Database: add slave_connection support

Nova is able to talk to a read-only database for some tables so it
improves the scalability of MySQL server and reduce the access to the
server in charge of writes.

More documentation: https://wiki.openstack.org/wiki/Slave_usage

Change-Id: I1d44332acb381b11d90b63535d274f535be26d55

manifests/db.pp

@@ -24,16 +24,22 @@
 #   (optional) Connection url to connect to nova database.
 #   Defaults to undef
 #
+# [*slave_connection*]
+#   (optional) Connection url to connect to nova slave database (read-only).
+#   Defaults to undef
+#
 # [*database_idle_timeout*]
 #   (optional) Timeout before idle db connections are reaped.
 #   Defaults to undef
 #
 class nova::db (
   $database_connection   = undef,
+  $slave_connection      = undef,
   $database_idle_timeout = undef,
 ) {
 
   $database_connection_real = pick($database_connection, $::nova::database_connection, false)
+  $slave_connection_real = pick($slave_connection, $::nova::slave_connection, false)
   $database_idle_timeout_real = pick($database_idle_timeout, $::nova::database_idle_timeout, false)
 
   if $database_connection_real {
@@ -51,6 +57,15 @@ class nova::db (
       'database/connection':   value => $database_connection_real, secret => true;
       'database/idle_timeout': value => $database_idle_timeout_real;
     }
+    if $slave_connection_real {
+      nova_config {
+        'database/slave_connection': value => $slave_connection_real, secret => true;
+      }
+    } else {
+      nova_config {
+        'database/slave_connection': ensure => absent;
+      }
+    }
   }
 
 }

manifests/init.pp

@@ -13,6 +13,10 @@
 #   (optional) Connection url to connect to nova database.
 #   Defaults to false
 #
+# [*slave_connection*]
+#   (optional) Connection url to connect to nova slave database (read-only).
+#   Defaults to false
+#
 # [*database_idle_timeout*]
 #   (optional) Timeout before idle db connections are reaped.
 #   Defaults to 3600
@@ -227,6 +231,7 @@
 class nova(
   $ensure_package           = 'present',
   $database_connection      = false,
+  $slave_connection         = false,
   $database_idle_timeout    = 3600,
   $rpc_backend              = 'rabbit',
   $image_service            = 'nova.image.glance.GlanceImageService',

spec/classes/nova_api_spec.rb

@@ -230,6 +230,7 @@ describe 'nova::api' do
       end
 
       it { should_not contain_nova_config('database/connection') }
+      it { should_not contain_nova_config('database/slave_connection') }
       it { should_not contain_nova_config('database/idle_timeout').with_value('3600') }
     end
 
@@ -237,12 +238,14 @@ describe 'nova::api' do
       let :pre_condition do
         "class { 'nova':
            database_connection   => 'mysql://user:pass@db/db',
+           slave_connection      => 'mysql://user:pass@slave/db',
            database_idle_timeout => '30',
          }
         "
       end
 
       it { should contain_nova_config('database/connection').with_value('mysql://user:pass@db/db').with_secret(true) }
+      it { should contain_nova_config('database/slave_connection').with_value('mysql://user:pass@slave/db').with_secret(true) }
       it { should contain_nova_config('database/idle_timeout').with_value('30') }
     end
 

spec/classes/nova_conductor_spec.rb

@@ -56,6 +56,7 @@ describe 'nova::conductor' do
       end
 
       it { should_not contain_nova_config('database/connection') }
+      it { should_not contain_nova_config('database/slave_connection') }
       it { should_not contain_nova_config('database/idle_timeout').with_value('3600') }
     end
 
@@ -63,12 +64,14 @@ describe 'nova::conductor' do
       let :pre_condition do
         "class { 'nova':
            database_connection   => 'mysql://user:pass@db/db',
+           slave_connection      => 'mysql://user:pass@slave/db',
            database_idle_timeout => '30',
          }
         "
       end
 
       it { should contain_nova_config('database/connection').with_value('mysql://user:pass@db/db').with_secret(true) }
+      it { should contain_nova_config('database/slave_connection').with_value('mysql://user:pass@slave/db').with_secret(true) }
       it { should contain_nova_config('database/idle_timeout').with_value('30') }
     end
 

spec/classes/nova_db_spec.rb

@@ -10,6 +10,7 @@ describe 'nova::db' do
 
     context 'with default parameters' do
       it { should_not contain_nova_config('database/connection') }
+      it { should_not contain_nova_config('database/slave_connection') }
       it { should_not contain_nova_config('database/idle_timeout') }
     end
 
@@ -17,11 +18,13 @@ describe 'nova::db' do
       before :each do
         params.merge!(
           :database_connection   => 'mysql://user:pass@db/db',
+          :slave_connection      => 'mysql://user:pass@slave/db',
           :database_idle_timeout => '30',
         )
       end
 
       it { should contain_nova_config('database/connection').with_value('mysql://user:pass@db/db').with_secret(true) }
+      it { should contain_nova_config('database/slave_connection').with_value('mysql://user:pass@slave/db').with_secret(true) }
       it { should contain_nova_config('database/idle_timeout').with_value('30') }
     end
 

spec/classes/nova_scheduler_spec.rb

@@ -49,6 +49,7 @@ describe 'nova::scheduler' do
       end
 
       it { should_not contain_nova_config('database/connection') }
+      it { should_not contain_nova_config('database/slave_connection') }
       it { should_not contain_nova_config('database/idle_timeout').with_value('3600') }
     end
 
@@ -56,12 +57,14 @@ describe 'nova::scheduler' do
       let :pre_condition do
         "class { 'nova':
            database_connection   => 'mysql://user:pass@db/db',
+           slave_connection      => 'mysql://user:pass@slave/db',
            database_idle_timeout => '30',
          }
         "
       end
 
       it { should contain_nova_config('database/connection').with_value('mysql://user:pass@db/db').with_secret(true) }
+      it { should contain_nova_config('database/slave_connection').with_value('mysql://user:pass@slave/db').with_secret(true) }
       it { should contain_nova_config('database/idle_timeout').with_value('30') }
     end