After being a happy Xen user for several years now, I’ve recently had to switch to an alternative virtualization solution. My colleague Arun (@iamclovin) actually struggled for a week with Xen VMs that locked up on Hardy; we’ve had much success with Hardy and Xen before, so we attributed it to a hardware problem since these were our first blade servers.

Out of ideas, we tried Karmic (Ubuntu 9.10) only to discover that Xen support via the apt package system is gone. I went down the path of compiling a paravirt_ops Dom0 kernel (this article was very useful) but ended up deciding the process took far too long despite being successful.

With KVM gaining official support from Ubuntu as the virtualization solution, I ended up ditching Xen and switching to KVM for these new servers on Karmic. The rest of the entry is a step-by-step guide on setting up KVM VMs on a Ubuntu server; I’m putting this down because like all wikis, the Ubuntu KVM wiki has grown a little too organically to be useful.

Preparing a host server for KVM

1. Update and upgrade apt packages (use your own discretion on whether this is necessary):

   aptitude update && aptitude dist-upgrade

2. Check whether CPU supports hardware virtualization:

   egrep '(vmx|svm)' --color=always /proc/cpuinfo

   You should see lines with either “vmx” or “svm” highlighted.

3. Install these packages:

   aptitude install kvm libvirt-bin ubuntu-vm-builder bridge-utils

   If you see a FATAL: Error inserting kvm_intel message during installation, it means that virtualization is not enabled in your machine’s BIOS. You’ll need to reboot your machine, enter the BIOS setup and enable virtualization (you’ll have to hunt for the option).
   
   After enabling virtualization in the BIOS and rebooting, run:

   modprobe kvm-intel

   There should be no error shown (in fact, no console response).

4. Optionally, install virt-top, a top-like tool for your VMs:

   aptitude install virt-top

5. Verify that you can connect to the hypervisor:

   virsh -c qemu:///system list

   You should see something like this:

   Connecting to uri: qemu:///system
    Id Name                 State
    ----------------------------------

6. Setup a network bridge on the server for VMs. Edit /etc/network/interfaces so it looks like this (use your own IPs):

   auto lo
   iface lo inet loopback
   
   auto eth0
   iface eth0 inet manual
   
   auto br0
   iface br0 inet static
    address 192.168.1.222
    netmask 255.255.255.0
    network 192.168.1.0
    broadcast 192.168.1.255
    gateway 192.168.1.167
    bridge_ports eth0
    bridge_stp off
    bridge_fd 9
    bridge_hello 2
    bridge_maxage 12
    bridge_maxwait 0

7. Make sure that you have a direct console to the server because you’re going to restart networking:

   /etc/init.d/networking restart

8. Verify that your changes took place with ifconfig. You should see 2 entries like these:

   br0       Link encap:Ethernet  HWaddr 00:11:22:33:44:55
             inet addr:192.168.1.215  Bcast:192.168.1.255  Mask:255.255.255.0
             inet6 addr: fe80::223:aeff:fefe:1f14/64 Scope:Link
             UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
             RX packets:1099 errors:0 dropped:0 overruns:0 frame:0
             TX packets:50 errors:0 dropped:0 overruns:0 carrier:0
             collisions:0 txqueuelen:0
             RX bytes:74665 (74.6 KB)  TX bytes:6223 (6.2 KB)
   
   eth0      Link encap:Ethernet  HWaddr 00:66:77:88:99:00
             inet6 addr: fe80::223:aeff:fefe:1f14/64 Scope:Link
             UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
             RX packets:4939 errors:0 dropped:0 overruns:0 frame:0
             TX packets:39 errors:0 dropped:0 overruns:0 carrier:0
             collisions:0 txqueuelen:1000
             RX bytes:532798 (532.7 KB)  TX bytes:5585 (5.5 KB)
             Interrupt:36 Memory:da000000-da012800

Setting up a VM

1. Setup a VM with vmbuilder:

   vmbuilder kvm ubuntu \
       -v \
       --suite=karmic \
       --libvirt=qemu:///system \
       --arch=amd64 \
       --cpus=2 \
       --mem=2048 \
       --swapsize=4096 \
       --rootsize=20480 \
       --flavour=server \
       --hostname=billiejean \
       --ip=192.168.1.240 \
       --mask=255.255.255.0 \
       --net=192.168.1.0 \
       --bcast=192.168.1.255 \
       --gw=192.168.1.167 \
       --dns='202.157.163.157 202.157.131.118' \
       --bridge=br0 \
       --mirror=http://archive.ubuntu.com/ubuntu \
       --components='main,universe' \
       --addpkg=openssh-server \
       --user=administrator \
       --pass=icanhaspasswd \
       --dest=/root/vm-billiejean \
       --tmpfs=-

