RWVHP

Avahi/Zeroconf or Rendezvous as your Mac would know it, can be used in published DNS records (unicast) as well as the normal LAN type setup (multicast), its already a standard why don’t we use this for discovering RESTful resources?

All this would require would be a service type registered eg. rest.tcp and a flag in the TXT record naming your resources eg. “resources=/users /articles /articles/comments”.

I brought this up (quite randomly) during a talk at my local Ruby Group (ncl.rb).

Gimme your feedback?

UPDATE Forgot to add from the initial post use the :resource/new to get an empty object (to_xml or whatever)

An example of discovering unicast Zeroconf services is

shift@carbon:~# avahi-browse -a -d 0pointer.de
+  n/a  n/a Lennart’s Blog                                _http-rss._tcp       0pointer.de
+  n/a  n/a tango                                         SSH Remote Terminal  0pointer.de
+  n/a  n/a dt115                                         SSH Remote Terminal  0pointer.de
+  n/a  n/a ring2                                         SSH Remote Terminal  0pointer.de
+  n/a  n/a PulseAudio Web Site                           Web Site             0pointer.de
+  n/a  n/a Avahi Web Site                                Web Site             0pointer.de
+  n/a  n/a Lennart's Blog                                Web Site             0pointer.de
+  n/a  n/a Lennart's Photos                              Web Site             0pointer.de
+  n/a  n/a Lennart's Homepage                            Web Site             0pointer.de

This isn’t so much a blog post as somewhere convenient to put some information for ncl.rb.

My Apache 2.2 + modproxybalancer virtualhost config

<VirtualHost *:80>
  ServerName yourapp.com
  DocumentRoot /home/web/yourapp.com/current/public/
  <Directory "/home/web/yourapp.com/current/public">
    Options FollowSymLinks
    AllowOverride None
    Order allow,deny
    Allow from all
  </Directory>
  # Configure the cluster member proxy
  <Proxy balancer://your_app_cluster>
    BalancerMember http://127.0.0.1:3000
    BalancerMember http://127.0.0.1:3001
    BalancerMember http://127.0.0.1:3002
    BalancerMember http://127.0.0.1:3003
  </Proxy>
  RewriteEngine On
  # If there is a maintenence.html file in your
  # public dir all requests will get rerouted to
  # this file.  This is for use with capistrano
  RewriteCond %{DOCUMENT_ROOT}/maintenance.html -f
  RewriteCond %{SCRIPT_FILENAME} !maintenance.html
  RewriteRule ^.*$ /maintenance.html [L]

  # Rewrite index to check for static index.html
  RewriteRule ^/$ /index.html [QSA]

  # Rewrite to check for Rails cached pages with .html extentions
  RewriteRule ^([^.]+)$ $1.html [QSA]

  # All dynamic requests get sent to the cluster
  RewriteCond %{DOCUMENT_ROOT}/%{REQUEST_FILENAME} !-f
  RewriteRule ^/(.*)$ balancer://your_app_cluster%{REQUEST_URI} [P,QSA,L]

  # Deflate for clients that support it.
  AddOutputFilterByType DEFLATE text/html text/plain text/xml
  BrowserMatch ^Mozilla/4 gzip-only-text/html
  BrowserMatch ^Mozilla/4.0[678] no-gzip
  BrowserMatch \bMSIE !no-gzip !gzip-only-text/html

  # Error and access logs.
  ErrorLog /var/log/apache/app_error.log
  CustomLog /var/log/apache/app_access.log combined
</VirtualHost>

Now if you take the above example it’ll send all requests to your pack of mongrels, but say you want to have more then one application running on your domain (say beast).

You’ll need to create another proxy balancer

  <Proxy balancer://your_second_app_cluster>
    BalancerMember http://127.0.0.1:3004
    BalancerMember http://127.0.0.1:3005
    BalancerMember http://127.0.0.1:3006
    BalancerMember http://127.0.0.1:3007
  </Proxy>

And then add the RewriteRule for it

RewriteRule ^/forums/(.*)$ balancer://your_second_app_cluster%{REQUEST_URI} [P,QSA,L]

Now anything going to / that isn’t /forums/.* will goto yourappcluster and anything with /forums/.* will goto yoursecondapp_cluster

<VirtualHost *:80>
  ServerName yourapp.com
  DocumentRoot /home/web/yourapp.com/current/public/
  <Directory "/home/web/yourapp.com/current/public">
    Options FollowSymLinks
    AllowOverride None
    Order allow,deny
    Allow from all
  </Directory>
  # Configure the cluster member proxy
  <Proxy balancer://your_app_cluster>
    BalancerMember http://127.0.0.1:3000
    BalancerMember http://127.0.0.1:3001
    BalancerMember http://127.0.0.1:3002
    BalancerMember http://127.0.0.1:3003
  </Proxy>
  <Proxy balancer://your_second_app_cluster>
    BalancerMember http://127.0.0.1:3004
    BalancerMember http://127.0.0.1:3005
    BalancerMember http://127.0.0.1:3006
    BalancerMember http://127.0.0.1:3007
  </Proxy>

  RewriteEngine On
  # If there is a maintenence.html file in your
  # public dir all requests will get rerouted to
  # this file.  This is for use with capistrano
  RewriteCond %{DOCUMENT_ROOT}/maintenance.html -f
  RewriteCond %{SCRIPT_FILENAME} !maintenance.html
  RewriteRule ^.*$ /maintenance.html [L]

  # Rewrite index to check for static index.html
  RewriteRule ^/$ /index.html [QSA]

  # Rewrite to check for Rails cached pages with .html extentions
  RewriteRule ^([^.]+)$ $1.html [QSA]

  # All dynamic requests get sent to the cluster
  RewriteCond %{DOCUMENT_ROOT}/%{REQUEST_FILENAME} !-f
  RewriteRule ^/forums/(.*)$ balancer://your_second_app_cluster%{REQUEST_URI} [P,QSA,L]
  RewriteRule ^/(.*)$ balancer://your_app_cluster%{REQUEST_URI} [P,QSA,L]

  # Deflate for clients that support it.
  AddOutputFilterByType DEFLATE text/html text/plain text/xml
  BrowserMatch ^Mozilla/4 gzip-only-text/html
  BrowserMatch ^Mozilla/4.0[678] no-gzip
  BrowserMatch \bMSIE !no-gzip !gzip-only-text/html

  # Error and access logs.
  ErrorLog /var/log/apache/app_error.log
  CustomLog /var/log/apache/app_access.log combined
</VirtualHost>

yourappcluster mongrel_cluster.yml

---
port: "3000" 
environment: production
address: 127.0.0.1
pid_file: log/mongrel.pid
servers: 4

yoursecondappcluster mongrelcluster.yml

---
port: "3004" 
environment: production
address: 127.0.0.1
pid_file: log/mongrel.pid
servers: 4

Hope that made sense, as its off the top of the head apart from the base apache 2.2 vhost config

UPDATE If your running a Rails app under a path remember to set

ActionController::AbstractRequest.relative_url_root = '/path'

In your environment.rb or your links will be wrong