Roman's tech blog » Rails http://blog.gugl.org ruby, perl and other stuff Sat, 25 Jun 2011 20:33:32 +0000 en hourly 1 http://wordpress.org/?v=3.3.1 Monit and Phusion Passenger http://blog.gugl.org/archives/120 http://blog.gugl.org/archives/120#comments Fri, 29 Apr 2011 22:21:24 +0000 Roman http://blog.gugl.org/?p=120 While there’re multiple tools available for monitoring, ranging from Dan Bernshtein’s daemontools to God, I found that Monit is a pretty balanced solution. On one hand, it’s quite powerful, and on the other – it’s not resource hungry. The only drawback that I found, is that for monitoring a process, the process must have a pid-file saved somewhere. The Monit FAQ states that the programs which don’t have pid-file support should be run with some wrapper which will create it on their behalf.

I wanted to use Monit to monitor Rails’ instances, so if they grow too fat, Monit will take care of that. The problem is that the pid file that the Passenger creates a) doesn’t have a predictable location (there’s something called “generation” or something like that), and b) doesn’t have children, as those processes are detached.

Of course there exists a possibility of patching Passenger for providing such pid files. But, luckily, Passenger provides extension points in form of callbacks which are fired when the application instance is created and when it’s taken down.

It was trivial to use this API to provide pid-file managing. The result of this work was the “passenger_monit” plugin.

So, go ahead, add ‘gem “passenger_monit”‘ to your Gemfile and give it a try!

The source is available from:
https://github.com/romanbsd/passenger_monit

]]> http://blog.gugl.org/archives/120/feed 0 http://blog.gugl.org/archives/114 http://blog.gugl.org/archives/114#comments Tue, 05 Apr 2011 09:46:54 +0000 Roman http://blog.gugl.org/?p=114 Logging line numbers in Ruby Logger can be done with a simple decorator:

  class LoggerDecorator
    def initialize(logger)
      @logger = logger
    end
 
    %w{debug info warn error fatal}.each do |method|
      eval(<<-eomethod)
        def #{method}(msg)
          @logger.#{method}(position) {msg}
        end
      eomethod
    end
 
    private
    def position
      caller.at(1).sub(%r{.*/},'').sub(%r{:in\s.*},'')
    end
  end
]]> http://blog.gugl.org/archives/114/feed 0 ExtJS with Rails 3 http://blog.gugl.org/archives/106 http://blog.gugl.org/archives/106#comments Sun, 06 Mar 2011 10:37:41 +0000 Roman http://blog.gugl.org/?p=106 In order to make ExtJS play nicely with Rails, the following tweaks are needed:

On the ExtJS javascript side, the following things are needed:

1. Ask server to server JSON:

Ext.Ajax.defaultHeaders = {'Accept': 'application/json'};

2. RailsJsonStore:

Ext.data.RailsJsonStore = Ext.extend(Ext.data.JsonStore, {
    constructor: function(config) {
        Ext.data.RailsJsonStore.superclass.constructor.call(this, Ext.applyIf(config, {
            messageProperty: 'message', //for store.reader.getMessage()
            restful: true,
            url: '/'+ config['root'] + 's',
            writer: {encode: false}
        }));
    }
});
Ext.reg('railsjsonstore', Ext.data.RailsJsonStore);

3. XSRF protection:

Ext.Ajax.on('beforerequest', function(o) {
        var csrf = Ext.select("meta[name='csrf-token']").first();
        if (csrf) {
                o.defaultHeaders = Ext.apply(o.defaultHeaders || {}, {'X-CSRF-Token': csrf.getAttribute('content')});
        }
});

On Rails side:

config.active_record.include_root_in_json = false
]]> http://blog.gugl.org/archives/106/feed 3 I18n support for validates_date_time http://blog.gugl.org/archives/77 http://blog.gugl.org/archives/77#comments Sun, 08 Feb 2009 10:39:29 +0000 Roman http://blog.gugl.org/?p=77 This simple fix uses the fact, that if the second argument to the ‘add’ method is a symbol, then a generate_message is called, which does all the voodoo of Rails 2.2 I18n.
I tried to contact the original author to no avail, therefore I’ll post it here, hoping that if anyone needs it, it’ll surface on a Google search.
The fix itself is quite simple:

Index: lib/validates_date_time.rb
===================================================================
--- lib/validates_date_time.rb  (revision 403)
+++ lib/validates_date_time.rb  (working copy)
@@ -114,7 +114,7 @@
       if options[:before]
         options[:before].each do |r|
           if r.value(record) and value >= r.last_value
-            record.errors.add(attr_name, options[:before_message] % r)
+            record.errors.add(attr_name, :before, :default => options[:before_message] % r)
             break
           end
         end
@@ -123,7 +123,7 @@
       if options[:after]
         options[:after].each do |r|
           if r.value(record) and value <= r.last_value
-            record.errors.add(attr_name, options[:after_message] % r)
+            record.errors.add(attr_name, :after, :default => options[:after_message] % r)
             break
           end
         end

I’ve a fork of the git-svn mirror here:
http://github.com/romanbsd/validates_date_time/tree/master

Then, for using it, you’ll just need to have the following path in your locale yml files (for example):

  activerecord:
    errors:
      models:
        user:
          attributes:
            birth_date:
              before: 'is wrong'
              after: 'is wrong'
]]> http://blog.gugl.org/archives/77/feed 2 Displaying recaptcha inside ModalBox http://blog.gugl.org/archives/72 http://blog.gugl.org/archives/72#comments Fri, 30 Jan 2009 13:22:45 +0000 Roman http://blog.gugl.org/?p=72 I just wanted to display reCAPTCHA inside a ModalBox.
This simple task turned out to be quite complicated.
After playing with innerHTML, creating <script> nodes manually and attaching them and other voodoo and black magic and failing to accomplish the desired effect, I settled with displaying the recaptcha inside iframe inside ModalBox.

 Modalbox.show('<iframe src="' + this.href + '?iframe=1"></iframe>', 
  {title: this.title, width: 600});

(The iframe parameter helps to select another layout).

]]> http://blog.gugl.org/archives/72/feed 0 Expire cache item in Rails ActiveSupport::Cache::FileStore http://blog.gugl.org/archives/65 http://blog.gugl.org/archives/65#comments Fri, 30 Jan 2009 13:11:51 +0000 Roman http://blog.gugl.org/?p=65 Wouldn’t it be nice to cache some item (e.g. action) for some amount of time, before expiring it? For example, if you’re displaying some page that parts of it change very often, but you don’t want to expire cache every time, since you prefer to serve stale information instead of expiring the page?
The answer is the options[:expires_in] which is supported by the Rails’ ActiveSupport::Cache::MemCacheStore.
The current implementation of ActiveSupport::Cache::FileStore, however, lacks such feature, despite the fact that it’s really easy to implement.

This is the fix accompanied by a unit-test.
cache_fix

And then you can happily add a line like this in your controllers:

caches_action :find, :expires_in => 10.minute

The check, by the way, adds about 7usec to cache read request, which IMHO is negligible.

The Rails core team doesn’t seem to be interested in this patch, though.

]]> http://blog.gugl.org/archives/65/feed 0 I18n support for recaptcha http://blog.gugl.org/archives/58 http://blog.gugl.org/archives/58#comments Thu, 22 Jan 2009 22:46:13 +0000 Roman http://blog.gugl.org/?p=58 There’s a nice plugin which adds helper for the reCAPTCHA. The downside is that it doesn’t support I18n at the moment.
This is a straight forward approach patch that adds this functionality. (I don’t know what will be the fate of I18n in Rails 3, thus the simple check for version).
The error message path then will be:
activerecord.errors.models.model_name.captcha

diff --git a/lib/recaptcha.rb b/lib/recaptcha.rb
index 87c26e9..44413bc 100644
--- a/lib/recaptcha.rb
+++ b/lib/recaptcha.rb
@@ -65,7 +65,11 @@ module Ambethia
             session[:recaptcha_error] = error
             if model = options[:model]
               model.valid?
-              model.errors.add_to_base "Captcha response is incorrect, please try again."
+              if Rails::VERSION::MAJOR >= 2 and Rails::VERSION::MINOR >= 2
+                model.errors.add_to_base I18n.translate("#{model.class.name.underscore}.captcha", :scope => %w(activerecord errors models), :default => "Captcha response is incorrect, please try again.")
+              else
+                model.errors.add_to_base "Captcha response is incorrect, please try again."
+              end
             end
             return false
           else

I wonder if this is the proper way of adding I18n support…
P.S. I reported this on lighthouse.

