fix(tracing): ensure 128 trace ids are propagated by datadog headers [backports #5510 to 1.11] (#5514)

Backport: #5510

## Checklist

- [x] Change(s) are motivated and described in the PR description.
- [x] Testing strategy is described if automated tests are not included
in the PR.
- [x] Risk is outlined (performance impact, potential for breakage,
maintainability, etc).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] [Library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/contributing.html#Release-Note-Guidelines)
are followed.
- [x] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/)).
- [x] PR description includes explicit acknowledgement/acceptance of the
performance implications of this PR as reported in the benchmarks PR
comment.

## Reviewer Checklist

- [x] Title is accurate.
- [x] No unnecessary changes are introduced.
- [x] Description motivates each change.
- [x] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes unless absolutely necessary.
- [x] Testing strategy adequately addresses listed risk(s).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] Release note makes sense to a user of the library.
- [x] Reviewer has explicitly acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment.

Author: mabdinur

ddtrace/propagation/http.py

@@ -266,19 +266,21 @@ def _extract(headers):
                 }
                 log.debug("failed to decode x-datadog-tags: %r", tags_value, exc_info=True)
 
-        if meta is not None and config._128_bit_trace_id_enabled:
-            # When 128 bit trace ids are propagated the 64 lowest order bits are encoded as an integer
-            # and set in the `x-datadog-trace-id` header (this was done for backwards compatibility).
-            # The 64 highest order bits are encoded in base 16 and store in the `_dd.p.tid` tag.
+        if meta and _HIGHER_ORDER_TRACE_ID_BITS in meta:
+            # When 128 bit trace ids are propagated the 64 lowest order bits are set in the `x-datadog-trace-id`
+            # header. The 64 highest order bits are encoded in base 16 and store in the `_dd.p.tid` tag.
             # Here we reconstruct the full 128 bit trace_id.
-            trace_id_hob_hex = meta.get(_HIGHER_ORDER_TRACE_ID_BITS)  # type: Optional[str]
-            if trace_id_hob_hex is not None:
-                # convert lowest order bits in trace_id to base 16
-                trace_id_lod_hex = "{:016x}".format(trace_id)
+            trace_id_hob_hex = meta[_HIGHER_ORDER_TRACE_ID_BITS]
+            try:
+                if len(trace_id_hob_hex) != 16:
+                    raise ValueError("Invalid size")
                 # combine highest and lowest order hex values to create a 128 bit trace_id
-                trace_id = int(trace_id_hob_hex + trace_id_lod_hex, 16)
-                # After the full trace id is reconstructed this tag is no longer required
-                del meta[_HIGHER_ORDER_TRACE_ID_BITS]
+                trace_id = int(trace_id_hob_hex + "{:016x}".format(trace_id), 16)
+            except ValueError:
+                meta["_dd.propagation_error"] = "malformed_tid {}".format(trace_id_hob_hex)
+                log.warning("malformed_tid: %s. Failed to decode trace id from http headers", trace_id_hob_hex)
+            # After the full trace id is reconstructed this tag is no longer required
+            del meta[_HIGHER_ORDER_TRACE_ID_BITS]
 
         # Try to parse values into their expected types
         try:

releasenotes/notes/fix-128bit-trace-id-propagation-b0e262f0fdf45044.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    tracing: Ensure datadog headers propagate 128 bit trace ids when ``DD_TRACE_128_BIT_TRACEID_GENERATION_ENABLED=False``

tests/tracer/test_propagation.py

@@ -217,28 +217,17 @@ def test_extract(tracer):
             }
 
 
-@pytest.mark.subprocess(
-    env=dict(DD_TRACE_128_BIT_TRACEID_GENERATION_ENABLED="true"),
-    parametrize={
-        "TEST_TRACE_ID": [
-            str(2 ** 128 - 1),
-            str(2 ** 127 + 1),
-            str(2 ** 65 - 1),
-            str(2 ** 64 + 1),
-            str(2 ** 127 + 2 ** 63),
-        ]
-    },
+@pytest.mark.parametrize(
+    "trace_id",
+    [
+        2 ** 128 - 1,
+        2 ** 127 + 1,
+        2 ** 65 - 1,
+        2 ** 64 + 1,
+        2 ** 127 + 2 ** 63,
+    ],
 )
-def test_extract_128bit_trace_ids():
-    import os
-
-    from ddtrace.internal.constants import HIGHER_ORDER_TRACE_ID_BITS
-    from ddtrace.propagation.http import HTTPPropagator
-    from tests.utils import DummyTracer
-
-    tracer = DummyTracer()
-
-    trace_id = int(os.getenv("TEST_TRACE_ID"))
+def test_extract_128bit_trace_ids(tracer, trace_id):
     trace_id_64bit = trace_id & 2 ** 64 - 1
     # Get the hex representation of the 64 most signicant bits
     trace_id_hob_hex = "{:032x}".format(trace_id)[:16]