Here’s the erb template for httpd.conf:

#
# Apache httpd.conf
# generated by cap. run by <%= user %> at <%= Time.now %>
#

ServerRoot "<%= current_release %>"
PidFile "<%= current_release %>/tmp/pids/httpd.pid"
LockFile "<%= current_release %>/log/accept.lock"
ServerName localhost
ServerAdmin "me"
Listen <%= web_port %>

# prefork MPM
# StartServers: number of server processes to start
# MinSpareServers: minimum number of server processes which are kept spare
# MaxSpareServers: maximum number of server processes which are kept spare
# MaxClients: maximum number of server processes allowed at a time
# MaxRequestsPerChild: maximum number of requests a server process serves until death
StartServers          <%= apache_processes %>
MinSpareServers       <%= apache_processes %>
MaxSpareServers       <%= apache_processes %>
MaxClients            100
MaxRequestsPerChild   0

ErrorLog "<%= current_release %>/log/apache_error_log"
# Possible values include: debug, info, notice, warn, error, crit, alert, emerg
LogLevel info
LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
CustomLog "<%= current_release %>/log/apache_access_log" combined
#RewriteLog "<%= current_release %>/log/apache_rewrite_log"
# 0-9, 0 = off, 2 and 3 is good for debugging
#RewriteLogLevel 3

ServerTokens Prod
ServerSignature Off

DefaultType text/plain
TypesConfig /usr/local/apache2/conf/mime.types
AddType application/x-compress .Z
AddType application/x-gzip .gz .tgz

<% if behind_https %>
# for envs that sit behind an https load balancer
RequestHeader set X-FORWARDED_PROTO https
<% end %>

# using Passenger (http://www.modrails.com/) to serve Rails
LoadModule passenger_module <%= gem_home %>/passenger-1.0.1/ext/apache2/mod_passenger.so
RailsSpawnServer            <%= gem_home %>/passenger-1.0.1/bin/passenger-spawn-server
RailsRuby             <%= ruby_binary %>

RailsUserSwitching    off
# max number of Rails processes to be spawned at a time
RailsMaxPoolSize      <%= max_rails_processes %>
# spawner processes will be killed if idle for 60 minutes
RailsPoolIdleTime     3600
RailsEnv              <%= environment %>

RailsAllowModRewrite  on
RewriteEngine On
# Check for maintenance file and redirect all requests
RewriteCond %{DOCUMENT_ROOT}/system/maintenance.html -f
RewriteCond %{SCRIPT_FILENAME} !maintenance.html
RewriteRule ^.*$ %{DOCUMENT_ROOT}/system/maintenance.html [L]

DocumentRoot "<%= current_release %>/public"
<Directory <%= current_release %>/public>
    Options FollowSymLinks
    AllowOverride None
    Order allow,deny
    Allow from all

    # Set the max size for file uploads to 10M
    LimitRequestBody 10485760
</Directory>

<Directory />
    Options FollowSymLinks
    AllowOverride None
    Order Deny,Allow
    Deny from all
</Directory>

Here is the cap task to generate httpd.conf and upload it to the server:

desc "Generate the apache httpd.conf file from the template"
task :generate_apache_httpd_conf_file, :roles => :app do
  require 'erb'
  # set up defaults for some vars to go into the template. others are required.
  apache_processes = fetch(:www_procs, 2)
  max_rails_processes = fetch(:max_rails_procs, 2)
  ruby_binary = fetch(:ruby_binary, "ruby")
  gem_home = fetch(:gem_home, '/usr/local/lib/ruby/gems/1.8/gems')
  behind_https = fetch(:fronted_by_https, false)
  template = ERB.new(File.read('config/templates/httpd.conf.erb'), nil, '<>')
  result = template.result(binding)
  put(result, "#{current_release}/httpd.conf")
end

It runs in an after_update_code task. This way, all server configs are under code control. This is huge! Each deployed environment’s settings are known and tracked – not just loosely keyed on each server. I treat Apache as part of our application – not a service that happens to be running that we deploy into. Using this technique, along with vendor_everything, we’ve minimized our host dependencies.