Handle worker errors and send an error response

* Also adds new `code` field to InnerEnvelope to allow the setting
  of a status code for responses.

Author: jimi-c

receptor/messages/envelope.py

@@ -37,8 +37,8 @@ def serialize(self):
 
 class InnerEnvelope:
     def __init__(self, receptor, message_id, sender, recipient, message_type, timestamp,
-                 raw_payload, directive=None, in_response_to=None, ttl=None,
-                 serial=1, expire_time_delta=300):
+                 raw_payload, directive=None, in_response_to=None, ttl=None, serial=1,
+                 code=0, expire_time_delta=300):
         self.receptor = receptor
         self.message_id = message_id
         self.sender = sender
@@ -53,6 +53,7 @@ def __init__(self, receptor, message_id, sender, recipient, message_type, timest
             self.expire_time = None
         self.expire_time = time.time() + expire_time_delta
         self.serial = serial # serial index of responses
+        self.code = code # optional code indicating an error
 
     @classmethod
     async def deserialize(cls, receptor, msg):
@@ -62,7 +63,7 @@ async def deserialize(cls, receptor, msg):
         return cls(receptor=receptor, **json.loads(payload))
 
     @classmethod
-    def make_response(cls, receptor, recipient, payload, in_response_to, serial, ttl=None):
+    def make_response(cls, receptor, recipient, payload, in_response_to, serial, ttl=None, code=0):
         if isinstance(payload, bytes):
             encoded_payload = base64.encodebytes(payload)
         else:
@@ -78,7 +79,8 @@ def make_response(cls, receptor, recipient, payload, in_response_to, serial, ttl
             directive=None,
             in_response_to=in_response_to,
             ttl=ttl,
-            serial=serial
+            serial=serial,
+            code=code,
         )
 
     def sign_and_serialize(self):

receptor/protocol.py

@@ -169,7 +169,8 @@ def connection_lost(self, exc):
     def emit_response(self, response):
         self.transport.write(json.dumps(dict(timestamp=response.timestamp,
                                              in_response_to=response.in_response_to,
-                                             payload=response.raw_payload)).encode())
+                                             payload=response.raw_payload,
+                                             code=response.code)).encode())
 
     def data_received(self, data):
         recipient, directive, payload = data.rstrip(DELIM).decode('utf8').split('\n', 2)
@@ -184,7 +185,7 @@ def data_received(self, data):
             message_type='directive',
             timestamp=sent_timestamp.isoformat(),
             raw_payload=payload,
-            directive=directive
+            directive=directive,
         )
         # TODO: Persistent registry?
         self.loop.create_task(self.receptor.router.send(inner_env,

receptor/security/__init__.py

@@ -25,6 +25,6 @@ async def sign_response(self, inner_envelope):
             {attr: getattr(inner_envelope, attr)
              for attr in ['message_id', 'sender', 'recipient', 'message_type',
                           'timestamp', 'raw_payload', 'directive',
-                          'in_response_to', 'ttl', 'serial']}
+                          'in_response_to', 'ttl', 'serial', 'code']}
         )
 

receptor/work.py

@@ -1,5 +1,5 @@
-import pkg_resources
 import logging
+import pkg_resources
 
 from . import exceptions
 from .messages import envelope
@@ -20,24 +20,37 @@ def load_receptor_worker(self, name):
     async def handle(self, inner_env):
         logger.info(f'Handling work for {inner_env.message_id} as {inner_env.directive}')
         namespace, action = inner_env.directive.split(':', 1)
-        worker_module = self.load_receptor_worker(namespace)
-        try:
-            action_method = getattr(worker_module, f'{action}')
-        except AttributeError:
-            logger.exception(f'Could not load action {action} from {namespace}')
-            raise exceptions.InvalidDirectiveAction(f'Invalid action {action} for {namespace}')
-        responses = action_method(inner_env)
         serial = 0
-        async for response in responses:
+        try:
+            worker_module = self.load_receptor_worker(namespace)
+            try:
+                action_method = getattr(worker_module, f'{action}')
+            except AttributeError:
+                logger.exception(f'Could not load action {action} from {namespace}')
+                raise exceptions.InvalidDirectiveAction(f'Invalid action {action} for {namespace}')
+
+            responses = action_method(inner_env)
+            async for response in responses:
+                serial += 1
+                logger.debug(f'Response emitted for {inner_env.message_id}, serial {serial}')
+                enveloped_response = envelope.InnerEnvelope.make_response(
+                    receptor=self.receptor,
+                    recipient=inner_env.sender,
+                    payload=response,
+                    in_response_to=inner_env.message_id,
+                    serial=serial
+                )
+                await self.receptor.router.send(enveloped_response)
+        except Exception as e:
             serial += 1
-            logger.debug(f'Response emitted for {inner_env.message_id}, serial {serial}')
+            logger.error(f'Error encountered while handling the response, replying with an error message ({e})')
             enveloped_response = envelope.InnerEnvelope.make_response(
                 receptor=self.receptor,
                 recipient=inner_env.sender,
-                payload=response,
+                payload=str(e),
                 in_response_to=inner_env.message_id,
-                serial=serial
+                serial=serial,
+                code=1,
             )
             await self.receptor.router.send(enveloped_response)
 
-