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vacuum.js

This is a small example program that demonstrates how you may access a Couchbase cluster from a node.js application. Please note that the idea with the example is to show you how to utilize a Couchbase cluster from your node app, and not to try to create an application you may find useful. You should also keep in mind that I'm not a JavaScript programmer (nor do I normally use node.js), so whenever you find yourself asking the question: "Why doesn't he just ...." you should remind yourself that I wasn't aware of that way of doing stuff ;-)

So what is this? It is a small "daemon" that is "monitoring" a directory and "moves" all files you put in the directory into a Couchbase cluster. So why do I say "monitor" with quotes? Well, it's because the watch API in the 'fs' module is marked as unstable and non-portable ;) To work around that we're just scanning the directory and upload files as long as there is any. When the scan reports no files in the directory we sleep for a specified number of milliseconds before doing another scan.

Given that you'll move files into the spool directory with one program, and it's read by another program there is a possibility for a race condition. To work around that the vacuumer will ignore all files starting with a dot. To safely instert a file into the cluster you should:

$ cp myfile /tmp/vacuum/.myfile
$ mv /tmp/vacuum/.myfile /tmp/vacuum/myfile

But wait, how do I specify a key for my data? well, the vacuumer will only accept "special" files... It has to be a JSON file, and it has to contain a special attribute: "_id" which will be the key its stored under.

So what happens if you try to store a file that isn't JSON? It'll be renamed to .filename.illegal ex:

$ cp /etc/passwd /tmp/vacuum/.passwd
$ mv /tmp/vacuum/.passwd /tmp/vacuum/passwd
$ ls -a /tmp/vacuum
.		..		.passwd.illegal

And if its JSON, but without a "_id" key? It will be renamed to .filename.unknown ex:

$ echo '{ "foo" : "bar" }' > /tmp/vacuum/.mykey
$ mv /tmp/vacuum/.mykey /tmp/vacuum/mykey
$ ls -a /tmp/vacuum
.		..		.mykey.unknown

Requirements

In order to run the example you'll need:

Setup

Clone the repository:

$ git clone git://github.com/trondn/vacuum.js.git
$ cd vacuum.js

Install the Couchbase driver from npm:

$ npm install couchbase

Usage

Create a configuration file named config.json with the following content:

{
    "hosts" : [ "localhost:9000" ],
    "user" : "vacuum",
    "password" : "secret",
    "bucket" : "vacuum",
    "spool" : "/tmp/vacuum",
    "sleeptime" : 2000
}

With the configuration in place you can start the vacuum program as:

$ node vacuum.js

With the "server" running, you can start dumping files into the spool directory, and see them appear in your Couchbase cluster :)