implemented reconnect and separated out the protocol driver from the messaging client

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk/qpid@806393 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 548 insertions, 244 deletions

diff --git a/python/qpid/messaging.py b/python/qpid/messaging.py
index 9b3fecbf9b..b66f681dcd 100644
--- a/python/qpid/messaging.py
+++ b/python/qpid/messaging.py
@@ -32,10 +32,11 @@ Areas that still need work:
 
 import connection, time, socket, sys, traceback
 from codec010 import StringCodec
-from datatypes import timestamp, uuid4, RangedSet, Message as Message010
+from datatypes import timestamp, uuid4, RangedSet, Message as Message010, Serial
+from exceptions import Timeout
 from logging import getLogger
-from ops import PRIMITIVE
-from session import Client, INCOMPLETE
+from ops import PRIMITIVE, delivery_mode
+from session import Client, INCOMPLETE, SessionDetached
 from threading import Thread, RLock, Condition
 from util import connect
 
@@ -101,7 +102,10 @@ class Constant:
 
 UNLIMITED = Constant("UNLIMITED", 0xFFFFFFFFL)
 
-class ConnectError(Exception):
+class ConnectionError(Exception):
+  pass
+
+class ConnectError(ConnectionError):
   pass
 
 class Connection(Lockable):
@@ -142,12 +146,29 @@ class Connection(Lockable):
     self.host = host
     self.port = default(port, AMQP_PORT)
     self.started = False
-    self._conn = None
     self.id = str(uuid4())
     self.session_counter = 0
     self.sessions = {}
+    self.reconnect = False
     self._lock = RLock()
     self._condition = Condition(self._lock)
+    self._modcount = Serial(0)
+    self.error = None
+    self._driver = Driver(self)
+    self._driver.start()
+
+  def wakeup(self):
+    self._modcount += 1
+    self._driver.wakeup()
+
+  def catchup(self, exc=ConnectionError):
+    mc = self._modcount
+    self.wait(lambda: not self._driver._modcount < mc)
+    self.check_error(exc)
+
+  def check_error(self, exc=ConnectionError):
+    if self.error:
+      raise exc(*self.error)
 
   @synchronized
   def session(self, name=None, transactional=False):
@@ -173,8 +194,7 @@ class Connection(Lockable):
     else:
       ssn = Session(self, name, self.started, transactional=transactional)
       self.sessions[name] = ssn
-      if self._conn is not None:
-        ssn._attach()
+      self.wakeup()
       return ssn
 
   @synchronized
@@ -186,38 +206,25 @@ class Connection(Lockable):
     """
     Connect to the remote endpoint.
     """
-    if self._conn is not None:
-      return
-    try:
-      self._socket = connect(self.host, self.port)
-    except socket.error, e:
-      raise ConnectError(e)
-    self._conn = connection.Connection(self._socket)
-    try:
-      self._conn.start()
-    except connection.VersionError, e:
-      raise ConnectError(e)
-
-    for ssn in self.sessions.values():
-      ssn._attach()
+    self._connected = True
+    self.wakeup()
+    self.catchup(ConnectError)
 
   @synchronized
   def disconnect(self):
     """
     Disconnect from the remote endpoint.
     """
-    if self._conn is not None:
-      self._conn.close()
-      self._conn = None
-    for ssn in self.sessions.values():
-      ssn._disconnected()
+    self._connected = False
+    self.wakeup()
+    self.catchup()
 
   @synchronized
   def connected(self):
     """
     Return true if the connection is connected, false otherwise.
     """
-    return self._conn is not None
+    return self._connected
 
   @synchronized
   def start(self):
@@ -255,6 +262,7 @@ class Pattern:
   def __init__(self, value):
     self.value = value
 
+  # XXX: this should become part of the driver
   def _bind(self, ssn, exchange, queue):
     ssn.exchange_bind(exchange=exchange, queue=queue,
                       binding_key=self.value.replace("*", "#"))
@@ -263,13 +271,33 @@ FILTER_DEFAULTS = {
   "topic": Pattern("*")
   }
 
