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dynamic robots.txt file in Rails 3.x

April 27th, 2012 No comments

We have a need for dynamic handling of robots.txt file as we have different requirements for production, staging, dev, test, etc.

Google-fu shows various way to do this, some for Rails 2.x, some for Rails 3.x. Here is my version.

First is to edit config/routes.rb and add this line:


match '/robots.txt' => RobotsGenerator

Then add the following to app_root/lib/classes/robots_generator.rb.

NOTE: We have an old domain, foo.com, that redirects to our newfoo.com. We don’t want foo.com to get indexed, so I have special treatment for that in production

class RobotsGenerator
  # Use the config/robots.txt in production.
  # Disallow everything for all other environments.
  def self.call(env)
    req = ActionDispatch::Request.new(env)
    headers = {}
    body = if Rails.env.production?
      if req.host.downcase =~ /foo.com$/
        headers = { 'X-Robots-Tag' => "noindex,nofollow" }
        "User-agent: *\nDisallow: /"
      else
        File.read Rails.root.join('config', 'robots.txt')
      end
    else
        "User-agent: *\nDisallow: /"
    end

    [200, headers, [body]]
  rescue Errno::ENOENT
    [404, {}, "User-agent: *\nDisallow: /"]
  end
end

Finally, you want to move public/robots.txt to config/robots.txt.

I want to give credits to the people that inspired my version.

Categories: Rails, Ruby, Tech Tags: , ,

ActionMailer SSLError hostname was not match with the server certificate

March 15th, 2012 1 comment

So I am setting up a Continous Integration server using CruiseControl.rb and was getting these errors. I am on a RoR 3.1.x env and pointing to my local (same server) postfix for SMTP. I don’t need SSL.

OpenSSL::SSL::SSLError (hostname was not match with the server certificate):
/usr/lib/ruby/1.8/openssl/ssl.rb:123:in `post_connection_check’
/usr/lib/ruby/1.8/net/smtp.rb:582:in `tlsconnect’
/usr/lib/ruby/1.8/net/smtp.rb:562:in `do_start’
/usr/lib/ruby/1.8/net/smtp.rb:525:in `start’

http://scottiestech.info/2009/12/21/fixing-the-actionmailer-hostname-not-match-server-certificate-error/

Gave me a clue as to the problem. But adding this line

# Turn off auto TLS for e-mail
ActionMailer::Base.smtp_settings[:enable_starttls_auto] = false

to my config/environments/ci.rb does not work. I was still getting the same error. So poking around in ActionMailer gem source code gave me the last piece of clue I needed.

I also need to set this flag:

:openssl_verify_mode => false

Putting everything together,


ActionMailer::Base.smtp_settings[:openssl_verify_mode] = false
ActionMailer::Base.smtp_settings[:enable_starttls_auto] = false

is all I need. Turning off starttls is not needed, but I’d do it anyway because I am talking to my local SMTP server and don’t want the overhead.

Summary of Overcoming RoR Performance Challenges Meetup on Wed 2/29/12

March 1st, 2012 No comments

Overcoming RoR Performance Challenges Meetup

The talk was on best practices and some tips on looking for problems and how the panelists worked around them. There are no “magic” bullet like Ruby or RoR has 🙂

Essentials:

  1. Watch out when using ActiveRecord. It make it too easy to use DB. It make it too easy to use DB. One more time, it make it too easy to use DB.

    Essentially, ActiveRecord and DB is not always the right tool. Sometime using other tool could work better for a particular problem.

    Things mentioned:

    • Using Redis as a queueing system, to buffer writes, which later go to DB. (this is what Blitz, Bleacher Report use to increase their performance).
    • Use NoSQL (CouchBase, Mongo and Cassandara were mentioned as being used by panelists).
    • Cache results as much as possible. Don’t hit DB all the time.
    • Hand optimize queries might be needed. ActiveRecord is not the best at generating optimized DB calls.
  2. Cache as much as possible. Bleacher Reports put in caching layer everywhere, memcache, front end web cache, etc. They also have scripts that pre-warmed their cache (“goal is to never have users be the one who triggered a cache request”).

    Use the cache in newer RoR (3.2).

  3. Write code in ways that make it easy to update to latest Ruby and RoR.

    Ruby EE has flags to allow you to use more memory for internal cache. Sometime it make sense to test for and try different memory configuration there (based on 2 panelists’ experiences).RoR 3.2 has good Rack/Rails cache. Read the doc and use them.

  4. Background processes.
    • Use bg proc whenever possible.
    • Anytime you need to make calls to external website (external API), use a bg process, to not tie up your RoR web process.
    • Blitz put jobs into Redis queue, then bg server check Q for job, run it and put partial results back into Redis, Ajax call then check and format/display result to web client.
    • Bleacher Reports and Mixbooks also do similar things. They use Redis as a job queueing system, among other things (see 1 above).
  5. They all mention using other web server for production (not using webrick). The following were mentioned as being used by panelists.
    • Passenger
    • Thin
    • Unicorn
  6. Related to (ActiveRecord) above is the N+1 problem. Where you add 1 line of code and the DB calls increased manifold.
    • Advice essentially say to develop and use coding best practices and train developers to look out for them.
    • There is a possible test that can be use to automated looking out for N+1 issue.
    • Solving n+1 problem with special tests: http://en.oreilly.com/rails2009/public/schedule/detail/8615 Query testing – see PDF of slides page 75
    • Panelists all recommended RSpec for automated testing.
  7. Monitoring for issues and performance.
    • All panelists point to NewRelic as the tool they use all the time.
    • The host of the meeting Blitz also did a marketing spiel on their tool to use for performance testing (it look really good, and available as a plugin on Heroku). I am going to test it and see about using it for performance/load testing our site.
  8. For ease of scaling infrastructure, leverage AWS EC2, Heroku, Engine Yard and other cloud providers.