Set prefetch count to 64 for Rabbit driver
we are ditching the downstream patch to oslo.messaging that silently
overwrote the default for this option from 0 to 64, and moving such
override explicitly to the configuration management.
Initial comment on why we are doing it is included in the rabbit section
template.
Change-Id: Id47d2b3128b06fe9ea124de2a84ff756184d7ba7
diff --git a/oslo_templates/files/queens/oslo/messaging/_rabbit.conf b/oslo_templates/files/queens/oslo/messaging/_rabbit.conf
index c20e233..cc7aa9d 100644
--- a/oslo_templates/files/queens/oslo/messaging/_rabbit.conf
+++ b/oslo_templates/files/queens/oslo/messaging/_rabbit.conf
@@ -150,7 +150,14 @@
# Specifies the number of messages to prefetch. Setting to zero allows
# unlimited messages. (integer value)
-#rabbit_qos_prefetch_count = 64
+
+# NOTE(dmescheryakov) hardcoding to >0 by default
+# Having no prefetch limit makes oslo.messaging consume all available
+# messages from the queue. That can lead to a situation when several
+# server processes hog all the messages leaving others out of business.
+# That leads to artificial high message processing latency and at the
+# extrime to MessagingTimeout errors.
+rabbit_qos_prefetch_count = 64
# Number of seconds after which the Rabbit broker is considered down
# if heartbeat's keep-alive fails (0 disable the heartbeat).