-def delegate(session):
+def delegate(handler, session):
   class Delegate(Client):
 
     def message_transfer(self, cmd):
-      session._message_transfer(cmd)
+      handler._message_transfer(session, cmd)
   return Delegate
 
+class SessionError(Exception):
+  pass
+
+class Disconnected(SessionError):
+  """
+  Exception raised when an operation is attempted that is illegal when
+  disconnected.
+  """
+  pass
+
+class NontransactionalSession(SessionError):
+  """
+  Exception raised when commit or rollback is attempted on a non
+  transactional session.
+  """
+  pass
+
+class TransactionAborted(SessionError):
+  pass
+
 class Session(Lockable):
 
   """
@@ -281,18 +309,26 @@ class Session(Lockable):
     self.connection = connection
     self.name = name
     self.started = started
+
     self.transactional = transactional
-    self._ssn = None
+
+    self.committing = False
+    self.committed = True
+    self.aborting = False
+    self.aborted = False
+
     self.senders = []
     self.receivers = []
-    self.closing = False
+    self.outgoing = []
     self.incoming = []
-    self.closed = False
     self.unacked = []
-    if self.transactional:
-      self.acked = []
-    self._lock = RLock()
-    self._condition = Condition(self._lock)
+    self.acked = []
+
+    self.closing = False
+    self.closed = False
+
+    self._lock = connection._lock
+    self._condition = connection._condition
     self.thread = Thread(target = self.run)
     self.thread.setDaemon(True)
     self.thread.start()
@@ -300,60 +336,14 @@ class Session(Lockable):
   def __repr__(self):
     return "<Session %s>" % self.name
 
-  def _attach(self):
-    self._ssn = self.connection._conn.session(self.name, delegate=delegate(self))
-    self._ssn.auto_sync = False
-    self._ssn.invoke_lock = self._lock
-    self._ssn.lock = self._lock
-    self._ssn.condition = self._condition
-    if self.transactional:
-      self._ssn.tx_select()
-    for link in self.senders + self.receivers:
-      link._link()
-
-  def _disconnected(self):
-    self._ssn = None
-    for link in self.senders + self.receivers:
-      link._disconnected()
+  def wakeup(self):
+    self.connection.wakeup()
 
-  @synchronized
-  def _message_transfer(self, cmd):
-    m = Message010(cmd.payload)
-    m.headers = cmd.headers
-    m.id = cmd.id
-    msg = self._decode(m)
-    rcv = self.receivers[int(cmd.destination)]
-    msg._receiver = rcv
-    log.debug("RECV [%s] %s", self, msg)
-    self.incoming.append(msg)
-    self.notifyAll()
-    return INCOMPLETE
+  def catchup(self, exc=SessionError):
+    self.connection.catchup(exc)
 
-  def _decode(self, message):
-    dp = message.get("delivery_properties")
-    mp = message.get("message_properties")
-    ap = mp.application_headers
-    enc, dec = get_codec(mp.content_type)
-    content = dec(message.body)
-    msg = Message(content)
-    msg.id = mp.message_id
-    if ap is not None:
-      msg.to = ap.get("to")
-      msg.subject = ap.get("subject")
-    msg.user_id = mp.user_id
-    if mp.reply_to is not None:
-      msg.reply_to = reply_to2addr(mp.reply_to)
-    msg.correlation_id = mp.correlation_id
-    msg.properties = mp.application_headers
-    msg.content_type = mp.content_type
-    msg._transfer_id = message.id
-    return msg
-
-  def _exchange_query(self, address):
-    # XXX: auto sync hack is to avoid deadlock on future
-    result = self._ssn.exchange_query(name=address, sync=True)
-    self._ssn.sync()
-    return result.get()
+  def check_error(self, exc=SessionError):
+    self.connection.check_error(exc)
 
   @synchronized
   def sender(self, target):
@@ -368,8 +358,7 @@ class Session(Lockable):
     """
     sender = Sender(self, len(self.senders), target)
     self.senders.append(sender)
-    if self._ssn is not None:
-      sender._link()
+    self.wakeup()
     return sender
 
