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Archive for March, 2012

Britely – what-to-buy-him-a-gift-guide-for-women

March 23rd, 2012 No comments

http://www.britely.com/replicant/what-to-buy-him-a-gift-guide-for-womenWhat to Buy Him: A Gift Guide for Women

Web site of the day.

Categories: 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.

google-spreadsheet-ruby and (Nokogiri::XML::XPath::SyntaxError)

March 13th, 2012 No comments

I have a Ruby script that update our Google Doc spreadsheet as part of releases. The script has been working for years, then suddenly started failing with errors like this one:


/usr/local/lib/ruby/gems/1.9.1/gems/nokogiri-1.5.2/lib/nokogiri/xml/node.rb:159:in `evaluate': Invalid expression: .//xmlns:link[@xmlns:@rel = 'http://schemas.google.com/spreadsheets/2006#cellsfeed'] (Nokogiri::XML::XPath::SyntaxError)
from /usr/local/lib/ruby/gems/1.9.1/gems/nokogiri-1.5.2/lib/nokogiri/xml/node.rb:159:in `block in xpath'
from /usr/local/lib/ruby/gems/1.9.1/gems/nokogiri-1.5.2/lib/nokogiri/xml/node.rb:150:in `map'
from /usr/local/lib/ruby/gems/1.9.1/gems/nokogiri-1.5.2/lib/nokogiri/xml/node.rb:150:in `xpath'
from /usr/local/lib/ruby/gems/1.9.1/gems/nokogiri-1.5.2/lib/nokogiri/xml/node.rb:214:in `css'
from /usr/local/lib/ruby/gems/1.9.1/gems/google-spreadsheet-ruby-0.1.6/lib/google_spreadsheet.rb:648:in `block in worksheets'
from /usr/local/lib/ruby/gems/1.9.1/gems/nokogiri-1.5.2/lib/nokogiri/xml/node_set.rb:239:in `block in each'
from /usr/local/lib/ruby/gems/1.9.1/gems/nokogiri-1.5.2/lib/nokogiri/xml/node_set.rb:238:in `upto'
from /usr/local/lib/ruby/gems/1.9.1/gems/nokogiri-1.5.2/lib/nokogiri/xml/node_set.rb:238:in `each'
from /usr/local/lib/ruby/gems/1.9.1/gems/google-spreadsheet-ruby-0.1.6/lib/google_spreadsheet.rb:646:in `worksheets'
from /home/tin/bin/google-spreadsheet:125:in `

'

It took a bit of sleuthing to find out that Nokogiri version 1.5.2 broke google-spreadsheet-ruby. Downgrading to v 1.5.0 made it work again.

I am documenting it here for those of you running into similar problems.

Addtions. It turns out nokogiri and google-spreadsheet gems are written by same author, and he is aware of the bug, but not fixing it at this time. He recommends using nokogiri v1.5.0

https://github.com/gimite/google-spreadsheet-ruby/issues/31#issuecomment-4451659

Google-fu show a solution, since I can’t keep gems from updating on my systems. I just have to force my script to request a particular version.

http://stackoverflow.com/questions/2693862/how-do-i-require-a-specific-version-of-a-ruby-gem

And here is how I solved my problem.


gem 'nokogiri', '=1.5.0'

require 'optparse'
require 'ostruct'
require 'csv'
require 'rubygems'
require 'nokogiri'
require 'google_spreadsheet'

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.