Force creation of a new trace in continue_trace with empty headers (#4682)

Co-authored-by: Ivana Kellyer <[email protected]>

Author: sl0thentr0py

MIGRATION_GUIDE.md

@@ -24,7 +24,20 @@ Looking to upgrade from Sentry SDK 2.x to 3.x? Here's a comprehensive list of wh
 - The default of `traces_sample_rate` changed to `0`. Meaning: Incoming traces will be continued by default. For example, if your frontend sends a `sentry-trace/baggage` headers pair, your SDK will create Spans and send them to Sentry. (The default used to be `None` meaning by default no Spans where created, no matter what headers the frontend sent to your project.) See also: https://docs.sentry.io/platforms/python/configuration/options/#traces_sample_rate
 - `sentry_sdk.start_span` now only takes keyword arguments.
 - `sentry_sdk.start_transaction`/`sentry_sdk.start_span` no longer takes the following arguments: `span`, `parent_sampled`, `trace_id`, `span_id` or `parent_span_id`.
-- `sentry_sdk.continue_trace` no longer returns a `Transaction` and is now a context manager.
+- `sentry_sdk.continue_trace` no longer returns a `Transaction` and is now a context manager. 
+
+    - Use it to continue an upstream trace with the `sentry-trace` and `baggage` headers.
+
+    ```python
+    headers = {"sentry-trace": "{trace_id}-{span_id}-{sampled_flag}", "baggage": "{baggage header}"}
+    with sentry_sdk.continue_trace(headers):
+        with sentry_sdk.start_span(name="continued span in trace"):
+            pass
+    ```
+
+    - If the headers are empty, a new trace will be started.
+    - If you want to force creation of a new trace, use the `sentry_sdk.new_trace` context manager.
+
 - You can no longer change the sampled status of a span with `span.sampled = False` after starting it. The sampling decision needs to be either be made in the `traces_sampler`, or you need to pass an explicit `sampled` parameter to `start_span`.
 - The `Span()` constructor does not accept a `hub` parameter anymore.
 - `Span.finish()` does not accept a `hub` parameter anymore.
@@ -227,7 +240,6 @@ Looking to upgrade from Sentry SDK 2.x to 3.x? Here's a comprehensive list of wh
 ### Deprecated
 
 - `sentry_sdk.start_transaction()` is deprecated. Use `sentry_sdk.start_span()` instead.
-  - If you want to force creation of a new trace, use the `sentry_sdk.new_trace()` context manager.
 - `Span.set_data()` is deprecated. Use `Span.set_attribute()` instead.
 
 

sentry_sdk/opentelemetry/scope.py

@@ -85,7 +85,9 @@ def continue_trace(
 
         span_context = self._incoming_otel_span_context()
         if span_context is None:
-            yield
+            # force a new trace since no incoming stuff
+            with use_span(INVALID_SPAN):
+                yield
         else:
             with use_span(NonRecordingSpan(span_context)):
                 yield

tests/test_api.py

@@ -97,6 +97,25 @@ def test_continue_trace(sentry_init):
             }
 
 
+def test_continue_trace_without_headers_starts_new_trace(sentry_init, capture_events):
+    sentry_init(traces_sample_rate=1.0)
+    events = capture_events()
+
+    with start_span(name="parent"):
+        with start_span(name="child"):
+            with continue_trace({}):
+                with start_span(name="parent2"):
+                    with start_span(name="child2"):
+                        pass
+
+    assert len(events) == 2
+    (tx1, tx2) = events
+    assert tx1["transaction"] == "parent2"
+    assert tx1["spans"][0]["description"] == "child2"
+    assert tx2["transaction"] == "parent"
+    assert tx2["spans"][0]["description"] == "child"
+
+
 def test_new_trace(sentry_init, capture_events):
     sentry_init(traces_sample_rate=1.0)
     events = capture_events()