LabRatz

Steve Yegge, denied access to Ruby on Rails at Google, flexes his hacker muscles to port RoR-like syntax to JavaScript. It's an amazing testament to his skills that he can do this with a small team at Google. It looks like Google places a limit on the languages allowed on company projects. There are strict guidelines on security, performance, etc. It's well-known that the creator of Python works at Google and it's one of the languages allowed. Now the benefit of this strictness is that they're able to have a clean code base and it probably boosts productivity and limits complexity in the long-term (paraphrased verbatim from Steve's blog. While it's very cool that there are projects like this coming out of Google it also makes me wonder about Google's future. Obviously, Google is a cool place to be as long as you "play by the rules". Basically, sell your soul in exchange for a coveted seat in one of their cubicles. They've basically got a college dorm exchange where you get all your needs taken care of from health care to free food in exchange for coding non-stop with little to no life outside the company. Hey, I admit it still sounds cool but the intellectual intensity must be stifling at times just like academia is. While the rationale for Google's policy of enforcing allowed languages, it still rings strange because it ultimately limits the level of innovation. The so-called 20% time is not as widely utilized as many think too. People are worked hard. I think that Google is more of a bureaucracy than most think and it's probably hard to feel like your changes are having an impact unless you get indirect satisfaction from being part of the world's largest search engine. Some notable startup founders that got "absorbed" into Google end up jumping out of the company feet first to start yet another company rather than bask in the comfort of the mother ship.

Stevey's Blog Rants: Rhino on Rails

Life not THAT Great Working at Google? - CyberNet News

One of the shocking things about going into production is to go on a little break or even get away from the house only to gasp in horror as you stare at a blank 404 where your earth shaking rails app should be when you get back online.

Integrating stuff like memcached into your rails app is mostly trivial thanks to the work of some wonderful rails hackers but keeping this moving parts moving is a task in itself. What’s the use of having a killer app that only works on your dev box right?

Naturally, the good thing about development is that everyone else has been there and done that. The other day I discovered monit thanks to igvita.com.

Sometimes a variety of bugs in plugins or your code can bring your web app down to its knees. This doesn’t even include those moments when your hosting service goes down for whatever reason whether it be maintenance or trouble. Smart developers (that’s you) will already have crucial parts of their service automatically restart along with any hardware restarting either by setting their chkconfig or whatever their system uses. Most of the libraries that we depend on are mostly reliable most of the time like the MySQL server that we only need to worry about start up initialization (although even this depends on how hard you push it).

Unfortunately, for most beginners, rails still continues to be a dream to develop in and a nightmare to deploy unless you know what you’re doing. Also random application crashes will increase the more moving parts you have such as memcached, mongrel, and acts_as_ferret.

Enter Monit

Monit is a wonderful little tool to ensure that your little web app keeps chugging along happily. It’ll monitor whatever you tell it to and ensure that they continue to run under the conditions you specify.

Using it with mongrel_cluster will ensure that users of your web app will be served a proper web page even as one of the other mongrels get culled for misbehaving.

In order to fully take advantage of mongrel_cluster and monit, you need to grab the mongrel_cluster prerelease. You can of course, use monit to serve as your cluster management but as Ezra notes, mongrel_cluster does a better job of keeping memory consumption in check as well as dealing with orphaned pids (only prerelease) that has given anyone that deploys rails a headache or two.

I can also vouch for the fact that monit has a slew of cool features to help you really keep the system humming along nicely. Remember memcached? Well, as much as it provides performace boosts to your app, it also introduces a potential headache. You see, when used in conjunction with mongrel you need to be careful to ensure that memcached is running before your mongrel starts. Otherwise you get weird behavior such as your flash[:notices] not showing up.

