How to install and use Homebrew

If you’re doing any Ruby on Rails or other open source development on your Mac, you’re going to need Homebrew.

What is Homebrew?

Homebrew is a package management system for your Mac. Homebrew makes it easy to install the software you generally need for Ruby on Rails development. Sometimes when you install RubyGems for your project, they will be dependent on software being installed on your Mac. One of the more obvious examples would be a MySQL gem and the actual MySQL Database Server. You install the MySQL Database Server using Homebrew! One of the less obvious examples would be the Nokogiri gem. This gem uses a software package named libxml2. You would install the libxml2 software package using Homebrew in order to install the Nokogiri RubyGem.

So how do you install Homebrew?

Installing Homebrew is dead simple. However, it does have a rather large dependency. You will need the command line tools addon of Xcode installed. Xcode is made by Apple and its used to write Mac and iOS applications. Xcode is free and all you need to do is search for it on the Mac App Store and click install. Its a rather large application, so it may take a while to download and install.

Once you’ve finished installing Xcode. You will need to open Xcode and choose Xcode -> Preferences. Choose the Downloads tab and install the Command Line Tools.

Xcode Command Line Tools

This will take some time, but when its done your Mac will be ready to install Homebrew!

If you visit the Homebrew website, you will see the following command:

ruby -e "$(curl -fsSL"

This command will need to be run in the OS X Terminal App. This means copy and pasting it into the Terminal window and pressing ENTER.

When the command is complete you should be able to run the following command in the Terminal window:

brew --version

If this works, then Homebrew is installed!

Now let’s go over a few common tasks you will have with Homebrew.

brew doctor

You want to use this command after system changes (such as OS X or Xcode updates) or if you think you need to troubleshoot your Homebrew installation. The output will tell you what’s wrong and generally how to fix it.

brew update

This will update your Homebrew formula list. Note, this doesn’t update all your installed packages! What this does is update the versions and availability of packages you could install. You want to run this often to keep your Homebrew installation up to date with the latest available software.

brew upgrade

This will upgrade your installed packages.

brew install [insert package name here]

This will install a software package onto your system.

brew list

This will list all the packages that are currently installed on your system.

brew info [insert package name here]

Sometimes after you install a package, you get a screenful of information or configuration steps. If you’re like me, you will probably blow right past that and keep working – then it will dawn on you that you probably should have read some of that stuff. This will let you go back and do that.

brew uninstall [insert package name here]

And finally, you may want to remove a package you previously installed. That’s what this is for.

So that’s a quick intro to Homebrew and how you can manage software dependencies for RubyGems on your Mac!

[FATAL] failed to allocate memory

I got this error today on my iMac. It was incredibly frustrating and I tried all of the following to fix it (the reason I list them is because I’m not entirely sure the final step I’ll mention at the end was the sole solution).

1. uninstall mysql2 gem (gem uninstall mysql2)
2. uninstall mysql on homebrew (brew uninstall mysql)
3. uninstall mysql-connector-c on homebrew (brew uninstall mysql-connector-c)
4. reinstall mysql on homebrew (brew install mysql)
5. reinstall mysql-connector-c on homebrew (brew install mysql-connector-c)
6. reinstall mysql2 gem (gem install mysql2)

After all that I still got the error… at this point I was about to set my hair on fire, but then I noticed I had receieved a difference error message in my logs…

ActionView::Template::Error (dyld: Library not loaded: /opt/local/lib/libssl.1.0.0.dylib
Referenced from: /usr/local/bin/node
Reason: image not found

Do you see that reference to node? WTF!

So then I did the following:

1. uninstall node on homebrew (brew uninstall node)
2. reinstall node on homebrew (brew install node)

WOOHOO! It worked again! My hair is safe and I can stand down from Defcon 1. Why did this happen? I have no idea. Hopefully this helps someone else and please let me know in the comments if you know why this happened.

using text_field_with_auto_complete and form_authenticity_token

Rails 2.0 introduced protection for Cross-site request forgery (CSRF). This is turned on by default in your Rails applications. However, many developers are turning off this valuable protection rather than making the changes necessary to use it. This seems the same to me as leaving your door unlocked while your friend visits because cutting keys is hard. Case in point: text_field_with_auto_complete

You know you have run into the new CSRF protection when you see this error in your Rails application:


This is the point where you Google the error and receive one of the following pieces of advice:

1. Turn off RequestForgeryProtection all together

# add the following line to your application.rb or one of your
# environment.rb files. why not production? (sarcasm)
config.action_controller.allow_forgery_protection = false

2. Turn off RequestForgeryProtection for just one controller

skip_before_filter :verify_authenticity_token

3. Turn off RequestForgeryProtection for just one action.

protect_from_forgery :except => :attack_me

So let’s see how easy it is to utilize this new feature!

