Class: GServer

Inherits:
Object
  • Object
show all
Defined in:
lib/gserver.rb

Overview

GServer implements a generic server, featuring thread pool management, simple logging, and multi-server management. See HttpServer in xmlrpc/httpserver.rb in the Ruby standard library for an example of GServer in action.

Any kind of application-level server can be implemented using this class. It accepts multiple simultaneous connections from clients, up to an optional maximum number. Several services (i.e. one service per TCP port) can be run simultaneously, and stopped at any time through the class method GServer.stop(port). All the threading issues are handled, saving you the effort. All events are optionally logged, but you can provide your own event handlers if you wish.

Example

Using GServer is simple. Below we implement a simple time server, run it, query it, and shut it down. Try this code in irb:

require 'gserver'

#
# A server that returns the time in seconds since 1970.
#
class TimeServer < GServer
  def initialize(port=10001, *args)
    super(port, *args)
  end
  def serve(io)
    io.puts(Time.now.to_s)
  end
end

# Run the server with logging enabled (it's a separate thread).
server = TimeServer.new
server.audit = true                  # Turn logging on.
server.start

# *** Now point your browser to http://localhost:10001 to see it working ***

# See if it's still running.
GServer.in_service?(10001)           # -> true
server.stopped?                      # -> false

# Shut the server down gracefully.
server.shutdown

# Alternatively, stop it immediately.
GServer.stop(10001)
# or, of course, "server.stop".

All the business of accepting connections and exception handling is taken care of. All we have to do is implement the method that actually serves the client.

Advanced

As the example above shows, the way to use GServer is to subclass it to create a specific server, overriding the serve method. You can override other methods as well if you wish, perhaps to collect statistics, or emit more detailed logging.

  • #connecting

  • #disconnecting

  • #starting

  • #stopping

The above methods are only called if auditing is enabled, via #audit=.

You can also override #log and #error if, for example, you wish to use a more sophisticated logging system.

Constant Summary collapse

DEFAULT_HOST = 
"127.0.0.1"
@@services =

Hash of opened ports, i.e. services

{}
@@servicesMutex = 
Mutex.new

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(port, host = DEFAULT_HOST, maxConnections = 4, stdlog = $stderr, audit = false, debug = false) ⇒ GServer

Create a new server

port

the port, as a FixNum, on which to listen.

host

the host to bind to

maxConnections

The maximum number of simultaneous connections to accept

stdlog

IO device on which to log messages

audit

if true, lifecycle callbacks will be called. See #audit

debug

if true, error messages are logged. See #debug



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# File 'lib/gserver.rb', line 222

def initialize(port, host = DEFAULT_HOST, maxConnections = 4,
  stdlog = $stderr, audit = false, debug = false)
  @tcpServerThread = nil
  @port = port
  @host = host
  @maxConnections = maxConnections
  @connections = []
  @connectionsMutex = Mutex.new
  @connectionsCV = ConditionVariable.new
  @stdlog = stdlog
  @audit = audit
  @debug = debug
end

Instance Attribute Details

#audit ⇒ Object

Set to true to cause the callbacks #connecting, #disconnecting, #starting, and #stopping to be called during the server's lifecycle



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# File 'lib/gserver.rb', line 153

def audit
  @audit
end

#debug ⇒ Object

Set to true to show more detailed logging



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# File 'lib/gserver.rb', line 155

def debug
  @debug
end

#host ⇒ Object (readonly)

Host on which to bind, as a String



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# File 'lib/gserver.rb', line 146

def host
  @host
end

#maxConnections ⇒ Object (readonly)

Maximum number of connections to accept at at ime, as a FixNum



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# File 'lib/gserver.rb', line 148

def maxConnections
  @maxConnections
end

#port ⇒ Object (readonly)

Port on which to listen, as a FixNum



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# File 'lib/gserver.rb', line 144

def port
  @port
end

#stdlog ⇒ Object

IO Device on which log messages should be written



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# File 'lib/gserver.rb', line 150

def stdlog
  @stdlog
end

Class Method Details

.in_service?(port, host = DEFAULT_HOST) ⇒ Boolean

Check if a server is running on the given port and host

port

port, as a FixNum, of the server to check

host

host on which to find the server to check

Returns true if a server is running on that port and host.

