major cleanup of client code + purge_request implemented

IPython/zmq/parallel/client.py

@@ -1,656 +1,818 b''
 """A semi-synchronous Client for the ZMQ controller"""
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2010  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 from __future__ import print_function
 
 import time
 from pprint import pprint
 
 import zmq
 from zmq.eventloop import ioloop, zmqstream
 
 from IPython.external.decorator import decorator
 
 import streamsession as ss
 from remotenamespace import RemoteNamespace
 from view import DirectView
 from dependency import Dependency, depend, require
 
 def _push(ns):
     globals().update(ns)
 
 def _pull(keys):
     g = globals()
-    if isinstance(keys, (list,tuple)):
+    if isinstance(keys, (list,tuple, set)):
         return map(g.get, keys)
     else:
         return g.get(keys)
 
 def _clear():
     globals().clear()
 
 def execute(code):
     exec code in globals()
 
-# decorators for methods:
+#--------------------------------------------------------------------------
+# Decorators for Client methods
+#--------------------------------------------------------------------------
+
 @decorator
-def spinfirst(f,self,*args,**kwargs):
+def spinfirst(f, self, *args, **kwargs):
+    """Call spin() to sync state prior to calling the method."""
     self.spin()
     return f(self, *args, **kwargs)
 
 @decorator
 def defaultblock(f, self, *args, **kwargs):
+    """Default to self.block; preserve self.block."""
     block = kwargs.get('block',None)
     block = self.block if block is None else block
     saveblock = self.block
     self.block = block
     ret = f(self, *args, **kwargs)
     self.block = saveblock
     return ret
 
+#--------------------------------------------------------------------------
+# Classes
+#--------------------------------------------------------------------------
+
+
 class AbortedTask(object):
+    """A basic wrapper object describing an aborted task."""
     def __init__(self, msg_id):
         self.msg_id = msg_id
-# @decorator
-# def checktargets(f):
-#     @wraps(f)
-#     def checked_method(self, *args, **kwargs):
-#         self._build_targets(kwargs['targets'])
-#         return f(self, *args, **kwargs)
-#     return checked_method
 
-
-# class _ZMQEventLoopThread(threading.Thread):
-#     
-#     def __init__(self, loop):
-#         self.loop = loop
-#         threading.Thread.__init__(self)
-#     
-#     def run(self):
-#         self.loop.start()
-# 
+class ControllerError(Exception):
+    def __init__(self, etype, evalue, tb):
+        self.etype = etype
+        self.evalue = evalue
+        self.traceback=tb
+    
 class Client(object):
     """A semi-synchronous client to the IPython ZMQ controller
     
+    Parameters
+    ----------
+    
+    addr : bytes; zmq url, e.g. 'tcp://127.0.0.1:10101
+        The address of the controller's registration socket.
+    
+    
     Attributes
     ----------
-    ids : set
-        a set of engine IDs
+    ids : set of int engine IDs
         requesting the ids attribute always synchronizes
         the registration state. To request ids without synchronization,
-        use _ids
+        use semi-private _ids.
     
     history : list of msg_ids
         a list of msg_ids, keeping track of all the execution
-        messages you have submitted
+        messages you have submitted in order.
     
     outstanding : set of msg_ids
         a set of msg_ids that have been submitted, but whose
-        results have not been received
+        results have not yet been received.
     
     results : dict
         a dict of all our results, keyed by msg_id
     
     block : bool
         determines default behavior when block not specified
         in execution methods
     
     Methods
     -------
     spin : flushes incoming results and registration state changes
             control methods spin, and requesting `ids` also ensures up to date
             
     barrier : wait on one or more msg_ids
     
-    execution methods: apply/apply_bound/apply_to
+    execution methods: apply/apply_bound/apply_to/applu_bount
         legacy: execute, run
     
-    query methods: queue_status, get_result
+    query methods: queue_status, get_result, purge
     
     control methods: abort, kill
     
-    
-    
     """
     
     
     _connected=False
     _engines=None
-    registration_socket=None
-    query_socket=None
-    control_socket=None
-    notification_socket=None
-    queue_socket=None
-    task_socket=None
+    _addr='tcp://127.0.0.1:10101'
+    _registration_socket=None
+    _query_socket=None
+    _control_socket=None
+    _notification_socket=None
+    _mux_socket=None
+    _task_socket=None
     block = False
     outstanding=None
     results = None
     history = None
     debug = False
     
