Add Test for simple allocation scenario

This test checks for the "perfect" or a "sane" allocation
when the total number of shards is separable by the total number of nodes
the index can be allocated on.

src/test/java/org/elasticsearch/test/integration/cluster/allocation/SimpleAllocationTests.java

@@ -0,0 +1,87 @@
+/*
+ * Licensed to ElasticSearch and Shay Banon under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. ElasticSearch licenses this
+ * file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.elasticsearch.test.integration.cluster.allocation;
+
+import static org.elasticsearch.common.settings.ImmutableSettings.settingsBuilder;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
+
+import java.util.Map;
+import java.util.Map.Entry;
+
+import org.elasticsearch.cluster.ClusterState;
+import org.elasticsearch.cluster.routing.RoutingNode;
+import org.elasticsearch.common.Priority;
+import org.elasticsearch.test.integration.AbstractSharedClusterTest;
+import org.testng.annotations.Test;
+
+public class SimpleAllocationTests extends AbstractSharedClusterTest {
+    
+    /**
+     * Test for 
+     * https://groups.google.com/d/msg/elasticsearch/y-SY_HyoB-8/EZdfNt9VO44J
+     */
+    @Test
+    public void testSaneAllocation() {
+        prepareCreate("test", 3,
+                        settingsBuilder().put("index.number_of_shards", 3)
+                        .put("index.number_of_replicas", 1))
+                        .execute().actionGet();
+        ensureGreen();            
+        ClusterState state = client().admin().cluster().prepareState().execute().actionGet().getState();
+        assertThat(state.routingNodes().unassigned().size(), equalTo(0));
+        Map<String, RoutingNode> nodesToShards = state.routingNodes().getNodesToShards();
+        for (Entry<String, RoutingNode> entry : nodesToShards.entrySet()) {
+            if (!entry.getValue().shards().isEmpty()) { 
+                assertThat(entry.getValue().shards().size(), equalTo(2));
+            }
+        }
+        client().admin().indices().prepareUpdateSettings("test").setSettings(settingsBuilder().put("index.number_of_replicas", 0)).execute().actionGet();
+        client().admin().cluster().prepareHealth().setWaitForEvents(Priority.LANGUID).setWaitForGreenStatus().execute().actionGet();
+        state = client().admin().cluster().prepareState().execute().actionGet().getState();
+
+        assertThat(state.routingNodes().unassigned().size(), equalTo(0));
+        nodesToShards = state.routingNodes().getNodesToShards();
+        for (Entry<String, RoutingNode> entry : nodesToShards.entrySet()) {
+            if (!entry.getValue().shards().isEmpty()) {
+                assertThat(entry.getValue().shards().size(), equalTo(1));
+            }
+        }
+        
+        // create another index
+        prepareCreate("test2", 3,
+                        settingsBuilder()
+                        .put("index.number_of_shards", 3)
+                        .put("index.number_of_replicas", 1))
+                        .execute()
+                .actionGet();
+        ensureGreen();            
+        client().admin().indices().prepareUpdateSettings("test").setSettings(settingsBuilder().put("index.number_of_replicas", 1)).execute().actionGet();
+        client().admin().cluster().prepareHealth().setWaitForEvents(Priority.LANGUID).setWaitForGreenStatus().execute().actionGet();
+        state = client().admin().cluster().prepareState().execute().actionGet().getState();
+
+        assertThat(state.routingNodes().unassigned().size(), equalTo(0));
+        nodesToShards = state.routingNodes().getNodesToShards();
+        for (Entry<String, RoutingNode> entry : nodesToShards.entrySet()) {
+            if (!entry.getValue().shards().isEmpty()) {
+                assertThat(entry.getValue().shards().size(), equalTo(4));
+            }
+        }
+    }
+}