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authorErik Johnston <erikj@matrix.org>2023-09-13 16:17:06 +0100
committerGitHub <noreply@github.com>2023-09-13 16:17:06 +0100
commit032cf84f524a972f38977a67d61163f08d9dcf2a (patch)
tree49915608908997fd0a4b630ac19e2c7a9027b1ec /synapse/metrics
parentFix using dehydrated devices (MSC2697) & refresh tokens (#16288) (diff)
downloadsynapse-032cf84f524a972f38977a67d61163f08d9dcf2a.tar.xz
Remove a reference cycle in background process (#16314)
Diffstat (limited to 'synapse/metrics')
-rw-r--r--synapse/metrics/background_process_metrics.py21
1 files changed, 20 insertions, 1 deletions
diff --git a/synapse/metrics/background_process_metrics.py b/synapse/metrics/background_process_metrics.py
index 9ea4e23b31..f1f1f0cdf9 100644
--- a/synapse/metrics/background_process_metrics.py
+++ b/synapse/metrics/background_process_metrics.py
@@ -322,13 +322,21 @@ class BackgroundProcessLoggingContext(LoggingContext):
         if instance_id is None:
             instance_id = id(self)
         super().__init__("%s-%s" % (name, instance_id))
-        self._proc = _BackgroundProcess(name, self)
+        self._proc: Optional[_BackgroundProcess] = _BackgroundProcess(name, self)
 
     def start(self, rusage: "Optional[resource.struct_rusage]") -> None:
         """Log context has started running (again)."""
 
         super().start(rusage)
 
+        if self._proc is None:
+            logger.error(
+                "Background process re-entered without a proc: %s",
+                self.name,
+                stack_info=True,
+            )
+            return
+
         # We've become active again so we make sure we're in the list of active
         # procs. (Note that "start" here means we've become active, as opposed
         # to starting for the first time.)
@@ -345,6 +353,14 @@ class BackgroundProcessLoggingContext(LoggingContext):
 
         super().__exit__(type, value, traceback)
 
+        if self._proc is None:
+            logger.error(
+                "Background process exited without a proc: %s",
+                self.name,
+                stack_info=True,
+            )
+            return
+
         # The background process has finished. We explicitly remove and manually
         # update the metrics here so that if nothing is scraping metrics the set
         # doesn't infinitely grow.
@@ -352,3 +368,6 @@ class BackgroundProcessLoggingContext(LoggingContext):
             _background_processes_active_since_last_scrape.discard(self._proc)
 
         self._proc.update_metrics()
+
+        # Set proc to None to break the reference cycle.
+        self._proc = None