   The options you need to care about are:

   1. suite: Version of Ubuntu to install (e.g. karmic, hardy).
   2. cpus: Number of CPUs to assign to VM.
   3. mem: Amount of RAM in MB to assign to VM.
   4. swapsize: Size of swap in MB of VM.
   5. rootsize: Size of root filesystem in MB of VM.
   6. flavour: The “flavour” of kernel to use in the VM. Either “virtual” or “server”.
   7. hostname: Hostname of VM.
   8. ip: IP address of VM.
   9. mask: Netmask of VM.
   10. net: Network of VM.
   11. bcast: Broadcast address of VM.
   12. gw: Gateway of VM.
   13. dns: DNS server(s) for VM.
   14. addpkg: APT packages to install in the VM. openssh-server is needed so that we can login to the VM to setup the virsh console.
   15. user and pass: User account that’s setup for you to access the VM.
   16. dest: Destination directory on server where VM disk image will reside.
2. If your VM is created successfully, there’ll be a config file for the VM in /etc/libvirt/qemu/ (e.g. /etc/libvirt/qemu/billiejean.xml), and a disk image in the directory specified in the --dest option (e.g. /root/vm-billiejean/disk0.qcow2).
3. You can verify that it works by starting the VM and SSHing into it (virsh console will not work yet).

   virsh start billiejean

Converting Disk Images to LVM Logical Volumes

Now, we have the VM setup but it’s running off a disk image. For better performance, running the VM off a LVM logical volume will optimize disk IO.

vmbuilder is supposed to support the --raw option to write the VM to a block device (such as a LVM logical volume), but I’ve had no success with it (as does Mark Imbriaco, sysadmin of 37signals: http://twitter.com/markimbriaco/status/7437688341 and http://twitter.com/markimbriaco/status/7437699338). We’re going to convert the disk images using qemu-img and write the bits into a LVM logical volume instead.

1. Stop the VM if it’s running:

   virsh shutdown billiejean

2. Convert the VM’s qcow2 (QEMU image format) disk image to a raw disk image:

   qemu-img convert disk0.qcow2 -O raw disk0.raw

3. Create a logical volume to house the VM, making sure it’s big enough for the VM’s rootsize and swapsize options:

   lvcreate -L24GB -n <logical_volume_name> <volume_group_name>

4. Copy raw image into the logical volume:

   dd if=disk0.raw of=/dev/<volume_group_name>/<logical_volume_name> bs=1M

   This will take awhile (the bigger your image, the longer it takes).

5. Edit the VM’s config so that it uses your new logical volume:

   virsh edit billiejean

   Change <disk> to point to the logical volume:

   <disk type='block' device='disk'>
     <source dev='/dev/<volume_group_name>/<logical_volume_name>'/>
     <target dev='hda' bus='ide'/>
   </disk>

6. Startup the VM. You might wanna rename the original disk0.qcow2 image first just to make sure your VM isn’t still using it.
7. Once you’re sure your VM is running off your LVM logical volume, you can delete or backup the original qcow2 disk image.

Getting a console to your VM from the Host Server

Now, we have to setup the VM so that virsh console works. This is a console to the VM from the host server that works even when the networking in the VM is not.

1. Edit the VM’s settings:

   virsh edit billiejean

   In the <devices> block, add:

   <serial type='pty'>
     <target port='0'/>
   </serial>

2. Startup your VM:

   virsh start billiejean

3. SSH into VM and create a file /etc/init/ttyS0.conf:

   start on stopped rc RUNLEVEL=[2345]
   stop on runlevel [!2345]
   
   respawn
   exec /sbin/getty -8 38400 ttyS0 vt102

   Start the tty with:

   start ttyS0

4. Still in the VM, install acpid so that the VM will respond to shutdown commands from the server:

   aptitude install acpid

5. Reboot the VM.
6. Verify the console works by opening a console to the VM from the server:

   virsh console billiejean

   You may have to hit “Enter” before you see any console output.

Miscellaneous VM Setup

That’s it, your VM is ready! You’ll probably want to do these:

• Set a root password and possibly delete the user you setup using vmbuilder.
• Set the timezone with dpkg-reconfigure tzdata.

It probably sounds like shameless self-promotion that I’m blogging about these changes since I’d contributed them. Well, yeah that’s true, but I’m also doing so because I doubt these changes will ever be made known since Curb doesn’t publicize any updates or changelogs.

Curb is my current number 1 HTTP client for Ruby so the more love it gets, the better.

Passing cookies as a string in Curb requests

Curl veterans will probably know how to do this with the curl binary:

curl -b "auth=abcdef; ASP.NET_SessionId=lotsatext;" example.com

This sends a request to example.com with 2 cookies named “auth” and “ASP.NET_SessionId” (I hate those big-ass ASP.NET cookies btw). There wasn’t a way to set this in Curb, so I looked up the libcurl C API docs and replicated the same option in Curb (commit on Github). An example:

curl = Curl::Easy.new('http://example.com/')
curl.cookies = 'auth=abcdef; ASP.NET_SessionId=big-wall-of-text;'
curl.perform

Of course, the cookies will more often be retrieved/constructed rather than a literal like in the example above. In my case, I was proxying cookies while trying to wrap an API around a site that doesn’t have one.

Passing cookies as a file via the “cookiefile” option

The second change is the new cookiefile option. This replicates curl commands like these:

curl -b cookies-to-send.txt www.example.com

with something like this in ruby:

curl = Curl::Easy.new('http://example.com/')
curl.cookiefile = '/path/to/cookies-to-send.txt'
curl.perform

The cookies file looks like this (you can get a sample with the --cookie-jar option to curl, e.g. curl --cookie-jar cookies.txt www.wego.com):

www.wego.com	FALSE	/	FALSE	0	lang
www.wego.com	FALSE	/	FALSE	0	user_country_code	SG

Check out the commit on Github if you’re interested.

Why would I use these?

Now you might be wondering how these 2 changes are useful – well, they are totally irrelevant to you if you’re not expecting any cookie support in Curb. However, if you’re accessing or scraping a site that uses cookie-based authentication, these changes allow you to keep your Curb client authenticated across sessions, even when doing HTTP POSTs (Curb doesn’t send cookies properly in POST requests even if curl.enable_cookies is set).

I’ve found these changes to Curb particularly useful since I vastly prefer Curb to most HTTP clients for its speed and lightweight implementation, and heavier scraper-type HTTP clients like Mechanize are a last resort.

Catch the new first edition – this one’s about the API changes since Rails 2.1.

I’ll be at (my first) Railsconf 2008 in Portland, Oregon this Thursday onwards – if anyone sees me and recognizes me from my Facebook picture please come and say hi (no head butting though).

This week’s report covers changes from 19th May 2008 to 25th May 2008 (the day the corresponding Rails Envy podcast was recorded).

first and last methods now work with associations and named_scope

Remember how the merging of the has_finder gem into Rails allowed you to do things like Post.first and Post.last?

Now you can go one step further and use the same methods on your ActiveRecord associations. For example:

post = Post.find(1)
first_comment = post.comments.first

If you have a named_scope named recent defined, you can even do this:

post.comments.recent.last

This neat little enhancement is courtesy of Ryan Bates (yes, that Ryan Bates of Railscasts fame).

Related changeset: http://github.com/rails/rails/commit/73c59638549686fccc749ffd3ac53cb533c5fd61

Cache stores now have an exist? method and controllers get fragment_exist?

The cache stores in Rails (Memcache, file stores, etc.) now have an exist? method that checks whether a cached value exists given a cache key. This allows Rails controllers to expose a fragment_exist?
method that allows you to check for existence of a cache fragment:

fragment_exist?('example.com/foo/bar')

This little enhancement is courtesy of José Valim.

Related changeset: http://github.com/rails/rails/commit/99860b72aebe0348f41e82d4710343498d89a84b#diff-2

Create association records with block argument

You can now create records for associations like so:

post.coments.create!(:title => 'Techcrunch') do |c|
  c.body = "Rails can't scale"
end

This is in keeping with the ActiveRecord::Base.create change previously mentioned.

Credit for this patch goes (once again) to Ryan Bates.

Related changeset: http://github.com/rails/rails/commit/6cba97d2a449faf21aec9fe9d4434067e414226f

As always, let me know of any suggestions or how I can improve the Living on the Edge (of Rails) series.

This week’s report covers changes from 12th May 2008 to 18th May 2008 (the day the corresponding Rails Envy podcast was recorded).

caches_action can has conditionals

caches_action now takes an :if option (just like caches_page does). For example:

caches_action :index, :if => Proc.new { |c| !c.request.format.json? }

This little enhancement is courtesy of José Valim.

Related changeset: http://github.com/rails/rails/commit/7708650f73ddb4db300ea2059c60c1d907a4384e

Bugfix: :select option is now scanned in ActiveRecord finders to ensure needed tables are included in generated SQL

Post.find(:all, :include => :author, :select => 'posts.*, authors.id as "author_id"', :limit => 2)

Would generate an SQL statement like this:

SELECT posts.*, authors.id as "author_id" FROM "posts" LIMIT 2

Notice how the authors table is not joined. This oversight is now fixed.

Thanks go to John Devine for this bugfix.

