Patch TracerProvider if it already exists (#4455)

If a `TracerProvider` already exists, patch it. `TracerProvider` is a
singleton, so if we aren't the first ones setting it up, we need to use
the existing one.

In tests, reset `TracerProvider` after each test so that we start with a
clean slate and it gets set up anew on init.

Author: sentrivana

sentry_sdk/opentelemetry/tracing.py

@@ -7,6 +7,7 @@
     SentrySampler,
     SentrySpanProcessor,
 )
+from sentry_sdk.utils import logger
 
 
 def patch_readable_span():
@@ -28,8 +29,31 @@ def sentry_patched_readable_span(self):
 
 def setup_sentry_tracing():
     # type: () -> None
-    provider = TracerProvider(sampler=SentrySampler())
-    provider.add_span_processor(SentrySpanProcessor())
-    trace.set_tracer_provider(provider)
+    # TracerProvider can only be set once. If we're the first ones setting it,
+    # there's no issue. If it already exists, we need to patch it.
+    from opentelemetry.trace import _TRACER_PROVIDER
+
+    if _TRACER_PROVIDER is not None:
+        logger.debug("[Tracing] Detected an existing TracerProvider, patching")
+        tracer_provider = _TRACER_PROVIDER
+        tracer_provider.sampler = SentrySampler()  # type: ignore[attr-defined]
+
+    else:
+        logger.debug("[Tracing] No TracerProvider set, creating a new one")
+        tracer_provider = TracerProvider(sampler=SentrySampler())
+        trace.set_tracer_provider(tracer_provider)
+
+    try:
+        existing_span_processors = (
+            tracer_provider._active_span_processor._span_processors  # type: ignore[attr-defined]
+        )
+    except Exception:
+        existing_span_processors = []
+
+    for span_processor in existing_span_processors:
+        if isinstance(span_processor, SentrySpanProcessor):
+            break
+    else:
+        tracer_provider.add_span_processor(SentrySpanProcessor())  # type: ignore[attr-defined]
 
     set_global_textmap(SentryPropagator())

sentry_sdk/tracing.py

@@ -188,7 +188,7 @@ def __init__(
         If otel_span is passed explicitly, just acts as a proxy.
 
         If span is passed explicitly, use it. The only purpose of this param
-        if backwards compatibility with start_transaction(transaction=...).
+        is backwards compatibility with start_transaction(transaction=...).
 
         If only_if_parent is True, just return an INVALID_SPAN
         and avoid instrumentation if there's no active parent span.

tests/conftest.py

@@ -2,6 +2,12 @@
 import os
 import socket
 import warnings
+from opentelemetry import trace as otel_trace
+
+try:
+    from opentelemetry.util._once import Once
+except ImportError:
+    Once = None
 from threading import Thread
 from http.server import BaseHTTPRequestHandler, HTTPServer
 
@@ -73,6 +79,14 @@ def clean_scopes():
     setup_initial_scopes()
 
 
+@pytest.fixture(autouse=True)
+def clear_tracer_provider():
+    """Reset TracerProvider so that we can set it up from scratch."""
+    if Once is not None:
+        otel_trace._TRACER_PROVIDER_SET_ONCE = Once()
+    otel_trace._TRACER_PROVIDER = None
+
+
 @pytest.fixture(autouse=True)
 def internal_exceptions(request):
     errors = []