chore(tracing): deprecate DD_TRACE_SPAN_AGGREGATOR_RLOCK (#10725)

DD_TRACE_SPAN_AGGREGATOR_RLOCK configuration exposes tracer
implementation details. ddtrace user's should not care about what type
of lock is acquired to aggregate span data. This functionality should
just work.

## Checklist
- [ ] PR author has checked that all the criteria below are met
- The PR description includes an overview of the change
- The PR description articulates the motivation for the change
- The change includes tests OR the PR description describes a testing
strategy
- The PR description notes risks associated with the change, if any
- Newly-added code is easy to change
- The change follows the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
- The change includes or references documentation updates if necessary
- Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist
- [ ] Reviewer has checked that all the criteria below are met 
- Title is accurate
- All changes are related to the pull request's stated goal
- Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- Testing strategy adequately addresses listed risks
- Newly-added code is easy to change
- Release note makes sense to a user of the library
- If necessary, author has acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment
- Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

ddtrace/settings/config.py

@@ -567,6 +567,14 @@ def __init__(self):
         self._ddtrace_bootstrapped = False
         self._subscriptions = []  # type: List[Tuple[List[str], Callable[[Config, List[str]], None]]]
         self._span_aggregator_rlock = asbool(os.getenv("DD_TRACE_SPAN_AGGREGATOR_RLOCK", True))
+        if self._span_aggregator_rlock is False:
+            deprecate(
+                "DD_TRACE_SPAN_AGGREGATOR_RLOCK is deprecated",
+                message="Soon the ddtrace library will only support using threading.Rlock to "
+                "aggregate and encode span data. If you need to disable the re-entrant lock and "
+                "revert to using threading.Lock, please contact Datadog support.",
+                removal_version="3.0.0",
+            )
 
         self.trace_methods = os.getenv("DD_TRACE_METHODS")
 

docs/configuration.rst

@@ -462,14 +462,6 @@ The following environment variables for the tracer are supported:
      default: True
      description: Send query strings in http.url tag in http server integrations.
 
-   DD_TRACE_SPAN_AGGREGATOR_RLOCK:
-     type: Boolean
-     default: True
-     description: Whether the ``SpanAggregator`` should use an RLock or a Lock.
-     version_added:
-       v1.16.2: added with default of False
-       v1.19.0: default changed to True
-
    DD_TRACE_METHODS:
      type: String
      default: ""

releasenotes/notes/deprecate-DD_TRACE_SPAN_AGGREGATOR_RLOCK-eb1ca91f7c1dd2b0.yaml

@@ -0,0 +1,4 @@
+---
+deprecations:
+  - |
+    tracing: Deprecates the ``DD_TRACE_SPAN_AGGREGATOR_RLOCK`` environment variable. It will be removed in 3.0.0.

tests/contrib/gunicorn/test_gunicorn.py

@@ -56,7 +56,6 @@ def _gunicorn_settings_factory(
     debug_mode=False,  # type: bool
     dd_service=None,  # type: Optional[str]
     schema_version=None,  # type: Optional[str]
-    rlock=True,  # type: bool
 ):
     # type: (...) -> GunicornServerSettings
     """Factory for creating gunicorn settings with simple defaults if settings are not defined."""
@@ -75,8 +74,6 @@ def _gunicorn_settings_factory(
         env["DD_SERVICE"] = dd_service
     if schema_version is not None:
         env["DD_TRACE_SPAN_ATTRIBUTE_SCHEMA"] = schema_version
-    if rlock is not None:
-        env["DD_TRACE_SPAN_AGGREGATOR_RLOCK"] = "true"
     return GunicornServerSettings(
         env=env,
         directory=directory,
@@ -168,12 +165,6 @@ def gunicorn_server(gunicorn_server_settings, tmp_path):
     debug_mode=True,
     enable_module_cloning=True,
 )
-SETTINGS_GEVENT_SPANAGGREGATOR_NO_RLOCK = _gunicorn_settings_factory(
-    worker_class="gevent",
-    use_ddtracerun=False,
-    import_auto_in_app=True,
-    rlock=False,
-)
 
 
 @flaky(until=1706677200)
@@ -185,7 +176,6 @@ def test_no_known_errors_occur(tmp_path):
         SETTINGS_GEVENT_DDTRACERUN,
         SETTINGS_GEVENT_DDTRACERUN_MODULE_CLONE,
         SETTINGS_GEVENT_DDTRACERUN_DEBUGMODE_MODULE_CLONE,
-        SETTINGS_GEVENT_SPANAGGREGATOR_NO_RLOCK,
     ]:
         with gunicorn_server(gunicorn_server_settings, tmp_path) as context:
             _, client = context