Improve MessageHandler resiliency

hippolyzer/lib/base/events.py

@@ -19,16 +19,17 @@ along with this program; if not, write to the Free Software Foundation,
 Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 """
 import asyncio
-from logging import getLogger
+import logging
 
-logger = getLogger('utilities.events')
+LOG = logging.getLogger(__name__)
 
 
 class Event:
     """ an object containing data which will be passed out to all subscribers """
 
-    def __init__(self):
+    def __init__(self, name=None):
         self.subscribers = []
+        self.name = name
 
     def subscribe(self, handler, *args, one_shot=False, predicate=None, **kwargs):
         """ establish the subscribers (handlers) to this event """
@@ -66,10 +67,19 @@ class Event:
                     unsubscribe = await handler(args, *inner_args, **kwargs)
                     if unsubscribe:
                         _ = self.unsubscribe(handler, *inner_args, **kwargs)
-                asyncio.create_task(_run_handler_wrapper())
+                task = asyncio.create_task(_run_handler_wrapper())
+                task.add_done_callback(self._log_task_failures)
             else:
-                if handler(args, *inner_args, **kwargs) and not one_shot:
-                    self.unsubscribe(handler, *inner_args, **kwargs)
+                try:
+                    if handler(args, *inner_args, **kwargs) and not one_shot:
+                        self.unsubscribe(handler, *inner_args, **kwargs)
+                except:
+                    # One handler failing shouldn't prevent notification of other handlers.
+                    LOG.exception(f"Failed in handler for {self.name}")
+
+    def _log_task_failures(self, task: asyncio.Task):
+        if task.exception():
+            LOG.exception(f"Failed in handler for {self.name}", exc_info=task.exception())
 
     def __len__(self):
         return len(self.subscribers)

hippolyzer/lib/base/message/message.py

@@ -75,8 +75,8 @@ class Block:
         for var_name, val in kwargs.items():
             self[var_name] = val
 
-    def get_variable(self, var_name):
-        return self.vars.get(var_name)
+    def get(self, var_name, default: Optional[VAR_TYPE] = None) -> Optional[VAR_TYPE]:
+        return self.vars.get(var_name, default)
 
     def __contains__(self, item):
         return item in self.vars

hippolyzer/lib/base/message/message_handler.py

@@ -31,7 +31,7 @@ _T = TypeVar("_T")
 _K = TypeVar("_K", bound=Hashable)
 MESSAGE_HANDLER = Callable[[_T], Any]
 PREDICATE = Callable[[_T], bool]
-# TODO: Can't do `Iterable[Union[_K, Literal["*"]]` apparently?
+# TODO: Can't do `Iterable[Union[_K, Literal["*"]]]` apparently?
 MESSAGE_NAMES = Iterable[Union[_K, str]]
 
 
@@ -42,7 +42,7 @@ class MessageHandler(Generic[_T, _K]):
 
     def register(self, message_name: _K) -> Event:
         LOG.debug('Creating a monitor for %s' % message_name)
-        return self.handlers.setdefault(message_name, Event())
+        return self.handlers.setdefault(message_name, Event(message_name))
 
     def subscribe(self, message_name: Union[_K, Literal["*"]], handler: MESSAGE_HANDLER):
         notifier = self.register(message_name)

hippolyzer/lib/base/message/template.py

@@ -37,7 +37,7 @@ class MessageTemplateVariable:
         return f"{self.__class__.__name__}(name={self.name!r}, tp={self.type!r}, size={self.size!r})"
 
     @property
-    def probably_binary(self):
+    def probably_binary(self) -> bool:
         if self._probably_binary is not None:
             return self._probably_binary
 
@@ -49,7 +49,7 @@ class MessageTemplateVariable:
         return self._probably_binary
 
     @property
-    def probably_text(self):
+    def probably_text(self) -> bool:
         if self._probably_text is not None:
             return self._probably_text
 
@@ -97,11 +97,11 @@ class MessageTemplateBlock:
         self.block_type: MsgBlockType = MsgBlockType.MBT_SINGLE
         self.number = 0
 
-    def add_variable(self, var):
+    def add_variable(self, var: MessageTemplateVariable):
         self.variable_map[var.name] = var
         self.variables.append(var)
 
-    def get_variable(self, name):
+    def get_variable(self, name) -> MessageTemplateVariable:
         return self.variable_map[name]
 
 
@@ -119,11 +119,11 @@ class MessageTemplate:
         self.deprecation = None
         self.encoding = None
 
-    def add_block(self, block):
+    def add_block(self, block: MessageTemplateBlock):
         self.block_map[block.name] = block
         self.blocks.append(block)
 
-    def get_block(self, name):
+    def get_block(self, name) -> MessageTemplateBlock:
         return self.block_map[name]
 
     def get_msg_freq_num_len(self):

hippolyzer/lib/base/message/template_dict.py

@@ -43,7 +43,7 @@ class TemplateDictionary:
 
         self.template_list: typing.List[MessageTemplate] = []
         # maps name to template
-        self.message_templates = {}
+        self.message_templates: typing.Dict[str, MessageTemplate] = {}
 
         # maps (freq,num) to template
         self.message_dict = {}