connection.py

import socket
import errno
import logging
from select import select

from protocol import Packet, ProtocolError
from event import IdleEvent

class BaseConnection(object):
    """A base connection."""
    def __init__(self, event_manager, handler, s = None, addr = None):
        self.em = event_manager
        self.s = s
        self.addr = addr
        self.handler = handler
        if s is not None:
            event_manager.register(self)

    def getSocket(self):
        return self.s

    def setSocket(self, s):
        if self.s is not None:
            raise RuntimeError, 'cannot overwrite a socket in a connection'
        if s is not None:
            self.s = s
            self.em.register(self)

    def getAddress(self):
        return self.addr

    def readable(self):
        raise NotImplementedError

    def writable(self):
        raise NotImplementedError

    def getHandler(self):
        return self.handler

    def setHandler(self):
        self.handler = handler

    def getEventManager(self):
        return self.em

class ListeningConnection(BaseConnection):
    """A listen connection."""
    def __init__(self, event_manager, handler, addr = None, **kw):
        logging.info('listening to %s:%d', *addr)
        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        try:
            s.setblocking(0)
            s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
            s.bind(addr)
            s.listen(5)
        except:
            s.close()
            raise
        BaseConnection.__init__(self, event_manager, handler, s = s, addr = addr)
        self.em.addReader(self)

    def readable(self):
        try:
            new_s, addr = self.s.accept()
            logging.info('accepted a connection from %s:%d', *addr)
            self.handler.connectionAccepted(self, new_s, addr)
        except socket.error, m:
            if m[0] == errno.EAGAIN:
                return
            raise

class Connection(BaseConnection):
    """A connection."""
    def __init__(self, event_manager, handler, s = None, addr = None):
        BaseConnection.__init__(self, handler, event_manager, s = s, addr = addr)
        if s is not None:
            event_manager.addReader(self)
        self.read_buf = []
        self.write_buf = []
        self.cur_id = 0
        self.event_dict = {}
        self.aborted = False
        self.uuid = None

    def getUUID(self):
        return self.uuid

    def setUUID(self, uuid):
        self.uuid = uuid

    def getNextId(self):
        next_id = self.cur_id
        self.cur_id += 1
        if self.cur_id > 0xffff:
            self.cur_id = 0
        return next_id

    def close(self):
        """Close the connection."""
        s = self.s
        em = self.em
        if s is not None:
            logging.debug('closing a socket for %s:%d', *(self.addr))
            em.removeReader(self)
            em.removeWriter(self)
            em.unregister(self)
            try:
                # This may fail if the socket is not connected.
                s.shutdown(socket.SHUT_RDWR)
            except socket.error:
                pass
            s.close()
            self.s = None
            for event in self.event_dict.itervalues():
                em.removeIdleEvent(event)
            self.event_dict.clear()

    def abort(self):
        """Abort dealing with this connection."""
        logging.debug('aborting a socket for %s:%d', *(self.addr))
        self.aborted = True

    def writable(self):
        """Called when self is writable."""
        self.send()
        if not self.pending():
            if self.aborted:
                self.close()
            else:
                self.em.removeWriter(self)

    def readable(self):
        """Called when self is readable."""
        self.recv()
        self.analyse()

        if self.aborted:
            self.em.removeReader(self)

    def analyse(self):
        """Analyse received data."""
        if self.read_buf:
            if len(self.read_buf) == 1:
                msg = self.read_buf[0]
            else:
                msg = ''.join(self.read_buf)

            while 1:
                try:
                    packet = Packet.parse(msg)
                except ProtocolError, m:
                    self.handler.packetMalformed(self, *m)
                    return

                if packet is None:
                    break

                # Remove idle events, if appropriate packets were received.
                for msg_id in (None, packet.getId()):
                    try:
                        event = self.event_dict[msg_id]
                        del self.event_dict[msg_id]
                        self.em.removeIdleEvent(event)
                    except KeyError:
                        pass

