fix(tracing): fix traceback max size for exceptions [backport 2.7]

ddtrace/_trace/span.py

@@ -505,9 +505,13 @@ def set_exc_info(self, exc_type, exc_val, exc_tb):
         self._set_exc_tags(exc_type, exc_val, exc_tb)
 
     def _set_exc_tags(self, exc_type, exc_val, exc_tb):
+        limit = config._span_traceback_max_size
+        if limit is None:
+            limit = 30
+
         # get the traceback
         buff = StringIO()
-        traceback.print_exception(exc_type, exc_val, exc_tb, file=buff, limit=30)
+        traceback.print_exception(exc_type, exc_val, exc_tb, file=buff, limit=limit)
         tb = buff.getvalue()
 
         # readable version of type (e.g. exceptions.ZeroDivisionError)

releasenotes/notes/fix-tracing-traceback-size-for-exceptions-3739fa96d09290fd.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    tracing: Fixes an issue where ``DD_TRACE_SPAN_TRACEBACK_MAX_SIZE`` was not applied to exception tracebacks.

tests/tracer/test_span.py

@@ -235,6 +235,32 @@ def test_custom_traceback_size(self):
             stack = s.get_tag(ERROR_STACK)
             assert len(stack.splitlines()) == tb_length_limit * 2, "stacktrace should contain two lines per entry"
 
+    def test_custom_traceback_size_with_error(self):
+        tb_length_limit = 2
+        with override_global_config(dict(_span_traceback_max_size=tb_length_limit)):
+            s = Span("test.span")
+
+            def divide_by_zero():
+                1 / 0
+
+            # Wrapper function to generate a larger traceback
+            def wrapper():
+                divide_by_zero()
+
+            try:
+                wrapper()
+            except ZeroDivisionError:
+                s.set_traceback()
+            else:
+                assert 0, "should have failed"
+
+            stack = s.get_tag(ERROR_STACK)
+            # one header "Traceback (most recent call last):" and one footer "ZeroDivisionError: division by zero"
+            header_and_footer_lines = 2
+            assert (
+                len(stack.splitlines()) == tb_length_limit * 2 + header_and_footer_lines
+            ), "stacktrace should contain two lines per entry"
+
     def test_ctx_mgr(self):
         s = Span("bar")
         assert not s.duration