Use run_in_background in preference to preserve_fn

While I was going through uses of preserve_fn for other PRs, I converted places
which only use the wrapped function once to use run_in_background, to avoid
creating the function object.

5 files changed, 11 insertions, 9 deletions

diff --git a/synapse/util/async.py b/synapse/util/async.py
index 0729bb2863..bd07067328 100644
--- a/synapse/util/async.py
+++ b/synapse/util/async.py
@@ -17,7 +17,7 @@
 from twisted.internet import defer, reactor
 
 from .logcontext import (
-    PreserveLoggingContext, make_deferred_yieldable, preserve_fn
+    PreserveLoggingContext, make_deferred_yieldable, run_in_background
 )
 from synapse.util import logcontext, unwrapFirstError
 
@@ -161,7 +161,7 @@ def concurrently_execute(func, args, limit):
             pass
 
     return logcontext.make_deferred_yieldable(defer.gatherResults([
-        preserve_fn(_concurrently_execute_inner)()
+        run_in_background(_concurrently_execute_inner)
         for _ in xrange(limit)
     ], consumeErrors=True)).addErrback(unwrapFirstError)
 
diff --git a/synapse/util/file_consumer.py b/synapse/util/file_consumer.py
index 3c8a165331..3380970e4e 100644
--- a/synapse/util/file_consumer.py
+++ b/synapse/util/file_consumer.py
@@ -15,7 +15,7 @@
 
 from twisted.internet import threads, reactor
 
-from synapse.util.logcontext import make_deferred_yieldable, preserve_fn
+from synapse.util.logcontext import make_deferred_yieldable, run_in_background
 
 from six.moves import queue
 
@@ -70,7 +70,9 @@ class BackgroundFileConsumer(object):
 
         self._producer = producer
         self.streaming = streaming
-        self._finished_deferred = preserve_fn(threads.deferToThread)(self._writer)
+        self._finished_deferred = run_in_background(
+            threads.deferToThread, self._writer
+        )
         if not streaming:
             self._producer.resumeProducing()
 
diff --git a/synapse/util/logcontext.py b/synapse/util/logcontext.py
index d59adc236e..c2edf87e58 100644
--- a/synapse/util/logcontext.py
+++ b/synapse/util/logcontext.py
@@ -341,7 +341,7 @@ def make_deferred_yieldable(deferred):
     returning a deferred. Then, when the deferred completes, restores the
     current logcontext before running callbacks/errbacks.
 
-    (This is more-or-less the opposite operation to preserve_fn.)
+    (This is more-or-less the opposite operation to run_in_background.)
     """
     if isinstance(deferred, defer.Deferred) and not deferred.called:
         prev_context = LoggingContext.set_current_context(LoggingContext.sentinel)
diff --git a/synapse/util/ratelimitutils.py b/synapse/util/ratelimitutils.py
index 1101881a2d..18424f6c36 100644
--- a/synapse/util/ratelimitutils.py
+++ b/synapse/util/ratelimitutils.py
@@ -18,7 +18,7 @@ from twisted.internet import defer
 from synapse.api.errors import LimitExceededError
 
 from synapse.util.async import sleep
-from synapse.util.logcontext import preserve_fn
+from synapse.util.logcontext import run_in_background
 
 import collections
 import contextlib
@@ -150,7 +150,7 @@ class _PerHostRatelimiter(object):
                 "Ratelimit [%s]: sleeping req",
                 id(request_id),
             )
-            ret_defer = preserve_fn(sleep)(self.sleep_msec / 1000.0)
+            ret_defer = run_in_background(sleep, self.sleep_msec / 1000.0)
 
             self.sleeping_requests.add(request_id)
 
diff --git a/synapse/util/retryutils.py b/synapse/util/retryutils.py
index 47b0bb5eb3..4e93f69d3a 100644
--- a/synapse/util/retryutils.py
+++ b/synapse/util/retryutils.py
@@ -203,8 +203,8 @@ class RetryDestinationLimiter(object):
                 )
             except Exception:
                 logger.exception(
-                    "Failed to store set_destination_retry_timings",
+                    "Failed to store destination_retry_timings",
                 )
 
         # we deliberately do this in the background.
-        synapse.util.logcontext.preserve_fn(store_retry_timings)()
+        synapse.util.logcontext.run_in_background(store_retry_timings)