From 624d8c5dc586edae9cff4a18c943b86d01b0a37c 2013-04-24 04:47:43
From: Brian E. Granger <ellisonbg@gmail.com>
Date: 2013-04-24 04:47:43
Subject: [PATCH] Adding KerelRestarter.

---

diff --git a/IPython/kernel/kernelrestarter.py b/IPython/kernel/kernelrestarter.py
new file mode 100644
index 0000000..66c377c
--- /dev/null
+++ b/IPython/kernel/kernelrestarter.py
@@ -0,0 +1,62 @@
+"""A basic in process kernel monitor with autorestarting.
+
+This watches a kernel's state using KernelManager.is_alive and auto
+restarts the kernel if it dies.
+"""
+
+#-----------------------------------------------------------------------------
+#  Copyright (C) 2013  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
+#-----------------------------------------------------------------------------
+
+import zmq
+from zmq.eventloop import ioloop
+
+
+from IPython.config.configurable import LoggingConfigurable
+from IPython.utils.traitlets import (
+    Instance, Float
+)
+
+#-----------------------------------------------------------------------------
+# Code
+#-----------------------------------------------------------------------------
+
+class KernelRestarter(LoggingConfigurable):
+    """Monitor and autorestart a kernel."""
+
+    loop = Instance('zmq.eventloop.ioloop.IOLoop', allow_none=False)
+    def _loop_default(self):
+        return ioloop.IOLoop.instance()
+
+    kernel_manager = Instance('IPython.kernel.kernelmanager.KernelManager')
+
+    time_to_dead = Float(3.0, config=True,
+        help="""Kernel heartbeat interval in seconds."""
+    )
+
+    def __init__(self, **kwargs):
+        super(KernelRestarter, self).__init__(**kwargs)
+
+    def start(self):
+        self.pc = ioloop.PeriodicCallback(self.poll, self.time_to_dead, self.ioloop)
+        self.pc.start()
+
+    def poll(self):
+        if not self.kernel_manager.is_alive():
+            self.stop()
+            # This restart event should leave the connection file in place so
+            # the ports are the same. Because this takes place below the
+            # MappingKernelManager, the kernel_id will also remain the same.
+            self.kernel_manager.restart_kernel(now=True);
+            self.start()
+
+    def stop(self):
+        self.pc.stop()
+        self.pc = None