-    def __init__(self, addr, context=None, username=None, debug=False):
+    def __init__(self, addr='tcp://127.0.0.1:10101', context=None, username=None, debug=False):
         if context is None:
             context = zmq.Context()
         self.context = context
-        self.addr = addr
+        self._addr = addr
         if username is None:
             self.session = ss.StreamSession()
         else:
             self.session = ss.StreamSession(username)
-        self.registration_socket = self.context.socket(zmq.PAIR)
-        self.registration_socket.setsockopt(zmq.IDENTITY, self.session.session)
-        self.registration_socket.connect(addr)
+        self._registration_socket = self.context.socket(zmq.PAIR)
+        self._registration_socket.setsockopt(zmq.IDENTITY, self.session.session)
+        self._registration_socket.connect(addr)
         self._engines = {}
         self._ids = set()
         self.outstanding=set()
         self.results = {}
         self.history = []
         self.debug = debug
         self.session.debug = debug
         
         self._notification_handlers = {'registration_notification' : self._register_engine,
                                     'unregistration_notification' : self._unregister_engine,
                                     }
         self._queue_handlers = {'execute_reply' : self._handle_execute_reply,
                                 'apply_reply' : self._handle_apply_reply}
         self._connect()
         
     
     @property
     def ids(self):
+        """Always up to date ids property."""
         self._flush_notifications()
         return self._ids
     
     def _update_engines(self, engines):
+        """Update our engines dict and _ids from a dict of the form: {id:uuid}."""
         for k,v in engines.iteritems():
             eid = int(k)
             self._engines[eid] = bytes(v) # force not unicode
             self._ids.add(eid)
     
     def _build_targets(self, targets):
+        """Turn valid target IDs or 'all' into two lists:
+        (int_ids, uuids).
+        """
         if targets is None:
             targets = self._ids
         elif isinstance(targets, str):
             if targets.lower() == 'all':
                 targets = self._ids
             else:
                 raise TypeError("%r not valid str target, must be 'all'"%(targets))
         elif isinstance(targets, int):
             targets = [targets]
         return [self._engines[t] for t in targets], list(targets)
     
     def _connect(self):
-        """setup all our socket connections to the controller"""
+        """setup all our socket connections to the controller. This is called from
+        __init__."""
         if self._connected:
             return
         self._connected=True
-        self.session.send(self.registration_socket, 'connection_request')
-        idents,msg = self.session.recv(self.registration_socket,mode=0)
+        self.session.send(self._registration_socket, 'connection_request')
+        idents,msg = self.session.recv(self._registration_socket,mode=0)
         if self.debug:
             pprint(msg)
         msg = ss.Message(msg)
         content = msg.content
         if content.status == 'ok':
             if content.queue:
-                self.queue_socket = self.context.socket(zmq.PAIR)
-                self.queue_socket.setsockopt(zmq.IDENTITY, self.session.session)
-                self.queue_socket.connect(content.queue)
+                self._mux_socket = self.context.socket(zmq.PAIR)
+                self._mux_socket.setsockopt(zmq.IDENTITY, self.session.session)
+                self._mux_socket.connect(content.queue)
             if content.task:
-                self.task_socket = self.context.socket(zmq.PAIR)
-                self.task_socket.setsockopt(zmq.IDENTITY, self.session.session)
-                self.task_socket.connect(content.task)
+                self._task_socket = self.context.socket(zmq.PAIR)
+                self._task_socket.setsockopt(zmq.IDENTITY, self.session.session)
+                self._task_socket.connect(content.task)
             if content.notification:
-                self.notification_socket = self.context.socket(zmq.SUB)
-                self.notification_socket.connect(content.notification)
-                self.notification_socket.setsockopt(zmq.SUBSCRIBE, "")
+                self._notification_socket = self.context.socket(zmq.SUB)
+                self._notification_socket.connect(content.notification)
+                self._notification_socket.setsockopt(zmq.SUBSCRIBE, "")
             if content.query:
-                self.query_socket = self.context.socket(zmq.PAIR)
-                self.query_socket.setsockopt(zmq.IDENTITY, self.session.session)
-                self.query_socket.connect(content.query)
+                self._query_socket = self.context.socket(zmq.PAIR)
+                self._query_socket.setsockopt(zmq.IDENTITY, self.session.session)
+                self._query_socket.connect(content.query)
             if content.control:
-                self.control_socket = self.context.socket(zmq.PAIR)
-                self.control_socket.setsockopt(zmq.IDENTITY, self.session.session)
-                self.control_socket.connect(content.control)
+                self._control_socket = self.context.socket(zmq.PAIR)
+                self._control_socket.setsockopt(zmq.IDENTITY, self.session.session)
+                self._control_socket.connect(content.control)
             self._update_engines(dict(content.engines))
                 
         else:
             self._connected = False
             raise Exception("Failed to connect!")
     
-    #### handlers and callbacks for incoming messages #######
+    #--------------------------------------------------------------------------
+    # handlers and callbacks for incoming messages
+    #--------------------------------------------------------------------------
+    
     def _register_engine(self, msg):
+        """Register a new engine, and update our connection info."""
         content = msg['content']
         eid = content['id']
         d = {eid : content['queue']}
         self._update_engines(d)
         self._ids.add(int(eid))
 
     def _unregister_engine(self, msg):
-        # print 'unregister',msg
+        """Unregister an engine that has died."""
         content = msg['content']
         eid = int(content['id'])
         if eid in self._ids:
             self._ids.remove(eid)
             self._engines.pop(eid)
         
     def _handle_execute_reply(self, msg):
-        # msg_id = msg['msg_id']
+        """Save the reply to an execute_request into our results."""
         parent = msg['parent_header']
         msg_id = parent['msg_id']
         if msg_id not in self.outstanding:
             print("got unknown result: %s"%msg_id)
         else:
             self.outstanding.remove(msg_id)
         self.results[msg_id] = ss.unwrap_exception(msg['content'])
     
     def _handle_apply_reply(self, msg):
-        # pprint(msg)
-        # msg_id = msg['msg_id']
+        """Save the reply to an apply_request into our results."""
         parent = msg['parent_header']
         msg_id = parent['msg_id']
         if msg_id not in self.outstanding:
             print ("got unknown result: %s"%msg_id)
         else:
             self.outstanding.remove(msg_id)
         content = msg['content']
         if content['status'] == 'ok':
             self.results[msg_id] = ss.unserialize_object(msg['buffers'])
         elif content['status'] == 'aborted':
             self.results[msg_id] = AbortedTask(msg_id)
         elif content['status'] == 'resubmitted':
             pass # handle resubmission
         else:
             self.results[msg_id] = ss.unwrap_exception(content)
     
     def _flush_notifications(self):
-        "flush incoming notifications of engine registrations"
-        msg = self.session.recv(self.notification_socket, mode=zmq.NOBLOCK)
+        """Flush notifications of engine registrations waiting
+        in ZMQ queue."""
+        msg = self.session.recv(self._notification_socket, mode=zmq.NOBLOCK)
         while msg is not None:
             if self.debug:
                 pprint(msg)
             msg = msg[-1]
             msg_type = msg['msg_type']
             handler = self._notification_handlers.get(msg_type, None)
             if handler is None:
                 raise Exception("Unhandled message type: %s"%msg.msg_type)
             else:
                 handler(msg)
-            msg = self.session.recv(self.notification_socket, mode=zmq.NOBLOCK)
+            msg = self.session.recv(self._notification_socket, mode=zmq.NOBLOCK)
     
     def _flush_results(self, sock):
-        "flush incoming task or queue results"
+        """Flush task or queue results waiting in ZMQ queue."""
         msg = self.session.recv(sock, mode=zmq.NOBLOCK)
         while msg is not None:
             if self.debug:
                 pprint(msg)
             msg = msg[-1]
             msg_type = msg['msg_type']
             handler = self._queue_handlers.get(msg_type, None)
             if handler is None:
                 raise Exception("Unhandled message type: %s"%msg.msg_type)
             else:
                 handler(msg)
             msg = self.session.recv(sock, mode=zmq.NOBLOCK)
     
     def _flush_control(self, sock):
-        "flush incoming control replies"
+        """Flush replies from the control channel waiting
+        in the ZMQ queue."""
         msg = self.session.recv(sock, mode=zmq.NOBLOCK)
         while msg is not None:
             if self.debug:
                 pprint(msg)
             msg = self.session.recv(sock, mode=zmq.NOBLOCK)
     
-    ###### get/setitem ########
+    #--------------------------------------------------------------------------
+    # getitem
+    #--------------------------------------------------------------------------
     
     def __getitem__(self, key):
+        """Dict access returns DirectView multiplexer objects."""
         if isinstance(key, int):
             if key not in self.ids:
                 raise IndexError("No such engine: %i"%key)
             return DirectView(self, key)
         
         if isinstance(key, slice):
             indices = range(len(self.ids))[key]
             ids = sorted(self._ids)
             key = [ ids[i] for i in indices ]
             # newkeys = sorted(self._ids)[thekeys[k]]
         
         if isinstance(key, (tuple, list, xrange)):
             _,targets = self._build_targets(list(key))
             return DirectView(self, targets)
         else:
             raise TypeError("key by int/iterable of ints only, not %s"%(type(key)))
     
-    ############ begin real methods #############
+    #--------------------------------------------------------------------------
+    # Begin public methods
+    #--------------------------------------------------------------------------
     
     def spin(self):
-        """flush incoming notifications and execution results."""
-        if self.notification_socket:
+        """Flush any registration notifications and execution results
+        waiting in the ZMQ queue.
+        """
+        if self._notification_socket:
             self._flush_notifications()
-        if self.queue_socket:
-            self._flush_results(self.queue_socket)
-        if self.task_socket:
-            self._flush_results(self.task_socket)
-        if self.control_socket:
-            self._flush_control(self.control_socket)
+        if self._mux_socket:
+            self._flush_results(self._mux_socket)
+        if self._task_socket:
+            self._flush_results(self._task_socket)
+        if self._control_socket:
+            self._flush_control(self._control_socket)
     
-    @spinfirst
-    def queue_status(self, targets=None, verbose=False):
-        """fetch the status of engine queues
+    def barrier(self, msg_ids=None, timeout=-1):
+        """waits on one or more `msg_ids`, for up to `timeout` seconds.
         
         Parameters
         ----------
-        targets : int/str/list of ints/strs
-                the engines on which to execute
-                default : all
-        verbose : bool
-                whether to return lengths only, or lists of ids for each element
-                
-        """
-        targets = self._build_targets(targets)[1]
-        content = dict(targets=targets)
-        self.session.send(self.query_socket, "queue_request", content=content)
-        idents,msg = self.session.recv(self.query_socket, 0)
-        if self.debug:
-            pprint(msg)
-        return msg['content']
+        msg_ids : int, str, or list of ints and/or strs
+                ints are indices to self.history
+                strs are msg_ids
+                default: wait on all outstanding messages
+        timeout : float
+                a time in seconds, after which to give up.
+                default is -1, which means no timeout
         
+        Returns
+        -------
+        True : when all msg_ids are done
+        False : timeout reached, some msg_ids still outstanding
+        """
+        tic = time.time()
+        if msg_ids is None:
+            theids = self.outstanding
+        else:
+            if isinstance(msg_ids, (int, str)):
+                msg_ids = [msg_ids]
+            theids = set()
+            for msg_id in msg_ids:
+                if isinstance(msg_id, int):
+                    msg_id = self.history[msg_id]
+                theids.add(msg_id)
+        self.spin()
+        while theids.intersection(self.outstanding):
+            if timeout >= 0 and ( time.time()-tic ) > timeout:
+                break
+            time.sleep(1e-3)
+            self.spin()
+        return len(theids.intersection(self.outstanding)) == 0
+    
+    #--------------------------------------------------------------------------
+    # Control methods
+    #--------------------------------------------------------------------------
+    
     @spinfirst
     @defaultblock
     def clear(self, targets=None, block=None):
-        """clear the namespace in target(s)"""
+        """Clear the namespace in target(s)."""
         targets = self._build_targets(targets)[0]
         for t in targets:
-            self.session.send(self.control_socket, 'clear_request', content={},ident=t)
+            self.session.send(self._control_socket, 'clear_request', content={},ident=t)
         error = False
         if self.block:
             for i in range(len(targets)):
-                idents,msg = self.session.recv(self.control_socket,0)
+                idents,msg = self.session.recv(self._control_socket,0)
                 if self.debug:
                     pprint(msg)
                 if msg['content']['status'] != 'ok':
                     error = msg['content']
         if error:
             return error
         
     
     @spinfirst
     @defaultblock
     def abort(self, msg_ids = None, targets=None, block=None):
-        """abort the Queues of target(s)"""
+        """Abort the execution queues of target(s)."""
         targets = self._build_targets(targets)[0]
         if isinstance(msg_ids, basestring):
             msg_ids = [msg_ids]
         content = dict(msg_ids=msg_ids)
         for t in targets:
-            self.session.send(self.control_socket, 'abort_request', 
+            self.session.send(self._control_socket, 'abort_request', 
                     content=content, ident=t)
         error = False
         if self.block:
             for i in range(len(targets)):
-                idents,msg = self.session.recv(self.control_socket,0)
+                idents,msg = self.session.recv(self._control_socket,0)
                 if self.debug:
                     pprint(msg)
                 if msg['content']['status'] != 'ok':
                     error = msg['content']
         if error:
             return error
     
     @spinfirst
     @defaultblock
     def kill(self, targets=None, block=None):
         """Terminates one or more engine processes."""
         targets = self._build_targets(targets)[0]
         for t in targets:
-            self.session.send(self.control_socket, 'kill_request', content={},ident=t)
+            self.session.send(self._control_socket, 'kill_request', content={},ident=t)
         error = False
         if self.block:
             for i in range(len(targets)):
-                idents,msg = self.session.recv(self.control_socket,0)
+                idents,msg = self.session.recv(self._control_socket,0)
                 if self.debug:
                     pprint(msg)
                 if msg['content']['status'] != 'ok':
                     error = msg['content']
         if error:
             return error
-        
+    
+    #--------------------------------------------------------------------------
+    # Execution methods
+    #--------------------------------------------------------------------------
+    
     @defaultblock
     def execute(self, code, targets='all', block=None):
-        """executes `code` on `targets` in blocking or nonblocking manner.
+        """Executes `code` on `targets` in blocking or nonblocking manner.
         
         Parameters
         ----------
         code : str
                 the code string to be executed
         targets : int/str/list of ints/strs
                 the engines on which to execute
                 default : all
         block : bool
-                whether or not to wait until done
+                whether or not to wait until done to return
+                default: self.block
         """
         # block = self.block if block is None else block
         # saveblock = self.block
         # self.block = block
         result = self.apply(execute, (code,), targets=targets, block=block, bound=True)
         # self.block = saveblock
         return result
     
     def run(self, code, block=None):
-        """runs `code` on an engine. 
+        """Runs `code` on an engine. 
         
         Calls to this are load-balanced.
         
         Parameters
         ----------
         code : str
                 the code string to be executed
         block : bool
                 whether or not to wait until done
         
         """
         result = self.apply(execute, (code,), targets=None, block=block, bound=False)
         return result
     
+    def apply(self, f, args=None, kwargs=None, bound=True, block=None, targets=None,
+                        after=None, follow=None):
+        """Call `f(*args, **kwargs)` on a remote engine(s), returning the result.
+        
+        This is the central execution command for the client.
+        
+        Parameters
+        ----------
+        
+        f : function
+            The fuction to be called remotely
+        args : tuple/list
+            The positional arguments passed to `f`
+        kwargs : dict
+            The keyword arguments passed to `f`
+        bound : bool (default: True)
+            Whether to execute in the Engine(s) namespace, or in a clean
+            namespace not affecting the engine.
+        block : bool (default: self.block)
+            Whether to wait for the result, or return immediately.
+            False:
+                returns msg_id(s)
+                if multiple targets:
+                    list of ids
+            True:
+                returns actual result(s) of f(*args, **kwargs)
+                if multiple targets:
+                    dict of results, by engine ID
+        targets : int,list of ints, 'all', None
+            Specify the destination of the job.
+            if None:
+                Submit via Task queue for load-balancing.
+            if 'all':
+                Run on all active engines
+            if list:
+                Run on each specified engine
+            if int:
+                Run on single engine
+            
+        after : Dependency or collection of msg_ids
+            Only for load-balanced execution (targets=None)
+            Specify a list of msg_ids as a time-based dependency.
+            This job will only be run *after* the dependencies
+            have been met.
+            
+        follow : Dependency or collection of msg_ids
+            Only for load-balanced execution (targets=None)
+            Specify a list of msg_ids as a location-based dependency.
+            This job will only be run on an engine where this dependency
+            is met.
+        
+        Returns
+        -------
+        if block is False:
+            if single target:
+                return msg_id
+            else:
+                return list of msg_ids
+                ? (should this be dict like block=True) ?
+        else:
+            if single target:
+                return result of f(*args, **kwargs)
+            else:
+                return dict of results, keyed by engine
+        """
+        
+        # defaults:
+        block = block if block is not None else self.block
+        args = args if args is not None else []
+        kwargs = kwargs if kwargs is not None else {}
+        
+        # enforce types of f,args,kwrags
+        if not callable(f):
+            raise TypeError("f must be callable, not %s"%type(f))
+        if not isinstance(args, (tuple, list)):
+            raise TypeError("args must be tuple or list, not %s"%type(args))
+        if not isinstance(kwargs, dict):
+            raise TypeError("kwargs must be dict, not %s"%type(kwargs))
+            
+        options  = dict(bound=bound, block=block, after=after, follow=follow)
+            
+        if targets is None:
+            return self._apply_balanced(f, args, kwargs, **options)
+        else:
+            return self._apply_direct(f, args, kwargs, targets=targets, **options)
+    
     def _apply_balanced(self, f, args, kwargs, bound=True, block=None,
                             after=None, follow=None):
-        """the underlying method for applying functions in a load balanced
-        manner."""
-        block = block if block is not None else self.block
+        """The underlying method for applying functions in a load balanced
+        manner, via the task queue."""
         if isinstance(after, Dependency):
             after = after.as_dict()
         elif after is None:
             after = []
         if isinstance(follow, Dependency):
             follow = follow.as_dict()
         elif follow is None:
             follow = []
         subheader = dict(after=after, follow=follow)
         
         bufs = ss.pack_apply_message(f,args,kwargs)
         content = dict(bound=bound)
-        msg = self.session.send(self.task_socket, "apply_request", 
+        msg = self.session.send(self._task_socket, "apply_request", 
                 content=content, buffers=bufs, subheader=subheader)
         msg_id = msg['msg_id']
         self.outstanding.add(msg_id)
         self.history.append(msg_id)
         if block:
             self.barrier(msg_id)
             return self.results[msg_id]
         else:
             return msg_id
     
     def _apply_direct(self, f, args, kwargs, bound=True, block=None, targets=None,
                                 after=None, follow=None):
-        """Then underlying method for applying functions to specific engines."""
-        
-        block = block if block is not None else self.block
+        """Then underlying method for applying functions to specific engines
+        via the MUX queue."""
         
         queues,targets = self._build_targets(targets)
         bufs = ss.pack_apply_message(f,args,kwargs)
         if isinstance(after, Dependency):
             after = after.as_dict()
         elif after is None:
             after = []
         if isinstance(follow, Dependency):
             follow = follow.as_dict()
         elif follow is None:
             follow = []
         subheader = dict(after=after, follow=follow)
         content = dict(bound=bound)
         msg_ids = []
         for queue in queues:
-            msg = self.session.send(self.queue_socket, "apply_request", 
+            msg = self.session.send(self._mux_socket, "apply_request", 
                     content=content, buffers=bufs,ident=queue, subheader=subheader)
             msg_id = msg['msg_id']
             self.outstanding.add(msg_id)
             self.history.append(msg_id)
             msg_ids.append(msg_id)
         if block:
             self.barrier(msg_ids)
         else:
             if len(msg_ids) == 1:
                 return msg_ids[0]
             else:
                 return msg_ids
         if len(msg_ids) == 1:
             return self.results[msg_ids[0]]
         else:
             result = {}
             for target,mid in zip(targets, msg_ids):
                     result[target] = self.results[mid]
             return result
     
-    def apply(self, f, args=None, kwargs=None, bound=True, block=None, targets=None,
-                        after=None, follow=None):
-        """calls f(*args, **kwargs) on a remote engine(s), returning the result.
-        
-        if self.block is False:
-            returns msg_id or list of msg_ids
-        else:
-            returns actual result of f(*args, **kwargs)
-        """
-        # enforce types of f,args,kwrags
-        args = args if args is not None else []
-        kwargs = kwargs if kwargs is not None else {}
-        if not callable(f):
-            raise TypeError("f must be callable, not %s"%type(f))
-        if not isinstance(args, (tuple, list)):
-            raise TypeError("args must be tuple or list, not %s"%type(args))
-        if not isinstance(kwargs, dict):
-            raise TypeError("kwargs must be dict, not %s"%type(kwargs))
-            
-        options  = dict(bound=bound, block=block, after=after, follow=follow)
-            
-        if targets is None:
-            return self._apply_balanced(f, args, kwargs, **options)
-        else:
-            return self._apply_direct(f, args, kwargs, targets=targets, **options)
+    #--------------------------------------------------------------------------
+    # Data movement
+    #--------------------------------------------------------------------------
     
+    @defaultblock
     def push(self, ns, targets=None, block=None):
-        """push the contents of `ns` into the namespace on `target`"""
+        """Push the contents of `ns` into the namespace on `target`"""
         if not isinstance(ns, dict):
             raise TypeError("Must be a dict, not %s"%type(ns))
-        result = self.apply(_push, (ns,), targets=targets, block=block,bound=True)
+        result = self.apply(_push, (ns,), targets=targets, block=block, bound=True)
         return result
     
-    @spinfirst
+    @defaultblock
     def pull(self, keys, targets=None, block=True):
-        """pull objects from `target`'s namespace by `keys`"""
-        
+        """Pull objects from `target`'s namespace by `keys`"""
+        if isinstance(keys, str):
+            pass
+        elif isistance(keys, (list,tuple,set)):
+            for key in keys:
+                if not isinstance(key, str):
+                    raise TypeError
         result = self.apply(_pull, (keys,), targets=targets, block=block, bound=True)
         return result
     
-    def barrier(self, msg_ids=None, timeout=-1):
-        """waits on one or more `msg_ids`, for up to `timeout` seconds.
+    #--------------------------------------------------------------------------
+    # Query methods
+    #--------------------------------------------------------------------------
+    
+    @spinfirst
+    def get_results(self, msg_ids, status_only=False):
+        """Returns the result of the execute or task request with `msg_ids`.
         
         Parameters
         ----------
-        msg_ids : int, str, or list of ints and/or strs
-                ints are indices to self.history
-                strs are msg_ids
-                default: wait on all outstanding messages
-        timeout : float
-                a time in seconds, after which to give up.
-                default is -1, which means no timeout
-        
-        Returns
-        -------
-        True : when all msg_ids are done
-        False : timeout reached, msg_ids still outstanding
+        msg_ids : list of ints or msg_ids
+            if int:
+                Passed as index to self.history for convenience.
+        status_only : bool (default: False)
+            if False:
+                return the actual results
         """
-        tic = time.time()
-        if msg_ids is None:
-            theids = self.outstanding
-        else:
-            if isinstance(msg_ids, (int, str)):
-                msg_ids = [msg_ids]
-            theids = set()
-            for msg_id in msg_ids:
-                if isinstance(msg_id, int):
-                    msg_id = self.history[msg_id]
-                theids.add(msg_id)
-        self.spin()
-        while theids.intersection(self.outstanding):
-            if timeout >= 0 and ( time.time()-tic ) > timeout:
-                break
-            time.sleep(1e-3)
-            self.spin()
-        return len(theids.intersection(self.outstanding)) == 0
-    
-    @spinfirst
-    def get_results(self, msg_ids,status_only=False):
-        """returns the result of the execute or task request with `msg_id`"""
         if not isinstance(msg_ids, (list,tuple)):
             msg_ids = [msg_ids]
         theids = []
         for msg_id in msg_ids:
             if isinstance(msg_id, int):
                 msg_id = self.history[msg_id]
+            if not isinstance(msg_id, str):
+                raise TypeError("msg_ids must be str, not %r"%msg_id)
             theids.append(msg_id)
         
-        content = dict(msg_ids=theids, status_only=status_only)
-        msg = self.session.send(self.query_socket, "result_request", content=content)
-        zmq.select([self.query_socket], [], [])
-        idents,msg = self.session.recv(self.query_socket, zmq.NOBLOCK)
+        completed = []
+        local_results = {}
+        for msg_id in list(theids):
+            if msg_id in self.results:
+                completed.append(msg_id)
+                local_results[msg_id] = self.results[msg_id]
+                theids.remove(msg_id)
+        
+        if msg_ids: # some not locally cached
+            content = dict(msg_ids=theids, status_only=status_only)
+            msg = self.session.send(self._query_socket, "result_request", content=content)
+            zmq.select([self._query_socket], [], [])
+            idents,msg = self.session.recv(self._query_socket, zmq.NOBLOCK)
+            if self.debug:
+                pprint(msg)
+            content = msg['content']
+            if content['status'] != 'ok':
+                raise ss.unwrap_exception(content)
+        else:
+            content = dict(completed=[],pending=[])
+        if not status_only:
+            # load cached results into result:
+            content['completed'].extend(completed)
+            content.update(local_results)
+            # update cache with results:
+            for msg_id in msg_ids:
+                if msg_id in content['completed']:
+                    self.results[msg_id] = content[msg_id]
+        return content
+
+    @spinfirst
+    def queue_status(self, targets=None, verbose=False):
+        """Fetch the status of engine queues.
+        
+        Parameters
+        ----------
+        targets : int/str/list of ints/strs
+                the engines on which to execute
+                default : all
+        verbose : bool
+                whether to return lengths only, or lists of ids for each element
+        """
+        targets = self._build_targets(targets)[1]
+        content = dict(targets=targets, verbose=verbose)
+        self.session.send(self._query_socket, "queue_request", content=content)
+        idents,msg = self.session.recv(self._query_socket, 0)
         if self.debug:
             pprint(msg)
+        content = msg['content']
+        status = content.pop('status')
+        if status != 'ok':
+            raise ss.unwrap_exception(content)
+        return content
+        
+    @spinfirst
+    def purge_results(self, msg_ids=[], targets=[]):
+        """Tell the controller to forget results.
         
-        # while True:
-        #     try:
-        #     except zmq.ZMQError:
-        #         time.sleep(1e-3)
-        #         continue
-        #     else:
-        #         break
-        return msg['content']
+        Individual results can be purged by msg_id, or the entire
+        history of specific targets can 
+        
+        Parameters
+        ----------
+        targets : int/str/list of ints/strs
+                the targets
+                default : None
+        """
+        if not targets and not msg_ids:
+            raise ValueError
+        if targets:
+            targets = self._build_targets(targets)[1]
+        content = dict(targets=targets, msg_ids=msg_ids)
+        self.session.send(self._query_socket, "purge_request", content=content)
+        idents, msg = self.session.recv(self._query_socket, 0)
+        if self.debug:
+            pprint(msg)
+        content = msg['content']
+        if content['status'] != 'ok':
+            raise ss.unwrap_exception(content)
 
 class AsynClient(Client):
-    """An Asynchronous client, using the Tornado Event Loop"""
+    """An Asynchronous client, using the Tornado Event Loop.
+    !!!unfinished!!!"""
     io_loop = None
-    queue_stream = None
-    notifier_stream = None
+    _queue_stream = None
+    _notifier_stream = None
+    _task_stream = None
+    _control_stream = None
     
     def __init__(self, addr, context=None, username=None, debug=False, io_loop=None):
         Client.__init__(self, addr, context, username, debug)
         if io_loop is None:
             io_loop = ioloop.IOLoop.instance()
         self.io_loop = io_loop
         
-        self.queue_stream = zmqstream.ZMQStream(self.queue_socket, io_loop)
-        self.control_stream = zmqstream.ZMQStream(self.control_socket, io_loop)
-        self.task_stream = zmqstream.ZMQStream(self.task_socket, io_loop)
-        self.notification_stream = zmqstream.ZMQStream(self.notification_socket, io_loop)
+        self._queue_stream = zmqstream.ZMQStream(self._mux_socket, io_loop)
+        self._control_stream = zmqstream.ZMQStream(self._control_socket, io_loop)
+        self._task_stream = zmqstream.ZMQStream(self._task_socket, io_loop)
+        self._notification_stream = zmqstream.ZMQStream(self._notification_socket, io_loop)
     
     def spin(self):
         for stream in (self.queue_stream, self.notifier_stream, 
                         self.task_stream, self.control_stream):
             stream.flush()
     
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