A Noted Path by Theodore Nguyen-Cao

Following up on my previous post , I’ve been experience slow load times (10-15 secs) on the initial request after application restarts. This has to do with the way mod_rails manages application instances (Although, I experienced this when using mongrel_cluster and proxy balancers). It will spin up instances on page request and each instance has an idle timeout. This just means after the timeout expires, mod_rails will shutdown that instance to conserve memory allocation. While you can change timeout value (see PassengerPoolIdleTime), this will only cause all instances that get spin up to live longer. After high load times, these instances will stick around longer than neccessary.

For low traffic sites (like mine), this idle timeout may be reached causing the next visitor to our website to experience a really long delay before page load. What we really want is an option to set a minimum number of instances. This would allow us to automatically spin up an instance during start up and keep it around. Unfortunately at this time, it doesn’t look like there is a way to set this.

As a workaround, I’ve setup a crontab that makes a request to my application every 5 minutes to prevent mod_rails from killing off all application instances.

To do this just run:

crontab -e

And then specific the following cron

*/5 * * * * wget -O /dev/null http://www.myapp.com 2>/dev/null

You can verify this is working correctly but just tailing your application logs and verify every 5 minutes you get a request.

You can also run

 passenger-status

You should see at least the count variable to be at least 1 instance.

Note, this workaround will not immediate start up an instance upon restart. You can add an initial request as part of your post deploy capistrano task though. You probably should be making sure your application is up after deploying or restarting the application anyways.

I had heard of mod_rails awhile back but never had the time to take a closer look at it. While setting up a new rails app, I was getting frustrated with all of the configuration I needed to do to get the mongrel clusters and proxy balancers setup. So I decided to give passenger a chance. I’m a fan now

The process was dead simple.

1. Install the passenger gem

   sudo gem install passenger

2. Install passenger as an Apache module

   passenger-install-apache2-module

3. Load the passenger apache module by editing the Apache config

   LoadModule passenger_module /usr/lib/ruby/gems/1.8/gems/passenger-2.0.5/ext/apache2/mod_passenger.so
   PassengerRoot /usr/lib/ruby/gems/1.8/gems/passenger-2.0.5
   PassengerRuby /usr/bin/ruby1.8
   

4. Restart Apache

If all things went well, you have everything installed you need. If there were some missing dependencies, you should be presented with how to install those dependencies.

In the installation output, it tells you how to mod_railsify your apps by creating a vhost as such:

<VirtualHost *:80>
    ServerName www.mywebsite.com
    DocumentRoot /home/deploy/mywebsite/public
</VirtualHost>

That’s it! No more of this proxy balancer and mongrel_cluster.yml configuration.

There’s some magic going on in the background. As requests come in, passenger will spin up more application instances. For more tweaking your configuration options check out the user guide.

Go to your website and you should see your rails app up and running.

So now we have your app up and running, how do we update or restart our app? Passenger provides two ways for us to do this.

The first is whenever apache is restarted, your application is restarted.

The second way allows us to restart a specified application without affecting Apache. Whenever passenger detects tmp/restart.txt, it will restart the application instances for us. We can integrate this into our Capistrano deploy flow by adding the following our config/deploy.rb

namespace :passenger do
  desc "Restart Application"
  task :restart do
    run "touch #{current_path}/tmp/restart.txt"
  end
end

after :deploy, "passenger:restart"

This will create that restart.txt after the cap:deploy task gets executed, causing the application to restart.

Finally, passenger comes with some pretty useful utilities.

Check out passenger-status which produces output showing current passenger server statuses.

Sample output:

----------- General information -----------
max      = 6
count    = 1
active   = 0
inactive = 1
Using global queue: no
Waiting on global queue: 0

----------- Applications -----------
/home/deploy/www.myapp.com/releases/20081206183156:
  PID: 30784     Sessions: 0

Another utility passenger-memory-status gives you insight into how much memory is being used by apache and passenger.

Sample output:

-------------- Apache processes ---------------
PID    PPID   Threads  VMSize    Private  Name
-----------------------------------------------
12841  1      1        225.9 MB  0.0 MB   /usr/sbin/apache2 -k start
28294  12841  1        248.4 MB  21.4 MB  /usr/sbin/apache2 -k start
28300  12841  1        243.7 MB  0.5 MB   /usr/sbin/apache2 -k start
28306  12841  1        248.4 MB  4.4 MB   /usr/sbin/apache2 -k start
28357  12841  1        249.1 MB  19.8 MB  /usr/sbin/apache2 -k start
29400  12841  1        249.4 MB  3.7 MB   /usr/sbin/apache2 -k start
29788  12841  1        249.3 MB  21.7 MB  /usr/sbin/apache2 -k start
29834  12841  1        245.8 MB  18.9 MB  /usr/sbin/apache2 -k start
29836  12841  1        245.8 MB  9.3 MB   /usr/sbin/apache2 -k start
29868  12841  1        245.8 MB  2.4 MB   /usr/sbin/apache2 -k start
29870  12841  1        246.5 MB  5.2 MB   /usr/sbin/apache2 -k start
### Processes: 11
### Total private dirty RSS: 107.44 MB

