add Client.spin_thread()

runs Client.spin() in a background thread at a set interval

IPython/parallel/client/client.py

@@ -18,6 +18,7 b' Authors:'
 import os
 import json
 import sys
+from threading import Thread, Event
 import time
 import warnings
 from datetime import datetime
@@ -36,7 +37,7 b' from IPython.utils.jsonutil import rekey'
 from IPython.utils.localinterfaces import LOCAL_IPS
 from IPython.utils.path import get_ipython_dir
 from IPython.utils.traitlets import (HasTraits, Integer, Instance, Unicode,
-                                    Dict, List, Bool, Set)
+                                    Dict, List, Bool, Set, Any)
 from IPython.external.decorator import decorator
 from IPython.external.ssh import tunnel
 
@@ -249,6 +250,8 b' class Client(HasTraits):'
     metadata = Instance('collections.defaultdict', (Metadata,))
     history = List()
     debug = Bool(False)
+    _spin_thread = Any()
+    _stop_spinning = Any()
 
     profile=Unicode()
     def _profile_default(self):
@@ -299,6 +302,7 b' class Client(HasTraits):'
         if context is None:
             context = zmq.Context.instance()
         self._context = context
+        self._stop_spinning = Event()
 
         self._setup_profile_dir(self.profile, profile_dir, ipython_dir)
         if self._cd is not None:
@@ -785,12 +789,59 b' class Client(HasTraits):'
     def close(self):
         if self._closed:
             return
+        self.stop_spin_thread()
         snames = filter(lambda n: n.endswith('socket'), dir(self))
         for socket in map(lambda name: getattr(self, name), snames):
             if isinstance(socket, zmq.Socket) and not socket.closed:
                 socket.close()
         self._closed = True
 
+    def _spin_every(self, interval=1):
+        """target func for use in spin_thread"""
+        while True:
+            if self._stop_spinning.is_set():
+                return
+            time.sleep(interval)
+            self.spin()
+
+    def spin_thread(self, interval=1):
+        """call Client.spin() in a background thread on some regular interval
+        
+        This helps ensure that messages don't pile up too much in the zmq queue
+        while you are working on other things, or just leaving an idle terminal.
+        
+        It also helps limit potential padding of the `received` timestamp
+        on AsyncResult objects, used for timings.
+        
+        Parameters
+        ----------
+        
+        interval : float, optional
+            The interval on which to spin the client in the background thread
+            (simply passed to time.sleep).
+        
+        Notes
+        -----
+        
+        For precision timing, you may want to use this method to put a bound
+        on the jitter (in seconds) in `received` timestamps used
+        in AsyncResult.wall_time.
+        
+        """
+        if self._spin_thread is not None:
+            self.stop_spin_thread()
+        self._stop_spinning.clear()
+        self._spin_thread = Thread(target=self._spin_every, args=(interval,))
+        self._spin_thread.daemon = True
+        self._spin_thread.start()
+    
+    def stop_spin_thread(self):
+        """stop background spin_thread, if any"""
+        if self._spin_thread is not None:
+            self._stop_spinning.set()
+            self._spin_thread.join()
+            self._spin_thread = None
+
     def spin(self):
         """Flush any registration notifications and execution results
         waiting in the ZMQ queue.

IPython/parallel/tests/test_client.py

@@ -316,4 +316,22 b' class TestClient(ClusterTestCase):'
         self.client.purge_results('all')
         hist = self.client.hub_history()
         self.assertEquals(len(hist), 0)
+    
+    def test_spin_thread(self):
+        self.client.spin_thread(0.01)
+        ar = self.client[-1].apply_async(lambda : 1)
+        time.sleep(0.1)
+        self.assertTrue(ar.wall_time < 0.1,
+            "spin should have kept wall_time < 0.1, but got %f" % ar.wall_time
+        )
+    
+    def test_stop_spin_thread(self):
+        self.client.spin_thread(0.01)
+        self.client.stop_spin_thread()
+        ar = self.client[-1].apply_async(lambda : 1)
+        time.sleep(0.15)
+        self.assertTrue(ar.wall_time > 0.1,
+            "Shouldn't be spinning, but got wall_time=%f" % ar.wall_time
+        )
+