Only use literal strings for process names (#16315)

Author: erikjohnston

changelog.d/16315.misc

@@ -0,0 +1 @@
+Only use literal strings for background process names.

synapse/appservice/scheduler.py

@@ -200,9 +200,7 @@ def start_background_request(self, service: ApplicationService) -> None:
         if service.id in self.requests_in_flight:
             return
 
-        run_as_background_process(
-            "as-sender-%s" % (service.id,), self._send_request, service
-        )
+        run_as_background_process("as-sender", self._send_request, service)
 
     async def _send_request(self, service: ApplicationService) -> None:
         # sanity-check: we shouldn't get here if this service already has a sender
@@ -478,14 +476,11 @@ def __init__(
         self.backoff_counter = 1
 
     def recover(self) -> None:
-        def _retry() -> None:
-            run_as_background_process(
-                "as-recoverer-%s" % (self.service.id,), self.retry
-            )
-
         delay = 2**self.backoff_counter
         logger.info("Scheduling retries on %s in %fs", self.service.id, delay)
-        self.clock.call_later(delay, _retry)
+        self.clock.call_later(
+            delay, run_as_background_process, "as-recoverer", self.retry
+        )
 
     def _backoff(self) -> None:
         # cap the backoff to be around 8.5min => (2^9) = 512 secs

synapse/metrics/background_process_metrics.py

@@ -48,6 +48,9 @@
 if TYPE_CHECKING:
     import resource
 
+    # Old versions don't have `LiteralString`
+    from typing_extensions import LiteralString
+
 
 logger = logging.getLogger(__name__)
 
@@ -191,7 +194,7 @@ def update_metrics(self) -> None:
 
 
 def run_as_background_process(
-    desc: str,
+    desc: "LiteralString",
     func: Callable[..., Awaitable[Optional[R]]],
     *args: Any,
     bg_start_span: bool = True,
@@ -259,7 +262,7 @@ async def run() -> Optional[R]:
 
 
 def wrap_as_background_process(
-    desc: str,
+    desc: "LiteralString",
 ) -> Callable[
     [Callable[P, Awaitable[Optional[R]]]],
     Callable[P, "defer.Deferred[Optional[R]]"],

synapse/util/caches/expiringcache.py

@@ -84,9 +84,7 @@ def __init__(
             return
 
         def f() -> "defer.Deferred[None]":
-            return run_as_background_process(
-                "prune_cache_%s" % self._cache_name, self._prune_cache
-            )
+            return run_as_background_process("prune_cache", self._prune_cache)
 
         self._clock.looping_call(f, self._expiry_ms / 2)