Improving the shutdown protocol for managers

Shutting down a manager *process* was previously possible only through
signal handling, which correctly shut down the manager itself, and the
enclosing rest server that exposed it to the outside world. Now the
shutdown logic is managed entirely by the rest server, who shuts down
the manager and itself, and exposes this functionality via a REST API
call, giving the possibility to send requests for shutdown remotely. The
corresponding functionality has also been added to the REST client.

Yes, not ideal from the point of view of security, but we haven't put
attention to security at any point in time and this is no exception.

Signed-off-by: Rodrigo Tobar <rtobar@icrar.org>

dlg/manager/client.py

@@ -43,6 +43,9 @@ def _request(self, url, method, content=None, headers={}):
         url = '/api' + url
         return RestClient._request(self, url, method, content=content, headers=headers)
 
+    def stop(self):
+        self._POST('/stop')
+
     def cancelSession(self, sessionId):
         self._POST('/sessions/%s/cancel' % urllib.quote(sessionId))
 

dlg/manager/cmdline.py

@@ -66,18 +66,13 @@ def handle_signal(signNo, stack_frame):
         _terminating = True
         logger.info("Exiting from %s" % (dmName))
 
-        dm.shutdown()
-        server.stop()
-
+        server.stop_manager()
         logger.info("Thanks for using our %s, come back again :-)" % (dmName))
 
     signal.signal(signal.SIGINT, handle_signal)
     signal.signal(signal.SIGTERM, handle_signal)
 
-    server_t = threading.Thread(target=server.start, args=(opts.host, opts.port), name="HTTP server")
-    server_t.start()
-    # Now simply wait...
-    signal.pause()
+    server.start(opts.host, opts.port)
 
 
 def addCommonOptions(parser, defaultPort):

dlg/manager/rest.py

@@ -27,6 +27,7 @@
 import functools
 import json
 import logging
+import threading
 
 import bottle
 import pkg_resources
@@ -113,6 +114,7 @@ def __init__(self, dm, maxreqsize=10):
 
         # Mappings
         app = self.app
+        app.post(  '/api/stop',                              callback=self.stop_manager)
         app.post(  '/api/sessions',                          callback=self.createSession)
         app.get(   '/api/sessions',                          callback=self.getSessions)
         app.get(   '/api/sessions/<sessionId>',              callback=self.getSessionInformation)
@@ -139,6 +141,14 @@ def initializeSpecifics(self, app):
         The default implementation does nothing.
         """
 
+    def _stop_manager(self):
+        self.dm.shutdown()
+        self.stop()
+
+    @daliuge_aware
+    def stop_manager(self):
+        threading.Thread(target=self._stop_manager).start()
+
     @daliuge_aware
     def createSession(self):
         newSession = bottle.request.json