Fix opentelemetry adapter (#510)

# What does this PR do?

This PR fixes some of the issues with our telemetry setup to enable logs
to be delivered to opentelemetry and jaeger. Main fixes
1) Updates the open telemetry provider to use the latest oltp exports
instead of deprected ones.
2) Adds a tracing middleware, which injects traces into each HTTP
request that the server recieves and this is going to be the root trace.
Previously, we did this in the create_dynamic_route method, which is
actually not the actual exectuion flow, but more of a config and this
causes the traces to end prematurely. Through middleware, we plugin the
trace start and end at the right location.
3) We manage our own methods to create traces and spans and this does
not fit well with Opentelemetry SDK since it does not support provide a
way to take in traces and spans that are already created. it expects us
to use the SDK to create them. For now, I have a hacky approach of just
maintaining a map from our internal telemetry objects to the open
telemetry specfic ones. This is not the ideal solution. I will explore
other ways to get around this issue. for now, to have something that
works, i am going to keep this as is.

Addresses: #509

llama_stack/distribution/server/server.py

@@ -17,13 +17,11 @@ import warnings
 
 from contextlib import asynccontextmanager
 from pathlib import Path
-from ssl import SSLError
-from typing import Any, Dict, Optional
+from typing import Any, Union
 
-import httpx
 import yaml
 
-from fastapi import Body, FastAPI, HTTPException, Request, Response
+from fastapi import Body, FastAPI, HTTPException, Request
 from fastapi.exceptions import RequestValidationError
 from fastapi.responses import JSONResponse, StreamingResponse
 from pydantic import BaseModel, ValidationError
@@ -35,7 +33,6 @@ from llama_stack.distribution.distribution import builtin_automatically_routed_a
 from llama_stack.providers.utils.telemetry.tracing import (
     end_trace,
     setup_logger,
-    SpanStatus,
     start_trace,
 )
 from llama_stack.distribution.datatypes import *  # noqa: F403
@@ -118,67 +115,6 @@ def translate_exception(exc: Exception) -> Union[HTTPException, RequestValidatio
         )
 
 
-async def passthrough(
-    request: Request,
-    downstream_url: str,
-    downstream_headers: Optional[Dict[str, str]] = None,
-):
-    await start_trace(request.path, {"downstream_url": downstream_url})
-
-    headers = dict(request.headers)
-    headers.pop("host", None)
-    headers.update(downstream_headers or {})
-
-    content = await request.body()
-
-    client = httpx.AsyncClient()
-    erred = False
-    try:
-        req = client.build_request(
-            method=request.method,
-            url=downstream_url,
-            headers=headers,
-            content=content,
-            params=request.query_params,
-        )
-        response = await client.send(req, stream=True)
-
-        async def stream_response():
-            async for chunk in response.aiter_raw(chunk_size=64):
-                yield chunk
-
-            await response.aclose()
-            await client.aclose()
-
-        return StreamingResponse(
-            stream_response(),
-            status_code=response.status_code,
-            headers=dict(response.headers),
-            media_type=response.headers.get("content-type"),
-        )
-
-    except httpx.ReadTimeout:
-        erred = True
-        return Response(content="Downstream server timed out", status_code=504)
-    except httpx.NetworkError as e:
-        erred = True
-        return Response(content=f"Network error: {str(e)}", status_code=502)
-    except httpx.TooManyRedirects:
-        erred = True
-        return Response(content="Too many redirects", status_code=502)
-    except SSLError as e:
-        erred = True
-        return Response(content=f"SSL error: {str(e)}", status_code=502)
-    except httpx.HTTPStatusError as e:
-        erred = True
-        return Response(content=str(e), status_code=e.response.status_code)
-    except Exception as e:
-        erred = True
-        return Response(content=f"Unexpected error: {str(e)}", status_code=500)
-    finally:
-        await end_trace(SpanStatus.OK if not erred else SpanStatus.ERROR)
-
-
 def handle_sigint(app, *args, **kwargs):
     print("SIGINT or CTRL-C detected. Exiting gracefully...")
 
@@ -217,7 +153,6 @@ async def maybe_await(value):
 
 
 async def sse_generator(event_gen):
-    await start_trace("sse_generator")
     try:
         event_gen = await event_gen
         async for item in event_gen:
@@ -235,14 +170,10 @@ async def sse_generator(event_gen):
                 },
             }
         )
-    finally:
-        await end_trace()
 
 
 def create_dynamic_typed_route(func: Any, method: str):
     async def endpoint(request: Request, **kwargs):
-        await start_trace(func.__name__)
-
         set_request_provider_data(request.headers)
 
         is_streaming = is_streaming_request(func.__name__, request, **kwargs)
@@ -257,8 +188,6 @@ def create_dynamic_typed_route(func: Any, method: str):
         except Exception as e:
             traceback.print_exception(e)
             raise translate_exception(e) from e
-        finally:
-            await end_trace()
 
     sig = inspect.signature(func)
     new_params = [
@@ -282,6 +211,19 @@ def create_dynamic_typed_route(func: Any, method: str):
     return endpoint
 
 
+class TracingMiddleware:
+    def __init__(self, app):
+        self.app = app
+
+    async def __call__(self, scope, receive, send):
+        path = scope["path"]
+        await start_trace(path, {"location": "server"})
+        try:
+            return await self.app(scope, receive, send)
+        finally:
+            await end_trace()
+
+
 def main():
     """Start the LlamaStack server."""
     parser = argparse.ArgumentParser(description="Start the LlamaStack server.")
@@ -338,6 +280,7 @@ def main():
     print(yaml.dump(config.model_dump(), indent=2))
 
     app = FastAPI(lifespan=lifespan)
+    app.add_middleware(TracingMiddleware)
 
     try:
         impls = asyncio.run(construct_stack(config))