feat: warn if LangfuseTracer initialized without tracing enabled (#1231)

* feat: warn if LangfuseTracer initialized without tracing enabled

* test: warn when lagnfuse tracer init with tracing disabled

integrations/langfuse/src/haystack_integrations/tracing/langfuse/tracer.py

@@ -7,7 +7,8 @@
 from haystack import logging
 from haystack.components.generators.openai_utils import _convert_message_to_openai_format
 from haystack.dataclasses import ChatMessage
-from haystack.tracing import Span, Tracer, tracer
+from haystack.tracing import Span, Tracer
+from haystack.tracing import tracer as proxy_tracer
 from haystack.tracing import utils as tracing_utils
 
 import langfuse
@@ -78,7 +79,7 @@ def set_content_tag(self, key: str, value: Any) -> None:
         :param key: The content tag key.
         :param value: The content tag value.
         """
-        if not tracer.is_content_tracing_enabled:
+        if not proxy_tracer.is_content_tracing_enabled:
             return
         if key.endswith(".input"):
             if "messages" in value:
@@ -126,6 +127,12 @@ def __init__(self, tracer: "langfuse.Langfuse", name: str = "Haystack", public:
         be publicly accessible to anyone with the tracing URL. If set to `False`, the tracing data will be private
         and only accessible to the Langfuse account owner.
         """
+        if not proxy_tracer.is_content_tracing_enabled:
+            logger.warning(
+                "Traces will not be logged to Langfuse because Haystack tracing is disabled. "
+                "To enable, set the HAYSTACK_CONTENT_TRACING_ENABLED environment variable to true "
+                "before importing Haystack."
+            )
         self._tracer = tracer
         self._context: List[LangfuseSpan] = []
         self._name = name

integrations/langfuse/tests/test_tracer.py

@@ -1,4 +1,6 @@
 import datetime
+import logging
+import sys
 from unittest.mock import MagicMock, Mock, patch
 
 from haystack.dataclasses import ChatMessage
@@ -149,3 +151,17 @@ def test_context_is_empty_after_tracing(self):
             pass
 
         assert tracer._context == []
+
+    def test_init_with_tracing_disabled(self, monkeypatch, caplog):
+        # Clear haystack modules because ProxyTracer is initialized whenever haystack is imported
+        modules_to_clear = [name for name in sys.modules if name.startswith('haystack')]
+        for name in modules_to_clear:
+            sys.modules.pop(name, None)
+
+        # Re-import LangfuseTracer and instantiate it with tracing disabled
+        with caplog.at_level(logging.WARNING):
+            monkeypatch.setenv("HAYSTACK_CONTENT_TRACING_ENABLED", "false")
+            from haystack_integrations.tracing.langfuse import LangfuseTracer
+
+            LangfuseTracer(tracer=MockTracer(), name="Haystack", public=False)
+            assert "tracing is disabled" in caplog.text