Related changeset: http://github.com/rails/rails/commit/b28b54cab090bed8f099ef375b419a8f92390dd4

As always, let me know of any suggestions or how I can improve the Living on the Edge (of Rails) series. Also, if anyone has any recommendations of (non-ruby-related) things to do in Portland, do let me know!

change_table for ActiveRecord migrations

Thanks to Jeff Dean, who also blogged about the new change_table feature in ActiveRecord migrations, you can now change a table with a block like so:

change_table :videos do |t|
  t.add_timestamps
  t.add_belongs_to :goat
  t.add_string :name, :email, :limit => 20
  t.remove_column :name, :email # takes multiple arguments
  t.rename :new_name
  t.string :new_string_column # executes against the renamed table name
end

Some key things to note:

• add_XXX would add a new column for you, e.g. add_string would add a new string field.
• Of course, add_timestamps would add the magic created_at and updated_at datetime fields.
• remove_column now takes multiple arguments.
• rename would rename the table.

Very nice, DRY enhancement, props to Jeff Dean once again.

Related changeset: http://github.com/rails/rails/commit/96980bd561d79824b6cb6efbcbecdcbf8785d452

ActiveRecord::Base.create takes a block like ActiveRecord::Base.new

Yup now you can also create ActiveRecord objects with a block argument just like you could for ActiveRecord::Base.new:

@person = Person.create(params[:person]) do |p|
  p.name = 'Konata Izumi'
  p.age = 17
end

Credit goes to Adam Meehan for this patch.

Related changeset: http://github.com/rails/rails/commit/dd120ede53eaf71dee76894998a81626b7a689fc

Bugfix: change_column should be able to use :null => true on a field that
formerly had false

You can now use change_column in your migrations to alter a column as nullable if it was previously NOT NULL.

This bugfix is courtesy of Nate Wiger.

Related changeset: http://github.com/rails/rails/commit/10ef65a3b054270ed3d458ec8eb7c2b9a3e638f7

As always, let me know of any suggestions or how I can improve the Living on the Edge (of Rails) series.

Not much interesting to report this week – there were mostly a bunch of bugfixes and Ruby 1.8.7-compatibility commits.

Introduce ActiveResource::Base.timeout and rescuing from Timeout::Error in ActiveResource::Connection

These are 2 changes that I’d talked about earlier this week so I won’t repeat myself – take a read through ActiveResource timeouts and why it matters.

Smart integer datatype for the MySQL adapter in migrations

The MySQL adapter in Rails now maps the integer column type in your migrations to either smallint, int, or bigint depending on the :limit option.

This means that a migration like this:

def self.up
  create_table :searches do |t|
    t.integer :foo, :limit => 2
  end

will create your foo column as a smallint(2) MySQL datatype (instead of int(2) before). (More information MySQL numeric datatypes.)

Credit goes to DHH for this patch.

Related changeset: http://github.com/rails/rails/commit/a37546517dad9f6d9a7de6e1dba4d960909d71e8

As always, let me know of any suggestions or how I can improve the Living on the Edge (of Rails) series.

This week’s report covers changes from 14 Apr 2008 to 20 Apr 2008 (the day the corresponding Rails Envy podcast was recorded).

Conditional caches_page

The caches_page now takes an :if option for specifying when a page can actually be cached via a Proc. You can now do this, for example:

caches_page :index, :if => Proc.new { |c| !c.request.format.json? }

That will only cache your index page if the requested format is not JSON.

Credit goes to Paul Horsfall for this enhancement.

Related changeset: http://github.com/rails/rails/commit/14a40804a29a57ad05ca6bffbe1e5334089593a9

New ActionView::TestCase for testing view helpers

Remember how you can now use specialized TestCase classes for testing controllers and ActionMailer classes? Now you can do the same with your Rails view helpers with the new ActionView::TestCase class.

Here’s a quick example:

module PeopleHelper
  def title(text)
    content_tag(:h1, text)
  end

  def homepage_path
    people_path
  end
end

class PeopleHelperTest < ActionView::TestCase
def setup
  ActionController::Routing::Routes.draw do |map|
    map.people 'people', :controller => 'people', :action => 'index'
    map.connect ':controller/:action/:id'
  end
end

def test_title
  assert_equal "<h1>Ruby on Rails</h1>", title("Ruby on Rails")
end

def test_homepage_path
  assert_equal "/people", homepage_path
end

Credit goes to Josh Peek for this sweet little enhancement.

ActiveSupport::Cache’s mem_cache_store accepts options

Even though Memcache-client was added to ActiveSupport recently, it didn’t allow you to specify any configuration options beyond just the IP of the memcached server. Now you can pass along more configuration options like so:

config.action_controller.fragment_cache_store = :mem_cache_store, 'localhost', { :compression => true, :debug => true, :namespace => 'foo' }

This patch is courtesy of Jonathan Weiss.

