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.

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.

Constants

DEFAULT_HOST

Attributes

audit[RW]

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

debug[RW]

Set to true to show more detailed logging

host[R]

Host on which to bind, as a String

maxConnections[R]

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

port[R]

Port on which to listen, as a FixNum

stdlog[RW]

IO Device on which log messages should be written

Public Class Methods

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

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.

               # File gserver.rb, line 109
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

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

               # File 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

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

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

               # File gserver.rb, line 97
def GServer.stop(port, host = DEFAULT_HOST)
  @@servicesMutex.synchronize {
    @@services[host][port].stop
  }
end

Public Instance Methods

connections() click to toggle source

Return the current number of connected clients

               # File gserver.rb, line 134
def connections
  @connections.size
end

join() click to toggle source

Join with the server thread

               # File gserver.rb, line 139
def join
  @tcpServerThread.join if @tcpServerThread
end

serve(io) click to toggle source

               # File gserver.rb, line 87
def serve(io)
end

shutdown() click to toggle source

Schedule a shutdown for the server

               # File gserver.rb, line 129
def shutdown
  @shutdown = true
end

start(maxConnections = -1) click to toggle source

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.

               # File 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() click to toggle source

Stop the server

               # File gserver.rb, line 115
def stop
  @connectionsMutex.synchronize  {
    if @tcpServerThread
      @tcpServerThread.raise "stop"
    end
  }
end

stopped?() click to toggle source

Returns true if the server has stopped.

               # File gserver.rb, line 124
def stopped?
  @tcpServerThread == nil
end

Protected Instance Methods

connecting(client) click to toggle source

Called when a client connects, if auditing is enabled.

client

a TCPSocket instances representing the client that connected

Return true to allow this client to connect, false to prevent it.

               # File gserver.rb, line 162
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

Called when a client disconnects, if audition is enabled.

clientPort

the port of the client that is connecting

               # File gserver.rb, line 173
def disconnecting(clientPort)
  log("#{self.class.to_s} #{@host}:#{@port} " +
    "client:#{clientPort} disconnect")
end

error(detail) click to toggle source

Called if debug is true whenever an unhandled exception is raised. This implementation simply logs the backtrace.

detail

The Exception that was caught

               # File gserver.rb, line 196
def error(detail)
  log(detail.backtrace.join("\n"))
end

log(msg) click to toggle source

Log a message to stdlog, if it’s defined. This implementation outputs the timestamp and message to the log.

msg

the message to log

               # File gserver.rb, line 204
def log(msg)
  if @stdlog
    @stdlog.puts("[#{Time.new.ctime}] %s" % msg)
    @stdlog.flush
  end
end

starting() click to toggle source

Called when the server is starting up, if auditing is enabled.

               # File gserver.rb, line 181
def starting()
  log("#{self.class.to_s} #{@host}:#{@port} start")
end

stopping() click to toggle source

Called when the server is shutting down, if auditing is enabled.

               # File gserver.rb, line 186
def stopping()
  log("#{self.class.to_s} #{@host}:#{@port} stop")
end

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