[feature] Add stdout/stderr streaming

This patch adds stdout/stderr streaming capabilities, based on partial
evaluation of a tornado.iostream callback. The bin/cmd CLI is updated to
wait until an exit message, although that doesn't guaranty anything on
message ordering...

The next step is obviously to figure out a message flow that allows the
CLI to send and receive the command IO properly, in order...

bin/cmd

@@ -75,8 +75,9 @@ class CommandLineInterface(object):
             # ignore other messages
             if isinstance(msg, dict) and msg.get('type') == 'container':
                 if msg['uuid'] == containerid:
-                    logger.info("container response: %r", msg)
-                    break
+                    logger.info("container msg: %r", msg)
+                    if msg['event'] == 'exit':
+                        break
 
     def do_list(self, argv):
         """Connect to the NRM and ask to list the containers present on the

nrm/daemon.py

@@ -2,6 +2,7 @@ from __future__ import print_function
 
 from containers import ContainerManager
 from resources import ResourceManager
+from functools import partial
 import json
 import logging
 import os
@@ -129,6 +130,13 @@ class Daemon(object):
                           'pid': process.pid,
                           }
                 self.upstream_pub.send_json(update)
+                # setup io callbacks
+                process.stdout.read_until_close(partial(self.do_children_io,
+                                                        msg['uuid'],
+                                                        'stdout'))
+                process.stderr.read_until_close(partial(self.do_children_io,
+                                                        msg['uuid'],
+                                                        'stderr'))
             elif command == 'kill':
                 logger.info("asked to kill container: %r", msg)
                 response = self.container_manager.kill(msg['uuid'])
@@ -144,6 +152,18 @@ class Daemon(object):
             else:
                 logger.error("invalid command: %r", command)
 
+    def do_children_io(self, uuid, io, data):
+        """Receive data from one of the children, and send it down the pipe.
+
+        Meant to be partially defined on a children basis."""
+        logger.info("%r received %r data: %r", uuid, io, data)
+        update = {'type': 'container',
+                  'event': io,
+                  'uuid': uuid,
+                  'payload': data or 'eof',
+                  }
+        self.upstream_pub.send_json(update)
+
     def do_sensor(self):
         self.machine_info = self.sensor.do_update()
         logger.info("current state: %r", self.machine_info)