add transaction.id to errors if a transaction is ongoing

CHANGELOG.asciidoc

@@ -16,6 +16,7 @@ https://github.com/elastic/apm-agent-python/compare/v1.0.0\...master[Check the H
  * added settings to enable/disable source code collection and local variables collection
    for errors and transactions ({pull}117[#117])
  * added `service.environment` to provide an environment name (e.g. "production", "staging") ({pull}123[#123])
+ * added `transaction.id` to errors to better correlate errors with transactions ({pull}122[#122])
  * BREAKING: Several settings and APIs have been renamed ({pull}111[#111], {pull}119[#119]):
  ** The decorator for custom instrumentation, `elasticapm.trace`, is now `elasticapm.capture_span`
  ** The setting `traces_send_frequency` has been renamed to `transaction_send_frequency`.

elasticapm/base.py

@@ -24,7 +24,7 @@
 
 import elasticapm
 from elasticapm.conf import Config, constants
-from elasticapm.traces import TransactionsStore
+from elasticapm.traces import TransactionsStore, get_transaction
 from elasticapm.transport.base import TransportException
 from elasticapm.utils import json_encoder as json
 from elasticapm.utils import compat, is_master_process, stacks, varmap
@@ -230,12 +230,13 @@ def begin_transaction(self, transaction_type):
         self.instrumentation_store.begin_transaction(transaction_type)
 
     def end_transaction(self, name, result=''):
-        self.instrumentation_store.end_transaction(result, name)
+        transaction = self.instrumentation_store.end_transaction(result, name)
         if self.instrumentation_store.should_collect():
             self._collect_transactions()
         if not self._send_timer:
             # send first batch of data after config._wait_to_first_send
             self._start_send_timer(timeout=min(self.config._wait_to_first_send, self.config.transaction_send_frequency))
+        return transaction
 
     def close(self):
         self._collect_transactions()
@@ -443,6 +444,10 @@ def _build_msg_for_logging(self, event_type, date=None, context=None, custom=Non
             'timestamp': date.strftime(constants.TIMESTAMP_FORMAT),
         })
 
+        transaction = get_transaction()
+        if transaction:
+            event_data['transaction'] = {'id': transaction.id}
+
         return self._build_msg({'errors': [event_data]})
 
     def _filter_exception_type(self, data):

tests/client/client_tests.py

@@ -530,3 +530,16 @@ def test_collect_source_transactions(should_collect, elasticapm_client):
         assert 'context_line' not in transaction['spans'][0]['stacktrace'][0], mode
         assert 'pre_context' not in transaction['spans'][0]['stacktrace'][0], mode
         assert 'post_context' not in transaction['spans'][0]['stacktrace'][0], mode
+
+
+def test_transaction_id_is_attached(elasticapm_client):
+    elasticapm_client.capture_message('noid')
+    elasticapm_client.begin_transaction('test')
+    elasticapm_client.capture_message('id')
+    transaction = elasticapm_client.end_transaction('test', 'test')
+    elasticapm_client.capture_message('noid')
+
+    errors = elasticapm_client.events
+    assert 'transaction' not in errors[0]['errors'][0]
+    assert errors[1]['errors'][0]['transaction']['id'] == transaction.id
+    assert 'transaction' not in errors[2]['errors'][0]