   @synchronized
@@ -386,8 +375,7 @@ class Session(Lockable):
     receiver = Receiver(self, len(self.receivers), source, filter,
                         self.started)
     self.receivers.append(receiver)
-    if self._ssn is not None:
-      receiver._link()
+    self.wakeup()
     return receiver
 
   @synchronized
@@ -419,6 +407,7 @@ class Session(Lockable):
                  timeout):
       msg = self._pop(predicate)
       if msg is not None:
+        msg._receiver.returned += 1
         self.unacked.append(msg)
         log.debug("RETR [%s] %s", self, msg)
         return msg
@@ -438,20 +427,13 @@ class Session(Lockable):
     else:
       messages = [message]
 
-    ids = RangedSet(*[m._transfer_id for m in messages])
-    for range in ids:
-      self._ssn.receiver._completed.add_range(range)
-    self._ssn.channel.session_completed(self._ssn.receiver._completed)
-    self._ssn.message_accept(ids, sync=True)
-    self._ssn.sync()
-
     for m in messages:
-      try:
-        self.unacked.remove(m)
-      except ValueError:
-        pass
-      if self.transactional:
-        self.acked.append(m)
+      self.unacked.remove(m)
+      self.acked.append(m)
+
+    self.wakeup()
+    self.wait(lambda: self.connection.error or not [m for m in messages if m in self.acked])
+    self.check_error()
 
   @synchronized
   def commit(self):
@@ -461,11 +443,13 @@ class Session(Lockable):
     """
     if not self.transactional:
       raise NontransactionalSession()
-    if self._ssn is None:
-      raise Disconnected()
-    self._ssn.tx_commit(sync=True)
-    del self.acked[:]
-    self._ssn.sync()
+    self.committing = True
+    self.wakeup()
+    self.catchup()
+    assert not self.committing
+    if self.aborted:
+      raise TransactionAborted()
+    assert self.committed
 
   @synchronized
   def rollback(self):
@@ -475,21 +459,10 @@ class Session(Lockable):
     """
     if not self.transactional:
       raise NontransactionalSession()
-    if self._ssn is None:
-      raise Disconnected()
-
-    ids = RangedSet(*[m._transfer_id for m in self.acked + self.unacked + self.incoming])
-    for range in ids:
-      self._ssn.receiver._completed.add_range(range)
-    self._ssn.channel.session_completed(self._ssn.receiver._completed)
-    self._ssn.message_release(ids)
-    self._ssn.tx_rollback(sync=True)
-
-    del self.incoming[:]
-    del self.unacked[:]
-    del self.acked[:]
-
-    self._ssn.sync()
+    self.aborting = True
+    self.wakeup()
+    self.catchup()
+    assert not self.aborting and self.aborted
 
   @synchronized
   def start(self):
@@ -538,13 +511,12 @@ class Session(Lockable):
       link.close()
 
     self.closing = True
-    self.notifyAll()
+    self.wakeup()
+    self.catchup()
     self.wait(lambda: self.closed)
     while self.thread.isAlive():
       self.thread.join(3)
     self.thread = None
-    self._ssn.close()
-    self._ssn = None
     self.connection._remove_session(self)
 
 def parse_addr(address):
@@ -562,18 +534,7 @@ def reply_to2addr(reply_to):
   else:
     return "%s/%s" % (reply_to.exchange, reply_to.routing_key)
 
-class Disconnected(Exception):
-  """
-  Exception raised when an operation is attempted that is illegal when
-  disconnected.
-  """
-  pass
-
-class NontransactionalSession(Exception):
-  """
-  Exception raised when commit or rollback is attempted on a non
-  transactional session.
-  """
+class SendError(SessionError):
   pass
 
 class Sender(Lockable):
@@ -587,29 +548,17 @@ class Sender(Lockable):
     self.index = index
     self.target = target
     self.closed = False
-    self._ssn = None
-    self._exchange = None
-    self._routing_key = None
-    self._subject = None
     self._lock = self.session._lock
     self._condition = self.session._condition
 
-  def _link(self):
-    self._ssn = self.session._ssn
-    node, self._subject = parse_addr(self.target)
-    result = self.session._exchange_query(node)
-    if result.not_found:
-      # XXX: should check 'create' option
-      self._ssn.queue_declare(queue=node, durable=False, sync=True)
-      self._ssn.sync()
-      self._exchange = ""
-      self._routing_key = node
-    else:
-      self._exchange = node
-      self._routing_key = self._subject
+  def wakeup(self):
+    self.session.wakeup()
 
