Add support for stopping/starting ProcessLogHandler from API

tfw/components/process_management/process_log_handler.py

@@ -16,10 +16,13 @@ class ProcessLogHandler:
         self._initial_log_tail = log_tail
 
         self.command_handlers = {
-            'process.log.set': self.handle_set
+            'process.log.set': self.handle_set,
+            'process.log.start': self.handle_start,
+            'process.log.stop': self.handle_stop
         }
 
     def start(self):
+        if not self._monitor:
             self._monitor = LogInotifyObserver(
                 connector=self.connector,
                 process_name=self.process_name,
@@ -40,5 +43,16 @@ class ProcessLogHandler:
         if data.get('tail'):
             self._monitor.log_tail = data['tail']
 
-    def cleanup(self):
+    def handle_start(self, _):
+        self.start()
+
+    def handle_stop(self, _):
+        self._stop_monitor()
+
+    def _stop_monitor(self):
+        if self._monitor:
             self._monitor.stop()
+            self._monitor = None
+
+    def cleanup(self):
+        self._stop_monitor()

tfw/fsm/fsm_base.py

@@ -1,6 +1,7 @@
 import logging
 from collections import defaultdict
 from datetime import datetime
+from contextlib import suppress
 
 from transitions import Machine, MachineError
 
@@ -62,14 +63,12 @@ class FSMBase(Machine, CallbackMixin):
         )
 
         if all(predicate_results):
-            try:
+            with suppress(AttributeError, MachineError):
                 from_state = self.state
-                self.trigger(trigger)
+                if self.trigger(trigger):
                     self.update_event_log(from_state, trigger)
                     return True
-            except (AttributeError, MachineError):
             LOG.debug('FSM failed to execute nonexistent trigger: "%s"', trigger)
-        return False
 
     def update_event_log(self, from_state, trigger):
         self.event_log.append({