Related changeset: http://github.com/rails/rails/commit/9e1d506a8cfedef2fdd605e4cbf4bf53651ad214

As always, let me know of any suggestions or how I can improve the Living on the Edge (of Rails) series.

This week’s report covers changes from 7 Apr 2008 to 13 Apr 2008 (the day the corresponding Rails Envy podcast was recorded).

A helpers proxy method for accessing helper methods from outside of views

A helpers method has been introduced to ActionController – you can now access your helpers like so:

ApplicationController.helpers.simple_format(text)

Credit goes to 19 year old Josh Peek, one of the more prolific Rails contributors (and most likely to join Pratik in Rails Core imo).

Related changeset: http://github.com/rails/rails/commit/917423d664038d6791738a73ad1446437dbb71df

json_escape for escaping HTML entities in JSON strings

A json_escape (aliased as j, similar to how html_escape is aliased as h) has been introduced by Rick Olson for escaping HTML entities in JSON strings. This is useful if you find yourself emitting JSON strings in HTML pages (e.g. for documenting a JSON API):

json_escape("is a > 0 & a < 10?")
# => is a \u003E 0 \u0026 a \u003C 10?

Of course, since json_escape is aliased as j, you can do this in your ERB templates:

<%=j @person.to_json %>

Related changeset: http://github.com/rails/rails/commit/0ff7a2d89fc95dcb0a32ed92aab7156b0778a7ea

Automatically parse posted JSON content for Mime::JSON requests

Rails will now accept POSTed JSON content! For example, you can now send a POST to “/posts” of your Post resource like this:

POST /posts
{"post": {"title": "Breaking News"}}

And your create action will automatically parse the POSTed JSON into the request params so that this code below just works:

def create
  @post = Post.create params[:post]
end

Credit goes to Rick Olson.

Related changeset: http://github.com/rails/rails/commit/4d594cffcfc93b37fad4e423ec8593299e50133c

schema_migrations table replaces the schema_info table, allowing for interleaved migrations

A new schema_migrations table for storing which migrations have been run has been introduced, and this replaces the existing schema_info table (which simply keeps track of the last applied schema version). This change makes it possible to add migrations (for example, after you’ve merged from someone’s branch) – when you migrate your database via rake db:migrate, those never-applied “interleaved” migrations will be run. Similarly, when migrating down schema versions, never-applied “interleaved” will be skipped.

See http://dev.rubyonrails.org/ticket/11493 for more information.

This useful patch is the brainchild of Jordi Bunster (WWR profile). I’m sure many Rails developers who branch extensively will thank Jordi for this excellent patch!

Related changeset: http://github.com/rails/rails/commit/8a5a9dcbf64843f064b6e8a0b9c6eea8f0b8536e

gems:unpack:dependencies Rake task

Remember how you can now run the gems:unpack Rake task to unpack a gem into your vendor/gems/ directory (this was mentioned in an earlier Living on the Edge)?

David Dollar (Github profile) has firmed up that patch quite a bit by adding the gems:unpack:dependencies Rake task that unpacks the dependencies of the gems as well. So running:

gems:unpack:dependencies GEM=activecouch

would unpack the full Rubygem dependency tree of gems that the activecouch gem depends upon.

Related changeset: http://github.com/rails/rails/commit/4364c361b599f99bc2345ce4eb2d145b07ed8a0f

As always, let me know of any suggestions or how I can improve the Living on the Edge (of Rails) series! Now go out there and start forking Rails!

From this week onwards, I’ll be following Pratik‘s suggestion to post about changes as they happen instead of after an entire week so expect a slight change in the format of Living on the edge for next week!

This week’s report covers changes from 31 Mar 2008 to 6 Apr 2008 (the day the corresponding Rails Envy podcast was recorded).

Rails.env, Rails.logger, Rails.cache, Rails.root

This has been a long time coming: You can now use Rails.env instead of RAILS_ENV, Rails.root instead of RAILS_ROOT, Rails.logger instead of RAILS_DEFAULT_LOGGER, and Rails.cache instead of RAILS_CACHE. Not having to use constants is nice because it always felt a bit dirty to have so many hard-coded constants in the Rails namespace.

Credit goes to Pratik Naik, the newest Rails core team member for this cleanup.

