Remove references to disposed SQLAlchemy engines from instrumentation singleton (#3053)

* Remove references to SQLAlchemy engines which are disposed of

EngineTracer in SQLAlchemy keeps weak references to a traced engine forever which
can cause a noticeable memory leak if engines are constantly getting creating.

* Updated changelog

---------

Co-authored-by: Emídio Neto <9735060+emdneto@users.noreply.github.com>
Co-authored-by: Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>

CHANGELOG.md

@@ -46,6 +46,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#3022](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3022))
 - Replace all instrumentor unit test `assertEqualSpanInstrumentationInfo` calls with `assertEqualSpanInstrumentationScope` calls
   ([#3037](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3037))
+- `opentelemetry-instrumentation-sqlalchemy`: Fix a remaining memory leak in EngineTracer
+  ([#3053](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3053))
 
 ### Breaking changes
 

instrumentation/opentelemetry-instrumentation-sqlalchemy/src/opentelemetry/instrumentation/sqlalchemy/engine.py

@@ -167,6 +167,13 @@ class EngineTracer:
         self._add_idle_to_connection_usage(-1)
         self._add_used_to_connection_usage(1)
 
+    @classmethod
+    def _dispose_of_event_listener(cls, obj):
+        try:
+            cls._remove_event_listener_params.remove(obj)
+        except ValueError:
+            pass
+
     @classmethod
     def _register_event_listener(cls, target, identifier, func, *args, **kw):
         listen(target, identifier, func, *args, **kw)
@@ -174,6 +181,12 @@ class EngineTracer:
             (weakref.ref(target), identifier, func)
         )
 
+        weakref.finalize(
+            target,
+            cls._dispose_of_event_listener,
+            (weakref.ref(target), identifier, func),
+        )
+
     @classmethod
     def remove_all_event_listeners(cls):
         for (

instrumentation/opentelemetry-instrumentation-sqlalchemy/tests/test_sqlalchemy.py

@@ -417,6 +417,10 @@ class TestSqlalchemyInstrumentation(TestBase):
 
         from sqlalchemy import create_engine
 
+        from opentelemetry.instrumentation.sqlalchemy.engine import (
+            EngineTracer,
+        )
+
         callback = mock.Mock()
 
         def make_shortlived_engine():
@@ -432,3 +436,4 @@ class TestSqlalchemyInstrumentation(TestBase):
 
         gc.collect()
         assert callback.call_count == 5
+        assert len(EngineTracer._remove_event_listener_params) == 0