I was working with the text_field_with_auto_complete in a pretty basic form:

For those of you who aren’t familiar with this there is a nice post on the Rails Wiki

When I tried to perform my auto complete I received the ActionController::InvalidAuthenticityToken error.

Why? Because basically my Ajax request did not include a security token that RequestForgeryProtection uses to validate my request is coming from the right place. All you need to do is add this token to the parameters sent with your request. Rails makes this easy with the helper: form_authenticity_token. The token name RequestForgeryProtection will be looking for is: authenticity_token.

So let’s add this to our text_field_with_auto_complete:

Now when I performed my auto complete it worked flawlessly! Now to refactor that string… any suggestions?

Update August 25, 2008

Learned two things working with this…

1. It’s automatically doing a POST, so by changing the method to GET I can avoid having to deal with the authenticity_token.

2. And with that out of the way I don’t need to specify the parameters since by default it will send back the value of the text field.

That’s a lot cleaner!

Learning Ruby on Rails with Heroku Episode 1

Ever since I saw Heroku I wanted to use it for a screencast on learning Ruby on Rails. This weekend I finished the very first episode! This episode is fairly light on Ruby on Rails content because I was so focused on screencasting and learning all about video and audio production for the web.

So take a look and tell me what you think. I used Vimeo for hosting the video. I also produced the video in HD… however I didn’t realize that Vimeo only streams the HD content on their site, not the embedded video. So to view the best possible video you should view it on Vimeo. here is the link. You can make it full screen and enjoy the HD in all its glory.

Please feel free to leave some constructive criticism regarding the screencast. This way I can make some changes before I start pushing this out more regularly.

In this first episode of Learning Ruby on Rails with Heroku:

  1. Introduction
  2. Goal of this screencast series
  3. What is Heroku?
  4. Getting an account
  5. Creating your first Ruby on Rails application
  6. Basic navigation of Heroku

Learning Ruby on Rails with Heroku Episode 1 from Matthew Carriere on Vimeo.

Using select, reject, collect, inject and detect.

I spend a lot of time convincing my friends to switch to a Mac. Some of my friends are also software developers so naturally, just when they think the evangelism has come to an end, I convince them to get on the Rails. However, learning Rails usually means learning Ruby for the first time as well. In this post I am going to address one of the issues I see for newcomers to Ruby. Looping.

Looping in Ruby seems to be a process of evolution for newcomers to the language. Newcomers will always find their way to the for loop almost immediately and when confronted with iterating an array, the first choice will generally be a

a = [1,2,3,4]
for n in a
  puts n

This works, but its not very… Ruby. The next stage of evolution will be using an iterator for the first time. So the for loop gets dropped all together and each is used. The Rubyist is born at this point:

a.each do |n|
  puts n

What I see next is a lot of conditional logic being used inside the each block. The logic is generally introduced to perform the following operations:

  1. Building a list of items from an array.
  2. Total the items in an array.
  3. Find an item in the array.

So if this is you, then stop. Ruby has plenty more iterators where each came from. Which one you should be using depends on what operation you are trying to perform. So let’s take a look at our previous list and see if we can find a more Ruby way to get them done.

Building a list of items from the array using select

For this operation you should be using select. The way select works is simple, it basically iterates through all the elements in your array and performs your logic on each one. If the logic returns TRUE, then it adds the item to a new array which it returns when the iteration is complete. Here’s an example:

a = [1,2,3,4] {|n| n > 2}

This will return the last two elements in the array: 3 and 4. Why? Because 3 and 4 are both greater than 2, which was the logic we placed in the block. It’s worth noting that select has an evil step sister named reject. This will perform the opposite operation of select. Logic which returns FALSE adds the item to the array that is returned. Here’s the same examples as before except we will swap select, with reject:

a = [1,2,3,4]
a.reject {|n| n > 2}

In this example the return value is [1,2] because these elements return false when the condition is tested.

I also have to mention another close sibling to select and reject; collect, which returns an array of values that are the RESULT of logic in the block. Previously we returned the item based on the result of the CONDITION in the block. So perhaps we need square the values in our array:

a = [1,2,3,4]
a.collect {|n| n*n}

This returns a new array with each item in our array squared.

Finally, note that using select, reject, and collect returns an array. If you want to return something different, because you are concatenating or totaling values, then check out inject.