Related changeset: http://dev.rubyonrails.org/changeset/9180

Render :partial now works with a collection of heterogeneous elements

You can now use render :partial to render a collection of different elements and Rails will figure out which partial template to use. For example:

render :partial => [ monkey, donkey, dramatic_chipmunk ]

will render the monkey with the ‘monkeys/_monkey.html.erb’ partial, donkey with the ‘donkeys/_donkey.html.erb’ partial, and last but definitely not lest, dramatic_gopher with the ‘dramatic_chipmunks/_dramatic_chipmunk.html.erb’ partial

This is especially useful if when using STI, where your ActiveRecord model would return objects of different types. The collection [ monkey, donkey, dramatic_chipmunk ] could very well be something returned from your Animal model that has subclasses of Monkey, Donkey and DramaticChipmunk via STI.

Credit: Zach Dennis of ar-extensions fame.

Related changeset: http://dev.rubyonrails.org/changeset/9177

ActiveModel work revived

It seems like work on ActiveModel (think unified ActiveRecord and ActiveResource behaviors) has been revived, if the latest commits (http://dev.rubyonrails.org/changeset/9171 and http://dev.rubyonrails.org/changeset/9173) by David (DHH) is anything to go by.

Bugfix: Assigning an invalid has_one association now causes #save to fail on parent

You could do this before:

firm = Firm.find(:first)
firm.account = Account.new # Associate INVALID account
firm.save # This doesn't fail

Now that’s fixed thanks to Pratik Naik.

Related changeset: http://dev.rubyonrails.org/changeset/9232

As usual, any feedback is respectfully appreciated!

There’re lots of big exciting changes this week on edge. Smells like 2.1 soon!

has_finder gem merged into Rails

Ryan Daigle has the scoop on the new has_finder-like functionality in Rails so head on over (I won’t repeat it here in the interests of DRY).

Credit goes to Nick Kallen for coming up with the has_finder gem.

Related changeset: http://dev.rubyonrails.org/changeset/9084

ActiveRecord: Unsaved attribute changes are now tracked

You can now ask an ActiveRecord model whether its attributes have been changed (and is unsaved) using the {attr_name}_changed? (magic) method. The {attr_name}_was method will return the original value of the attribute, and the {attr_name}_change method will return an array with 2 members, the 1st being the original value, the 2nd being the changed (and unsaved) value.

# Change person's name.
person.name = 'Jason Seifer'
person.changed?       # => true
person.name_changed?  # => true
person.name_was       # => 'jseifer'
person.name_change    # => ['jseifer', 'Jason Seifer']
person.name = 'Ceiling Cat'
person.name_change    # => ['jseifer', 'Ceiling Cat']

Credit goes to Rails core team member Jeremy Kemper (bitsweat) for this patch (which originated from Jeremy’s very own Dirty plugin).

Related changeset: http://dev.rubyonrails.org/changeset/9127

ActiveRecord#Base.all/first/last

Now you can do:

Post.all.each { |post| # something }
Post.first
Post.last

Kinda like how some other ORMs do (like DataMapper).

Credit: thechrisoshow and again, Nick Kallen for has_finder.

Related changeset: http://dev.rubyonrails.org/changeset/9085

Timestamped Migrations

This is more useful than it sounds: migrations are now timestamped instead of using incremental numbers in your db/migrate folder. This eliminates the problem of migrations having the same version number when working on a multi-developer Rails app.

Two new Rake tasks, rake db:migrate:up/down, have been added to allow running of the up and down methods of individual migrations.

Credit goes to John Barnette, the guy who gave you foxy fixtures.

Related changeset: http://dev.rubyonrails.org/changeset/9122

New config.gem option for specifying which gems are required by the application + rake tasks for installing and freezing gems

Specify which gems are required by your Rails app in your Rails environment.rb! “Vendor everything” supported right in Rails :). An example:

Rails::Initializer.run do |config|
  config.gems 'chronic'
  config.gems "hpricot", :version => '0.6', :source => "http://code.whytheluckystiff.net"
  config.gems "aws-s3", :lib => "aws/s3"
end

There are also new Rake tasks:

# List required gems.
rake gems 

# Install all required gems:
rake gems:install 

# Unpack specified gem to vendor/gems/gem_name-x.x.x
rake gems:unpack GEM=chronic

Credit goes to the prolific Rick Olson for this gem of a patch.

Related changeset: http://dev.rubyonrails.org/changeset/9140

ActiveResource #clone

You can now clone an existing resource:

gregg = Person.find(1)
borg = gregg.clone

This doesn’t clone child ActiveResource members though, just the straight up attributes of resource.

Contribors: Ryan Daigle and thechrisoshow.

Related changeset: http://dev.rubyonrails.org/changeset/9121

Big documentation patch

A big doc patch consisting of all the efforts going on in the doc-rails repository on Github has been committed. Check out Pratik’s post for more info on what doc-rails is. Though with Rails moving to Git soon, doc-rails may no longer be necessary!

