Add cache client retry options for the pymemcache backend

This patch specifies a set of options required to setup the retrying
wrapper feature of pymemcache (dogpile.cache) cache backend.

Original oslo.cache change:
https://review.opendev.org/c/openstack/oslo.cache/+/803747

Co-Authored-By: Hervé Beraud <hberaud@redhat.com>
Depends-On: https://review.opendev.org/826869
Change-Id: I34a35b8be54983b926d2d7303dfb400dbf49a8f7

manifests/cache.pp

@@ -144,6 +144,21 @@
 #   be available.
 #   Default to $::os_service_default
 #
+# [*enable_retry_client*]
+#   (Optional) Enable retry client mechanisms to handle failure.
+#   Those mechanisms can be used to wrap all kind of pymemcache
+#   clients. The wrapper allows you to define how many attempts
+#   to make and how long to wait between attemots.
+#   Default to $::os_service_default
+#
+# [*retry_attempts*]
+#   (Optional) Number of times to attempt an action before failing.
+#   Default to $::os_service_default
+#
+# [*retry_delay*]
+#   (Optional) Number of seconds to sleep between each attempt.
+#   Default to $::os_service_default
+#
 class keystone::cache(
   $config_prefix                        = $::os_service_default,
   $expiration_time                      = $::os_service_default,
@@ -169,6 +184,9 @@ class keystone::cache(
   $tls_certfile                         = $::os_service_default,
   $tls_keyfile                          = $::os_service_default,
   $tls_allowed_ciphers                  = $::os_service_default,
+  $enable_retry_client                  = $::os_service_default,
+  $retry_attempts                       = $::os_service_default,
+  $retry_delay                          = $::os_service_default,
 ){
 
   include keystone::deps
@@ -205,6 +223,9 @@ class keystone::cache(
     tls_certfile                         => $tls_certfile,
     tls_keyfile                          => $tls_keyfile,
     tls_allowed_ciphers                  => $tls_allowed_ciphers,
+    enable_retry_client                  => $enable_retry_client,
+    retry_attempts                       => $retry_attempts,
+    retry_delay                          => $retry_delay,
   }
 
 }

releasenotes/notes/add_cache_retry_options-a3a2e152e34198c9.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - |
+    Add cache client retry options for the pymemcache (dogpile.cache) backend.

spec/classes/keystone_cache_spec.rb

@@ -35,6 +35,9 @@ describe 'keystone::cache' do
           :tls_certfile                         => '<SERVICE DEFAULT>',
           :tls_keyfile                          => '<SERVICE DEFAULT>',
           :tls_allowed_ciphers                  => '<SERVICE DEFAULT>',
+          :enable_retry_client                  => '<SERVICE DEFAULT>',
+          :retry_attempts                       => '<SERVICE DEFAULT>',
+          :retry_delay                          => '<SERVICE DEFAULT>',
           :manage_backend_package               => true,
         )
       end
@@ -60,6 +63,9 @@ describe 'keystone::cache' do
           :memcache_pool_unused_timeout         => '120',
           :memcache_pool_connection_get_timeout => '360',
           :tls_enabled                          => false,
+          :enable_retry_client                  => false,
+          :retry_attempts                       => 2,
+          :retry_delay                          => 0,
           :manage_backend_package               => false,
           :token_caching                        => true,
         }
@@ -91,6 +97,9 @@ describe 'keystone::cache' do
           :tls_certfile                         => '<SERVICE DEFAULT>',
           :tls_keyfile                          => '<SERVICE DEFAULT>',
           :tls_allowed_ciphers                  => '<SERVICE DEFAULT>',
+          :enable_retry_client                  => false,
+          :retry_attempts                       => 2,
+          :retry_delay                          => 0,
           :manage_backend_package               => false,
         )
       end