GServer (Class)

In: gserver.rb
Parent: Object

GServer implements a generic server, featuring thread pool management, simple logging, and multi-server management. See 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.

Methods

connections   in_service?   join   new   serve   shutdown   start   stop   stop   stopped?  

Constants

DEFAULT_HOST = "127.0.0.1"

Attributes

audit  [RW] 
debug  [RW] 
host  [R] 
maxConnections  [R] 
port  [R] 
stdlog  [RW] 

Public Class methods

in_service?(port, host = DEFAULT_HOST)

[Source]

# File gserver.rb, line 98
  def GServer.in_service?(port, host = DEFAULT_HOST)
    @@services.has_key?(host) and
      @@services[host].has_key?(port)
  end
new(port, host = DEFAULT_HOST, maxConnections = 4, stdlog = $stderr, audit = false, debug = false)

[Source]

# File gserver.rb, line 167
  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
stop(port, host = DEFAULT_HOST)

[Source]

# File gserver.rb, line 92
  def GServer.stop(port, host = DEFAULT_HOST)
    @@servicesMutex.synchronize {
      @@services[host][port].stop
    }
  end

Public Instance methods

connections()

[Source]

# File gserver.rb, line 119
  def connections
    @connections.size
  end
join()

[Source]

# File gserver.rb, line 123
  def join
    @tcpServerThread.join if @tcpServerThread
  end
serve(io)

[Source]

# File gserver.rb, line 86
  def serve(io)
  end
shutdown()

[Source]

# File gserver.rb, line 115
  def shutdown
    @shutdown = true
  end
start(maxConnections = -1)

[Source]

# File gserver.rb, line 181
  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()

[Source]

# File gserver.rb, line 103
  def stop
    @connectionsMutex.synchronize  {
      if @tcpServerThread
        @tcpServerThread.raise "stop"
      end
    }
  end
stopped?()

[Source]

# File gserver.rb, line 111
  def stopped?
    @tcpServerThread == nil
  end

[Validate]