--------- Passenger processes ----------
PID    Threads  VMSize    Private  Name
----------------------------------------
28031  10       15.3 MB   0.1 MB   /usr/lib/ruby/gems/1.8/gems/passenger-2.0.5/ext/apache2/ApplicationPoolServerExecutable 0 /usr/lib/ruby/gems/1.8/gems/passenger-2.0.5/bin/passenger-spawn-server  /usr/bin/ruby1.8  /tmp/passenger_status.12841.fifo
28032  2        48.7 MB   0.6 MB   Passenger spawn server
29161  1        114.8 MB  0.7 MB   Passenger FrameworkSpawner: 2.1.2
30461  1        122.8 MB  32.3 MB  Passenger ApplicationSpawner: /home/deploy/www.myapp.com/releases/20081206183156
30784  1        129.3 MB  33.4 MB  Rails: /home/deploy/www.myapp.com/releases/20081206183156
### Processes: 5
### Total private dirty RSS: 67.08 MB

Pretty sweet.

I fired up Photoshop for the first time in a long time. I created a transparent PNG for an image that would be used as a CSS background-image. It keeps displaying with a gray background even though the page background color was something else.

This is a pretty well documented bug. Luckily, there are a couple of ways to fix this.

Here are my two favorites:

The first solution is well documented:

Download iepngfix.zip. The development version 2.0 Alpha 3 has support for background position and repeat. Extract the zip and copy iepngfix.htc and blank.gif somewhere. I put in under stylesheets.

Add the following snippet to your CSS stylesheet:

img {
	behavior: url(/stylesheets/iepngfix.htc);
}

And you’re done! Hit refresh in IE6 and transparent PNG images should render correctly now.

You can add apply this fix to other elements that may be using PNG images as CSS background images as such:

img, #logo {
	behavior: url(/stylesheets/iepngfix.htc);
}

where logo is a div that has a background-image that is a transparent PNG.

Note: If you are using v2.0 and want to take advantage of background-repeat and position support, copy iepngfix_tilebg.js to your javascripts folder and include the js file in the HTML files you need it for.

The second way to fix this is to get everyone off IE6 but I guess that’s just wishful thinking…

I decided I wanted to dedicate some time this weekend working on some side projects. Of course before I start, I needed to get the latest and greatest updates so I ran gem update and got the following error

theo@theo~/dev $ sudo gem update
Updating installed gems
...
Updating rubygems-update
Successfully installed rubygems-update-1.3.1
ERROR:  While executing gem ... (NameError)
    undefined local variable or method `remote_gemspecs' for #

Reading the release notes:

NOTE: RubyGems 1.1 and 1.2 have problems upgrading when there is no
rubygems-update installed. You will need to follow the second set of update
instructions if you see “Nothing to update”.

