Adds more replica provider primitives

This commit introduces several basic building blocks
for replication providers:

* PoolReplicaProvider returns replica from the prepopulated pool (that
  can become empty over time). Released replicas are returned to the pool.

* RoundrobinReplicaProvider returns items from the prepopulated
  list. When the list is exhausted it returns them again thus reusing
  the items. This is usually needed to spread the load between
  fixed number of servers or other cloud resources.

 * CompositeReplicaProvider allows to combine several replica
   providers into one. When new replica is requested it tries to
   obtain it from the underlay providers one by so if the first
   replica provider goes out of resources the second is used
   for further allocations.

 Also refactor replica release interface to better handle
 down-scaling by more than 1 item

Change-Id: I923b2c6d0cd3a881be323399b7b13481e9a4a459

meta/io.murano.applications/Classes/replication.yaml

@@ -45,17 +45,16 @@ Methods:
   deploy:
     Body:
       # release excessive replicas
-      - $newItems: $this.items.take($this.numItems)
+      - $oldItems: $this.items.take($this.numItems)
       - $itemsToRelease: $this.items.skip($this.numItems)
       - $this.provider.releaseReplicas($itemsToRelease)
-      - $this.items: $newItems
 
       - $delta: $this.numItems - len($this.items)
       - $startIndex: len($this.items) + 1
       - $endIndex: $startIndex + $delta
       - $createdItems: range($startIndex, $endIndex).select(
-                             $this.provider.createReplica($, $this))
-      - $this.items: $this.items + $createdItems
+          $this.provider.createReplica($, $this)).takeWhile($ != null)
+      - $this.items: $oldItems + $createdItems
 
   scale:
     Arguments:
@@ -69,11 +68,10 @@ Methods:
           - $this.numItems: min($this.numItems, $this.maxItems)
       - $this.deploy()
 
-  releaseItems:
-    Arguments:
-      items:
-        Contract:
-          - $.class(std:Object)
+    .destroy:
+      Body:
+        - $this.numItems: 0
+        - $this.deploy()
 
 --- # ------------------------------------------------------------------ # ---
 
@@ -92,6 +90,8 @@ Methods:
       replicas:
         Contract:
           - $.class(std:Object)
+    Body:
+      Return: $replicas
 
 
 --- # ------------------------------------------------------------------ # ---
@@ -114,3 +114,105 @@ Methods:
 
     Body:
       - Return: new($this.template, $owner)
+
+--- # ------------------------------------------------------------------ # ---
+# Replica provider that is a composition of other replica providers
+
+Name: CompositeReplicaProvider
+Extends: ReplicaProvider
+
+Properties:
+  providers:
+    Contract:
+      - $.class(ReplicaProvider).notNull()
+
+Methods:
+  createReplica:
+    Arguments:
+      - index:
+          Contract: $.int().notNull()
+      - owner:
+          Contract: $.class(std:Object)
+    Body:
+      - Return: $this.providers.select($.createReplica($index, $owner)).where($ != null).first(null)
+
+  releaseReplicas:
+    Arguments:
+      replicas:
+        Contract:
+          - $.class(std:Object)
+    Body:
+      - For: provider
+        In: $this.providers
+        Do:
+          - $replicas: $provider.releaseReplicas($replicas)
+          - If: $replicas = null or not $replicas.any()
+            Then:
+              Break:
+      - Return: $replicas
+
+--- # ------------------------------------------------------------------ # ---
+# A replica provider from the prepopulated pool
+
+Name: PoolReplicaProvider
+Extends: ReplicaProvider
+
+Properties:
+  pool:
+    Contract:
+      - $.class(std:Object).notNull()
+
+  consumedItems:
+    Usage: Out
+    Contract:
+      - $.class(std:Object).notNull()
+
+Methods:
+  createReplica:
+    Arguments:
+      - index:
+          Contract: $.int().notNull()
+      - owner:
+          Contract: $.class(std:Object)
+    Body:
+      - $item: $this.pool.where(not $this.consumedItems.contains($)).first(null)
+      - If: $item != null
+        Then:
+          - $this.consumedItems: $this.consumedItems.append($item)
+      - Return: $item
+
+  releaseReplicas:
+    Arguments:
+      replicas:
+        Contract:
+          - $.class(std:Object)
+    Body:
+      - $poolReplicas: $replicas.where($this.consumedItems.contains($))
+      - $this.consumedItems: $this.consumedItems.where(not $poolReplicas.contains($))
+      - Return: $replicas.where(not $poolReplicas.contains($))
+
+--- # ------------------------------------------------------------------ # ---
+# Replica provider with a load balancing that returns instance from the
+# prepopulated list. Once the provider runs out of free items it goes to
+# beginning of the list and returns the same instances again.
+
+Name: RoundrobinReplicaProvider
+Extends: ReplicaProvider
+
+Properties:
+  items:
+    Contract:
+      - $.class(std:Object).notNull()
+      - 1
+
+Methods:
+  createReplica:
+    Arguments:
+      - index:
+          Contract: $.int().notNull()
+      - owner:
+          Contract: $.class(std:Object)
+    Body:
+      - $index: $.getAttr(lastIndex, 0)
+      - $.setAttr(lastIndex, ($index + 1) mod len($this.items))
+      - Return: $this.items[$index]

