GServer

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.

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

Constants

DEFAULT_HOST

Attributes

audit[RW]

debug[RW]

host[R]

maxConnections[R]

port[R]

stdlog[RW]

Public Class Methods

in_service?(port, host = DEFAULT_HOST) click to toggle source

 
               # File gserver.rb, line 102
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) click to toggle source

 
               # File 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

stop(port, host = DEFAULT_HOST) click to toggle source

 
               # File gserver.rb, line 96
def GServer.stop(port, host = DEFAULT_HOST)
  @@servicesMutex.synchronize {
    @@services[host][port].stop
  }
end

Public Instance Methods

connections() click to toggle source

 
               # File gserver.rb, line 123
def connections
  @connections.size
end

join() click to toggle source

 
               # File gserver.rb, line 127
def join
  @tcpServerThread.join if @tcpServerThread
end

serve(io) click to toggle source

 
               # File gserver.rb, line 90
def serve(io)
end

shutdown() click to toggle source

 
               # File gserver.rb, line 119
def shutdown
  @shutdown = true
end

start(maxConnections = -1) click to toggle source

 
               # File 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() click to toggle source

 
               # File gserver.rb, line 107
def stop
  @connectionsMutex.synchronize  {
    if @tcpServerThread
      @tcpServerThread.raise "stop"
    end
  }
end

stopped?() click to toggle source

 
               # File gserver.rb, line 115
def stopped?
  @tcpServerThread == nil
end

Protected Instance Methods

connecting(client) click to toggle source

 
               # File gserver.rb, line 134
def connecting(client)
  addr = client.peeraddr
  log("#{self.class.to_s} #{@host}:#{@port} client:#{addr[1]} " +
      "#{addr[2]}<#{addr[3]}> connect")
  true
end

disconnecting(clientPort) click to toggle source

 
               # File gserver.rb, line 141
def disconnecting(clientPort)
  log("#{self.class.to_s} #{@host}:#{@port} " +
    "client:#{clientPort} disconnect")
end

error(detail) click to toggle source

 
               # File gserver.rb, line 158
def error(detail)
  log(detail.backtrace.join("\n"))
end

log(msg) click to toggle source

 
               # File gserver.rb, line 162
def log(msg)
  if @stdlog
    @stdlog.puts("[#{Time.new.ctime}] %s" % msg)
    @stdlog.flush
  end
end

starting() click to toggle source

 
               # File gserver.rb, line 148
def starting()
  log("#{self.class.to_s} #{@host}:#{@port} start")
end

stopping() click to toggle source

 
               # File gserver.rb, line 152
def stopping()
  log("#{self.class.to_s} #{@host}:#{@port} stop")
end

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