Hank Beaver

Introduction

At my current gig with Primedia, we have some pretty high volume Rails sites. Since having highly available sites are essential for our core business, we have to be very attentive to production issues. Below is a list that I’ve compiled recently in my head and by working with some very bright folks. This doc is to help Ops/Dev remember some basics and tricks when debugging issues. So remember to try this stuff.

Non-Technical (READ FIRST)

1. If the issue is not a major impact on production, make sure all your troubleshooting is passive! You might introduce an outage if you try serious troubleshooting.
2. Confirm the issue with Ops/Infrastructure in your presence, this gets buy-in from with the folks who have official root access.
3. As a developer, you should not work alone on production systems except to gather information (if you get temporary access). All changes (in seeking issue mitigation) should be paired with Ops/Infra. This will avoid finger-pointing and headaches later.

Technical

Elimination + log files is my troubleshooting method of choice.

1. Skip the load balancer if possible and hit direct IP/Port of a single app server to eliminate load balancer in mix.
2. Enable DEBUG log level and restart app server(s). Preferably, take an app server out of load balancer pool and work on in isolation. Regardless, DEBUG can slow response signficantly so be aware. However, there are situations where DEBUG is the only way to get an indication from Rails what is going on.
3. Tail log file of single app IP/Port to squelch noise from other servers and hit just that app server.
4. Make sure that the PIDs are not hung,old versions. Look at time/date of PIDS. If the deploy is screwed up, you can be deploying new code and yet the processes running are code from a month ago.
5. To be thorough, look at the kernel logs too. In Linux, /var/log/messages etc. You could have something else that is going on.
6. The logs should give status regarding database(s), but especially look for the words “timeout” if you have any custom network libraries that fetch data (we do) or “ActiveRecord”.  Perhaps even, grep for it.
7. Use a non-browser client, like Curl or wget to eliminate possible browser issues. Case in point, we had an issue related to ActiveRecord sessions that were migrated to another datacenter. When accessed via Curl there was no issue (Curl does not save cookies by default).

Other

1. If you cannot duplicate issue in development, remember to change your configs to look like production mode and run your development workstation in production mode. Rails behaves different in its modes.

• Grab Package from EnterpriseDB.
• Find exact version location in /Library/PostgreSQL/x.x/
• Put above dir + bin in PATH
• sudo gem install ruby-pg

Ironically, the two most interesting items for me personally were not directory related to Merb at all. I was quite impressed with the CSS capabilities of SASS and CouchDB gave me hope that being stuck in the rigidity of columns in SQL is not always my path. Here’s my my Merbday summary,  iteration retrospective format:

STOP:

• Assuming Merb is “fragmentation” (so said someone smarter than me ) of the Rails community and a real effort to improve on Ruby as the defacto web programming language.

START:

• Using ruby-prof in Rails projects and Kcachegrind to profile apps. (thanks for Yehuda Katz at www.engineyard.com )
• Playing with Merb on a real project and focus on understand slices and interaction with other slices.
• Investigate writing an Admin or basic CMS slice with someone else.

CONTINUE:

• Loving Rails and not abandon it as yet.

MERB does not have development logging turned on by default something I like very much in Rails. To turn it on, uncomment this line:

c[:log_file]  = Merb.root / "log" / "development.log"

In the config/environments/development.rb file.

Motivation:
As an avid Ruby/Rails programmer and longtime CMS coder and user the following is yet another effort to keep a list of current Ruby/Rails CMS’s. That is the goal of this post. I will use comments from others to update the list and hopefully keep and up-to-date list for all (including myself) to use. Heck, I would love to have others help review and keep list up to date.

External Resources:

http://www.widgetfinger.com/
http://www.ajaxlines.com/ajax/stuff/article/top_ruby_cms.php

http://webscripts.softpedia.com/downloadTag/ruby+cms

I want to move all files in this svn dir:

svn list http://svn.atld1/svn-prodops/sysadmin

to:

svn list http://svn.atld1/svn-prodops/sysadmin/scripts

Doing svn mv would see obvious and using xargs or -exec might work. I prefer not to use any brain energy on a shell script. I just do it in ruby in 5 minutes:

svn list http://svn.atld1/svn-prodops/sysadmin > /tmp/script.list

Write this to a ruby file:

f = File.open("/tmp/script.list")

f.each_line {|line|

cmd = "svn mv http://svn.atld1/svn-prodops/sysadmin/#{line.strip}
http://svn.atld1/svn-prodops/sysadmin/scripts/ -m
\"moving #{line} to scripts \" "

puts "running: #{cmd}"
`#{cmd}"

}

Now execute the file above after double checking. Viola done even with relevant comments for each move!

Soon the rest of this blog will deal with a basic overview of has_many associations and a practical use. For now look at this simple tag that uses has_many of a Blog model to show the Interests (or topics) for a given blog. You would use this helper_tag like so in your view, given that you have a single instance of a blog object called ‘blog’

<%= more_ugly_interests_tag(blog) %>

I hope this small article might help others:

#########################################
#Tag to show usage of has_many for a model.
#Ruby on Rails
#*this_model* is the actual instance of a blog or photo
#which has a list of interests.
#
#Call tag like this:
# <%= more_ugly_interests_tag(blog) %>
#the syntax below uses what Ruby calls a 'block'
#this is the format:
# some_variable_that_has_a_list.each { |list_item
# #do something with each item
# puts list_item + " !!!!"
# }
#########################################
def more_ugly_interests_tag(this_model)

to_return = "INTERESTS"

this_model.interests.each { |each_interest|

to_return =  << each_interest << "
"

}

#now we have end the whole function/method with what we want to return/print
to_return

end