Total the items in an array using inject

When you think of accumulating, concatenating, or totaling values in an array, then think of inject. The main difference between select and inject is that inject gives you another variable for use in the block. This variable, referred to as the accumulator, is used to store the running total or concatenation of each iteration. The value added to the accumulator is the result of the logic you place in the block. At the end of each iteration, whatever that value is, can be added to the accumulator. For example, let’s sum all the numbers together in our array:

a = [1,2,3,4]
a.inject {|acc,n| acc + n}

This will return 10. The total value of all the elements in our array. The logic in our block is simple: add the current element to the accumulator. Remember, you must do something to the accumulator in each iteration. If we had simply placed n in the block the final value of the accumulator would have been 4. Why? Because its the last value in the array and since we did not add it to the accumulator explicitly the accumulator would be replaced in each iteration.

You can also use a parameter with the inject call to determine what the default value for the accumulator is:

a = [1,2,3,4]
a.inject(10) {|acc,n| acc + n}

In this example the result is 20 because we assigned the accumulator an initial value of 10.

If you need to return a string or an array from inject, then you will need to treat the accumulator variable that way. You can use the default value parameter of inject to do this:

a = [1,2,3,4]
a.inject([]) {|acc,n| acc << n+n}

In this example I add n to itself and then append it to the accumulator variable. I initialized the accumulator as an empty array using the default value parameter.

Find an item in the array using detect

Our last example operation was to find an element in the array. Let’s just put it out there and say that other iterators could be used to select the correct value from the array, but I am going to show you how to use detect to round out our exploration of these iterators.

So let’s find the value 3 in our array using detect:

a = [1,2,3,4]
a.detect {|n| n == 3}

This returns 3. The value we were looking for. If the value had not been found, then the iterator returns nil.

So if your head is spinning at this point as to which iterator to use for when, then remember this:

  1. Use select or reject if you need to select or reject items based on a condition.
  2. Use collect if you need to build an array of the results from logic in the block.
  3. Use inject if you need to accumulate, total, or concatenate array values together.
  4. Use detect if you need to find an item in an array.

By using these iterators you will be one step closer to mastering… Ruby-Fu.

Installing MySQL on Mac OS X Leopard using MacPorts

There comes a time in every Rails developers life that they need to work with MySQL. Often this means that your development comes to a screeching halt as you wade through the various options for getting MySQL installed on your Mac.

This guide won’t help you install it anywhere else… because I am a zealot and I don’t care how to install it anywhere else.

Install MySQL using macports, go get a coffee while this runs its course.

sudo port install mysql5 +server

Next up, create the initial databases used by MySQL.

sudo /opt/local/lib/mysql5/bin/mysql_install_db --user=mysql

Configure MySQL to start at system start up.

sudo launchctl load -w /Library/LaunchDaemons/org.macports.mysql5.plist

Start MySQL.

sudo /opt/local/bin/mysqld_safe5 &

You can always stop the service manually as well:

mysqladmin5 -u root -p shutdown

Confirm that that MySQL is running.

mysqladmin5 -u root -p ping

Just hit enter at the password prompt, as it is blank. We are about to change that.

Secure your server.

mysqladmin5 -u root password [your password goes here]

At this point you should have your MySQL server up and running. However, your Rails project may complain about not being able to find the socket file. You can find that using the ‘status’ command.

First log into MySQL.

mysql5 -u root -p

At the prompt, run the command.


In the output you will see an entry listing the socket being used by MySQL. You can use this in the database.yml file.

And finally, I really don’t like typing that ’5′ after all the commands… I can’t explain it, it just upsets me. So I like to create a symbolic link for the mysql5 and mysqladmin5 commands.

sudo ln -s /opt/local/bin/mysql5 /opt/local/bin/mysql
sudo ln -s /opt/local/bin/mysqladmin5 /opt/local/bin/mysqladmin

That should get you coding again against a MySQL database!

Learn to use your new Mac like a pro

Have you just switched to a Mac? Or have you switched sometime ago and still have those “how do I do this on a mac?” moments… well then this is for you! Apple has recently added a “Find out how” section to its website with videos on common computing tasks that should help your transition from the dark side.

Find out how

Getting Started with SQLite

SQLite is an extremely lightweight (dare I say agile) database. It uses files and doesn’t require you to start and stop services or spend a great deal of time configuring it. SQLite will be a good choice if you have a load under 100,000 requests and few concurrent writes. If you have a simple site that does nothing but serve content, then SQLite may just fit the bill.

