added support for chained exceptions (#596)

If an exception has a `__context__` set, we use its traceback for the
chained exception. The exception type and value are either taken from
`__cause__` (if set) or `__context__`.

closes #526

Also removed Python 2.7 from Windows test matrix on AppVeyor, because it proved difficult to ignore test files with Python 3 syntax only.

Author: beniwohli

.appveyor.yml

@@ -1,8 +1,5 @@
 environment:
   matrix:
-    - PYTHON: "C:\\Python27"
-      WEBFRAMEWORK: "django-1.11"
-      ASYNCIO: "false"
     - PYTHON: "C:\\Python34"
       WEBFRAMEWORK: "django-1.8"
       ASYNCIO: "false"
@@ -12,9 +9,6 @@ environment:
     - PYTHON: "C:\\Python35"
       WEBFRAMEWORK: "django-1.10"
       ASYNCIO: "true"
-    - PYTHON: "C:\\Python27-x64"
-      WEBFRAMEWORK: "flask-0.11"
-      ASYNCIO: "false"
     - PYTHON: "C:\\Python34-x64"
       DISTUTILS_USE_SDK: "1"
       WEBFRAMEWORK: "flask-0.12"

CHANGELOG.md

@@ -8,6 +8,9 @@
  * added `logging` filter and record factory for adding transaction, trace, and span IDs (#520, #586)
  * added `structlog` processor for adding transaction, trace, and span IDs (#520, #586)
  * added new public API calls for getting transaction, trace, and span IDs (#520, #586)
+ * added support for chained exceptions in Python 3 (#596).
+   Note that chained exceptions will be captured and stored in Elasticsearch, but not yet
+   visualized in the APM UI. The UI component will be released in an upcoming Kibana release (7.5 or later).
 
 ### Bugfixes
  * drop events immediately if a processor returns a falsy value (#585)

Makefile

@@ -8,9 +8,9 @@ flake8:
 	flake8
 
 test:
-	if [[ "$$PYTHON_VERSION" =~ ^(3.5|3.6|nightly|pypy3)$$ ]] ; then \
+	if [[ "$$PYTHON_VERSION" =~ ^(3.5|3.6|3.7|3.8|nightly|pypy3)$$ ]] ; then \
 	py.test -v $(PYTEST_ARGS) $(PYTEST_MARKER) $(PYTEST_JUNIT); \
-	else py.test -v $(PYTEST_ARGS) $(PYTEST_MARKER) $(PYTEST_JUNIT) --ignore=tests/asyncio; fi
+	else py.test -v $(PYTEST_ARGS) $(PYTEST_MARKER) $(PYTEST_JUNIT) --ignore=tests/asyncio --ignore-glob='*/py3_*.py'; fi
 
 coverage: PYTEST_ARGS=--cov --cov-report xml:coverage.xml
 coverage: test

elasticapm/conf/constants.py

@@ -45,6 +45,8 @@
 
 MASK = 8 * "*"
 
+EXCEPTION_CHAIN_MAX_DEPTH = 50
+
 ERROR = "error"
 TRANSACTION = "transaction"
 SPAN = "span"

elasticapm/events.py

@@ -33,7 +33,8 @@
 import random
 import sys
 
-from elasticapm.utils import varmap
+from elasticapm.conf.constants import EXCEPTION_CHAIN_MAX_DEPTH
+from elasticapm.utils import compat, varmap
 from elasticapm.utils.encoding import keyword_field, shorten, to_unicode
 from elasticapm.utils.stacks import get_culprit, get_stack_info, iter_traceback_frames
 
@@ -109,7 +110,9 @@ def capture(client, exc_info=None, **kwargs):
                 ),
             )
 
-            culprit = get_culprit(frames, client.config.include_paths, client.config.exclude_paths)
+            culprit = kwargs.get("culprit", None) or get_culprit(
+                frames, client.config.include_paths, client.config.exclude_paths
+            )
 
             if hasattr(exc_type, "__module__"):
                 exc_module = exc_type.__module__
@@ -129,7 +132,7 @@ def capture(client, exc_info=None, **kwargs):
         else:
             message = "%s: %s" % (exc_type, to_unicode(exc_value)) if exc_value else str(exc_type)
 
-        return {
+        data = {
             "id": "%032x" % random.getrandbits(128),
             "culprit": keyword_field(culprit),
             "exception": {
@@ -139,6 +142,30 @@ def capture(client, exc_info=None, **kwargs):
                 "stacktrace": frames,
             },
         }
+        if compat.PY3:
+            depth = kwargs.get("_exc_chain_depth", 0)
+            if depth > EXCEPTION_CHAIN_MAX_DEPTH:
+                return
+            cause = exc_value.__cause__
+            chained_context = exc_value.__context__
+
+            # we follow the pattern of Python itself here and only capture the chained exception
+            # if cause is not None and __suppress_context__ is False
+            if chained_context and not (exc_value.__suppress_context__ and cause is None):
+                if cause:
+                    chained_exc_type = type(cause)
+                    chained_exc_value = cause
+                else:
+                    chained_exc_type = type(chained_context)
+                    chained_exc_value = chained_context
+                chained_exc_info = chained_exc_type, chained_exc_value, chained_context.__traceback__
+
+                chained_cause = Exception.capture(
+                    client, exc_info=chained_exc_info, culprit="None", _exc_chain_depth=depth + 1
+                )
+                if chained_cause:
+                    data["exception"]["cause"] = [chained_cause["exception"]]
+        return data
 
 
 class Message(BaseEvent):