add env var to disable runtime tracing (#6681)

Recently a PR merged to enable GENAI semantic convention tracing,
however, when using component loading it's not currently possible to
disable the runtime tracing.

---------

Signed-off-by: Eitan Yarmush <eitan.yarmush@solo.io>
Co-authored-by: Eric Zhu <ekzhu@users.noreply.github.com>

Author: EItanya

python/packages/autogen-core/docs/src/user-guide/agentchat-user-guide/tracing.ipynb

@@ -98,6 +98,8 @@
     "In turn, the runtime is already instrumented to log, see [Core Telemetry Guide](../core-user-guide/framework/telemetry.md).\n",
     "To disable the agent runtime telemetry, you can set the `trace_provider` to\n",
     "`opentelemetry.trace.NoOpTraceProvider` in the runtime constructor.\n",
+    "\n",
+    "Additionally, you can set the environment varibale `AUTOGEN_DISABLE_RUNTIME_TRACING` to `true` to disable the agent runtime telemetry if you don't have access to the runtime constructor. For example, if you are using `ComponentConfig`.\n",
     "```"
    ]
   },

python/packages/autogen-core/src/autogen_core/_single_threaded_agent_runtime.py

@@ -160,6 +160,7 @@ class SingleThreadedAgentRuntime(AgentRuntime):
         intervention_handlers (List[InterventionHandler], optional): A list of intervention
             handlers that can intercept messages before they are sent or published. Defaults to None.
         tracer_provider (TracerProvider, optional): The tracer provider to use for tracing. Defaults to None.
+            Additionally, you can set environment variable `AUTOGEN_DISABLE_RUNTIME_TRACING` to `true` to disable the agent runtime telemetry if you don't have access to the runtime constructor. For example, if you are using `ComponentConfig`.
         ignore_unhandled_exceptions (bool, optional): Whether to ignore unhandled exceptions in that occur in agent event handlers. Any background exceptions will be raised on the next call to `process_next` or from an awaited `stop`, `stop_when_idle` or `stop_when`. Note, this does not apply to RPC handlers. Defaults to True.
 
     Examples:

python/packages/autogen-core/src/autogen_core/_telemetry/_tracing.py

@@ -1,4 +1,5 @@
 import contextlib
+import os
 from typing import Dict, Generic, Iterator, Optional
 
 from opentelemetry.trace import NoOpTracerProvider, Span, SpanKind, TracerProvider, get_tracer_provider
@@ -22,11 +23,18 @@ def __init__(
         tracer_provider: TracerProvider | None,
         instrumentation_builder_config: TracingConfig[Operation, Destination, ExtraAttributes],
     ) -> None:
+        self.instrumentation_builder_config = instrumentation_builder_config
+
+        disable_runtime_tracing = os.environ.get("AUTOGEN_DISABLE_RUNTIME_TRACING") == "true"
+        if disable_runtime_tracing:
+            self.tracer_provider: TracerProvider = NoOpTracerProvider()
+            self.tracer = self.tracer_provider.get_tracer(f"autogen {instrumentation_builder_config.name}")
+            return
+
         # Evaluate in order: first try tracer_provider param, then get_tracer_provider(), finally fallback to NoOp
         # This allows for nested tracing with a default tracer provided by the user
         self.tracer_provider = tracer_provider or get_tracer_provider() or NoOpTracerProvider()
         self.tracer = self.tracer_provider.get_tracer(f"autogen {instrumentation_builder_config.name}")
-        self.instrumentation_builder_config = instrumentation_builder_config
 
     @contextlib.contextmanager
     def trace_block(