shows that we need to install and run the rubygem-update gem to get this fixed

  theo@theo~/dev $ sudo gem install rubygems-update
Successfully installed rubygems-update-1.3.1
1 gem installed
  theo@theo~/dev $ sudo update_rubygems
Installing RubyGems 1.3.1
mkdir -p /Library/Ruby/Site/1.8
mkdir -p /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin
install -c -m 0644 rbconfig/datadir.rb /Library/Ruby/Site/1.8/rbconfig/datadir.rb
install -c -m 0644 rubygems/builder.rb /Library/Ruby/Site/1.8/rubygems/builder.rb
install -c -m 0644 rubygems/command.rb /Library/Ruby/Site/1.8/rubygems/command.rb
install -c -m 0644 rubygems/command_manager.rb /Library/Ruby/Site/1.8/rubygems/command_manager.rb
install -c -m 0644 rubygems/commands/build_command.rb /Library/Ruby/Site/1.8/rubygems/commands/build_command.rb
install -c -m 0644 rubygems/commands/cert_command.rb /Library/Ruby/Site/1.8/rubygems/commands/cert_command.rb
install -c -m 0644 rubygems/commands/check_command.rb /Library/Ruby/Site/1.8/rubygems/commands/check_command.rb
install -c -m 0644 rubygems/commands/cleanup_command.rb /Library/Ruby/Site/1.8/rubygems/commands/cleanup_command.rb
install -c -m 0644 rubygems/commands/contents_command.rb /Library/Ruby/Site/1.8/rubygems/commands/contents_command.rb
install -c -m 0644 rubygems/commands/dependency_command.rb /Library/Ruby/Site/1.8/rubygems/commands/dependency_command.rb
install -c -m 0644 rubygems/commands/environment_command.rb /Library/Ruby/Site/1.8/rubygems/commands/environment_command.rb
install -c -m 0644 rubygems/commands/fetch_command.rb /Library/Ruby/Site/1.8/rubygems/commands/fetch_command.rb
install -c -m 0644 rubygems/commands/generate_index_command.rb /Library/Ruby/Site/1.8/rubygems/commands/generate_index_command.rb
install -c -m 0644 rubygems/commands/help_command.rb /Library/Ruby/Site/1.8/rubygems/commands/help_command.rb
install -c -m 0644 rubygems/commands/install_command.rb /Library/Ruby/Site/1.8/rubygems/commands/install_command.rb
install -c -m 0644 rubygems/commands/list_command.rb /Library/Ruby/Site/1.8/rubygems/commands/list_command.rb
install -c -m 0644 rubygems/commands/lock_command.rb /Library/Ruby/Site/1.8/rubygems/commands/lock_command.rb
install -c -m 0644 rubygems/commands/mirror_command.rb /Library/Ruby/Site/1.8/rubygems/commands/mirror_command.rb
install -c -m 0644 rubygems/commands/outdated_command.rb /Library/Ruby/Site/1.8/rubygems/commands/outdated_command.rb
install -c -m 0644 rubygems/commands/pristine_command.rb /Library/Ruby/Site/1.8/rubygems/commands/pristine_command.rb
install -c -m 0644 rubygems/commands/query_command.rb /Library/Ruby/Site/1.8/rubygems/commands/query_command.rb
install -c -m 0644 rubygems/commands/rdoc_command.rb /Library/Ruby/Site/1.8/rubygems/commands/rdoc_command.rb
install -c -m 0644 rubygems/commands/search_command.rb /Library/Ruby/Site/1.8/rubygems/commands/search_command.rb
install -c -m 0644 rubygems/commands/server_command.rb /Library/Ruby/Site/1.8/rubygems/commands/server_command.rb
install -c -m 0644 rubygems/commands/sources_command.rb /Library/Ruby/Site/1.8/rubygems/commands/sources_command.rb
install -c -m 0644 rubygems/commands/specification_command.rb /Library/Ruby/Site/1.8/rubygems/commands/specification_command.rb
install -c -m 0644 rubygems/commands/stale_command.rb /Library/Ruby/Site/1.8/rubygems/commands/stale_command.rb
install -c -m 0644 rubygems/commands/uninstall_command.rb /Library/Ruby/Site/1.8/rubygems/commands/uninstall_command.rb
install -c -m 0644 rubygems/commands/unpack_command.rb /Library/Ruby/Site/1.8/rubygems/commands/unpack_command.rb
install -c -m 0644 rubygems/commands/update_command.rb /Library/Ruby/Site/1.8/rubygems/commands/update_command.rb
install -c -m 0644 rubygems/commands/which_command.rb /Library/Ruby/Site/1.8/rubygems/commands/which_command.rb
install -c -m 0644 rubygems/config_file.rb /Library/Ruby/Site/1.8/rubygems/config_file.rb
install -c -m 0644 rubygems/custom_require.rb /Library/Ruby/Site/1.8/rubygems/custom_require.rb
install -c -m 0644 rubygems/defaults.rb /Library/Ruby/Site/1.8/rubygems/defaults.rb
install -c -m 0644 rubygems/dependency.rb /Library/Ruby/Site/1.8/rubygems/dependency.rb
install -c -m 0644 rubygems/dependency_installer.rb /Library/Ruby/Site/1.8/rubygems/dependency_installer.rb
install -c -m 0644 rubygems/dependency_list.rb /Library/Ruby/Site/1.8/rubygems/dependency_list.rb
install -c -m 0644 rubygems/digest/digest_adapter.rb /Library/Ruby/Site/1.8/rubygems/digest/digest_adapter.rb
install -c -m 0644 rubygems/digest/md5.rb /Library/Ruby/Site/1.8/rubygems/digest/md5.rb
install -c -m 0644 rubygems/digest/sha1.rb /Library/Ruby/Site/1.8/rubygems/digest/sha1.rb