meta/io.murano.applications/Classes/servers.yaml

@@ -79,7 +79,7 @@ Methods:
 
   .destroy:
     Body:
-      - $this.releaseServers($this.items)
+      - $this.releaseServers($this.servers)
 
   getServers:
     Body:
@@ -156,10 +156,6 @@ Methods:
       - cast($this, ReplicationGroup).deploy()
       - $this.deployServers($this, $this.items)
 
-  .destroy:
-    Body:
-      - $this.releaseServers($this.items)
-
   getServers:
     Body:
       Return: $.items
@@ -197,6 +193,14 @@ Properties:
   serverNamePattern:
     Contract: $.string().notNull()
 
+  allocated:
+    Usage: Out
+    Contract: $.int().notNull()
+    Default: 0
+
+  capacity:
+    Contract: $.int()
+
 Methods:
   createReplica:
     Arguments:
@@ -205,22 +209,31 @@ Methods:
       - owner:
           Contract: $.class(std:Object)
     Body:
-      - $template: $this.template
-      - $template.name: $this.serverNamePattern.format($index)
-      - $ownerGroup: $this.find(ServerGroup)
-      - If: $ownerGroup and name($ownerGroup)
+      - If: $this.capacity = null or $this.allocated < $this.capacity
         Then:
+        - $template: $this.template
+        - $template.name: $this.serverNamePattern.format($index)
+        - $ownerGroup: $this.find(ServerGroup)
+        - If: $ownerGroup and name($ownerGroup)
+          Then:
           - $groupName: format(' ({0})', name($ownerGroup))
-        Else:
+          Else:
           - $groupName: ''
-      - $template['?'].name: format('Server {0}{1}', $index, $groupName)
-      - Return: new($template, $owner)
+        - $template['?'].name: format('Server {0}{1}', $index, $groupName)
+        - $this.allocated: $this.allocated + 1
+        - Return: new($template, $owner)
+        Else:
+        - Return: null
 
   releaseReplicas:
     Arguments:
       replicas:
         Contract:
-          - $.class(std:Object)
+          - $.class(res:Instance)
     Body:
       - $replicas.select($.beginReleaseResources())
       - $replicas.select($.endReleaseResources())
+      - $this.allocated: max(0, $this.allocated - len($replicas))
+      - Return: []
+
+

meta/io.murano.applications/Classes/tests/TestReplication.yaml

@@ -93,3 +93,91 @@ Methods:
       - $.assertEqual(1, len($group.items))
       - $.assertEqual(1, $this.provider.allocated)
 
