changes-loader

Store CouchDB _changes handlers in your design docs and have Node.JS execute them.

Setup dependencies

You'll need felixge's node-couchdb library:

mkdir -p ~/.node_libraries/
git clone git://github.com/felixge/node-couchdb.git ~/.node_libraries/node-couchdb

Run the changes-loader.js script

Keep the changes-loader.js script running:

node /path/to/changes-loader.js [COUCHDB_ROOT_URL]

This script looks through all databases for any design docs with _changes handlers code to be loaded and run. New databases will be detected every 60 seconds.

The COUCHDB_ROOT_URL argument defaults to http://localhost:5984

(TODO: include example Upstart and launchd scripts)

Define _changes handlers

Each design document can define any number of _changes handlers by having a property off the root of the object called "changes":

{
  "views": { ... },
  "lists": { ... },
  "changes": {
    "foo": function(change) {
      // Respond to changes here...
    },
    "bar": function(change) {
      // Do other stuff here...
    }
  }
}

Note that in this example "foo" and "bar" are the names of two different changes handlers defined by this design document.

Changes handler context

From your _changes handler, you'll have access to the following objects:

• db — the database that host the loaded changes function (from felixge's node-couchdb)
• ddoc — the design document that hosts the loaded changes function
• log(msg) — this will show up in the stdout of the changes-loader.js script
• require(moduleID) — load CommonJS modules, as follows:
  • if the moduleID begins with ./ or ../ load a module from the design document
  • otherwise Node.JS will load the module from its require() paths

Node.JS compatibility

This code has been known to work with version 0.1.91 of Node. As always, YMMV (^_-)