class PhusionPassenger::AbstractServer

An abstract base class for a server that has the following properties:

The server will also reset all signal handlers. That is, it will respond to all signals in the default manner. The only exception is SIGHUP, which is ignored. One may define additional signal handlers using #define_signal_handler().

Before an AbstractServer can be used, it must first be started by calling start(). When it is no longer needed, stop() should be called.

Here's an example on using AbstractServer:

class MyServer < PhusionPassenger::AbstractServer
   def initialize
      super()
      define_message_handler(:hello, :handle_hello)
   end

   def hello(first_name, last_name)
      connect do |channel|
         channel.write('hello', first_name, last_name)
         reply, pointless_number = channel.read
         puts "The server said: #{reply}"
         puts "In addition, it sent this pointless number: #{pointless_number}"
      end
   end

private
   def handle_hello(channel, first_name, last_name)
      channel.write("Hello #{first_name} #{last_name}, how are you?", 1234)
   end
end

server = MyServer.new
server.start
server.hello("Joe", "Dalton")
server.stop

Attributes

ignore_password_errors[RW]
max_idle_time[RW]

The maximum time that this AbstractServer may be idle. Used by AbstractServerCollection to determine when this object should be cleaned up. nil or 0 indicate that this object should never be idle cleaned.

next_cleaning_time[RW]

Used by AbstractServerCollection to remember when this AbstractServer should be idle cleaned.

password[R]

Public Class Methods

new(socket_filename = nil, password = nil) click to toggle source
# File lib/phusion_passenger/abstract_server.rb, line 115
def initialize(socket_filename = nil, password = nil)
        @socket_filename = socket_filename
        @password = password
        @socket_filename ||= "#{passenger_tmpdir}/spawn-server/socket.#{Process.pid}.#{object_id}"
        @password ||= generate_random_id(:base64)
        
        @message_handlers = {}
        @signal_handlers = {}
        @orig_signal_handlers = {}
end

Public Instance Methods

connect() { |channel| ... } click to toggle source

Connects to the server and yields a channel for communication. The first message's name must match a handler name. The connection can only be used for a single handler cycle; after the handler is done, the connection will be closed.

server.connect do |channel|
   channel.write("a message")
   ...
end

Raises: SystemCallError, IOError, SocketError

# File lib/phusion_passenger/abstract_server.rb, line 266
def connect
        channel = MessageChannel.new(UNIXSocket.new(@socket_filename))
        begin
                channel.write_scalar(@password)
                yield channel
        ensure
                channel.close
        end
end
server_pid() click to toggle source

Return the PID of the started server. This is only valid if start has been called.

# File lib/phusion_passenger/abstract_server.rb, line 251
def server_pid
        return @pid
end
start() click to toggle source

Start the server. This method does not block since the server runs asynchronously from the current process.

You may only call this method if the server is not already started. Otherwise, a ServerAlreadyStarted will be raised.

Derived classes may raise additional exceptions.

# File lib/phusion_passenger/abstract_server.rb, line 133
def start
        if started?
                raise ServerAlreadyStarted, "Server is already started"
        end
        
        a, b = UNIXSocket.pair
        File.unlink(@socket_filename) rescue nil
        server_socket = UNIXServer.new(@socket_filename)
        File.chmod(0700, @socket_filename)
        
        before_fork
        @pid = fork
        if @pid.nil?
                has_exception = false
                begin
                        STDOUT.sync = true
                        STDERR.sync = true
                        a.close
                        
                        # During Passenger's early days, we used to close file descriptors based
                        # on a white list of file descriptors. That proved to be way too fragile:
                        # too many file descriptors are being left open even though they shouldn't
                        # be. So now we close file descriptors based on a black list.
                        #
                        # Note that STDIN, STDOUT and STDERR may be temporarily set to
                        # different file descriptors than 0, 1 and 2, e.g. in unit tests.
                        # We don't want to close these either.
                        file_descriptors_to_leave_open = [0, 1, 2,
                                b.fileno, server_socket.fileno,
                                fileno_of(STDIN), fileno_of(STDOUT), fileno_of(STDERR)
                        ].compact.uniq
                        NativeSupport.close_all_file_descriptors(file_descriptors_to_leave_open)
                        # In addition to closing the file descriptors, one must also close
                        # the associated IO objects. This is to prevent IO.close from
                        # double-closing already closed file descriptors.
                        close_all_io_objects_for_fds(file_descriptors_to_leave_open)
                        
