chore: merge x-upstream-time into server-timing header

Author: alukach

src/stac_auth_proxy/handlers/reverse_proxy.py

@@ -9,6 +9,8 @@
 from starlette.datastructures import MutableHeaders
 from starlette.responses import Response
 
+from stac_auth_proxy.utils.requests import build_server_timing_header
+
 logger = logging.getLogger(__name__)
 
 
@@ -86,11 +88,15 @@ async def proxy_request(self, request: Request) -> Response:
         start_time = time.perf_counter()
         rp_resp = await self.client.send(rp_req, stream=True)
         proxy_time = time.perf_counter() - start_time
-
+        rp_resp.headers["Server-Timing"] = build_server_timing_header(
+            rp_resp.headers.get("Server-Timing"),
+            name="upstream",
+            dur=proxy_time,
+            desc="Upstream processing time",
+        )
         logger.debug(
             f"Received response status {rp_resp.status_code!r} from {rp_req.url} in {proxy_time:.3f}s"
         )
-        rp_resp.headers["X-Upstream-Time"] = f"{proxy_time:.3f}"
 
         # We read the content here to make use of HTTPX's decompression, ensuring we have
         # non-compressed content for the middleware to work with.

src/stac_auth_proxy/middleware/AddProcessTimeHeaderMiddleware.py

@@ -5,6 +5,8 @@
 from fastapi import Request, Response
 from starlette.middleware.base import BaseHTTPMiddleware
 
+from stac_auth_proxy.utils.requests import build_server_timing_header
+
 
 class AddProcessTimeHeaderMiddleware(BaseHTTPMiddleware):
     """Middleware to add Server-Timing header with proxy processing time."""
@@ -16,16 +18,11 @@ async def dispatch(self, request: Request, call_next) -> Response:
         process_time = time.perf_counter() - start_time
 
         # Add Server-Timing header with proxy processing time
-        # Format: Server-Timing: proxy;dur=123.456
-        server_timing_value = f"proxy;dur={process_time:.3f}"
-
-        # If there's already a Server-Timing header, append to it
-        existing_timing = response.headers.get("Server-Timing")
-        if existing_timing:
-            response.headers["Server-Timing"] = (
-                f"{existing_timing}, {server_timing_value}"
-            )
-        else:
-            response.headers["Server-Timing"] = server_timing_value
+        response.headers["Server-Timing"] = build_server_timing_header(
+            response.headers.get("Server-Timing"),
+            name="proxy",
+            dur=process_time,
+            desc="Proxy processing time",
+        )
 
         return response

src/stac_auth_proxy/utils/requests.py

@@ -3,7 +3,7 @@
 import json
 import re
 from dataclasses import dataclass, field
-from typing import Sequence
+from typing import Optional, Sequence
 from urllib.parse import urlparse
 
 from ..config import EndpointMethods
@@ -80,3 +80,13 @@ class MatchResult:
 
     is_private: bool
     required_scopes: Sequence[str] = field(default_factory=list)
+
+
+def build_server_timing_header(
+    current_value: Optional[str] = None, *, name: str, desc: str, dur: float
+):
+    """Append a timing header to headers."""
+    metric = f'{name};desc="{desc}";dur={dur:.3f}'
+    if current_value:
+        return f"{current_value}, {metric}"
+    return metric