PostgreSQL and Ruby on Rails
1
Steve Madsen
PostgreSQL and Ruby on Rails

The current state state of PostgreSQL on Rails (early 2009) is a bit of a muddy mess. There are three different gems you can use to connect ActiveRecord to PostgreSQL and no guidance I can find about which of the two native adapters to use. I’m going to try and clear this up.

postgres-pr is a pure Ruby adapter. It doesn’t require native libraries and should work in most situations. However, because it isn’t native, it’s the low performer and likely won’t offer access to all of PostgreSQL’s features.

postgres is the old adapter. It appears to be maintained now by Jeff Davis, who forked it from Dave Lee. If you are compiling against PostgreSQL 8.3, you must use Jeff’s version (currently 0.7.9.2008.01.28), which includes build fixes for 8.3.

pg is the new adapter, also maintained by Jeff Davis. He says this one has a better design than postgres and offers more features. It does not work prior to Rails 2.1, however. Rails 2.1 and later will attempt to load this driver first and fall back to postgres. If you use any plug-ins that monkeypatch the database driver, you might have problems with pg (my own sql_logging, for one, is broken — I’ll fix this shortly).

So:

  • If you can build native extensions, are on Rails 2.1 or later, use pg.
  • If you can build native extensions, but are on Rails 2.0 or earlier, use postgres.
  • If you cannot build native extensions, use postgres-pr.

Building native extensions on OS X can be tricky, though. Here’s what I use on an Intel Mac, using the Ruby and Rubygems that ship with OS X and PostgreSQL 8.3 from MacPorts. (Unlike Robby’s guide, I do not advocate moving the system’s Ruby out of the way. You’re likely to break other stuff if you do so.)

sudo env ARCHFLAGS='-arch i386' gem install pg --remote -- --with-pgsql-include=/opt/local/include/postgresql83 --with-pgsql-lib=/opt/local/lib/postgresql83

If you use a different version of PostgreSQL than 8.3, make the appropriate substitution. If you’re still on PowerPC, change the ARCHFLAGS to -arch ppc. If you want to use postgres instead of pg:

sudo env ARCHFLAGS='-arch i386' gem install postgres --remote -- --with-pgsql-include=/opt/local/include/postgresql83 --with-pgsql-lib=/opt/local/lib/postgresql83

Generate wsesslog Workloads for httperf
2
Steve Madsen
Generate wsesslog Workloads for httperf

Over the last couple of days I’ve been bringing up an isolated test environment for a customer’s new site. (As an aside, one of the great things about moving to an Intel Mac is that I can run nearly any OS I want under VMware Fusion at near native speeds. You can’t beat testing in an identical environment, and I can throw pretty respectable virtual hardware at it, too: up to a 4-core with gigs of memory. If only Apple would let me virtualize OS X client.)

I’m using httperf to simulate client load on the test server and quickly decided that --wsesslog looked like the best choice for simulating an actual browser’s effect on the server.

A problem: how to generate those session workloads? I certainly don’t want to do this by hand for even one page. I want to generate a hit on every file referenced by the target page, but ignore anything hosted elsewhere.

A solution:

#!/usr/bin/env ruby
 
require 'rubygems'
require 'hpricot'
require 'open-uri'
 
if ARGV.length < 1
  $stderr.puts "usage: #{$0} url
 
  'url' must include the protocol prefix, e.g. http://"
  exit 1
end
 
url = ARGV.shift
if url =~ %r{^(https?://)([-a-z0-9.]+(:\d+)?)(.*/)([^/]*)$}i
  $protocol = $1
  $host = $2
  $document_dir = $4
  document_url = $5
else
  $stderr.puts 'Could not parse protocol and host from URL'
  exit 1
end
 
doc = Hpricot(open(url))
 
def puts_link(uri)
  return if uri.nil?
 
  if uri =~ %r{^#{$protocol}#{$host}(.*)$}
    puts "    #{$1}"
  elsif uri !~ %r{^https?://}
    if uri =~ %r{^/}
      puts "    #{uri}"
    else
      puts "    #{$document_dir}#{uri}"
    end
  end
end
 
puts "# httperf wsesslog for #{url} generated #{Time.now}"
puts
 
puts "#{$document_dir}#{document_url}"
 
(doc/"link[@rel='stylesheet']").each do |stylesheet|
  puts_link stylesheet.attributes['href']
end
 
(doc/"style").each do |style|
  style.inner_html.scan(/@import\s+(['"])([^\1]+)\1;/).each do |match|
    puts_link match[1]
  end
end
 
(doc/"script").each do |script|
  puts_link script.attributes['src']
end
 
(doc/"img").each do |img|
  puts_link img.attributes['src']
end
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