
    "type": "s3",
    "options": {
      "namePrefix": "v",
      "bucket": "my-bucket",
      "key": "my-s3-key",
      "secret": "my-s3-secret",
      "contentType": "text/html"
  "feedbackStore": {
    "type": "local",
    "options": {
      "root": "./view",
      "namePrefix": "feedback",
      "nameSuffix": ".json"
  "crashStore": {
    "type": "local",
    "options": {
      "root": "./view",
      "namePrefix": "crash",
      "nameSuffix": ".json"
  "imageStore": {
    "type": "local",
    "options": {
      "root": "./view",
      "namePrefix": "images",
      "nameSuffix": ".png",

Getting Involved

  • Chat with the Popcorn community on irc.mozilla.org in the #popcorn channel. The developers hang out here on a daily basis.
  • We also have a mailing list that you can subscribe to.
  • File bugs and feature requests on our issue tracker.
  • The latest code can be found on our Github repository.
  • If you’d like to contribute code, file a ticket on our issue tracker, and link to it from your Github pull request.

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