Log dead link verification request timings (#4508)

* Reduce logging from dead link checks

Each call to `get_aiohttp_session` logs a line about whether a new session is created or being reused. This adds a huge number of log lines with zero value, as for each request, they will be identical. Instead, they just fill up the logs and make them harder to read and visually scan

* Log dead link verification request timings

* Use perf counter

api/api/utils/check_dead_links/__init__.py

@@ -43,22 +43,34 @@ def _get_expiry(status, default):
 _timeout = aiohttp.ClientTimeout(total=2)
 
 
-async def _head(url: str) -> tuple[str, int]:
+async def _head(url: str, session: aiohttp.ClientSession) -> tuple[str, int]:
+    start_time = time.perf_counter()
+
     try:
-        session = await get_aiohttp_session()
         response = await session.head(
             url, allow_redirects=False, headers=HEADERS, timeout=_timeout
         )
-        return url, response.status
+        status = response.status
     except (aiohttp.ClientError, asyncio.TimeoutError) as exception:
         _log_validation_failure(exception)
-        return url, -1
+        status = -1
+
+    end_time = time.perf_counter()
+    logger.info(
+        "dead_link_validation_timing",
+        url=url,
+        status=status,
+        time=end_time - start_time,
+    )
+
+    return url, status
 
 
 # https://stackoverflow.com/q/55259755
 @async_to_sync
 async def _make_head_requests(urls: list[str]) -> list[tuple[str, int]]:
-    tasks = [asyncio.ensure_future(_head(url)) for url in urls]
+    session = await get_aiohttp_session()
+    tasks = [asyncio.ensure_future(_head(url, session)) for url in urls]
     responses = asyncio.gather(*tasks)
     await responses
     return responses.result()