Set rsync to not perform reverse lookups

We don't setup hosts entries for replication addresses on storage hosts,
by default. Rsync is performing a reverse lookup on each rsync, and
failing. We should turn this reverse lookup off by default, but allow
this to be set to True.

This PR adds the "swift_rsync_reverse_lookup" boolean which is defaulted
to false.

Change-Id: Ie98113fd71a70ce9c74c3812046be6959b9a353f

defaults/main.yml

@@ -240,6 +240,9 @@ swift_object_max_rsync_connections: "{{ swift_max_rsync_connections }}"
 # Set Swift to use rsync module per object server drive
 swift_rsync_module_per_drive: False
 
+# Set Swift to use reverse lookup - requires name resolution or hosts entries
+swift_rsync_reverse_lookup: False
+
 # Set the managed regions as a list of swift regions to manage
 # Use for global clusters, default when not set is all regions.
 # swift_managed_regions:

releasenotes/notes/rsync_reverse_lookup-609fb68be712a5e4.yaml

@@ -0,0 +1,11 @@
+---
+features:
+  - The ``swift_rsync_reverse_lookup`` option has been added. This setting
+    will handle whether rsync performs reverse lookups on client IP
+    addresses, and will default to ``False``. We recommend leaving this
+    option at ``False``, unless DNS or host entries exist for each swift
+    host's replication address.
+upgrade:
+  - The default behaviour of rsync, to perform reverse lookups, has
+    been changed to ``False``. This can be set to ``True`` by
+    setting the ``swift_rsync_reverse_lookup`` variable to ``True``.

templates/rsyncd.conf.j2

@@ -4,6 +4,7 @@ uid = {{ swift_system_user_name }}
 gid = {{ swift_system_group_name }}
 log file = /var/log/rsyncd.log
 pid file = /var/run/rsyncd.pid
+reverse lookup = {{ swift_rsync_reverse_lookup | bool }}
 address = {{ swift_replication_address }}
 
 [account]