Deprecate oslo.messaging rpc_backend option parameter

Oslo.messaging uses the transport_url to represent the rpc and
notification messaging driver to use and its full configuration. The
rpc_backend configuration option is deprecated for removal and
should not gate oslo.messaging driver configuration options.

This patch:
* deprecate rpc_backend
* remove conditional check
* update spec tests
* add release note

Change-Id: Icc6fa09cdd5ea20b8126aab577cf9ff9a33d93f7
Closes-Bug: #1708976

manifests/init.pp

@@ -24,13 +24,6 @@
 #   option.
 #   Defaults to $::os_service_default
 #
-# [*rpc_backend*]
-#   (optional) The rpc backend implementation to use, can be:
-#     amqp (for AMQP 1.0 protocol)
-#     rabbit (for rabbitmq)
-#     zmq (for zeromq)
-#   Defaults to 'rabbit'
-#
 # [*rabbit_use_ssl*]
 #   (optional) Connect over SSL for RabbitMQ
 #   Defaults to $::os_service_default
@@ -181,12 +174,18 @@
 #   (optional) The state of aodh packages
 #   Defaults to undef
 #
+# [*rpc_backend*]
+#   (optional) The rpc backend implementation to use, can be:
+#     amqp (for AMQP 1.0 protocol)
+#     rabbit (for rabbitmq)
+#     zmq (for zeromq)
+#   Defaults to 'rabbit'
+#
 class octavia (
   $package_ensure                     = 'present',
   $default_transport_url              = $::os_service_default,
   $rpc_response_timeout               = $::os_service_default,
   $control_exchange                   = $::os_service_default,
-  $rpc_backend                        = 'rabbit',
   $rabbit_use_ssl                     = $::os_service_default,
   $rabbit_heartbeat_timeout_threshold = $::os_service_default,
   $rabbit_heartbeat_rate              = $::os_service_default,
@@ -221,6 +220,7 @@ class octavia (
   $purge_config                       = false,
   # DEPRECATED PARAMETERS
   $ensure_package                     = undef,
+  $rpc_backend                        = 'rabbit',
 ) inherits octavia::params {
 
   include ::octavia::deps
@@ -234,6 +234,10 @@ the future release. Please use octavia::package_ensure instead.")
     $package_ensure_real = $package_ensure
   }
 
+  if $rpc_backend {
+    warning('The rpc_backend parameter has been deprecated, please use default_transport_url instead.')
+  }
+
   package { 'octavia':
     ensure => $package_ensure_real,
     name   => $::octavia::params::common_package_name,
@@ -244,7 +248,6 @@ the future release. Please use octavia::package_ensure instead.")
     purge => $purge_config,
   }
 
-  if $rpc_backend == 'rabbit' {
   oslo::messaging::rabbit { 'octavia_config':
     rabbit_ha_queues            => $rabbit_ha_queues,
     heartbeat_timeout_threshold => $rabbit_heartbeat_timeout_threshold,
@@ -258,8 +261,7 @@ the future release. Please use octavia::package_ensure instead.")
     kombu_compression           => $kombu_compression,
     amqp_durable_queues         => $amqp_durable_queues,
   }
-  }
-  elsif $rpc_backend == 'amqp' {
+
   oslo::messaging::amqp { 'octavia_config':
     server_request_prefix  => $amqp_server_request_prefix,
     broadcast_prefix       => $amqp_broadcast_prefix,
@@ -278,7 +280,6 @@ the future release. Please use octavia::package_ensure instead.")
     username               => $amqp_username,
     password               => $amqp_password,
   }
-  }
 
   oslo::messaging::default { 'octavia_config':
     transport_url        => $default_transport_url,

releasenotes/notes/deprecate_rpc_backend_parameter-d0a8b677bcf5b39e.yaml

@@ -0,0 +1,4 @@
+---
+deprecations:
+  - octavia::rpc_backend is deprecated and will be removed in a future
+    release. Please use octavia::default_transport_url instead.

spec/classes/octavia_init_spec.rb

@@ -32,7 +32,6 @@ describe 'octavia' do
       end
 
       it 'configures rabbit' do
-        is_expected.to contain_octavia_config('DEFAULT/rpc_backend').with_value('rabbit')
         is_expected.to contain_octavia_config('DEFAULT/transport_url').with_value('<SERVICE DEFAULT>')
         is_expected.to contain_octavia_config('DEFAULT/rpc_response_timeout').with_value('<SERVICE DEFAULT>')
         is_expected.to contain_octavia_config('DEFAULT/control_exchange').with_value('<SERVICE DEFAULT>')
@@ -67,7 +66,6 @@ describe 'octavia' do
       end
 
       it 'configures rabbit' do
-        is_expected.to contain_octavia_config('DEFAULT/rpc_backend').with_value('rabbit')
         is_expected.to contain_octavia_config('DEFAULT/transport_url').with_value('rabbit://rabbit_user:password@localhost:5673')
         is_expected.to contain_octavia_config('DEFAULT/rpc_response_timeout').with_value('120')
         is_expected.to contain_octavia_config('DEFAULT/control_exchange').with_value('octavia')
@@ -170,12 +168,7 @@ describe 'octavia' do
       end
     end
 
-    context 'with amqp rpc_backend' do
-      let :params do
-        { :rpc_backend => 'amqp' }
-      end
-
-      context 'with default parameters' do
+    context 'with amqp default parameters' do
       it 'configures amqp' do
         is_expected.to contain_octavia_config('oslo_messaging_amqp/server_request_prefix').with_value('<SERVICE DEFAULT>')
         is_expected.to contain_octavia_config('oslo_messaging_amqp/broadcast_prefix').with_value('<SERVICE DEFAULT>')
@@ -195,12 +188,10 @@ describe 'octavia' do
         is_expected.to contain_octavia_config('oslo_messaging_amqp/password').with_value('<SERVICE DEFAULT>')
       end
     end
-    end
 
     context 'with overriden amqp parameters' do
       let :params do
-        { :rpc_backend           => 'amqp',
-          :default_transport_url => 'amqp://amqp_user:password@localhost:5672',
+        { :default_transport_url => 'amqp://amqp_user:password@localhost:5672',
           :amqp_idle_timeout     => '60',
           :amqp_trace            => true,
           :amqp_ssl_ca_file      => '/etc/ca.cert',