                        # At this point, RubyGems might have open file handles for which
                        # the associated file descriptors have just been closed. This can
                        # result in mysterious 'EBADFD' errors. So we force RubyGems to
                        # clear all open file handles.
                        Gem.clear_paths
                        
                        # Reseed pseudo-random number generator for security reasons.
                        srand
                        
                        start_synchronously(@socket_filename, @password, server_socket, b)
                rescue Interrupt
                        # Do nothing.
                        has_exception = true
                rescue Exception => e
                        has_exception = true
                        print_exception(self.class.to_s, e)
                ensure
                        exit!(has_exception ? 1 : 0)
                end
        end
        server_socket.close
        b.close
        @owner_socket = a
end
start_synchronously(socket_filename, password, server_socket, owner_socket) click to toggle source

Start the server, but in the current process instead of in a child process. This method blocks until the server's main loop has ended.

All hooks will be called, except #before_fork().

# File lib/phusion_passenger/abstract_server.rb, line 199
def start_synchronously(socket_filename, password, server_socket, owner_socket)
        @owner_socket = owner_socket
        begin
                reset_signal_handlers
                initialize_server
                begin
                        server_main_loop(password, server_socket)
                ensure
                        finalize_server
                end
        rescue Interrupt
                # Do nothing
        ensure
                @owner_socket = nil
                revert_signal_handlers
                File.unlink(socket_filename) rescue nil
                server_socket.close
        end
end
started?() click to toggle source

Return whether the server has been started.

# File lib/phusion_passenger/abstract_server.rb, line 246
def started?
        return !!@owner_socket
end
stop() click to toggle source

Stop the server. The server will quit as soon as possible. This method waits until the server has been stopped.

When calling this method, the server must already be started. If not, a ServerNotStarted will be raised.

# File lib/phusion_passenger/abstract_server.rb, line 224
def stop
        if !started?
                raise ServerNotStarted, "Server is not started"
        end
        
        begin
                @owner_socket.write("x")
        rescue Errno::EPIPE
        end
        @owner_socket.close
        @owner_socket = nil
        File.unlink(@socket_filename) rescue nil
        
        # Wait at most 4 seconds for server to exit. If it doesn't do that,
        # we kill it forcefully with SIGKILL.
        if !Process.timed_waitpid(@pid, 4)
                Process.kill('SIGKILL', @pid) rescue nil
                Process.timed_waitpid(@pid, 1)
        end
end

Protected Instance Methods

before_fork() click to toggle source

A hook which is called when the server is being started, just before forking a new process. The default implementation does nothing, this method is supposed to be overrided by child classes.

# File lib/phusion_passenger/abstract_server.rb, line 279
def before_fork
end
define_message_handler(message_name, handler) click to toggle source

Define a handler for a message. message_name is the name of the message to handle, and handler is the name of a method to be called (this may either be a String or a Symbol).

A message is just a list of strings, and so handler will be called with the message as its arguments, excluding the first element. See also the example in the class description.

# File lib/phusion_passenger/abstract_server.rb, line 299
def define_message_handler(message_name, handler)
        @message_handlers[message_name.to_s] = handler
end
define_signal_handler(signal, handler) click to toggle source

Define a handler for a signal.

# File lib/phusion_passenger/abstract_server.rb, line 304
def define_signal_handler(signal, handler)
        @signal_handlers[signal.to_s] = handler
end
fileno_of(io) click to toggle source
# File lib/phusion_passenger/abstract_server.rb, line 308
def fileno_of(io)
        return io.fileno
rescue
        return nil
end
finalize_server() click to toggle source

A hook which is called when the server is being stopped. This is called in the child process, after the main loop has been left. The default implementation does nothing, this method is supposed to be overrided by child classes.

# File lib/phusion_passenger/abstract_server.rb, line 291
def finalize_server
end
initialize_server() click to toggle source

A hook which is called when the server is being started. This is called in the child process, before the main loop is entered. The default implementation does nothing, this method is supposed to be overrided by child classes.

# File lib/phusion_passenger/abstract_server.rb, line 285
def initialize_server
end