metadata: If an alias and index share the same name then a descriptiv…

…e error should be thrown

In 1.x it is possible via index templates to create an index with an alias with the same name as the index. The index name must match the index template and have an alias with the same name as the index being created.

core/src/main/java/org/elasticsearch/cluster/metadata/MetaData.java

@@ -44,6 +44,7 @@
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.logging.ESLogger;
+import org.elasticsearch.common.logging.support.LoggerMessageFormat;
 import org.elasticsearch.common.regex.Regex;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.settings.loader.SettingsLoader;
@@ -1024,12 +1025,18 @@ public MetaData build() {
 
                 for (ObjectObjectCursor<String, AliasMetaData> aliasCursor : indexMetaData.getAliases()) {
                     AliasMetaData aliasMetaData = aliasCursor.value;
-                    AliasOrIndex.Alias aliasOrIndex = (AliasOrIndex.Alias) aliasAndIndexLookup.get(aliasMetaData.getAlias());
+                    AliasOrIndex aliasOrIndex = aliasAndIndexLookup.get(aliasMetaData.getAlias());
                     if (aliasOrIndex == null) {
                         aliasOrIndex = new AliasOrIndex.Alias(aliasMetaData, indexMetaData);
                         aliasAndIndexLookup.put(aliasMetaData.getAlias(), aliasOrIndex);
+                    } else if (aliasOrIndex instanceof AliasOrIndex.Alias) {
+                        AliasOrIndex.Alias alias = (AliasOrIndex.Alias) aliasOrIndex;
+                        alias.addIndex(indexMetaData);
+                    } else if (aliasOrIndex instanceof AliasOrIndex.Index) {
+                        AliasOrIndex.Index index = (AliasOrIndex.Index) aliasOrIndex;
+                        throw new IllegalStateException("index and alias names need to be unique, but alias [" + aliasMetaData.getAlias() + "] and index [" + index.getIndex().getIndex() + "] have the same name");
                     } else {
-                        aliasOrIndex.addIndex(indexMetaData);
+                        throw new IllegalStateException("unexpected alias [" + aliasMetaData.getAlias() + "][" + aliasOrIndex + "]");
                     }
                 }
             }

core/src/test/java/org/elasticsearch/cluster/metadata/MetaDataTests.java

@@ -0,0 +1,44 @@
+/*
+ * Licensed to Elasticsearch 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.cluster.metadata;
+
+import org.elasticsearch.Version;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.test.ESTestCase;
+
+import static org.hamcrest.Matchers.equalTo;
+
+public class MetaDataTests extends ESTestCase {
+
+    public void testIndexAndAliasWithSameName() {
+        IndexMetaData.Builder builder = IndexMetaData.builder("index")
+                .settings(Settings.builder().put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT))
+                .numberOfShards(1)
+                .numberOfReplicas(0)
+                .putAlias(AliasMetaData.builder("index").build());
+        try {
+            MetaData.builder().put(builder).build();
+            fail("expection should have been thrown");
+        } catch (IllegalStateException e) {
+            assertThat(e.getMessage(), equalTo("index and alias names need to be unique, but alias [index] and index [index] have the same name"));
+        }
+    }
+
+}