Related changeset: http://dev.rubyonrails.org/changeset/9093

This week’s report covers changes from 17 Mar 2008 to 23 Mar 2008 (the day the corresponding Rails Envy podcast was recorded).

script/plugin install works for Git repositories

Yup you can now install plugins from Git repositories simply by running:

script/plugin install git://github.com/foo/kung_fu

What this really does is to clone a git repository (sans the entire git history by passing the —depth 1 option) into your plugins directory. If you’re looking for a Piston-like way to manage external Git repositories though, you’d still be better off with the development version of Piston (François Beausoleil, is posting frequently on his progress with adding Git support).

Credit goes to Jack Danger, a long-time Rails contributor for this patch.

Related changeset: http://dev.rubyonrails.org/changeset/9049

has_one :through

It’s been a long time coming – now you can do has_one :through (like has_many :through) for your join models. Ryan Daigle has example code on how to use it if you’re curious (though really, it’s just like has_many).

Credit goes to the Art of Mission guys and Chris O’Sullivan for pulling it all together.

Related changeset: http://dev.rubyonrails.org/changeset/9067

rake tasks time:zones:all, time:zones:us and time:zones:local

Some timezone-related rake tasks have been added to list the names of time zones recognized by the TimeZone class for the config.time_zone option you can put in your environment.rb. For example

rake time:zones:local

* UTC +08:00 *
Beijing
Chongqing
Hong Kong
Irkutsk
Kuala Lumpur
Perth
Singapore
Taipei
Ulaan Bataar
Urumqi

Credit: Geoff Buesing (core team member)

Related changeset: http://dev.rubyonrails.org/changeset/9074

#number_to_currency helper now supports a :format option

Now you can do something like:

number_to_currency(123.50, :unit => "£", :format => "%n %u")
# => 123.50 £

Instead of being stuck with the {currency_code} {amount} format which doesn’t work in some locales (such as “42 pounds”).

Related changeset: http://dev.rubyonrails.org/changeset/9052

Custom JavaScript and stylesheet symbols

Remember how you can do something like:

javascript_include_tag :defaults

and Rails would load all the Prototype JavaScript files and your application.js?

You can now register your own custom expansion symbol too:

# In a Rails initializer.
ActionView::Helpers::AssetTagHelper.register_javascript_expansion :yui => ['yahoo', 'autocomplete', 'calendar']

# In your view.
javascript_include_tag :yui

would result in:

<script type="text/javascript" src="/javascripts/yahoo.js"></script>
<script type="text/javascript" src="/javascripts/autocomplete.js"></script>
<script type="text/javascript" src="/javascripts/calendar.js"></script>

You can do the same with the stylesheet_link_tag by registering a custom expansion symbol via register_stylesheet_expansion.

This is useful for anyone but in particular plugin developers who have a multiple asset files would appreciate being able to tell users to include JavaScript or stylesheets using a single symbol.

Warning: This patch currently breaks the default symbols like :all (check out the ticket for more info).

Related changeset: http://dev.rubyonrails.org/changeset/9016

Sexy default timestamps in migrations

Remember how you can say timestamps in a migration and Rails will create the ‘created_at’ and ‘updated_at’ columns for you? You can now also do add_timestamps :table_name and remove_timestamps :table_name in your migrations if you decide to add these columns later to a table:

def self.up
  add_timestamps :posts
end

def self.down
  remove_timestamps :posts
end

Related changeset: http://dev.rubyonrails.org/changeset/9014

ActiveRecord::Base#find(:last)

Just like Comment.find(:first), you can now do something like Comment.find(:last). There’s some controversy over whether this is bloat, but DHH makes a good case for it with this example:

class Person
  has_many :comments, :order => 'created_at'
end

@some_person.comments.find(:last) # => Returns the most recent comment.

Related changeset: http://dev.rubyonrails.org/changeset/9012

Database rake tasks fixes

rake db:create used to ignore the ‘charset’ and ‘collation’ options in your database.yml configuration file. This has been fixed so that your created databases now respect those options.

rake db:drop and rake db:migrate:reset also no longer crash with an unhelpful exception if the database has already been dropped, and instead shows a proper error message.

Related changeset: http://dev.rubyonrails.org/changeset/9004

Rails’ logger now creates the log directory if it doesn’t exist

This is a blessing to those of us who use version control systems that don’t support empty directories (like Git). Rails’ default logger (the BufferedLogger), now creates a log/ directory if it doesn’t already exist. This should save you the step of creating/symlinking a log/ directory (or symlinking) on deploy.

Related changeset: http://dev.rubyonrails.org/changeset/9013

String#squish is faster

A faster implementation of the String#squish (and String#squish!) core extension has been committed.

