mongo - ruby connection problem

I have installed mongo and bson_ext
now I have created a .rb file with the following contents ::

require 'rubygems'
require 'mongo'

db = Mongo::Connection.new.db("mydb")
db = Mongo::Connection.new("localhost").db("mydb")
db = Mongo::Connection.new("localhost", 27017).db("mydb")


However I am getting following error on running the code

yuzaki@ubuntu:~$ ruby firstruby.rb
/home/ryuzaki/.rvm/gems/ruby-1.9.2-p136/gems/mongo-1.2.0/lib/mongo/connection.rb:451:in `connect': Failed to connect to a master node at localhost:27017 (Mongo::ConnectionFailure)
from /home/ryuzaki/.rvm/gems/ruby-1.9.2-p136/gems/mongo-1.2.0/lib/mongo/connection.rb:554:in `setup'
from /home/ryuzaki/.rvm/gems/ruby-1.9.2-p136/gems/mongo-1.2.0/lib/mongo/connection.rb:98:in `initialize'
from firstruby.rb:4:in `new'
from firstruby.rb:4:in `<main>'

Please help!

If you're on a Mac and used Brew, restarting the service solved it for me:

launchctl unload ~/Library/LaunchAgents/homebrew.mxcl.mongodb.plist
launchctl load ~/Library/LaunchAgents/homebrew.mxcl.mongodb.plist

You can find this info by running `brew info mongodb`.

Sometimes there is simply not enough space.

> exception in initAndListen: 15926 Insufficient free space for
> journals, terminating

On a mac, using brew I found that `brew info mongodb` and then using then

`ln -sfv /usr/local/opt/mongodb/*.plist ~/Library/LaunchAgents` or `mongod --config /usr/local/etc/mongod.conf` worked!

I just encountered this due to my /etc/hosts file not containing an entry for "localhost" - consequently Ruby couldn't resolve "localhost". I suppose you can hardcode 127.0.0.1 into your code rather than "localhost" - or fix /etc/hosts to contain:

> 127.0.0.1 localhost

had this happen several times now, and here is the solution that works for me:

sudo rm /var/lib/mongodb/mongod.lock
sudo -u mongodb mongod -f /etc/mongodb.conf --repair
sudo start mongodb
sudo status mongodb

This is definitely due to your mongo server not running. Since you're on Ubuntu, try doing a `sudo /etc/init.d/mongodb start` and then see if your code works.