So, suppose your memcached crashes but mongrel stays up. Even if memcached got restarted, you’re only half way there since you need to restart mongrel immediately after that. Fortunately, this is trivial with monit because you can simply set a hierarchy by stipulating a depends on condition. This will ensure that whatever is being depended on will be restarted by monit first before the other processes get started.

  set daemon 60
  set init
  set mailserver localhost
  set mail-format { from: monit@monit.com }
  set alert who@gmail.com

  set httpd port 2812 and
      use address localhost
      allow localhost        

  check process mongrel_8000
     with pidfile /var/run/mongrel_cluster/mongrel.pid
     start program = "/usr/local/bin/mongrel_rails cluster::start -C /root/inbited.com/current/config/mongrel_cluster.yml --clean --only 8000" 
     stop program = "/usr/local/bin/mongrel_rails cluster::stop -C /root/current/config/mongrel_cluster.yml --clean --only 8000" 

     if totalmem is greater than 60.0 MB for 5 cycles then restart
     if cpu is greater than 50% for 2 cycles then alert                  
     if cpu is greater than 80% for 3 cycles then restart                
     if loadavg(5min) greater than 10 for 8 cycles then restart          
     if 3 restarts within 5 cycles then timeout
     depends on memcached                          

     if failed port 8000 protocol http                
         with timeout 10 seconds
         then restart
     group mongrel

  check process mongrel_8001
     with pidfile /var/run/mongrel_cluster/mongrel.pid
     start program = "/usr/local/bin/mongrel_rails cluster::start -C /root/inbited.com/current/config/mongrel_cluster.yml --clean --only 8001" 
     stop program = "/usr/local/bin/mongrel_rails cluster::stop -C /root/current/config/mongrel_cluster.yml --clean --only 8001" 

     if totalmem is greater than 60.0 MB for 5 cycles then restart       
     if cpu is greater than 50% for 2 cycles then alert                  
     if cpu is greater than 80% for 3 cycles then restart                
     if loadavg(5min) greater than 10 for 8 cycles then restart          
     if 3 restarts within 5 cycles then timeout  
     depends on memcached                               

     if failed port 8001 protocol http                
         with timeout 10 seconds
         then restart
     group mongrel

  check process mongrel_8002
     with pidfile /var/run/mongrel_cluster/mongrel.pid
     start program = "/usr/local/bin/mongrel_rails cluster::start -C /root/inbited.com/current/config/mongrel_cluster.yml --clean --only 8002" 
     stop program = "/usr/local/bin/mongrel_rails cluster::stop -C /root/current/config/mongrel_cluster.yml --clean --only 8002" 

     if totalmem is greater than 60.0 MB for 5 cycles then restart       
     if cpu is greater than 50% for 2 cycles then alert                  
     if cpu is greater than 80% for 3 cycles then restart                
     if loadavg(5min) greater than 10 for 8 cycles then restart          
     if 3 restarts within 5 cycles then timeout 
     depends on memcached                         

     if failed port 8002 protocol http              
         with timeout 10 seconds
         then restart
     group mongrel

  check process memcached
     with pidfile /tmp/memcached.pid
     start program = "/etc/init.d/memcached start" 
     stop program =  "/etc/init.d/memcached stop" 
     if failed host 127.0.0.1 port 11211 then restart

This sample config is based on igvita and Ezra’s. As you can see there’s a “depends on memcached” call. What this does is set a hierarchy so if memcached gets restarted, mongrels will get restarted afterwards. On initialization, memcached will get started first so your web app can function properly.

I plan on tweaking this so that I can be extra sure to have essential services like mysql and nginx humming along properly as well (although I’ve yet to see these go out, the load on my service is currently close to nil).

I’ve only touched on the tip of the iceberg really and I just think I might even check out how to use this to keep rogue apps from eating up too many resources on my mac.

Now, apps should never ever be crashing to start but things happen and rails will always have its kinks until well it’s… enterprise ready™. But hey, it’s more important that your app stays humming especially if you have moving parts like memcached or ferret that form an integral part of your service.

Monit will also dutifully email you of any incidences that trigger it. This combined with exception notification can provide you with valuable debugging info.

Monit makes Mongrel play nice! – igvita.com

Mongrel Mongrel Cluster 1.0.1.1 Prerelease: Healing power of the pack!

