Deprecate creation of dot-prefixed index names except for hidden and system indices

docs/reference/index-modules.asciidoc

@@ -79,7 +79,7 @@ indices.
     Indicates whether <<query-filter-context, cached filters>> are pre-loaded for
     nested queries. Possible values are `true` (default) and `false`.
 
-`index.hidden`::
+[[index-hidden]] `index.hidden`::
 
     Indicates whether the index should be hidden by default. Hidden indices are not
     returned by default when using a wildcard expression. This behavior is controlled

docs/reference/indices/create-index.asciidoc

@@ -19,7 +19,7 @@ PUT /twitter
 
 [[indices-create-api-desc]]
 ==== {api-description-title}
-You can use the create index API to add a new index to an {es} cluster. When 
+You can use the create index API to add a new index to an {es} cluster. When
 creating an index, you can specify the following:
 
 * Settings for the index
@@ -44,6 +44,7 @@ Index names must meet the following criteria:
 - Cannot start with `-`, `_`, `+`
 - Cannot be `.` or `..`
 - Cannot be longer than 255 bytes (note it is bytes, so multi-byte characters will count towards the 255 limit faster)
+- Names starting with `.` are deprecated, except for <<index-hidden,hidden indices>> and internal indices managed by plugins
 // end::index-name-reqs[]
 --
 

modules/tasks/build.gradle

@@ -0,0 +1,25 @@
+/*
+ * 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.
+ */
+
+esplugin {
+  description 'Supports the Tasks API'
+  classname 'org.elasticsearch.tasksplugin.TasksPlugin'
+}
+
+integTest.enabled = false

modules/tasks/src/main/java/org/elasticsearch/tasksplugin/TasksPlugin.java

@@ -0,0 +1,40 @@
+/*
+ * 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.tasksplugin;
+
+import org.elasticsearch.indices.SystemIndexDescriptor;
+import org.elasticsearch.plugins.Plugin;
+import org.elasticsearch.plugins.SystemIndexPlugin;
+
+import java.util.Collection;
+import java.util.Collections;
+
+import static org.elasticsearch.tasks.TaskResultsService.TASK_INDEX;
+
+/**
+ * This plugin currently only exists to register `.tasks` as a system index.
+ */
+public class TasksPlugin extends Plugin implements SystemIndexPlugin {
+
+    @Override
+    public Collection<SystemIndexDescriptor> getSystemIndexDescriptors() {
+        return Collections.singletonList(new SystemIndexDescriptor(TASK_INDEX, this.getClass().getSimpleName()));
+    }
+}

modules/tasks/src/test/java/org/elasticsearch/tasksplugin/TasksPluginTests.java

@@ -0,0 +1,32 @@
+/*
+ * 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.tasksplugin;
+
+import org.elasticsearch.test.ESTestCase;
+import org.hamcrest.Matchers;
+
+public class TasksPluginTests extends ESTestCase {
+
+    public void testDummy() {
+        // This is a dummy test case to satisfy the conventions
+        TasksPlugin plugin = new TasksPlugin();
+        assertThat(plugin.getSystemIndexDescriptors(), Matchers.hasSize(1));
+    }
+}

server/src/main/java/org/elasticsearch/action/admin/indices/rollover/TransportRolloverAction.java

@@ -122,9 +122,9 @@ protected void masterOperation(Task task, final RolloverRequest rolloverRequest,
             ? rolloverRequest.getNewIndexName()
             : generateRolloverIndexName(sourceProvidedName, indexNameExpressionResolver);
         final String rolloverIndexName = indexNameExpressionResolver.resolveDateMathExpression(unresolvedName);
-        MetaDataCreateIndexService.validateIndexName(rolloverIndexName, state); // will fail if the index already exists
         final Boolean isHidden = IndexMetaData.INDEX_HIDDEN_SETTING.exists(rolloverRequest.getCreateIndexRequest().settings()) ?
             IndexMetaData.INDEX_HIDDEN_SETTING.get(rolloverRequest.getCreateIndexRequest().settings()) : null;
+        createIndexService.validateIndexName(rolloverIndexName, state, isHidden); // fails if the index already exists
         checkNoDuplicatedAliasInIndexTemplate(metaData, rolloverIndexName, rolloverRequest.getAlias(), isHidden);
         IndicesStatsRequest statsRequest = new IndicesStatsRequest().indices(rolloverRequest.getAlias())
             .clear()

server/src/main/java/org/elasticsearch/cluster/metadata/MetaDataCreateIndexService.java

@@ -53,6 +53,7 @@
 import org.elasticsearch.common.ValidationException;
 import org.elasticsearch.common.compress.CompressedXContent;
 import org.elasticsearch.common.io.PathUtils;
+import org.elasticsearch.common.logging.DeprecationLogger;
 import org.elasticsearch.common.settings.IndexScopedSettings;
 import org.elasticsearch.common.settings.Setting;
 import org.elasticsearch.common.settings.Settings;
@@ -70,6 +71,7 @@
 import org.elasticsearch.indices.IndexCreationException;
 import org.elasticsearch.indices.IndicesService;
 import org.elasticsearch.indices.InvalidIndexNameException;
+import org.elasticsearch.indices.SystemIndexDescriptor;
 import org.elasticsearch.indices.cluster.IndicesClusterStateService.AllocatedIndices.IndexRemovalReason;
 import org.elasticsearch.threadpool.ThreadPool;
 
