ref(sdk): Add metrics between capturing and sending the envelope (#26171)

* ref(sdk): Add metrics between capturing and sending the envelope

The sent requests for the relay transport are lower then the captured envelopes, which implies there is somewhere in between where the events are not making it out. This again bisects the space somewhat, between the existing capture_envelope check and the send_request, checking that events are being submitted to a worker and how many send_envelopes result out of that should give more insight.

Author: k-fish

src/sentry/utils/sdk.py

@@ -212,9 +212,27 @@ def traces_sampler(sampling_context):
     return float(settings.SENTRY_BACKEND_APM_SAMPLING or 0)
 
 
-# Patches the send_request function to check outgoing requests and patches the update_rate_limits function as it is first to be called after the response.
+# Patches transport functions to add metrics to improve resolution around events sent to our ingest
 # TODO(k-fish): Remove after backend transaction findings are in.
 def patch_transport_for_instrumentation(transport, transport_name):
+    _worker_submit = transport._worker.submit
+    if _worker_submit:
+
+        def patched_worker_submit(*args, **kwargs):
+            metrics.incr(f"internal.worker_submit.{transport_name}.events")
+            return _worker_submit(*args, **kwargs)
+
+        transport._worker.submit = patched_worker_submit
+
+    _send_envelope = transport._send_envelope
+    if _send_envelope:
+
+        def patched_send_envelope(*args, **kwargs):
+            metrics.incr(f"internal.send_envelope.{transport_name}.events")
+            return _send_envelope(*args, **kwargs)
+
+        transport._send_envelope = patched_send_envelope
+
     _send_request = transport._send_request
     if _send_request: