Merge pull request #141 from minrk/manager-is-alive

Fix wait_for_ready() dying early for slow-starting kernels

Author: minrk

jupyter_client/blocking/client.py

@@ -34,6 +34,16 @@ def wait_for_ready(self, timeout=None):
         else:
             abs_timeout = time.time() + timeout
 
+        from ..manager import KernelManager
+        if not isinstance(self.parent, KernelManager):
+            # This Client was not created by a KernelManager,
+            # so wait for kernel to become responsive to heartbeats
+            # before checking for kernel_info reply
+            while not self.is_alive():
+                if time.time() > abs_timeout:
+                    raise RuntimeError("Kernel didn't respond to heartbeats in %d seconds and timed out" % timeout)
+                time.sleep(0.2)
+
         # Wait for kernel info reply on shell channel
         while True:
             try:

jupyter_client/client.py

@@ -181,9 +181,14 @@ def hb_channel(self):
 
     def is_alive(self):
         """Is the kernel process still running?"""
+        from .manager import KernelManager
+        if isinstance(self.parent, KernelManager):
+            # This KernelClient was created by a KernelManager,
+            # we can ask the parent KernelManager:
+            return self.parent.is_alive()
         if self._hb_channel is not None:
-            # We didn't start the kernel with this KernelManager so we
-            # use the heartbeat.
+            # We don't have access to the KernelManager,
+            # so we use the heartbeat.
             return self._hb_channel.is_beating()
         else:
             # no heartbeat and not local, we can't tell if it's running,

jupyter_client/tests/signalkernel.py

@@ -56,13 +56,15 @@ def kernel_info_request(self, *args, **kwargs):
         
         triggers slow-response code in KernelClient.wait_for_ready
         """
-        time.sleep(1)
         return super(SignalTestKernel, self).kernel_info_request(*args, **kwargs)
 
 class SignalTestApp(IPKernelApp):
     kernel_class = SignalTestKernel
     def init_io(self):
         pass # disable stdout/stderr capture
-    
+
 if __name__ == '__main__':
+    # make startup artificially slow,
+    # so that we exercise client logic for slow-starting kernels
+    time.sleep(2)
     SignalTestApp.launch_instance()