-  def _disconnected(self):
-    self._ssn = None
+  def catchup(self, exc=SendError):
+    self.session.catchup(exc)
+
+  def check_error(self, exc=SendError):
+    self.session.check_error(exc)
 
   @synchronized
   def send(self, object):
@@ -623,56 +572,36 @@ class Sender(Lockable):
     @param object: the message or content to send
     """
 
-    if self._ssn is None:
+    if not self.session.connection._connected or self.session.closing:
       raise Disconnected()
 
     if isinstance(object, Message):
       message = object
     else:
       message = Message(object)
-    # XXX: what if subject is specified for a normal queue?
-    if self._routing_key is None:
-      rk = message.subject
-    else:
-      rk = self._routing_key
-    # XXX: do we need to query to figure out how to create the reply-to interoperably?
-    if message.reply_to:
-      rt = self._ssn.reply_to(*parse_addr(message.reply_to))
-    else:
-      rt = None
-    dp = self._ssn.delivery_properties(routing_key=rk)
-    mp = self._ssn.message_properties(message_id=message.id,
-                                      user_id=message.user_id,
-                                      reply_to=rt,
-                                      correlation_id=message.correlation_id,
-                                      content_type=message.content_type,
-                                      application_headers=message.properties)
-    if message.subject is not None:
-      if mp.application_headers is None:
-        mp.application_headers = {}
-      mp.application_headers["subject"] = message.subject
-    if message.to is not None:
-      if mp.application_headers is None:
-        mp.application_headers = {}
-      mp.application_headers["to"] = message.to
-    enc, dec = get_codec(message.content_type)
-    body = enc(message.content)
-    self._ssn.message_transfer(destination=self._exchange,
-                               message=Message010(dp, mp, body),
-                               sync=True)
-    log.debug("SENT [%s] %s", self.session, message)
-    self._ssn.sync()
+
+    # XXX: what if we send the same message to multiple senders?
+    message._sender = self
+    self.session.outgoing.append(message)
+
+    self.wakeup()
+    self.catchup()
+    assert message not in self.session.outgoing
 
   @synchronized
   def close(self):
     """
     Close the Sender.
     """
+    # XXX: should make driver do something here
     if not self.closed:
       self.session.senders.remove(self)
       self.closed = True
 
-class Empty(Exception):
+class ReceiveError(SessionError):
+  pass
+
+class Empty(ReceiveError):
   """
   Exception raised by L{Receiver.fetch} when there is no message
   available within the alloted time.
@@ -693,43 +622,32 @@ class Receiver(Lockable):
     self.destination = str(self.index)
     self.source = source
     self.filter = filter
+
     self.started = started
     self.capacity = UNLIMITED
+    self.granted = Serial(0)
+    self.drain = False
+    self.impending = Serial(0)
+    self.received = Serial(0)
+    self.returned = Serial(0)
+
     self.closed = False
     self.listener = None
-    self._ssn = None
-    self._queue = None
     self._lock = self.session._lock
     self._condition = self.session._condition
 
-  def _link(self):
-    self._ssn = self.session._ssn
-    result = self.session._exchange_query(self.source)
-    if result.not_found:
-      self._queue = self.source
-      # XXX: should check 'create' option
-      self._ssn.queue_declare(queue=self._queue, durable=False)
-    else:
-      self._queue = "%s.%s" % (self.session.name, self.destination)
-      self._ssn.queue_declare(queue=self._queue, durable=False, exclusive=True, auto_delete=True)
-      if self.filter is None:
-        f = FILTER_DEFAULTS[result.type]
-      else:
-        f = self.filter
-      f._bind(self._ssn, self.source, self._queue)
-    self._ssn.message_subscribe(queue=self._queue, destination=self.destination,
-                                sync=True)
-    self._ssn.message_set_flow_mode(self.destination, self._ssn.flow_mode.credit)
-    self._ssn.sync()
-    if self.started:
-      self._start()
-
-  def _disconnected(self):
-    self._ssn = None
+  def wakeup(self):
+    self.session.wakeup()
+
+  def catchup(self, exc=ReceiveError):
+    self.session.catchup()
+
+  def check_error(self, exc=ReceiveError):
+    self.session.check_error(exc)
 