Now that Ruby on Rails is using SQLite as its default database here are some tips for working with it.

Right off, you will need a Ruby SQLite adapter if you intend to work with SQLite at all, so let’s get that installed first:

sudo gem install sqlite3-ruby

Next up we need a database, and with SQLite all we need to do is pass a filename when we fire up SQLite:

sqlite test.db

At this point the database will operate similar to MySQL. You are sitting at a command prompt and can enter various SQL commands to create tables, perform crud operations etc.

When you are done with the database quit using the following command:


Another handy command to take a look at is:


This will produce a list of commands you can use in SQLite. For example, trying to find the equivalent of show databases in SQLite?


If you are not at all interested in working with SQLite or you know ahead of time it won’t fit the bill then let Rails know when you create your application:

rails -d mysql my_app

Take it to the next level with the Ruby on Rails console

If you are not using the Rails console while your developing then now is the time to start! I learn best by example, so that’s how I am going to structure this.

Here’s the scenario:

You are writing code against a class and need to determine which attributes you have available to you. In Rails, your attributes are largely driven by the database schema, so you will not see them in the class definition. At this point most developers will take a look at the table in the database and find the column they need, then determine the type of data stored there. There is a better way…

Let’s use the command line.

We start by firing up our Rails application in console mode:
You must be in your Rails application directory to issue this command.


So now what? Well now you have command line access to your entire Rails application! For example, let’s say you have a class named Person (which would map to a people table in the database). You want a new instance of this class? Then issue the following:

p =

Perhaps you want to view a Person from the database:

p = Person.find(1)

By default the results are displayed below each command and they are not very friendly, so let’s output them in YAML as it will be much more readable:

y p

‘y’ is like calling ‘puts p.to_yaml’ on the resulting value that follows it. There is also a ‘p’ shortcut that is the equivalent of issuing ‘puts’ on the value.

So how does this help with determining attributes? At first glance you may think you have to look at the list of values returned in your YAML command and find what your looking for… no… it gets better. Remember that all Ruby objects inherit certain methods, watch this:

You want to get the methods associated with your object:

y p.methods

You can also get the private, public, and protected methods using the following commands:

y p.public_methods
y p.private_methods
y p.protected_methods

So this class could return a huge YAML result which may not seem as efficient as scanning the schema in the database, and you’re right. So let’s get to what we are really looking for using ‘grep’:

y p.methods.grep /method_name/

This will return any method which contains method_name. You can write pass any regular expression you like into this command and really drill into your class methods, and for help putting those regular expressions together I really like using Rubular a web-based Ruby regular expression editor.

And what about the type of an object?

y p.class

This is just a taste of what you can do with the console… I use the console everyday as I develop. I will post some more console tips in future posts!

Running Ruby on Rails with Mongrel Clustering and Apache Proxy

Being a Rails coder is easy, deploying a Rails application can be hard. Through a great deal of effort, we’ll call it blood, sweat and tears, I have put together the following guidance on how to get your Ruby on Rails application up and running behind a Mongrel cluster using Apache Proxy.

Here’s the deal, I am going to install all the necessary applications to get this up and running, so if you have some of these installed on your server already you may just skip ahead, however, if you have any issues with this you may want to read over those sections you skipped and understand why I installed a specific version or what pitfalls I encountered that may be affecting your setup. Also, I am running Ubuntu, so if you are running a different distribution, then the paths to specific configuration files on your system may be different. Let’s get started!

Installing MySQL

Install MySQL using the package manager in Ubuntu:

sudo apt-get install mysql-server

After the installation you should be able to run the command mysql or mysqladmin. If you cannot run these then you may have to create symbolic links to these commands or add them to your path.

By default, MySQL only listens on localhost, in order to change that you need to comment out the line which reads: bind-address =

Change this by editing the following file on your system:

sudo vi /etc/mysql/my.cnf

You can search for text in vi using a forward slash.

You should restart MySQL after making a change to the config file:

/etc/init.d/mysql restart

Now verify that MySQL is listening to the network. The output of the following command should show an entry for MySQL:

netstat -tap

You need to set a password for the root account of MySQL, otherwise anyone can access it!

mysqladmin -u root password your_password
mysqladmin -h server_name -u root password your_password

In case it is not clear, your_password should be replaced with a strong password of your choosing.

Installing Ruby

apt-get install ruby ri irb

Install Ruby Gems

cd /tmp
tar -zxvf rubygems-0.9.2.tgz
cd /rubygems-0.9.2.tgz
ruby setup.rb

Update rubygems

gem update --system
gem update
gem cleanup

Why the two calls to gem update? –system will update the RubyGems itself and without that parameter you will only be updating the gems.

