Tag Archives: ruby

Rails redirect_back_or_default

In a recent project I found myself writing recirect_to :back alot, and then found myself worrying that what if for some reason there is no :back.

Drawing inspiration from this blog, I wrote two helpers in my application_controller.rb.

The store_location stores current URI (or referer URI in case of non-GET request) into session[:return_to] for later usage:

def store_location
  session[:return_to] = if request.get?
    request.request_uri
  else
    request.referer
  end
end

And redirect_back_or_default tries its best to redirect the user to somewhere, in the following order:

  1. previously stored session[:return_to]
  2. Referer URI
  3. Given default URI
  4. or root_url if all else fails

The code itself

def redirect_back_or_default(default = root_url, options)
  redirect_to(session.delete(:return_to) || request.referer || default, options)
end

I’ve found that when rewriting redirect_to :back, notice: 'something' into redirect_back_or_default-call, adding this alias helps:

alias_method :redirect_to_back_or_default, :redirect_back_or_default

But of course, if you are testing your code (and you should be), it’s better to stick to one variant of above and use tests to catch all erroneous incarnations.

Rails 3: Merge scopes

I run into a case where I had User.search method and I wanted the GroupMember model be searchable by the user’s attributes. The most DRY way to accomplish this in Rails 3 is to merge scopes. In the User model:

# user.rb
class User < ActiveRecord::Base
  has_many :memberships, :class_name => "GroupMember", :foreign_key => "user_id"

  def self.search(search)
    if search.present?
      query = []
      params = []
      %w(uid email name).each do |field|
        # The field name must be fully qualified to merge scopes
        query << "#{self.table_name}.#{field} LIKE ?"
        params << "%#{search}%"
      end
      query = query.join(" OR ")
      where(query, *params)
    else
      scoped
    end
  end
end

NB! It’s important to have the User’s field names fully qualified so that they won’t be applied to the GroupMember table. And in the GroupMember model:

# group_member.rb
class GroupMember < ActiveRecord::Base
  belongs_to :user
  belongs_to :group

  def self.search(search)
    if search.present?
      # We search GroupMembers by the user attributes
      scoped.joins(:user).merge(User.search(search))
    else
      scoped
    end
  end
end

Now it’s possible to search for GroupMembers by the User attributes:

group = Group.find 1
group.group_members.search('david')

This results in SQL query:

SELECT "group_members".* FROM "group_members" INNER JOIN "users"
ON "users"."id" = "group_members"."user_id" WHERE "group_members"."group_id" = 1
AND (users.uid LIKE '%david%' OR users.email LIKE '%david%'
OR users.name LIKE '%david%')

uses of Ruby’s Object#tap

Ruby 1.9′s Object#tap method has always seemed useful to me, but until now I hadn’t met the chance to use it. Every other time it seemed like abusing it in some way.

Now I came to an old code. Consider this:

cgi.text_field( "name" => "myfield",
                "value" => value,
                "size" => 20,
                "maxlength" => maxlength
              )

I needed to turn that maxlength into a conditional attribute (omiting it if it’s nil).
One way would have been extracting the attributes into a separate variable:

attrs = {
          "name" => "myfield",
          "value" => value,
          "size" => 20
        }
attrs['maxlength'] = maxlength if maxlength
cgi.text_field( attrs )

But this separates visually the cgi.text_field() call from it’s arguments, which I don’t like. Tap to the resque:

cgi.text_field({  "name" => "myfield",
                  "value" => value,
                  "size" => 20
                }.tap{|attrs| 
                  attrs['maxlength'] = maxlength if maxlength
                })

Now, isn’t that nice! (OK, maybe it isn’t, but at least it is encompassed in the method call and makes it easy to spot all attributes).

Ruby (on Rails) toolchest for Windows users

Setting up solid Ruby on Rails developer box based on Windows can be tedious task. More so than on other platforms, because vanilla Windows is meant for end user and lacks proper development tools that exist on other platforms. But fear not, there are many good people out there that have jumped through multitude of hoops to get different parts of the ecosystem working. All that remains is to build a solid foundation for developmer from them. Read more »

Ruby Rack servers benchmark

Facing the question which Ruby Rack server perform best behind Nginx front-end and failing to google out any exact comparison, I decided to do a quick test myself.

The servers:

Later I tried to test UWSGI server too as it now boasts built-in RACK module, but dropped it for two reasons: (1) it required tweaking OS to raise kern.ipc.somaxconn above 128 (which none other server needed) and later Nginx’s worker_connections above 1024 too and (2) it still lagged far behind at ~ 130 req/s, so after successful concurrency of 1000 requests, I got tired of waiting for the tests to complete and gave up seeking it’s break point. Still, UWSGI is very interesting project that I will keep my eye on, mostly because of it’s Emperor and Zerg modes and ease of deployment for dynamic mass-hosting Rack apps.

As UWSGI was originally developed for Python, I wasted a bit of time trying to get it working with some simple Python framework for comparison, but probably lack of knowledge on my part was the failure of it.