   @synchronized
   def pending(self):
-    return self.session._count(self._pred)
+    return self.received - self.returned
 
   def _capacity(self):
     if not self.started:
@@ -762,58 +680,64 @@ class Receiver(Lockable):
     @type timeout: float
     @param timeout: the time to wait for a message to be available
     """
-    if self.capacity is not UNLIMITED or not self.started:
-      self._ssn.message_flow(self.destination, self._ssn.credit_unit.byte,
-                             UNLIMITED.value)
-      self._ssn.message_flow(self.destination, self._ssn.credit_unit.message, 1)
+    if self._capacity() == 0:
+      self.granted = self.returned + 1
+      self.wakeup()
+      self.catchup()
+      assert self.impending == self.granted
     msg = self.session._get(self._pred, timeout=timeout)
     if msg is None:
-      self._ssn.message_flush(self.destination)
-      self._start()
-      self._ssn.sync()
+      self.drain = True
+      self.wakeup()
+      self.catchup()
+      assert self.granted == self.received
+      self.drain = False
+      if self.capacity is not UNLIMITED:
+        self.granted += self._capacity()
+        self.wakeup()
       msg = self.session._get(self._pred, timeout=0)
       if msg is None:
         raise Empty()
+    if self._capacity() not in (0, UNLIMITED.value):
+      self.granted += 1
+      self.wakeup()
     return msg
 
-  def _start(self):
-    self._ssn.message_flow(self.destination, self._ssn.credit_unit.byte, UNLIMITED.value)
-    self._ssn.message_flow(self.destination, self._ssn.credit_unit.message, self._capacity())
-
   @synchronized
   def start(self):
     """
     Start incoming message delivery for this receiver.
     """
     self.started = True
-    if self._ssn is not None:
-      self._start()
-
-  def _stop(self):
-    self._ssn.message_stop(self.destination)
+    if self.capacity is UNLIMITED:
+      self.granted = UNLIMITED
+    else:
+      self.granted = self.received + self._capacity()
+    self.wakeup()
 
   @synchronized
   def stop(self):
     """
     Stop incoming message delivery for this receiver.
     """
-    if self._ssn is not None:
-      self._stop()
+    self.granted = self.received
     self.started = False
+    self.wakeup()
+    self.catchup()
+    assert self.granted == self.received
 
   @synchronized
   def close(self):
     """
     Close the receiver.
     """
-    if not self.closed:
-      self.closed = True
-      self._ssn.message_cancel(self.destination, sync=True)
-      self._ssn.sync()
+    self.closed = True
+    self.wakeup()
+    try:
+      self.catchup()
+    finally:
       self.session.receivers.remove(self)
 
-
-
 def codec(name):
   type = PRIMITIVE[name]
 
@@ -889,6 +813,7 @@ class Message:
     self.to = None
     self.reply_to = None
     self.correlation_id = None
+    self.durable = False
     self.properties = {}
     self.content_type = get_type(content)
     self.content = content
@@ -896,5 +821,384 @@ class Message:
   def __repr__(self):
     return "Message(%r)" % self.content
 
