Attach the message associated with an error to KafkaException.

Append the name of the target topic to error messages when it may be relevant.
This latter feature uses a hard-coded list of error codes, which is not ideal, but seems tolerable, as this only affects the exception error message, is never technically wrong (since the error arose from a message being sent to the referenced topic), the full information is always available though the `error` and `message` subobjects, and the set of relevant errors changes infrequently.

Author: cnweaver

adc/errors.py

@@ -34,21 +34,69 @@ def log_delivery_errors(
 def raise_delivery_errors(kafka_error: confluent_kafka.KafkaError,
                           msg: confluent_kafka.Message) -> None:
     if kafka_error is not None:
-        raise KafkaException.from_kafka_error(kafka_error)
+        raise KafkaException.from_kafka_error(kafka_error, msg)
     elif msg.error() is not None:
-        raise KafkaException.from_kafka_error(msg.error())
+        raise KafkaException.from_kafka_error(msg.error(), msg)
+
+
+def _get_topic_related_errors():
+    """Build a set of all Kafka error codes which seem to relate to a specific topic.
+
+    This uses a list extracted from all documented error codes up to confluent_kafka v2.4,
+    but some of these errors did not exist or were not exposed in earlier versions.
+    To maintain backward compatibility, this function checks whether each error exists before
+    attempting to otherwise refer to it.
+    """
+    err_names = [
+        "_UNKNOWN_TOPIC",
+        "_NO_OFFSET",
+        "_LOG_TRUNCATION",
+        "OFFSET_OUT_OF_RANGE",
+        "UNKNOWN_TOPIC_OR_PART",
+        "NOT_LEADER_FOR_PARTITION",
+        "TOPIC_EXCEPTION",
+        "NOT_ENOUGH_REPLICAS",
+        "NOT_ENOUGH_REPLICAS_AFTER_APPEND",
+        "INVALID_COMMIT_OFFSET_SIZE",
+        "TOPIC_AUTHORIZATION_FAILED",
+        "TOPIC_ALREADY_EXISTS",
+        "INVALID_PARTITIONS",
+        "INVALID_REPLICATION_FACTOR",
+        "INVALID_REPLICA_ASSIGNMENT",
+        "REASSIGNMENT_IN_PROGRESS",
+        "TOPIC_DELETION_DISABLED",
+        "OFFSET_NOT_AVAILABLE",
+        "PREFERRED_LEADER_NOT_AVAILABLE",
+        "NO_REASSIGNMENT_IN_PROGRESS",
+        "GROUP_SUBSCRIBED_TO_TOPIC",
+        "UNSTABLE_OFFSET_COMMIT",
+        "UNKNOWN_TOPIC_ID",
+    ]
+    errors = set()
+    for name in err_names:
+        if hasattr(confluent_kafka.KafkaError, name):
+            errors.add(getattr(confluent_kafka.KafkaError, name))
+        else:
+            logger.debug(f"{name} does not exist in confluent_kafka version "
+                         f"{confluent_kafka.__version__} ({confluent_kafka.libversion()})")
+    return errors
 
 
 class KafkaException(Exception):
     @classmethod
-    def from_kafka_error(cls, error):
-        return cls(error)
+    def from_kafka_error(cls, error, msg=None):
+        return cls(error, msg)
+
+    topic_related_errors = _get_topic_related_errors()
 
-    def __init__(self, error):
+    def __init__(self, error, msg=None):
         self.error = error
         self.name = error.name()
         self.reason = error.str()
         self.retriable = error.retriable()
         self.fatal = error.fatal()
-        msg = f"Error communicating with Kafka: code={self.name} {self.reason}"
-        super(KafkaException, self).__init__(msg)
+        self.message = msg
+        ex_msg = f"Error communicating with Kafka: code={self.name} {self.reason}"
+        if msg and error.code() in KafkaException.topic_related_errors:
+            ex_msg += f" on topic {msg.topic()}"
+        super(KafkaException, self).__init__(ex_msg)