(fmn) Use on-disk cache but in-memory lock

roles/notifs/backend/templates/fmn.consumer.py

@@ -8,6 +8,31 @@ ircnick = "fedora-notifs"
 
 base = "https://apps.%s/notifications/" % domain
 
+from dogpile.core.readwrite_lock import ReadWriteMutex
+from dogpile.cache.backends.file import AbstractFileLock
+
+class MutexLock(AbstractFileLock):
+    """ Use an in-memory lock for our dogpile cache
+    in an attempt to reduce thread competition.
+    """
+    def __init__(self, filename):
+        self.mutex = ReadWriteMutex()
+
+    def acquire_read_lock(self, wait):
+        ret = self.mutex.acquire_read_lock(wait)
+        return wait or ret
+
+    def acquire_write_lock(self, wait):
+        ret = self.mutex.acquire_write_lock(wait)
+        return wait or ret
+
+    def release_read_lock(self):
+        return self.mutex.release_read_lock()
+
+    def release_write_lock(self):
+        return self.mutex.release_write_lock()
+
+
 config = {
     {% if env == 'staging' %}
     # Pull in messages from production so we can more thoroughly test in stg.
@@ -56,6 +81,7 @@ config = {
         "expiration_time": 56700,
         "arguments": {
             "filename": "/dev/shm/fmn-cache.dbm",
+            "lock_factory": MutexLock,  # Use on-disk cache but in-memory lock.
         },
     },