Testing

The test platform consisted of:

To set up a basic testcase, I wrote a simple Rack app that responds every request with the request IP address. I dediced to output IP because this involves some Ruby code in the app, but should be rather simple still.

ip = lambda do |env|
  [200, {"Content-Type" => "text/plain"}, [env["REMOTE_ADDR"]]]
end
run ip

Tweaking the concurrency number N (see below) with resolution of 100, I found out the break point of each of the servers (when they started giving errors) and recorded the previous throughput (the one that didn’t give any errors).

Results

The results are as follows:

  1. Unicorn – 2451 req/s @ 1500 concurrent request
  2. Thin – 2102 req/s @ 900 concurrent requests
  3. Passenger – 1549 req/s @ 400 concurrent requests

The following are screenshots from JMeter results:

Unicorn @1500 concurrent request

Thin @900 concurrent requests

Passenger @400 concurrent requests

None of these throughputs are bad, but still Unicorn and Thin beat the crap out of Passenger.

Details

The JMeter testcase

  1. ramp up to N requests concurrently
  2. send request to the server
  3. assert that response contains IP address
  4. loop all of this 10 times

Nginx configuration:

    # Passenger
    server {
      listen 8080;
      server_name localhost;
      root /Users/laas/proged/rack_test/public;
      passenger_enabled on;
      rack_env production;
      passenger_min_instances 4;
    }
 
    # Unicorn
    upstream unicorn_server {
      server unix:/Users/laas/proged/rack_test/tmp/unicorn.sock fail_timeout=0;
    }
 
    server {
      listen 8081;
      server_name localhost;
      root /Users/laas/proged/rack_test/public;
 
      location / {
        proxy_pass http://unicorn_server;
      }
    }
 
    # Thin
    upstream thin_server{
      server unix:/Users/laas/proged/rack_test/tmp/thin.0.sock fail_timeout=0;
      server unix:/Users/laas/proged/rack_test/tmp/thin.1.sock fail_timeout=0;
      server unix:/Users/laas/proged/rack_test/tmp/thin.2.sock fail_timeout=0;
      server unix:/Users/laas/proged/rack_test/tmp/thin.3.sock fail_timeout=0;
    }
 
    server {
      listen 8082;
      server_name localhost;
      root /Users/laas/proged/rack_test/public;
 
      location / {
        proxy_pass http://thin_server;
      }
    }

As is only logical, having processes match the number of cores (dual HT = 4 cores) gave best results for both Thin and Unicorn (thouch the variations were small).

Unicorn configuration

Passenger requires no additional configuration and Thin was configured from command line to use 4 servers and Unix sockets, but Unicorn required a separate file (I modified Unicorn example config for my purpose):

worker_processes 4
working_directory "/Users/laas/proged/rack_test/"
listen '/Users/laas/proged/rack_test/tmp/unicorn.sock', :backlog => 512
timeout 120
pid "/Users/laas/proged/rack_test/tmp/pids/unicorn.pid"
 
preload_app true
  if GC.respond_to?(:copy_on_write_friendly=)
  GC.copy_on_write_friendly = true
end

Disclaimer

I admit that this is extremely basic test and with better configuration much can be squeezed out from all of these servers, but this simple test surved my purpose and hopefully is of help to others too.

Inkscape CSV merge

I just uploaded inkscape_merge gem v0.1.0.

This is a script to merge SVG files with CSV data-files using Inkscape, to produce one outputfile (e.g. PDF) per data-row.

Script inspired by and based on Aurélio A. Heckert excellent InkscapeGenerator (wiki.colivre.net/Aurium/InkscapeGenerator)

Heckert’s original script unfortunately broke for me several times and I took the opportunity to rewrite it and make it more extendable for future.

 

USAGE

Install the gem

gem install inkscape_merge

Create files

Create CSV data file with first row as a header. The values from this row are used as keys in the SVG file substitution.

Create SVG file that contains some variables in the form:

%VAR_name%

Where `name` is the name of a column in the CSV file created previously. These variables can be anywhere inside the SVG, from plain text nodes to color values. This script just brute-forcedly `gsubs` these values as text w/o any thought.

Run the script

The script requires at least three arguments:

  • the input SVG file
  • the input CSV file
  • and the output file `pattern`

Note: output pattern undergoes the same substitutions as the SVG file, so to create easily unique file names. Additionally the output pattern can contain `%d` which is replaced with current row number.

Example:

inkscape_merge -f postcard.svg -d names.csv -o postcards/card_%d.pdf

This produces files like:

  • postcards/
    • card_1.pdf
    • card_2.pdf

Ruby lambda

I stumbled upon a problem with one of my scripts: how do you split a yielded block between two different callers while conforming to the DRY principe? The answer is lambda method.

Read more »

Building iPhone apps with Rake

Building and releasing iPhone apps and at the same time versioning them easily can be a bit tedious. Several posts (like this or this) show how to use agvtool for automated versioning. But for me this is still not automated enough.

Read more »

Aardwolf kill script

This script can be used in e.g. KMuddy to automatically practice all known skills to attack mobs.

Once upon a time, when I played Aardwolf a bit. To make my life easier, I wrote a simple script to practice all known kill methods on mobs. This script chooses a random skill (some skills can be favored by specifying them multiple times in skill array) and attack the mob. It even tries it’s best to guess which mob you are figthing (if there are many) and when that mob was killed. Read more »