                self.handler.packetReceived(self, packet)
                msg = msg[len(packet):]

            if msg:
                self.read_buf = [msg]
            else:
                del self.read_buf[:]

    def pending(self):
        return self.s is not None and len(self.write_buf) != 0

    def recv(self):
        """Receive data from a socket."""
        s = self.s
        try:
            r = s.recv(4096)
            if not r:
                logging.error('cannot read')
                self.handler.connectionClosed(self)
                self.close()
            else:
                self.read_buf.append(r)
        except socket.error, m:
            if m[0] == errno.EAGAIN:
                pass
            else:
                logging.error('%s', m[1])
                self.handler.connectionClosed(self)
                self.close()

    def send(self):
        """Send data to a socket."""
        s = self.s
        if self.write_buf:
            if len(self.write_buf) == 1:
                msg = self.write_buf[0]
            else:
                msg = ''.join(self.write_buf)
            try:
                r = s.send(msg)
                if not r:
                    logging.error('cannot write')
                    self.handler.connectionClosed(self)
                    self.close()
                elif r == len(msg):
                    del self.write_buf[:]
                else:
                    self.write_buf = [msg[:r]]
            except socket.error, m:
                if m[0] == errno.EAGAIN:
                    return
                else:
                    logging.error('%s', m[1])
                    self.handler.connectionClosed(self)
                    self.close()

    def addPacket(self, packet):
        """Add a packet into the write buffer."""
        try:
            self.write_buf.append(packet.encode())
        except ProtocolError, m:
            logging.critical('trying to send a too big message')
            return self.addPacket(packet.internalError(packet.getId(), m[1]))

        # If this is the first time, enable polling for writing.
        if len(self.write_buf) == 1:
            self.em.addWriter(self.s)

    def expectMessage(self, msg_id = None, timeout = 5, additional_timeout = 30):
        """Expect a message for a reply to a given message ID or any message.
        
        The purpose of this method is to define how much amount of time is
        acceptable to wait for a message, thus to detect a down or broken
        peer. This is important, because one error may halt a whole cluster
        otherwise. Although TCP defines a keep-alive feature, the timeout
        is too long generally, and it does not detect a certain type of reply,
        thus it is better to probe problems at the application level.

        The message ID specifies what ID is expected. Usually, this should
        be identical with an ID for a request message. If it is None, any
        message is acceptable, so it can be used to check idle time.
        
        The timeout is the amount of time to wait until keep-alive messages start.
        Once the timeout is expired, the connection starts to ping the peer.
        
        The additional timeout defines the amount of time after the timeout
        to invoke a timeoutExpired callback. If it is zero, no ping is sent, and
        the callback is executed immediately."""
        event = IdleEvent(self, msg_id, timeout, additional_timeout)
        self.event_dict[msg_id] = event
        self.em.addIdleEvent(event)

class ClientConnection(Connection):
    """A connection from this node to a remote node."""
    def __init__(self, event_manager, handler, addr = None, **kw):
        Connection.__init__(self, event_manager, handler, addr = addr)
        self.connecting = False
        handler.connectionStarted(self)
        try:
            s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            self.setSocket(s)

            try:
                s.setblocking(0)
                s.connect(addr)
            except socket.error, m:
                if m[0] == errno.EINPROGRESS:
                    self.connecting = True
                    event_manager.addWriter(self)
                else:
                    raise
            else:
                self.handler.connectionCompleted()
                event_manager.addReader(self)
        except:
            handler.connectionFailed(self)
            self.close()

    def writable(self):
        """Called when self is writable."""
        if self.connecting:
            err = self.s.getsockopt(socket.SOL_SOCKET, socket.SO_ERROR)
            if err:
                self.connectionFailed()
                self.close()
                return
            else:
                self.connecting = False
                self.handler.connectionCompleted(self)
                self.cm.addReader(self.s)
        else:
            Connection.writable(self)

class ServerConnection(Connection):
    """A connection from a remote node to this node."""
    pass