+--- # ------------------------------------------------------------------ # ---
+
+Name: TestPoolReplicaProvider
+Extends: tst:TestFixture
+
+Methods:
+  setUp:
+    Body:
+      - $this.object1: new(std:Object)
+      - $this.object2: new(std:Object)
+      - $this.provider: new(apps:PoolReplicaProvider, pool => [$this.object1, $this.object2])
+
+  testReplicas:
+    Body:
+      - $.assertEqual(2, len($this.provider.pool))
+      - $.assertEqual(0, len($this.provider.consumedItems))
+      - $obj: $this.provider.createReplica(1, $this)
+      - $.assertEqual($this.object1, $obj)
+      - $.assertEqual(2, len($this.provider.pool))
+      - $.assertEqual(1, len($this.provider.consumedItems))
+      - $obj: $this.provider.createReplica(2, $this)
+      - $.assertEqual($this.object2, $obj)
+      - $.assertEqual(2, len($this.provider.pool))
+      - $.assertEqual(2, len($this.provider.consumedItems))
+      - $obj: $this.provider.createReplica(3, $this)
+      - $.assertEqual(null, $obj)
+      - $.assertEqual(2, len($this.provider.pool))
+      - $.assertEqual(2, len($this.provider.consumedItems))
+
+  testReleaseReplicas:
+    Body:
+      - $obj: $this.provider.createReplica(1, $this)
+      - $.assertEqual(1, len($this.provider.consumedItems))
+      - $foreignObj: new(std:Object)
+      - $res: $this.provider.releaseReplicas([$obj, $this.object1, $this.object2, $foreignObj])
+      - $.assertEqual(0, len($this.provider.consumedItems))
+      - $.assertEqual([$this.object2, $foreignObj], $res)
+      - $this.testReplicas()
+
+--- # ------------------------------------------------------------------ # ---
+
+Name: TestRoundrobinReplicaProvider
+Extends: tst:TestFixture
+
+Methods:
+  setUp:
+    Body:
+      - $this.object1: new(std:Object)
+      - $this.object2: new(std:Object)
+      - $this.provider: new(apps:RoundrobinReplicaProvider, items => [$this.object1, $this.object2])
+
+  testReplicas:
+    Body:
+      - $obj: $this.provider.createReplica(1, $this)
+      - $.assertEqual($this.object1, $obj)
+      - $obj: $this.provider.createReplica(2, $this)
+      - $.assertEqual($this.object2, $obj)
+      - $obj: $this.provider.createReplica(3, $this)
+      - $.assertEqual($this.object1, $obj)
+      - $obj: $this.provider.createReplica(4, $this)
+      - $.assertEqual($this.object2, $obj)
+
+--- # ------------------------------------------------------------------ # ---
+
+Name: TestCompositeReplicaProvider
+Extends: tst:TestFixture
+
+Methods:
+  setUp:
+    Body:
+      - $this.objects: range(4).select(new(std:Object))
+      - $this.object2: new(std:Object)
+      - $this.provider1: new(apps:PoolReplicaProvider, pool => [$this.objects[0], $this.objects[1]])
+      - $this.provider2: new(apps:RoundrobinReplicaProvider, items => [$this.objects[2], $this.objects[3]])
+      - $this.provider: new(apps:CompositeReplicaProvider, providers => [$this.provider1, $this.provider2])
+
+  testReplicas:
+    Body:
+      - $obj: $this.provider.createReplica(1, $this)
+      - $.assertEqual($this.objects[0], $obj)
+      - $obj: $this.provider.createReplica(2, $this)
+      - $.assertEqual($this.objects[1], $obj)
+      - $obj: $this.provider.createReplica(3, $this)
+      - $.assertEqual($this.objects[2], $obj)
+      - $obj: $this.provider.createReplica(4, $this)
+      - $.assertEqual($this.objects[3], $obj)
+      - $obj: $this.provider.createReplica(5, $this)
+      - $.assertEqual($this.objects[2], $obj)

meta/io.murano.applications/manifest.yaml

@@ -10,7 +10,7 @@
 #  License for the specific language governing permissions and limitations
 #  under the License.
 
-Format: 1.3
+Format: 1.4
 
 Type: Library
 
@@ -27,6 +27,10 @@ Classes:
   io.murano.applications.ReplicaProvider: replication.yaml
   io.murano.applications.ReplicationGroup: replication.yaml
   io.murano.applications.CloneReplicaProvider: replication.yaml
+  io.murano.applications.CompositeReplicaProvider: replication.yaml
+  io.murano.applications.PoolReplicaProvider: replication.yaml
+  io.murano.applications.RoundrobinReplicaProvider: replication.yaml
+
   io.murano.applications.Event: events.yaml
 
   io.murano.applications.ServerGroup: servers.yaml
@@ -51,6 +55,9 @@ Classes:
 
   # Tests
   io.murano.applications.tests.TestReplication: tests/TestReplication.yaml
+  io.murano.applications.tests.TestPoolReplicaProvider: tests/TestReplication.yaml
+  io.murano.applications.tests.TestRoundrobinReplicaProvider: tests/TestReplication.yaml
+  io.murano.applications.tests.TestCompositeReplicaProvider: tests/TestReplication.yaml
   io.murano.applications.tests.TestEvents: tests/TestEvents.yaml
   io.murano.applications.tests.TestMockedServerFactory: tests/TestServerProviders.yaml
   io.murano.applications.tests.TestSoftwareComponent: tests/TestSoftwareComponent.yaml