fix(telemetry): ensure integrations are queued on startup (#3471) (#3505)

Currently integrations are not sent to the trace agent (telemetry is enabled after patching occurs).

This change ensures integrations are queued when ``patch`` or ``patch_all()`` is called.

If telemetry is never enabled we will queue configuration data for up to 64 integrations and these values will persist in memory. The cost of each integration entry is ~100 bytes.

## Checklist
- [ ] Added to the correct milestone.
- [ ] Tests provided or description of manual testing performed is included in the code or PR.
- [ ] Library documentation is updated.
- [ ] [Corp site](https://github.com/DataDog/documentation/) documentation is updated (link to the PR).

(cherry picked from commit 9df403f)

Co-authored-by: Munir Abdinur <[email protected]>

Author: mergify[bot]

ddtrace/internal/telemetry/writer.py

@@ -40,7 +40,9 @@ def __init__(self, agent_url=None):
         # type: (Optional[str]) -> None
         super(TelemetryWriter, self).__init__(interval=_get_interval_or_default())
 
-        self._enabled = False  # type: bool
+        # _enabled is None at startup, and is only set to true or false
+        # after the config has been processed
+        self._enabled = None  # type: Optional[bool]
         self._agent_url = agent_url or get_trace_url()
 
         self._encoder = JSONEncoderV2()
@@ -145,7 +147,7 @@ def add_integration(self, integration_name, auto_enabled):
         :param bool auto_enabled: True if module is enabled in _monkey.PATCH_MODULES
         """
         with self._lock:
-            if not self._enabled:
+            if self._enabled is not None and not self._enabled:
                 return
 
             integration = {
@@ -217,17 +219,18 @@ def _restart(self):
     def disable(self):
         # type: () -> None
         """
-        Disable the telemetry collection service.
+        Disable the telemetry collection service and drop the existing integrations and events
         Once disabled, telemetry collection can be re-enabled by calling ``enable`` again.
         """
         with self._lock:
+            self._integrations_queue = []
+            self._enabled = False
             if self.status == ServiceStatus.STOPPED:
                 return
 
             forksafe.unregister(self._restart)
 
             self.stop()
-            self._enabled = False
 
             self.join()
 

tests/tracer/telemetry/test_writer.py

@@ -43,8 +43,9 @@ def telemetry_writer():
 @pytest.fixture
 def telemetry_writer_disabled():
     telemetry_writer = TelemetryWriter()
-    # TelemetryWriter should be disabled by default
-    assert telemetry_writer._enabled is False
+    # TelemetryWriter _enabled should be None by default
+    assert telemetry_writer._enabled is None
+    telemetry_writer._enabled = False
     yield telemetry_writer