install -c -m 0644 rubygems/digest/sha2.rb /Library/Ruby/Site/1.8/rubygems/digest/sha2.rb
install -c -m 0644 rubygems/doc_manager.rb /Library/Ruby/Site/1.8/rubygems/doc_manager.rb
install -c -m 0644 rubygems/exceptions.rb /Library/Ruby/Site/1.8/rubygems/exceptions.rb
install -c -m 0644 rubygems/ext/builder.rb /Library/Ruby/Site/1.8/rubygems/ext/builder.rb
install -c -m 0644 rubygems/ext/configure_builder.rb /Library/Ruby/Site/1.8/rubygems/ext/configure_builder.rb
install -c -m 0644 rubygems/ext/ext_conf_builder.rb /Library/Ruby/Site/1.8/rubygems/ext/ext_conf_builder.rb
install -c -m 0644 rubygems/ext/rake_builder.rb /Library/Ruby/Site/1.8/rubygems/ext/rake_builder.rb
install -c -m 0644 rubygems/ext.rb /Library/Ruby/Site/1.8/rubygems/ext.rb
install -c -m 0644 rubygems/format.rb /Library/Ruby/Site/1.8/rubygems/format.rb
install -c -m 0644 rubygems/gem_openssl.rb /Library/Ruby/Site/1.8/rubygems/gem_openssl.rb
install -c -m 0644 rubygems/gem_path_searcher.rb /Library/Ruby/Site/1.8/rubygems/gem_path_searcher.rb
install -c -m 0644 rubygems/gem_runner.rb /Library/Ruby/Site/1.8/rubygems/gem_runner.rb
install -c -m 0644 rubygems/indexer.rb /Library/Ruby/Site/1.8/rubygems/indexer.rb
install -c -m 0644 rubygems/install_update_options.rb /Library/Ruby/Site/1.8/rubygems/install_update_options.rb
install -c -m 0644 rubygems/installer.rb /Library/Ruby/Site/1.8/rubygems/installer.rb
install -c -m 0644 rubygems/local_remote_options.rb /Library/Ruby/Site/1.8/rubygems/local_remote_options.rb
install -c -m 0644 rubygems/old_format.rb /Library/Ruby/Site/1.8/rubygems/old_format.rb
install -c -m 0644 rubygems/package/f_sync_dir.rb /Library/Ruby/Site/1.8/rubygems/package/f_sync_dir.rb
install -c -m 0644 rubygems/package/tar_header.rb /Library/Ruby/Site/1.8/rubygems/package/tar_header.rb
install -c -m 0644 rubygems/package/tar_input.rb /Library/Ruby/Site/1.8/rubygems/package/tar_input.rb
install -c -m 0644 rubygems/package/tar_output.rb /Library/Ruby/Site/1.8/rubygems/package/tar_output.rb
install -c -m 0644 rubygems/package/tar_reader/entry.rb /Library/Ruby/Site/1.8/rubygems/package/tar_reader/entry.rb
install -c -m 0644 rubygems/package/tar_reader.rb /Library/Ruby/Site/1.8/rubygems/package/tar_reader.rb
install -c -m 0644 rubygems/package/tar_writer.rb /Library/Ruby/Site/1.8/rubygems/package/tar_writer.rb
install -c -m 0644 rubygems/package.rb /Library/Ruby/Site/1.8/rubygems/package.rb
install -c -m 0644 rubygems/platform.rb /Library/Ruby/Site/1.8/rubygems/platform.rb
install -c -m 0644 rubygems/remote_fetcher.rb /Library/Ruby/Site/1.8/rubygems/remote_fetcher.rb
install -c -m 0644 rubygems/require_paths_builder.rb /Library/Ruby/Site/1.8/rubygems/require_paths_builder.rb
install -c -m 0644 rubygems/requirement.rb /Library/Ruby/Site/1.8/rubygems/requirement.rb
install -c -m 0644 rubygems/rubygems_version.rb /Library/Ruby/Site/1.8/rubygems/rubygems_version.rb
install -c -m 0644 rubygems/security.rb /Library/Ruby/Site/1.8/rubygems/security.rb
install -c -m 0644 rubygems/server.rb /Library/Ruby/Site/1.8/rubygems/server.rb
install -c -m 0644 rubygems/source_index.rb /Library/Ruby/Site/1.8/rubygems/source_index.rb
install -c -m 0644 rubygems/source_info_cache.rb /Library/Ruby/Site/1.8/rubygems/source_info_cache.rb
install -c -m 0644 rubygems/source_info_cache_entry.rb /Library/Ruby/Site/1.8/rubygems/source_info_cache_entry.rb
install -c -m 0644 rubygems/spec_fetcher.rb /Library/Ruby/Site/1.8/rubygems/spec_fetcher.rb
install -c -m 0644 rubygems/specification.rb /Library/Ruby/Site/1.8/rubygems/specification.rb
install -c -m 0644 rubygems/test_utilities.rb /Library/Ruby/Site/1.8/rubygems/test_utilities.rb
install -c -m 0644 rubygems/timer.rb /Library/Ruby/Site/1.8/rubygems/timer.rb
install -c -m 0644 rubygems/uninstaller.rb /Library/Ruby/Site/1.8/rubygems/uninstaller.rb
install -c -m 0644 rubygems/user_interaction.rb /Library/Ruby/Site/1.8/rubygems/user_interaction.rb
install -c -m 0644 rubygems/validator.rb /Library/Ruby/Site/1.8/rubygems/validator.rb
install -c -m 0644 rubygems/version.rb /Library/Ruby/Site/1.8/rubygems/version.rb
install -c -m 0644 rubygems/version_option.rb /Library/Ruby/Site/1.8/rubygems/version_option.rb
install -c -m 0644 rubygems.rb /Library/Ruby/Site/1.8/rubygems.rb
install -c -m 0644 ubygems.rb /Library/Ruby/Site/1.8/ubygems.rb
cp gem /tmp/gem
install -c -m 0755 /tmp/gem /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/gem
rm /tmp/gem
rm -f /Users/theo/.gem/source_cache
rm -f /Library/Ruby/Gems/1.8/source_cache
Removing old RubyGems RDoc and ri
rm -rf /Library/Ruby/Gems/1.8/doc/rubygems-1.2.0
Installing rubygems-1.3.1 ri into /Library/Ruby/Gems/1.8/doc/rubygems-1.3.1/ri
Installing rubygems-1.3.1 rdoc into /Library/Ruby/Gems/1.8/doc/rubygems-1.3.1/rdoc

