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: If116745a74baec288570b03a1c0dfcd0b9fa4a6c

manifests/cache.pp

@@ -140,6 +140,21 @@
 #   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 nova::cache (
   $config_prefix                        = $::os_service_default,
   $expiration_time                      = $::os_service_default,
@@ -164,6 +179,9 @@ class nova::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 nova::deps
@@ -192,5 +210,8 @@ class nova::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-0c96612c73d576cf.yaml

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

spec/classes/nova_cache_spec.rb

@@ -33,6 +33,9 @@ describe 'nova::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
@@ -58,6 +61,9 @@ describe 'nova::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,
         }
       end
@@ -86,6 +92,9 @@ describe 'nova::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