fix(kafka.py): avoid setting headers in Kafka V0/V1 (#323)

Author: ranrib

epsagon/modules/kafka.py

@@ -32,12 +32,14 @@ def _wrapper(wrapped, instance, args, kwargs):
     """KafkaProducer.send wrapper"""
     new_args, new_kwargs = _parse_args(*args, **kwargs)
 
-    # Adds epsagon header
-    if not new_kwargs.get('headers'):
-        new_kwargs['headers'] = []
-    new_kwargs['headers'].append(
-        (EPSAGON_HEADER, get_epsagon_http_trace_id().encode())
-    )
+    # Adds epsagon header only on Kafka record V2. V0/V1 don't support it
+    # pylint: disable=protected-access
+    if instance._max_usable_produce_magic() == 2:
+        if not new_kwargs.get('headers'):
+            new_kwargs['headers'] = []
+        new_kwargs['headers'].append(
+            (EPSAGON_HEADER, get_epsagon_http_trace_id().encode())
+        )
 
     return wrapper(KafkaEventFactory, wrapped, instance, new_args, new_kwargs)
 

tests/events/test_kafka.py

@@ -7,14 +7,14 @@
 
 TEST_URL = 'https://example.test/'
 
-def test(*args, **kwargs):
+def record_mock(*args, **kwargs):
     return [{}, False, False]
 
 
 @mock.patch('epsagon.trace.TraceFactory.add_event')
 @mock.patch('kafka.producer.kafka.KafkaProducer._wait_on_metadata')
 @mock.patch('kafka.producer.kafka.KafkaProducer._partition')
-@mock.patch('kafka.producer.record_accumulator.RecordAccumulator.append', side_effect=test)
+@mock.patch('kafka.producer.record_accumulator.RecordAccumulator.append', side_effect=record_mock)
 def test_sanity(append_mock, partition_mock, wait_on_metadata_mock, add_event_mock):
     retval = 'success'
     body = {'test': 1}
@@ -49,3 +49,34 @@ def wrapped_function():
         epsagon.constants.EPSAGON_HEADER in
         event.resource['metadata']['messaging.headers']
     )
+
+
+@mock.patch('epsagon.trace.TraceFactory.add_event')
+@mock.patch('kafka.producer.kafka.KafkaProducer._wait_on_metadata')
+@mock.patch('kafka.producer.kafka.KafkaProducer._partition')
+@mock.patch('kafka.producer.record_accumulator.RecordAccumulator.append', side_effect=record_mock)
+def test_no_header_injection(append_mock, partition_mock, wait_on_metadata_mock, add_event_mock):
+    # Verify header is not injected in older kafka api versions (V1)
+    retval = 'success'
+    body = {'test': 1}
+
+    @epsagon.wrappers.python_function.python_wrapper
+    def wrapped_function():
+        producer = KafkaProducer(
+            bootstrap_servers=['host:10'],
+            client_id='test_client_id',
+            api_version=(0, 10, 0),
+            value_serializer=lambda x: json.dumps(x).encode('ascii'),
+        )
+        response = producer.send('topic', body)
+        return retval
+    assert wrapped_function() == retval
+    wait_on_metadata_mock.assert_called()
+    partition_mock.assert_called()
+    append_mock.assert_called()
+    add_event_mock.assert_called()
+    event = add_event_mock.call_args_list[0].args[0]
+    assert (
+        epsagon.constants.EPSAGON_HEADER not in
+        event.resource['metadata']
+    )