------------------------------------------------------------------------------

= Announce: RubyGems Release 1.3.0

NOTE:  RubyGems 1.1 and 1.2 have problems upgrading when there is no
rubygems-update installed.  You will need to follow the second set of update
instructions if you see "Nothing to update".

Release 1.3.0 fixes some bugs.

Bugs fixed:

* Disregard ownership of ~ under Windows while creating ~/.gem.  Fixes
  issues related to no uid support under Windows.
* Fix requires for Gem::inflate, Gem::deflate, etc.
* Make Gem.dir respect :gemhome value from config.  (Note: this feature may be
  removed since it is hard to implement on 1.9.)
* Kernel methods are now private.  Patch #20801 by Stefan Rusterholz.
* Gem::location_of_caller now behaves on Windows.  Patch by Daniel Berger.
* Silence PATH warning.

Deprecation Notices:

* Gem::manage_gems will be removed on or after March 2009.

For a full list of changes to RubyGems and the contributor for each change, see
the ChangeLog file.

Special thanks to Chad Wooley for backwards compatibility testing and Luis
Lavena for continuing windows support.

== How can I get RubyGems?

NOTE:  If you have installed RubyGems using a package system you may want to
install a new RubyGems through the same packaging system.

If you have a recent version of RubyGems (0.8.5 or later), then all
you need to do is:

  $ gem update --system   (you might need to be admin/root)

NOTE:  RubyGems 1.1 and 1.2 have problems upgrading when there is no
rubygems-update installed.  You will need to follow the second set of update
instructions if you see "Nothing to update".

NOTE: You may have to run the command twice if you have any previosly
installed rubygems-update gems.

If you have an older version of RubyGems installed, then you can still
do it in two steps:

  $ gem install rubygems-update  (again, might need to be admin/root)
  $ update_rubygems              (... here too)

If you don't have any gems install, there is still the pre-gem
approach to getting software ... doing it manually:

1. DOWNLOAD FROM: http://rubyforge.org/frs/?group_id=126
2. UNPACK INTO A DIRECTORY AND CD THERE
3. INSTALL WITH:  ruby setup.rb  (you may need admin/root privilege)

== To File Bugs

The RubyGems bug tracker can be found on RubyForge at:

http://rubyforge.org/tracker/?func=add&group_id=126&atid=575

When filing a bug, `gem env` output will be helpful in diagnosing the issue.

If you find a bug where RubyGems crashes, please provide debug output. You can
do that with `gem --debug the_command`.

== Thanks

Keep those gems coming!

-- Jim & Chad & Eric (for the RubyGems team)

------------------------------------------------------------------------------

RubyGems installed the following executables:
	/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/gem

If `gem` was installed by a previous RubyGems installation, you may need
to remove it by hand.