Returns:

  • (Boolean) 


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# File 'lib/gserver.rb', line 109

def GServer.in_service?(port, host = DEFAULT_HOST)
  @@services.has_key?(host) and
    @@services[host].has_key?(port)
end

.stop(port, host = DEFAULT_HOST) ⇒ Object

Stop the server running on the given port, bound to the given host

port

port, as a FixNum, of the server to stop

host

host on which to find the server to stop



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# File 'lib/gserver.rb', line 97

def GServer.stop(port, host = DEFAULT_HOST)
  @@servicesMutex.synchronize {
    @@services[host][port].stop
  }
end

Instance Method Details

#connections ⇒ Object

Return the current number of connected clients



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# File 'lib/gserver.rb', line 134

def connections
  @connections.size
end

#join ⇒ Object

Join with the server thread



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# File 'lib/gserver.rb', line 139

def join
  @tcpServerThread.join if @tcpServerThread
end

#serve(io) ⇒ Object 



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# File 'lib/gserver.rb', line 87

def serve(io)
end

#shutdown ⇒ Object

Schedule a shutdown for the server



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# File 'lib/gserver.rb', line 129

def shutdown
  @shutdown = true
end

#start(maxConnections = -1)) ⇒ Object

Start the server if it isn't already running

maxConnections

override maxConnections given to the constructor. A negative value indicates that the value from the constructor should be used.



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# File 'lib/gserver.rb', line 241

def start(maxConnections = -1)
  raise "server is already running" if !stopped?
  @shutdown = false
  @maxConnections = maxConnections if maxConnections > 0
  @@servicesMutex.synchronize  {
    if GServer.in_service?(@port,@host)
      raise "Port already in use: #{host}:#{@port}!"
    end
    @tcpServer = TCPServer.new(@host,@port)
    @port = @tcpServer.addr[1]
    @@services[@host] = {} unless @@services.has_key?(@host)
    @@services[@host][@port] = self;
  }
  @tcpServerThread = Thread.new {
    begin
      starting if @audit
      while !@shutdown
        @connectionsMutex.synchronize  {
           while @connections.size >= @maxConnections
             @connectionsCV.wait(@connectionsMutex)
           end
        }
        client = @tcpServer.accept
        @connections << Thread.new(client)  { |myClient|
          begin
            myPort = myClient.peeraddr[1]
            serve(myClient) if !@audit or connecting(myClient)
          rescue => detail
            error(detail) if @debug
          ensure
            begin
              myClient.close
            rescue
            end
            @connectionsMutex.synchronize {
              @connections.delete(Thread.current)
              @connectionsCV.signal
            }
            disconnecting(myPort) if @audit
          end
        }
      end
    rescue => detail
      error(detail) if @debug
    ensure
      begin
        @tcpServer.close
      rescue
      end
      if @shutdown
        @connectionsMutex.synchronize  {
           while @connections.size > 0
             @connectionsCV.wait(@connectionsMutex)
           end
        }
      else
        @connections.each { |c| c.raise "stop" }
      end
      @tcpServerThread = nil
      @@servicesMutex.synchronize  {
        @@services[@host].delete(@port)
      }
      stopping if @audit
    end
  }
  self
end

#stop ⇒ Object

Stop the server



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# File 'lib/gserver.rb', line 115

def stop
  @connectionsMutex.synchronize  {
    if @tcpServerThread
      @tcpServerThread.raise "stop"
    end
  }
end

#stopped? ⇒ Boolean

Returns true if the server has stopped.

Returns:

  • (Boolean) 


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# File 'lib/gserver.rb', line 124

def stopped?
  @tcpServerThread == nil
end