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_i)
  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.

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

Returns a new instance of GServer.



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# File 'lib/gserver.rb', line 171

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

Returns the value of attribute audit.



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# File 'lib/gserver.rb', line 132

def audit
  @audit
end

#debug ⇒ Object

Returns the value of attribute debug.



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# File 'lib/gserver.rb', line 132

def debug
  @debug
end

#host ⇒ Object (readonly)

Returns the value of attribute host.



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# File 'lib/gserver.rb', line 131

def host
  @host
end

#maxConnections ⇒ Object (readonly)

Returns the value of attribute maxConnections.



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# File 'lib/gserver.rb', line 131

def maxConnections
  @maxConnections
end

#port ⇒ Object (readonly)

Returns the value of attribute port.



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# File 'lib/gserver.rb', line 131

def port
  @port
end

#stdlog ⇒ Object

Returns the value of attribute stdlog.



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# File 'lib/gserver.rb', line 132

def stdlog
  @stdlog
end

Class Method Details

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

Returns:

  • (Boolean) 


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# File 'lib/gserver.rb', line 102

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 



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# File 'lib/gserver.rb', line 96

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

Instance Method Details

#connections ⇒ Object 



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# File 'lib/gserver.rb', line 123

def connections
  @connections.size
end

#join ⇒ Object 



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# File 'lib/gserver.rb', line 127

def join
  @tcpServerThread.join if @tcpServerThread
end

#serve(io) ⇒ Object 



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# File 'lib/gserver.rb', line 90

def serve(io)
end

#shutdown ⇒ Object 



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# File 'lib/gserver.rb', line 119

def shutdown
  @shutdown = true
end

#start(maxConnections = -1)) ⇒ Object 



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# File 'lib/gserver.rb', line 185

def start(maxConnections = -1)
  raise "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 



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# File 'lib/gserver.rb', line 107

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

#stopped? ⇒ Boolean

Returns:

  • (Boolean) 


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

def stopped?
  @tcpServerThread == nil
end