Module: WEBrick

WEB server toolkit.

WEBrick is an HTTP server toolkit that can be configured as an HTTPS server, a proxy server, and a virtual-host server. WEBrick features complete logging of both server operations and HTTP access. WEBrick supports both basic and digest authentication in addition to algorithms not in RFC 2617.

A WEBrick server can be composed of multiple WEBrick servers or servlets to provide differing behavior on a per-host or per-path basis. WEBrick includes servlets for handling CGI scripts, ERB pages, Ruby blocks and directory listings.

WEBrick also includes tools for daemonizing a process and starting a process at a higher privilege level and dropping permissions.

Starting an HTTP server

To create a new HTTPServer that will listen to connections on port 8000 and serve documents from the current user’s public_html folder:

require 'webrick'

root = File.expand_path '~/public_html'
server = WEBrick::HTTPServer.new :Port => 8000, :DocumentRoot => root

To run the server you will need to provide a suitable shutdown hook as starting the server blocks the current thread:

trap 'INT' do server.shutdown end

server.start

Custom Behavior

The easiest way to have a server perform custom operations is through HTTPServer#mount_proc. The block given will be called with a HTTPRequest with request info and a HTTPResponse which must be filled in appropriately:

server.mount_proc '/' do |req, res|
  res.body = 'Hello, world!'
end

Remember that server.mount_proc must precede server.start.

Servlets

Advanced custom behavior can be obtained through mounting a subclass of ::WEBrick::HTTPServlet::AbstractServlet. Servlets provide more modularity when writing an HTTP server than mount_proc allows. Here is a simple servlet:

class Simple < WEBrick::HTTPServlet::AbstractServlet
  def do_GET request, response
    status, content_type, body = do_stuff_with request

    response.status = 200
    response['Content-Type'] = 'text/plain'
    response.body = 'Hello, World!'
  end
end

To initialize the servlet you mount it on the server:

server.mount '/simple', Simple

See ::WEBrick::HTTPServlet::AbstractServlet for more details.

Virtual Hosts

A server can act as a virtual host for multiple host names. After creating the listening host, additional hosts that do not listen can be created and attached as virtual hosts:

server = WEBrick::HTTPServer.new # ...

vhost = WEBrick::HTTPServer.new :ServerName => 'vhost.example',
                                :DoNotListen => true, # ...
vhost.mount '/', ...

server.virtual_host vhost

If no :DocumentRoot is provided and no servlets or procs are mounted on the main server it will return 404 for all URLs.

HTTPS

To create an HTTPS server you only need to enable SSL and provide an SSL certificate name:

require 'webrick'
require 'webrick/https'

cert_name = [
  %w[CN localhost],
]

server = WEBrick::HTTPServer.new(:Port => 8000,
                                 :SSLEnable => true,
                                 :SSLCertName => cert_name)

This will start the server with a self-generated self-signed certificate. The certificate will be changed every time the server is restarted.

To create a server with a pre-determined key and certificate you can provide them:

require 'webrick'
require 'webrick/https'
require 'openssl'

cert = OpenSSL::X509::Certificate.new File.read '/path/to/cert.pem'
pkey = OpenSSL::PKey::RSA.new File.read '/path/to/pkey.pem'

server = WEBrick::HTTPServer.new(:Port => 8000,
                                 :SSLEnable => true,
                                 :SSLCertificate => cert,
                                 :SSLPrivateKey => pkey)

Proxy Server

WEBrick can act as a proxy server:

require 'webrick'
require 'webrick/httpproxy'

proxy = WEBrick::HTTPProxyServer.new :Port => 8000

trap 'INT' do proxy.shutdown end

See WEBrick::HTTPProxy for further details including modifying proxied responses.

Basic and Digest authentication

WEBrick provides both Basic and Digest authentication for regular and proxy servers. See HTTPAuth, ::WEBrick::HTTPAuth::BasicAuth and ::WEBrick::HTTPAuth::DigestAuth.

WEBrick as a Production Web Server

WEBrick can be run as a production server for small loads.

Daemonizing

To start a WEBrick server as a daemon simple run Daemon.start before starting the server.

Dropping Permissions

WEBrick can be started as one user to gain permission to bind to port 80 or 443 for serving HTTP or HTTPS traffic then can drop these permissions for regular operation. To listen on all interfaces for HTTP traffic:

sockets = WEBrick::Utils.create_listeners nil, 80

Then drop privileges:

WEBrick::Utils.su 'www'

Then create a server that does not listen by default:

server = WEBrick::HTTPServer.new :DoNotListen => true, # ...

Then overwrite the listening sockets with the port 80 sockets:

server.listeners.replace sockets

Logging

WEBrick can separately log server operations and end-user access. For server operations:

log_file = File.open '/var/log/webrick.log', 'a+'
log = WEBrick::Log.new log_file

For user access logging:

access_log = [
  [log_file, WEBrick::AccessLog::COMBINED_LOG_FORMAT],
]

server = WEBrick::HTTPServer.new :Logger => log, :AccessLog => access_log

See AccessLog for further log formats.

Log Rotation

To rotate logs in WEBrick on a HUP signal (like syslogd can send), open the log file in ‘a+’ mode (as above) and trap ‘HUP’ to reopen the log file:

trap 'HUP' do log_file.reopen '/path/to/webrick.log', 'a+'

Copyright

Author: IPR – Internet Programming with Ruby – writers

Copyright © 2000 TAKAHASHI Masayoshi, GOTOU YUUZOU Copyright © 2002 Internet Programming with Ruby writers. All rights reserved.