Related changeset: http://dev.rubyonrails.org/changeset/9015

The #excerpt TextHelper no longer includes 1 character too many

Turns out that the #excerpt helper method was consistently including an extra character. This has been fixed.

Related changeset: http://dev.rubyonrails.org/changeset/9030

As usual, let me know of any inaccuracies or any suggestions you may have in the comments!

Improve performance on :include/:conditions/:limit queries by selectively joining in the pre-query

This is another ActiveRecord performance boost related to the pre-loading any eager-loaded :includes mentioned previously. Basically what this patch does is to only join referenced tables when needed. It does this by checking the :conditions and :limit options to determine whether a table should be joined or can be left out and pre-loaded instead. You can find out more in tickets #9560 and #9497.

Credit goes to Gabe da Silveira (dasil003 on Trac) for this awesome performance patch.

Related changeset: http://dev.rubyonrails.org/changeset/8977

Better error message for type errors when parsing request parameters

Now when you pass an incorrectly formed request (e.g. GET, POST) parameter to your controller, it will raise an exception that includes a friendlier error message that indicates exactly what you passed to it. This is helpful when trying to debug whether you constructed your form correctly.

Contributors: Chad Humphries and matt.

Related changeset: http://dev.rubyonrails.org/changeset/8986

Make MimeResponds::Responder#any work without explicit types.

Here’s something I didn’t know: you can actually use any in your respond_to blocks as a catch-all response. E.g.

respond_to do |format|
  format.html do
    redirect_to :action => 'login'
  end
  format.any(:js, :xml) do
    request_http_basic_authentication 'Web Password'
  end
end

Contrary to its name, using ‘any’ actually requires you to pass a list of types to respond to. This has been enhanced now so that if you don’t pass any arguments, it’ll function as a real catch-all.

respond_to do |format|
  format.any do
    request_http_basic_authentication 'Web Password'
  end
end

Credit goes to Joshua Wehner for this patch.

Related changeset: http://dev.rubyonrails.org/changeset/8987

Add readonly option to has_many :through associations

Turns out the :readonly option for associations mentioned earlier was left out for has_many :through associations. This oversight has been fixed.

Thanks to Emilio Tagua for this bugfix.

Related changeset: http://dev.rubyonrails.org/changeset/8989

As usual, let me know of any inaccuracies or any suggestions you may have in the comments!

In other interesting news, Pratik Naik (lifofifo), a long-time Rails contributor has been given commit rights to Rails. Congrats Pratik, well-deserved and it has been long overdue in my opinion! Pratik keeps an interesting blog at http://m.onkey.org/ (where he’s not afraid to say “fuck” in his posts and his code) and hangs out an awful lot on #rubyonrails and #rails-contrib on IRC.

As a sidenote, Capistrano 2.2.0 was released by Jamis last week.

This week’s report covers changes from 25 Feb 2008 to 2 Mar 2008 (the day the corresponding Rails Envy podcast was recorded).

Time#end_of_XXX methods

A bunch of Time core extension methods have been added. These are: Time#end_of_day, Time#end_of_week, Time#end_of_year, and Time#end_of_quarter, which all return exactly what you expect them to return:

Time.now.end_of_week # => Sun Mar 09 00:00:00 0800 2008

Credit goes to Juanjo Bazán (a former Rails Hackfest winner) and Tarmo Tänav for contributing this patch.

Related changeset: http://dev.rubyonrails.org/changeset/8934

Date helpers now accept HTML options

ActionView’s date helpers (such as date_select, time_select, select_datetime) did not support any HTML options, unlike the other helpers (like f.text_field(:name, :class => 'my_css_class', :size => 20)). This inconsistency has been fixed and you can now finally do:

<%= date_select 'user', 'birthday', :order => [:day], :class => 'my_css_class' %>

Murray Steele (h-lame on the Rails Trac) and Jakob Skjerning contributed this patch.

Related changeset: http://dev.rubyonrails.org/changeset/8968

No need for explicit respond_to for RJS templates

ActionController has been changed so that JS requests will automatically render action.js.rjs files without the need to specify an explicit respond_to block. This means that your .rjs files work the same way as your .html.erb files – just put them in the right place and Rails will use it.

Related changeset: http://dev.rubyonrails.org/changeset/8956

Bugfixes

• http://dev.rubyonrails.org/changeset/8937 – Prevent Rails from crashing when trying to deserialize an XML representation of a model named “Type” (using Hash#from_xml). Contributed by Juanjo Bazán and Isaac Feliu.
• http://dev.rubyonrails.org/changeset/8942 – Fix eager loading so that it doesn’t pull in duplicate records in some cases. Contributed by Catfish.

As usual, let me know of any inaccuracies or any suggestions you may have in the comments!