Deprecate the Spares Pool feature for removal in X

Use of the spares pool was originally recommended to increase provisioning
speed, but since Nova's server groups do not support adding existing VMs,
Octavia cannot support use of the spares pool with the Active-Standby
topology. Since this is our recommended topology for production deployments,
and speed is less essential in development/testing environments (the
only place we could recommend the use of Single topology), the overhead of
maintaining spares pool support exceeds its theoretical usefulness.

Change-Id: I7375e9758c7ae80e2370189117e8e63c79446490

doc/source/admin/guides/operator-maintenance.rst

@@ -185,6 +185,10 @@ the Octavia services (except octavia-api).
 Rotating spare Amphorae
 -----------------------
 
+.. warning::
+
+    Spares pool support is deprecated as of the Victoria release.
+
 If the spare pool is enabled in Octavia, spare amphorae must be rotated
 first, so a new load balancer will use the new amphora image from a newly
 spawned spare amphora.

doc/source/contributor/guides/dev-quick-start.rst

@@ -376,6 +376,11 @@ You must:
 
 Spares pool considerations
 ^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. warning::
+
+    Spares pool support is deprecated as of the Victoria release.
+
 One configuration directive deserves some extra consideration in this document:
 
 Depending on the specifics of your production environment, you may decide to

etc/octavia.conf

@@ -402,6 +402,8 @@
 # enable_proxy_headers_parsing = False
 
 [house_keeping]
+
+# Note: Spares pools support is deprecated as of the Victoria release.
 # Interval in seconds to initiate spare amphora checks
 # spare_check_interval = 30
 # spare_amphora_pool_size = 0

octavia/common/config.py

@@ -577,9 +577,17 @@ certificate_opts = [
 
 house_keeping_opts = [
     cfg.IntOpt('spare_check_interval',
+               deprecated_for_removal=True,
+               deprecated_since='Victoria',
+               deprecated_reason='Spares Pool support will be removed in the '
+                                 'X release.',
                default=30,
                help=_('Spare check interval in seconds')),
     cfg.IntOpt('spare_amphora_pool_size',
+               deprecated_for_removal=True,
+               deprecated_since='Victoria',
+               deprecated_reason='Spares Pool support will be removed in the '
+                                 'X release.',
                default=0,
                help=_('Number of spare amphorae')),
     cfg.IntOpt('cleanup_interval',

releasenotes/notes/deprecating-spares-pool-9f92787ec9809a78.yaml

@@ -0,0 +1,11 @@
+---
+deprecations:
+  - |
+    Spares pool support is deprecated, pending removal in the X release. Use of
+    the spares pool was originally recommended to increase provisioning speed,
+    but since Nova's server groups do not support adding existing VMs, Octavia
+    cannot support use of the spares pool with the Active-Standby topology.
+    Since this is our recommended topology for production deployments, and
+    speed is less essential in development/testing environments (the only place
+    we could recommend the use of Single topology), the overhead of maintaining
+    spares pool support exceeds its theoretical usefulness.