+class Attachment:
+
+  def __init__(self, target):
+    self.target = target
+
+DURABLE_DEFAULT=True
+
+class Driver(Lockable):
+
+  def __init__(self, connection):
+    self.connection = connection
+    self._lock = self.connection._lock
+    self._condition = self.connection._condition
+    self._wakeup_cond = Condition()
+    self._socket = None
+    self._conn = None
+    self._attachments = {}
+    self._modcount = self.connection._modcount
+    self.thread = Thread(target=self.run)
+    self.thread.setDaemon(True)
+    # XXX: need to figure out how to join on this thread
+
+  def start(self):
+    self.thread.start()
+
+  def wakeup(self):
+    self._wakeup_cond.acquire()
+    try:
+      self._wakeup_cond.notifyAll()
+    finally:
+      self._wakeup_cond.release()
+
+  def start(self):
+    self.thread.start()
+
+  def run(self):
+    while True:
+      self._wakeup_cond.acquire()
+      try:
+        if self.connection._modcount <= self._modcount:
+          self._wakeup_cond.wait(10)
+      finally:
+        self._wakeup_cond.release()
+      self.dispatch(self.connection._modcount)
+
+  @synchronized
+  def dispatch(self, modcount):
+    try:
+      if self._conn is None and self.connection._connected:
+        self.connect()
+      elif self._conn is not None and not self.connection._connected:
+        self.disconnect()
+
+      if self._conn is not None:
+        for ssn in self.connection.sessions.values():
+          self.attach(ssn)
+          self.process(ssn)
+      exi = None
+    except:
+      exi = sys.exc_info()
+
+    if exi:
+      msg = traceback.format_exc()
+      recoverable = ["aborted", "Connection refused", "SessionDetached", "Connection reset by peer",
+                     "Bad file descriptor", "start timed out", "Broken pipe"]
+      for r in recoverable:
+        if self.connection.reconnect and r in msg:
+          print "waiting to retry"
+          self.reset()
+          time.sleep(3)
+          print "retrying..."
+          return
+      else:
+        self.connection.error = (msg,)
+
+    self._modcount = modcount
+    self.notifyAll()
+
+  def connect(self):
+    if self._conn is not None:
+      return
+    try:
+      self._socket = connect(self.connection.host, self.connection.port)
+    except socket.error, e:
+      raise ConnectError(e)
+    self._conn = connection.Connection(self._socket)
+    try:
+      self._conn.start(timeout=10)
+    except connection.VersionError, e:
+      raise ConnectError(e)
+    except Timeout:
+      print "start timed out"
+      raise ConnectError("start timed out")
+
+  def disconnect(self):
+    self._conn.close()
+    self.reset()
+
+  def reset(self):
+    self._conn = None
+    self._attachments.clear()
+    for ssn in self.connection.sessions.values():
+      for m in ssn.acked + ssn.unacked + ssn.incoming:
+        m._transfer_id = None
+      for rcv in ssn.receivers:
+        rcv.impending = rcv.received
+        rcv.returned = rcv.received
+
+  def connected(self):
+    return self._conn is not None
+
+  def attach(self, ssn):
+    _ssn = self._attachments.get(ssn)
+    if _ssn is None:
+      _ssn = self._conn.session(ssn.name, delegate=delegate(self, ssn))
+      _ssn.auto_sync = False
+      _ssn.invoke_lock = self._lock
+      _ssn.lock = self._lock
+      _ssn.condition = self._condition
+      if ssn.transactional:
+        # XXX: adding an attribute to qpid.session.Session
+        _ssn.acked = []
+        _ssn.tx_select()
+      self._attachments[ssn] = _ssn
+
+    for snd in ssn.senders:
+      self.link_out(snd)
+    for rcv in ssn.receivers:
+      self.link_in(rcv)
+
+    if ssn.closing:
+      _ssn.close()
+      del self._attachments[ssn]
+
+  def _exchange_query(self, ssn, address):
+    # XXX: auto sync hack is to avoid deadlock on future
+    result = ssn.exchange_query(name=address, sync=True)
+    ssn.sync()
+    return result.get()
+
+  def link_out(self, snd):
+    _ssn = self._attachments[snd.session]