Making your rails app aware of time zones can be a real pain. There's really nothing special about it. You simply want your app to display dates and time according to whatever time zone the end user happens to be in. The problem is that you have the server's time and the user's time and whatever values stored in the database for dates and time. This isn't supposed to be a detailed guide from beginning to end but a simple walk through to explain some things that tripped me up. Your mileage will vary. The first thing you need to do is follow all the steps in this excellent guide from Caboo.se. In my approach, I changed the set_timezone filter in application.rb to the following:

  private
  
  def set_timezone
    if logged_in? && !current_user.time_zone.nil?
      TzTime.zone = current_user.tz
    else
      TzTime.zone = TZInfo::Timezone.new(ENV['TZ'])
    end
    yield
    TzTime.reset!
  end

This takes advantage of the fact that I have this in environment.rb:

  config.active_record.default_timezone = :utc
  ENV['TZ'] = 'America/Los_Angeles'

You can of course, replace "ENV['TZ']" in the filter above with a valid time zone string such as 'America/Los_Angeles'. You always need to have a valid TZInfo::Timezone object when setting the time zone which is why we convert the string to a time zone object by calling TZInfo::Timezone.new("the_time_zone_string") otherwise you get funky errors like "TZInfo::Timezone constructed directly" and a mess of others. For my views I always format the date time into something more user friendly using strftime so I have this in one of my modules to convert the time in views.

  def tz_convert
    TzTime.zone.nil? ? self : TzTime.zone.utc_to_local(self.utc)
  end
  
  def full_date
    self.tz_convert.strftime("%m/%d/%Y %H:%M")
  end
  
  def short_date
    self.tz_convert.strftime("%m/%d %H:%M")
  end

The tz_convert method is written so it wont throw an error if the time zone isn't set. Like I said, this is an incomplete guide so you definitely want to read up on the other blogs out there:

caboose adding timezone to your rails app

Peter Marklund's Home : Rails Recipe: A Timezone Aware Datetime Picker

One thing you might come up against trying to make your view templates more readable and concise is stringing together a bunch of tags generated by link_to or some other method. For example, I wanted to create nested comments with a thumbnail of the member profile, a link to the topic, and show the actual content. All the stuff generated by link_to and other helpers are ultimately spit out as strings. This will allow you to combine helpers by using the property of strings. Here are two ways to create the same output:

		def nested_comments(comments)
		  ul(comments) do |item|
		    member_thumb(User.find(item["user_id"])) +
		    link_to(item["title"], :controller  => 'communities', :action  => 'show_topic', :id  => item["id"]) +
		    "
" + item["content"] + "
"
		  end
		end

		def nested_comments(comments)
		  ul(comments) do |item|
		    string = ""
		    string << member_thumb(User.find(item["user_id"]))
		    string << link_to(item["title"], :controller  => 'communities', :action  => 'show_topic', :id  => item["id"])
		    string << "
"
		    string << item["content"]
		    string << "
"
		    string
		  end
		end

The bottom version is more readable in a larger sense but top is way more concise. They use one of the available ruby concatenation methods.

UPDATE: Evan has updated has_many_polypmorphs so that child and parent can access each other both ways. For the average user, this means just use it like you normally would.

One of the things about being a rails beginner is that you don’t know whether you can’t do something efficiently because you don’t know how to do it or because Rails just doesn’t support it.

I think polymorphic associations as they currently stand are pretty limited or at least you could say they impose limitations. Just read Josh Susser’s blog for various examples.

That’s how I ended up arriving on the has\_many\_polymorphs doorstep. If polymorphic associations are the flexible joints of associations has\_many\_polymorphs takes it to a new level with joints that can flex 360 degrees in every direction.

It was hard to find friendly documentation suitable for a beginner but it really is simply once you have it. My example is probably one of the most basic uses but it’ll have to do. Check the documentation on Evan Weaver’s blog or fish through the plugin directory for examples within the tests(it’s pretty well-documented).

In my application I have Pictures and I have a bunch of other models that will use pictures like Profiles or Communities. This is easy to understand. One way to do it is documented in the wiki How to Use Polymorphic Associations. This document is a bit old so I’m not sure if it’s still the most efficient way of doing it but you end up with two models solely for tying together two different models. You need a Folder model and Linkings model. Not only that you have to set up all the association statements correctly and specify callbacks and other stuff to make them useful.

With has\_many\_polymorphs you’ll get all this for free.

