add message_id in log to keep track of an email processing

app/log.py

@@ -9,9 +9,30 @@ from app.config import (
 )
 
 # this format allows clickable link to code source in PyCharm
-_log_format = '%(asctime)s - %(name)s - %(levelname)s - "%(pathname)s:%(lineno)d" - %(funcName)s() - %(message)s'
+_log_format = '%(asctime)s - %(name)s - %(levelname)s - "%(pathname)s:%(lineno)d" - %(funcName)s() - %(message_id)s - %(message)s'
 _log_formatter = logging.Formatter(_log_format)
 
+# used to keep track of an email lifecycle
+_MESSAGE_ID = None
+
+
+def set_message_id(message_id):
+    global _MESSAGE_ID
+    print("set message_id", message_id)
+    _MESSAGE_ID = message_id
+
+
+class EmailHandlerFilter(logging.Filter):
+    """automatically add message-id to keep track of an email processing"""
+
+    def filter(self, record):
+        message_id = self.get_message_id()
+        record.message_id = message_id if message_id else ""
+        return True
+
+    def get_message_id(self):
+        return _MESSAGE_ID
+
 
 def _get_console_handler():
     console_handler = logging.StreamHandler(sys.stdout)
@@ -29,6 +50,8 @@ def _get_logger(name):
     # leave the handlers level at NOTSET so the level checking is only handled by the logger
     logger.addHandler(_get_console_handler())
 
+    logger.addFilter(EmailHandlerFilter())
+
     # no propagation to avoid propagating to root logger
     logger.propagate = False
 

email_handler.py

@@ -114,7 +114,7 @@ from app.email_utils import (
 )
 from app.extensions import db
 from app.greylisting import greylisting_needed
-from app.log import LOG
+from app.log import LOG, set_message_id
 from app.models import (
     Alias,
     Contact,
@@ -1779,6 +1779,9 @@ class MailHandler:
             envelope.rcpt_tos,
         )
 
+        # generate a different message_id to keep track of an email lifecycle
+        set_message_id(str(uuid.uuid4()))
+
         app = new_app()
         with app.app_context():
             ret = handle(envelope)