Explain how to cancel a distbuild

Cancelling a distbuild with ctrl+c no longer cancels the build
itself. This commit adds some output explaining what should be
done to cancel the build as well as the local process.

This commit also fixes a bug where the BuildStarted event would
be sent each time a chunk finished building, since it was being
sent in _queue_worker_builds. This is fixed by adding a new
function to be called when the build graph annotation is
complete which sends BuildStarted and then calls
_queue_worker_builds, which no longer sends the BuildStarted
event.

Change-Id: I26ddea2c9080887f449e87004411ddffe4e583b7

3 files changed, 33 insertions, 16 deletions

diff --git a/distbuild/build_controller.py b/distbuild/build_controller.py
index 3a099b82..9b934da6 100644
--- a/distbuild/build_controller.py
+++ b/distbuild/build_controller.py
@@ -252,7 +252,7 @@ class BuildController(distbuild.StateMachine):
                 'annotating', self._maybe_handle_cache_response),
             ('annotating', self, BuildFailed, None, None),
             ('annotating', self, _Annotated, 'building', 
-                self._queue_worker_builds),
+                self._start_building),
             ('annotating', distbuild.InitiatorConnection,
                 distbuild.CancelRequest, 'annotating',
                 self._maybe_notify_build_cancelled),
@@ -478,23 +478,32 @@ class BuildController(distbuild.StateMachine):
                                        self._components)
         return [a for a in artifacts if is_ready_to_build(a)]
 
-    def _queue_worker_builds(self, event_source, event):
-        distbuild.crash_point()
-
+    def _build_complete(self):
         if not self._components:
             if self._artifact.state == BUILT:
                 logging.info('Requested artifact is built')
                 self.mainloop.queue_event(self, _Built())
-                return
-
+                return True
         else:
             if not any(c.state != BUILT for c in self._components):
                 logging.info('Requested components are built')
                 self.mainloop.queue_event(self, _Built())
-                return
+                return True
+        return False
+
+    def _start_building(self, event_source, event):
+        if self._build_complete():
+            return
 
         self.mainloop.queue_event(BuildController,
                                   BuildStarted(self._request['id']))
+        self._queue_worker_builds(event_source, event)
+
+    def _queue_worker_builds(self, event_source, event):
+        distbuild.crash_point()
+
+        if self._build_complete():
+            return
 
         logging.debug('Queuing more worker-builds to run')
         if self.debug_graph_state:
diff --git a/distbuild/initiator.py b/distbuild/initiator.py
index 5fc74086..f1facdfe 100644
--- a/distbuild/initiator.py
+++ b/distbuild/initiator.py
@@ -75,6 +75,7 @@ class Initiator(distbuild.StateMachine):
         self._step_outputs = {}
         self.debug_transitions = False
         self.allow_detach = False
+        self.connection_id = None
 
         # The build-log output dir is set up in _open_output() when we
         # receive the first log message. Thus if we never get that far, we
@@ -126,7 +127,7 @@ class Initiator(distbuild.StateMachine):
         logging.debug('Initiator: from controller: %s' % repr(event.msg))
 
         handlers = {
-            'build-started': lambda msg: None,
+            'build-started': self._handle_build_started_message,
             'build-finished': self._handle_build_finished_message,
             'build-failed': self._handle_build_failed_message,
             'build-cancelled': self._handle_build_cancelled_message,
@@ -144,6 +145,15 @@ class Initiator(distbuild.StateMachine):
         handler = handlers[event.msg['type']]
         handler(event.msg)
 
+    def _handle_build_started_message(self, msg):
+        self._app.status(msg='Distbuild started with build request '
+                             'ID: %(id)s. To cancel, use `morph '
+                             'distbuild-cancel %(id)s`.',
+                         id=msg['id'])
+        if self.allow_detach:
+            self.mainloop.queue_event(self._cm, distbuild.StopConnecting())
+            self._jm.close()
+
     def _handle_build_finished_message(self, msg):
         self.mainloop.queue_event(self, _Finished(msg))
 
@@ -158,6 +168,7 @@ class Initiator(distbuild.StateMachine):
         self._app.status(msg='Progress: %(msgtext)s', msgtext=msg['message'])
 
     def _handle_graphing_started_message(self, msg):
+        self.connection_id = msg['id']
         self._app.status(msg='Computing build graph')
 
     def _handle_graphing_finished_message(self, msg):
@@ -323,14 +334,6 @@ class InitiatorStart(Initiator):
             handler = handlers[msg_type]
             handler(event.msg)
 
-    def _handle_build_started_message(self, msg):
-        self._app.status(msg='Detaching distbuild from controller (build'
-                             ' will continue on the distbuild network): '
-                             'build request ID: %s' % msg['id'])
-
-        self.mainloop.queue_event(self._cm, distbuild.StopConnecting())
-        self._jm.close()
-
 class InitiatorCancel(distbuild.StateMachine):
 
     def __init__(self, cm, conn, app, job_id):
diff --git a/morphlib/buildcommand.py b/morphlib/buildcommand.py
index 6a5373ab..c5d86a08 100644
--- a/morphlib/buildcommand.py
+++ b/morphlib/buildcommand.py
@@ -572,4 +572,9 @@ class InitiatorBuildCommand(BuildCommand):
             # Python exceptions.
             logging.info('Received KeyboardInterrupt, aborting.')
             for initiator in loop.state_machines_of_type(distbuild.Initiator):
+                connection_id = initiator.connection_id or 'ID'
+                self.app.status(msg='Stopping initiator process. To cancel '
+                                    'the build use `morph distbuild-cancel '
+                                    '%(initiator_connection)s`.',
+                                initiator_connection=connection_id)
                 initiator.handle_cancel()