@@ -78,6 +80,7 @@
 import java.nio.file.Path;
 import java.time.Instant;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
@@ -89,6 +92,7 @@
 import java.util.function.BiFunction;
 import java.util.function.Predicate;
 import java.util.function.Supplier;
+import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
 import static java.util.stream.Collectors.toList;
@@ -103,6 +107,7 @@
  */
 public class MetaDataCreateIndexService {
     private static final Logger logger = LogManager.getLogger(MetaDataCreateIndexService.class);
+    private static final DeprecationLogger deprecationLogger = new DeprecationLogger(logger);
 
     public static final int MAX_INDEX_NAME_BYTES = 255;
 
@@ -115,19 +120,21 @@ public class MetaDataCreateIndexService {
     private final IndexScopedSettings indexScopedSettings;
     private final ActiveShardsObserver activeShardsObserver;
     private final NamedXContentRegistry xContentRegistry;
+    private final Collection<SystemIndexDescriptor> systemIndexDescriptors;
     private final boolean forbidPrivateIndexSettings;
 
     public MetaDataCreateIndexService(
-            final Settings settings,
-            final ClusterService clusterService,
-            final IndicesService indicesService,
-            final AllocationService allocationService,
-            final AliasValidator aliasValidator,
-            final Environment env,
-            final IndexScopedSettings indexScopedSettings,
-            final ThreadPool threadPool,
-            final NamedXContentRegistry xContentRegistry,
-            final boolean forbidPrivateIndexSettings) {
+        final Settings settings,
+        final ClusterService clusterService,
+        final IndicesService indicesService,
+        final AllocationService allocationService,
+        final AliasValidator aliasValidator,
+        final Environment env,
+        final IndexScopedSettings indexScopedSettings,
+        final ThreadPool threadPool,
+        final NamedXContentRegistry xContentRegistry,
+        final Collection<SystemIndexDescriptor> systemIndexDescriptors,
+        final boolean forbidPrivateIndexSettings) {
         this.settings = settings;
         this.clusterService = clusterService;
         this.indicesService = indicesService;
@@ -137,17 +144,40 @@ public MetaDataCreateIndexService(
         this.indexScopedSettings = indexScopedSettings;
         this.activeShardsObserver = new ActiveShardsObserver(clusterService, threadPool);
         this.xContentRegistry = xContentRegistry;
+        this.systemIndexDescriptors = systemIndexDescriptors;
         this.forbidPrivateIndexSettings = forbidPrivateIndexSettings;
     }
 
     /**
      * Validate the name for an index against some static rules and a cluster state.
      */
-    public static void validateIndexName(String index, ClusterState state) {
+    public void validateIndexName(String index, ClusterState state, @Nullable Boolean isHidden) {
         validateIndexOrAliasName(index, InvalidIndexNameException::new);
         if (!index.toLowerCase(Locale.ROOT).equals(index)) {
             throw new InvalidIndexNameException(index, "must be lowercase");
         }
+
+        if (index.charAt(0) == '.') {
+            List<SystemIndexDescriptor> matchingDescriptors = systemIndexDescriptors.stream()
+                .filter(descriptor -> descriptor.matchesIndexPattern(index))
+                .collect(toList());
+            if (matchingDescriptors.isEmpty() && (isHidden == null || isHidden == Boolean.FALSE)) {
+                deprecationLogger.deprecated("index name [{}] starts with a dot '.', in the next major version, index names " +
+                    "starting with a dot are reserved for hidden indices and system indices", index);
+            } else if (matchingDescriptors.size() > 1) {
+                // This should be prevented by erroring on overlapping patterns at startup time, but is here just in case.
+                StringBuilder errorMessage = new StringBuilder()
+                    .append("index name [")
+                    .append(index)
+                    .append("] is claimed as a system index by multiple system index patterns: [")
+                    .append(matchingDescriptors.stream()
+                        .map(descriptor -> "pattern: [" + descriptor.getIndexPattern() +
+                            "], description: [" + descriptor.getDescription() + "]").collect(Collectors.joining("; ")));
+                // Throw AssertionError if assertions are enabled, or a regular exception otherwise:
+                assert false : errorMessage.toString();
+                throw new IllegalStateException(errorMessage.toString());
+            }
+        }
         if (state.routingTable().hasIndex(index)) {
             throw new ResourceAlreadyExistsException(state.routingTable().index(index).getIndex());
         }
@@ -653,7 +683,8 @@ private static IndexService validateActiveShardCountAndCreateIndexService(String
     }
 
     private void validate(CreateIndexClusterStateUpdateRequest request, ClusterState state) {
-        validateIndexName(request.index(), state);
+        boolean isHidden = IndexMetaData.INDEX_HIDDEN_SETTING.get(request.settings());
+        validateIndexName(request.index(), state, isHidden);
         validateIndexSettings(request.index(), request.settings(), forbidPrivateIndexSettings);
     }