Add seed parameter to ringbuilder::rebalance.

This patch adds an optional seed parameter to the
swift::ringbuilder::rebalance definition. The seed
parameter can be useful if you want to (manually)
generate rings on independant servers and ensure that
the partition assignments are the same.

Change-Id: I840b8fe0125ed25e84f7681fada1b1102e48f32b

manifests/ringbuilder/rebalance.pp

@@ -6,12 +6,19 @@
 #
 # [*name*] Type of ring to rebalance. The ring file is assumed to be at the path
 #   /etc/swift/${name}.builder
-define swift::ringbuilder::rebalance() {
+#
+# [*seed*] Optional. Seed value used to seed pythons pseudo-random for ringbuilding.
+define swift::ringbuilder::rebalance(
+  $seed = undef
+) {
 
   validate_re($name, '^object|container|account$')
+  if $seed {
+    validate_re($seed, '^\d+$')
+  }
 
   exec { "rebalance_${name}":
-    command     => "swift-ring-builder /etc/swift/${name}.builder rebalance",
+    command     => strip("swift-ring-builder /etc/swift/${name}.builder rebalance ${seed}"),
     path        => ['/usr/bin'],
     refreshonly => true,
   }

spec/defines/swift_ringbuilder_rebalance_spec.rb

@@ -14,6 +14,30 @@ describe 'swift::ringbuilder::rebalance' do
       end
     end
   end
+  describe 'with valid seed' do
+    let :params do
+      { :seed => '999' }
+    end
+    let :title do
+      'object'
+    end
+    it { should contain_exec("rebalance_object").with(
+      {:command     => "swift-ring-builder /etc/swift/object.builder rebalance 999",
+       :path        => '/usr/bin',
+       :refreshonly => true}
+    )}
+  end
+  describe 'with an invalid seed' do
+    let :title do
+      'object'
+    end
+    let :params do
+      { :seed => 'invalid' }
+    end
+    it 'should raise an error' do
+      expect { subject }.to raise_error(Puppet::Error)
+    end
+  end
   describe 'with an invalid title' do
     let :title do
       'invalid'