Install Rails

Install Rails using Rubygems:

gem install rails

Now let’s test the rails installation:

rails /tmp/railstest
cd /tmp/railstest

This will start the default WeBrick web server, so open a web browser to http://localhost:3000 If all is well you will see the Ruby on Rails welcome screen. Once you are finished staring at your success, press CTRL + d to kill the web server.

Install Mongrel

Install the build tools:

apt-get install build-essential ruby1.8-dev

Install Mongrel:

gem install mongrel mongrel_cluster --include-dependencies

Now let’s test the Mongrel installation:

cd /tmp/railstest
mongrel_rails start

This will start the Mongrel web server (now default), so open a web browser to http://localhost:3000 If all is well you will see the Ruby on Rails welcome screen… again. Now kill the web server.

Configure Mongrel Rails cluster

Add a user for our mongrel cluster:

useradd mongrel

Add the group for our mongrel user:

groupadd mongrel

Configure the directory security for your application:

chown -R mongrel:mongrel /tmp/railstest

Now we need to configure the Rails cluster for the test application. This command will write a YAML file to the config directory in your Rails application so you will only have to enter all these parameters once. After that, simply firing the command mongrel_rails cluster::start will use this configuration:

cd /tmp/railstest
mongrel_rails cluster::configure -e production 
-p 8000 -N 8 --user mongrel --group mongrel

You can reconfigure by running this command and using different parameters, you can also safely delete the YAML file from your config directory to blow these settings away.

Time to start the cluster:

cd /tmp/railstest
mongrel_rails cluster::start

You should be able to test your application by going to http://localhost:8000. You could also hit any of the 8 ports you have configured.

Install Apache

We have come to the last part of this lengthy installation. Apache. Now, it must be understood that you MUST install Apache 2.2 or higher. The reason for this is the Apache Proxy Balance Module. This module is required to glue all this together and is ONLY available in Apache 2.2 or higher. I am going to build from source on this one because the current version available to me in the apt-get library is not the sufficient version required.

Download Apache, unpack it, and then change to the directory which contains the unpacked files.

tar xvfz httpd-2.2.3.tar.gz
cd httpd-2.2.3

Configure the source tree for compiling Apache on your system:

./configure --prefix=/usr/local/apache2 

Build and install using the following commands:

sudo make install

Start Apache and navigate to your server through a browser. You should see the default Apache homepage.

sudo /usr/local/apache2/bin/apachectl start

There are several options for configuring and securing Apache that should be considered before taking this setup into production.

In order to configure Apache to serve your Mongrel cluster you will need to add the following to the Apache conf file:

<Proxy balancer://mongrel_cluster>
# Indexes + Directory Root.
DirectoryIndex test.html
DocumentRoot /tmp/railstest/public/
<Directory "/tmp/railstest/public">
Options FollowSymLinks
AllowOverride None
Order allow,deny
Allow from all
RewriteEngine On
RewriteCond %{HTTP_HOST} ^$ [NC]
RewriteRule ^(.*)$ http://www.$1 [R=301,L]
# Check for maintenance file and redirect all requests
RewriteCond %{DOCUMENT_ROOT}/system/maintenance.html -f
RewriteCond %{SCRIPT_FILENAME} !maintenance.html
RewriteRule ^.*$ /system/maintenance.html [L]
# Rewrite index to check for static
RewriteRule ^/$ /index.html [QSA]
# Rewrite to check for Rails cached page
RewriteRule ^([^.]+)$ $1.html [QSA]
# Redirect all non-static requests to cluster
RewriteRule ^/(.*)$ balancer://mongrel_cluster%{REQUEST_URI} [P,QSA,L]
# Logfiles
ErrorLog  /tmp/railstest/log/error.log
CustomLog /tmp/railstest/access.log combined

Now, there are 3 pieces to take note of here. First, you need to create a Proxy group for the mongrel cluster we created. Since we created 8 nodes, there are 8 BalancerMembers. Second, you will need a VirtualHost entry for your Rails site (in this case the railstest site we created earlier). And Finally, you have to add the NameVirtualHost entry for your VirtualHost (I can’t tell you how many times I forget that).

That should get you going with a Mongrel Cluster behind Apache Proxy. If you want to setup more than one site, then just create 3 more entries in your Apache conf file. You may want to think about separating the declarations from the main httpd.conf file, but for this example I just wanted to get you going. Have Fun!