+    _snd = self._attachments.get(snd)
+    if _snd is None:
+      _snd = Attachment(snd)
+      node, _snd._subject = parse_addr(snd.target)
+      result = self._exchange_query(_ssn, node)
+      if result.not_found:
+        # XXX: should check 'create' option
+        _ssn.queue_declare(queue=node, durable=DURABLE_DEFAULT, sync=True)
+        _ssn.sync()
+        _snd._exchange = ""
+        _snd._routing_key = node
+      else:
+        _snd._exchange = node
+        _snd._routing_key = _snd._subject
+      self._attachments[snd] = _snd
+
+    if snd.closed:
+      del self._attachments[snd]
+
+  def link_in(self, rcv):
+    _ssn = self._attachments[rcv.session]
+    _rcv = self._attachments.get(rcv)
+    if _rcv is None:
+      _rcv = Attachment(rcv)
+      result = self._exchange_query(_ssn, rcv.source)
+      if result.not_found:
+        _rcv._queue = rcv.source
+        # XXX: should check 'create' option
+        _ssn.queue_declare(queue=_rcv._queue, durable=DURABLE_DEFAULT)
+      else:
+        _rcv._queue = "%s.%s" % (rcv.session.name, rcv.destination)
+        _ssn.queue_declare(queue=_rcv._queue, durable=DURABLE_DEFAULT, exclusive=True, auto_delete=True)
+        if rcv.filter is None:
+          f = FILTER_DEFAULTS[result.type]
+        else:
+          f = rcv.filter
+        f._bind(_ssn, rcv.source, _rcv._queue)
+      _ssn.message_subscribe(queue=_rcv._queue, destination=rcv.destination)
+      _ssn.message_set_flow_mode(rcv.destination, _ssn.flow_mode.credit, sync=True)
+      self._attachments[rcv] = _rcv
+      # XXX: need to kill syncs
+      _ssn.sync()
+
+    if rcv.closed:
+      _ssn.message_cancel(rcv.destination, sync=True)
+      # XXX: need to kill syncs
+      _ssn.sync()
+      del self._attachments[rcv]
+
+  def process(self, ssn):
+    if ssn.closing: return
+
+    _ssn = self._attachments[ssn]
+
+    while ssn.outgoing:
+      msg = ssn.outgoing[0]
+      snd = msg._sender
+      self.send(snd, msg)
+      ssn.outgoing.pop(0)
+
+    for rcv in ssn.receivers:
+      self.process_receiver(rcv)
+
+    if ssn.acked:
+      messages = ssn.acked[:]
+      ids = RangedSet(*[m._transfer_id for m in messages if m._transfer_id is not None])
+      for range in ids:
+        _ssn.receiver._completed.add_range(range)
+      ch = _ssn.channel
+      if ch is None:
+        raise SessionDetached()
+      ch.session_completed(_ssn.receiver._completed)
+      _ssn.message_accept(ids, sync=True)
+      # XXX: really need to make this async so that we don't give up the lock
+      _ssn.sync()
+
+      for m in messages:
+        ssn.acked.remove(m)
+        if ssn.transactional:
+          _ssn.acked.append(m)
+
+    if ssn.committing:
+      _ssn.tx_commit(sync=True)
+      # XXX: need to kill syncs
+      _ssn.sync()
+      del _ssn.acked[:]
+      ssn.committing = False
+      ssn.committed = True
+      ssn.aborting = False
+      ssn.aborted = False
+
+    if ssn.aborting:
+      for rcv in ssn.receivers:
+        _ssn.message_stop(rcv.destination)
+      _ssn.sync()
+
+      messages = _ssn.acked + ssn.unacked + ssn.incoming
+      ids = RangedSet(*[m._transfer_id for m in messages])
+      for range in ids:
+        _ssn.receiver._completed.add_range(range)
+      _ssn.channel.session_completed(_ssn.receiver._completed)
+      _ssn.message_release(ids)
+      _ssn.tx_rollback(sync=True)
+      _ssn.sync()
+
+      del ssn.incoming[:]
+      del ssn.unacked[:]
+      del _ssn.acked[:]
+
+      for rcv in ssn.receivers:
+        rcv.impending = rcv.received
+        rcv.returned = rcv.received
+        # XXX: do we need to update granted here as well?
+
+      for rcv in ssn.receivers:
+        self.process_receiver(rcv)
+
+      ssn.aborting = False
+      ssn.aborted = True
+      ssn.committing = False
+      ssn.committed = False
+
+  def grant(self, rcv):
+    _ssn = self._attachments[rcv.session]
+    _rcv = self._attachments[rcv]
+
+    if rcv.granted is UNLIMITED:
+      if rcv.impending is UNLIMITED:
+        delta = 0
+      else:
+        delta = UNLIMITED.value
+    else:
+      delta = rcv.granted - rcv.impending
+
+    if delta > 0:
+      _ssn.message_flow(rcv.destination, _ssn.credit_unit.byte, UNLIMITED.value)
+      _ssn.message_flow(rcv.destination, _ssn.credit_unit.message, delta)
+      rcv.impending += delta
+    elif delta < 0:
+      _ssn.message_stop(rcv.destination, sync=True)
+      # XXX: need to kill syncs
+      _ssn.sync()
+      rcv.impending = rcv.received
+      # XXX: this can recurse infinitely if granted drops below received
+      self.grant(rcv)
+
+  def process_receiver(self, rcv):
+    if rcv.closed: return
+    _ssn = self._attachments[rcv.session]
+    _rcv = self._attachments[rcv]
+
+    self.grant(rcv)
+
+    if rcv.drain:
+      _ssn.message_flush(rcv.destination, sync=True)
+      # XXX: really need to make this async so that we don't give up the lock
+      _ssn.sync()
+      rcv.granted = rcv.received
+      rcv.impending = rcv.received
+
+  def send(self, snd, msg):
+    _ssn = self._attachments[snd.session]
+    _snd = self._attachments[snd]
+
+    # XXX: what if subject is specified for a normal queue?
+    if _snd._routing_key is None:
+      rk = msg.subject
+    else:
+      rk = _snd._routing_key
+    # XXX: do we need to query to figure out how to create the reply-to interoperably?
+    if msg.reply_to:
+      rt = _ssn.reply_to(*parse_addr(msg.reply_to))
+    else:
+      rt = None
+    dp = _ssn.delivery_properties(routing_key=rk)
+    mp = _ssn.message_properties(message_id=msg.id,
+                                 user_id=msg.user_id,
+                                 reply_to=rt,
+                                 correlation_id=msg.correlation_id,
+                                 content_type=msg.content_type,
+                                 application_headers=msg.properties)
+    if msg.subject is not None:
+      if mp.application_headers is None:
+        mp.application_headers = {}
+      mp.application_headers["subject"] = msg.subject
+    if msg.to is not None:
+      if mp.application_headers is None:
+        mp.application_headers = {}
+      mp.application_headers["to"] = msg.to
+    if msg.durable:
+      dp.delivery_mode = delivery_mode.persistent
+    enc, dec = get_codec(msg.content_type)
+    body = enc(msg.content)
+    _ssn.message_transfer(destination=_snd._exchange,
+                          message=Message010(dp, mp, body),
+                          sync=True)
+    log.debug("SENT [%s] %s", snd.session, msg)
+    # XXX: really need to make this async so that we don't give up the lock
+    _ssn.sync()
+    # XXX: should we log the ack somehow too?
+
+  @synchronized
+  def _message_transfer(self, ssn, cmd):
+    m = Message010(cmd.payload)
+    m.headers = cmd.headers
+    m.id = cmd.id
+    msg = self._decode(m)
+    rcv = ssn.receivers[int(cmd.destination)]
+    msg._receiver = rcv
+    rcv.received += 1
+    log.debug("RECV [%s] %s", ssn, msg)
+    ssn.incoming.append(msg)
+    self.notifyAll()
+    return INCOMPLETE
+
+  def _decode(self, message):
+    dp = message.get("delivery_properties")
+    mp = message.get("message_properties")
+    ap = mp.application_headers
+    enc, dec = get_codec(mp.content_type)
+    content = dec(message.body)
+    msg = Message(content)
+    msg.id = mp.message_id
+    if ap is not None:
+      msg.to = ap.get("to")
+      msg.subject = ap.get("subject")
+    msg.user_id = mp.user_id
+    if mp.reply_to is not None:
+      msg.reply_to = reply_to2addr(mp.reply_to)
+    msg.correlation_id = mp.correlation_id
+    msg.durable = dp.delivery_mode == delivery_mode.persistent
+    msg.properties = mp.application_headers
+    msg.content_type = mp.content_type
+    msg._transfer_id = message.id
+    return msg
+
 __all__ = ["Connection", "Pattern", "Session", "Sender", "Receiver", "Message",
            "Empty", "timestamp", "uuid4"]
+\