]]> http://blog.gugl.org/archives/58/feed 0 Caching of complex queries http://blog.gugl.org/archives/51 http://blog.gugl.org/archives/51#comments Tue, 06 Jan 2009 15:58:23 +0000 Roman http://blog.gugl.org/?p=51 Proc.new {|controller| controller.request.get?} , for example), since I think that I know what I’m doing. So [...]]]> This trick is great for actions which receive lots of parameters, for example – search controller. Obviously, you wouldn’t want to do that with something that receives a POST, but I omitted the check for it (using :if => Proc.new {|controller| controller.request.get?} , for example), since I think that I know what I’m doing.
So the idea is to map all the parameters to some unique key, and then use that key as an :id for the url_for.

  # This caches the find action by the parameters
  require 'digest/sha1'
  caches_action :find, :expires_in => 10.minute,
    :cache_path => Proc.new { |controller|
        search_key = Digest::SHA1.hexdigest(controller.params.inspect)
        logger.debug "Current search key: #{search_key}"
        controller.url_for(:action => 'find', :id => search_key)
      }

The only minor issue that might arise, is that if you’re using pagination, the page number 1 when reached from the pagination links will have page=1 parameter, but when it’s initially presented, the parameter is absent. Adding such parameter won’t do any good, since the order of keys in hash in undefined. It’s possible, though, to build the key using some other technique, for example by massaging the request string. But since the case is quite rare, I think that any fix will be a waste of CPU cycles.

]]> http://blog.gugl.org/archives/51/feed 0 Better logging in Rails in production mode http://blog.gugl.org/archives/47 http://blog.gugl.org/archives/47#comments Sun, 28 Dec 2008 15:03:22 +0000 Roman http://blog.gugl.org/?p=47 I’m quite surprised, that even of version 2.2.2 of Rails, the logs are written in a way that makes them almost useless, as there’s no time stamp or severity level.
The solution I’ve come up with, is (instead of monkey patching the BufferedLogger) to create a new type of logger which inherits from the BufferedLogger and then change the ‘add’ method in order to produce nicer logs.
This file is lib/audit_logger.rb :

class AuditLogger < ActiveSupport::BufferedLogger
 
  SEVERITIES = Severity.constants.inject([]) {|arr,c| arr[Severity.const_get(c)] = c; arr}
 
  # Redefine the ActiveSupport::BufferedLogger#add
  def add(severity, message = nil, progname = nil, &block)
    return if @level > severity
    message = (message || (block && block.call) || progname).to_s
    # This is the line that was changed:
    message = "#{Time.now.to_formatted_s(:db)} #{SEVERITIES[severity]} #{message.strip}\n"
    buffer << message
    auto_flush
    message
  end
end

Then, in config/environments/production.rb you need to add:

require 'audit_logger'
config.logger = AuditLogger.new(config.log_path)
config.logger.level = AuditLogger::INFO #or other level
# This is what Rails does by default in production mode when using the default logger
config.logger.auto_flushing = false
]]> http://blog.gugl.org/archives/47/feed 3 Improved Rails’ delegate method http://blog.gugl.org/archives/41 http://blog.gugl.org/archives/41#comments Sun, 07 Sep 2008 11:38:43 +0000 Roman http://blog.gugl.org/?p=41 The Rails framework includes a simple “delegate” method, which is mixed in the models, and can be used in order to delegate methods to other classes. However it’s limited at least in the following:
1. It doesn’t prevent “train wrecks” – e.g. if the class that the method is delegated to is nil, then there will be an attempt to call this method on the nil class.
2. It doesn’t allow renaming of the methods, e.g. if you have a method called “name” in your class, and a method called “name” in other class you want to delegate to, you have no means of doing this.
The implementation below remedies these shortcomings.

class Module
  def delegate(*methods)
    options = methods.pop
    unless options.is_a?(Hash) && to = options[:to]
      raise ArgumentError, "Delegation needs a target. Supply an options hash with a :to key as the last argument (e.g. delegate :hello, :to => :greeter)."
    end
 
    prefix = options[:prefix] || ''
    orig_prefix = prefix
    if prefix != true and !prefix.empty? 
      prefix += '_'
    end
 
    methods.each do |method|
      prefix = to.to_s + '_' if orig_prefix == true
      module_eval(<<-EOS, "(__DELEGATION__)", 1)
        def #{prefix}#{method}(*args, &block)
          return nil unless #{to}
          #{to}.__send__(#{method.inspect}, *args, &block)
        end
      EOS
    end
  end
end

You can use it like this:

delegate :name, :to=> :other, :prefix=>true

and it will delegate a method “name” in “other” class as “other_name” in your class.
Or, alternatively

delegate :name, :to=> :other, :prefix=>'some'

will delegate “some_name” to class “other”, method “name”.

]]> http://blog.gugl.org/archives/41/feed 2