It’s really easy with examples so here we go:

class Picture < ActiveRecord::Base
  has_many_polymorphs :consumers, :from => [:profiles, :communities], :through  => :picture_consumers

class PictureConsumer < ActiveRecord::Base
  belongs_to :picture
  belongs_to :consumer, :polymorphic => true

class Community < ActiveRecord::Base

This is what the PictureConsumer scheme looks like:

create_table "picture_consumers", :force => true do |t|
  t.column "picture_id",    :integer
  t.column "consumer_id",   :integer
  t.column "consumer_type", :string
  t.column "created_at",    :datetime, :null => false
  t.column "updated_at",    :datetime, :null => false
end

As you can see, the Community class (and neither does the profile class) require any association to be declared. This is because has\_many\_polymorphs takes care of it for us. Really, it’s that simple. With those you can now do:

@some_community.pictures
or
@some_picture.communities

You can associate pictures with as many models that you would like. Has\_many\_polymorphs also allows you to create joins that are polymorphic on both sides. Less configuration and more flexibility is certainly a plus.

One big snag waiting for you is the above may not work as is (especially in the controller). You need a declaration in application.rb and your environment file for Rails to properly load the associations.

For me these include the below. For application.rb:

require 'app/models/picture'
class ApplicationController < ActionController::Base

(update: no longer needed since update, see link below or note at the very top)

In development.rb for my environment: config.after_initialize do config.has_many_polymorphs_cache_classes = true end

This ensures the associations get loaded properly even when used in the console under development or for rendering in views.

UPDATE: Don’t do this either. It may unload some model methods after the second request. If you don’t know what that means you’re safe not putting the above in your environment file. Everything works fine out of the box thanks to Evan’s hard work.

The entirety of the information here was ripped out of Evan’s blog so please check it out and send him your regards. It’s marvellous work that I’m surprised is not already part of Rails.

has_many_polymorphs activerecord plugin :: evan weaver

has_many :through: The other side of polymorphic :through associations

has_many :through: Many-to-many Dance-off!

dependency injection for rails models :: evan weaver

Sorry for not writing in a while. I've been busy doing other stuff and on top of that DreamHost has been real brutal to this Mephisto blog. My blog was inaccessible for a long long time and there really wasn't anything I could do. Support requests simply came back as "can't do anything for third party software". Oh well, I'm not complaining but it's a shame. I'm using WordPress for another blog and I've got to say it's a pleasure to use a mature blog with lots of plugins to meet every need. I'm going to be tool agnostic from now on. That's not to say I want to do PHP. Mephisto is great for seeing a top class rails coder in action.

So anyways, as lot as DreamHost lets me run this blog, I'll try to write something up.

Today, I came across a great snippet you can add in your helpers to iterate over html lists, you know the typical ol ul elements.

Which lets you write: <%= ul @pages.map { |x| link_to_page(x) } %>

Well, this is a great time saver and way better than hand-coding it yourself but I wanted something that could produce a nested list from an array of arrays. Now my code isn't the most elegant but it works. It uses recursion to produce a nested list (although the spacing and newlines aren't included so the source looks garbled in real life).

So this in your views: <%= ol ["first", "first", ["third", ["second", "second", "second"], "third", "third", ["second", "second", "second"]]] %>

Becomes:

1. first
2. first
1. third
1. second
2. second
3. second
2. third
3. third
1. second
2. second
3. second

Here's the snippet:

    def html_list(type, elements, options = {})
      items = elements.map  do |element|
        if element.is_a?(Array)
          element = html_list(type, element, options = {})
        else
          content_tag("li", element)
        end
      end
      content_tag(type, items, options)
    end

Haven't tried it for something nested deeper than two elements so mileage may vary. What can you use it for? I was thinking nested comments (will have to figure that one out).

vemod.net - List Helper for Rails

Whoa! Don't how this guy scored a one-on-one tutoring session with the one and only DHH but I'm sure glad I found this. There's really nothing new here that you wouldn't find in the original screencasts other than DHH fumbling with the scaffold and looking up the rails API!!! I'm not trying to make fun or put down DHH but seeing that is such a sigh of relief for people like me doing much more fumbling. It's okay. For all the hype and some of the negative press he gets you can't deny the fact that DHH is very generous for doing this and an all around nice guy. It's also true for some serious rails hackers like Rick. These people are constantly giving people like me the gift of their time by providing their talents to open source projects. That's definitely one of the things I love about the rails community.

CoderPath via Rails Christmas gift