AutoCreate should work for non-primary system indices (#77045)

Previously, we handled the case of a write request to a system index
alias without a backing index by auto-creating the primary index. This
had the unfortunate side-effect of making it impossible to auto-create
non-primary system indices. This commit fixes the bug so that we can
handle both cases.

* Add internal cluster test for system index auto create
* Allow auto-creation of non-primary indices for a system index pattern
* Use primary index if autocreate is called with system index alias name

server/src/internalClusterTest/java/org/elasticsearch/action/admin/indices/create/AutoCreateSystemIndexIT.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+package org.elasticsearch.action.admin.indices.create;
+
+import org.elasticsearch.action.admin.indices.get.GetIndexResponse;
+import org.elasticsearch.common.util.CollectionUtils;
+import org.elasticsearch.indices.TestSystemIndexPlugin;
+import org.elasticsearch.plugins.Plugin;
+import org.elasticsearch.test.ESIntegTestCase;
+
+import java.util.Collection;
+
+import static org.elasticsearch.indices.TestSystemIndexDescriptor.INDEX_NAME;
+import static org.elasticsearch.indices.TestSystemIndexDescriptor.PRIMARY_INDEX_NAME;
+import static org.hamcrest.Matchers.is;
+
+@ESIntegTestCase.ClusterScope(scope = ESIntegTestCase.Scope.TEST, numDataNodes = 0)
+public class AutoCreateSystemIndexIT extends ESIntegTestCase {
+
+    @Override
+    protected Collection<Class<? extends Plugin>> nodePlugins() {
+        return CollectionUtils.appendToCopy(super.nodePlugins(), TestSystemIndexPlugin.class);
+    }
+
+    public void testAutoCreatePrimaryIndex() throws Exception {
+        CreateIndexRequest request = new CreateIndexRequest(PRIMARY_INDEX_NAME);
+        client().execute(AutoCreateAction.INSTANCE, request).get();
+
+        GetIndexResponse response = client().admin().indices().prepareGetIndex().addIndices(PRIMARY_INDEX_NAME).get();
+        assertThat(response.indices().length, is(1));
+    }
+
+    public void testAutoCreatePrimaryIndexFromAlias() throws Exception {
+        CreateIndexRequest request = new CreateIndexRequest(INDEX_NAME);
+        client().execute(AutoCreateAction.INSTANCE, request).get();
+
+        GetIndexResponse response = client().admin().indices().prepareGetIndex().addIndices(PRIMARY_INDEX_NAME).get();
+        assertThat(response.indices().length, is(1));
+    }
+
+    public void testAutoCreateNonPrimaryIndex() throws Exception {
+        CreateIndexRequest request = new CreateIndexRequest(INDEX_NAME + "-2");
+        client().execute(AutoCreateAction.INSTANCE, request).get();
+
+        GetIndexResponse response = client().admin().indices().prepareGetIndex().addIndices(INDEX_NAME + "-2").get();
+        assertThat(response.indices().length, is(1));
+    }
+}

server/src/internalClusterTest/java/org/elasticsearch/action/admin/indices/create/CreateSystemIndicesIT.java

@@ -52,7 +52,7 @@ protected Collection<Class<? extends Plugin>> nodePlugins() {
      * settings when it is first used, when it is referenced via its alias.
      */
     public void testSystemIndexIsAutoCreatedViaAlias() {
-        doCreateTest(() -> indexDoc(INDEX_NAME, "1", "foo", "bar"));
+        doCreateTest(() -> indexDoc(INDEX_NAME, "1", "foo", "bar"), PRIMARY_INDEX_NAME);
     }
 
     /**
@@ -61,15 +61,25 @@ public void testSystemIndexIsAutoCreatedViaAlias() {
      * index name.
      */
     public void testSystemIndexIsAutoCreatedViaConcreteName() {
-        doCreateTest(() -> indexDoc(PRIMARY_INDEX_NAME, "1", "foo", "bar"));
+        doCreateTest(() -> indexDoc(PRIMARY_INDEX_NAME, "1", "foo", "bar"), PRIMARY_INDEX_NAME);
+    }
+
+    /**
+     * Check that a system index is auto-created with the expected mappings and
+     * settings when it is first used, when it is referenced via its concrete
+     * index name.
+     */
+    public void testNonPrimarySystemIndexIsAutoCreatedViaConcreteName() {
+        final String nonPrimarySystemIndex = INDEX_NAME + "-2";
+        doCreateTest(() -> indexDoc(nonPrimarySystemIndex, "1", "foo", "bar"), nonPrimarySystemIndex);
     }
 
     /**
      * Check that a system index is created with the expected mappings and
      * settings when it is explicitly created, when it is referenced via its alias.
      */
     public void testCreateSystemIndexViaAlias() {
-        doCreateTest(() -> assertAcked(prepareCreate(INDEX_NAME)));
+        doCreateTest(() -> assertAcked(prepareCreate(INDEX_NAME)), PRIMARY_INDEX_NAME);
     }
 
     /**
@@ -78,21 +88,21 @@ public void testCreateSystemIndexViaAlias() {
      * concrete index name.
      */
     public void testCreateSystemIndexViaConcreteName() {
-        doCreateTest(() -> assertAcked(prepareCreate(PRIMARY_INDEX_NAME)));
+        doCreateTest(() -> assertAcked(prepareCreate(PRIMARY_INDEX_NAME)), PRIMARY_INDEX_NAME);
     }
 
-    private void doCreateTest(Runnable runnable) {
+    private void doCreateTest(Runnable runnable, String concreteIndex) {
         internalCluster().startNodes(1);
 
         // Trigger the creation of the system index
         runnable.run();
         ensureGreen(INDEX_NAME);
 
-        assertMappingsAndSettings(TestSystemIndexDescriptor.getOldMappings());
+        assertMappingsAndSettings(TestSystemIndexDescriptor.getOldMappings(), concreteIndex);
 
         // Remove the index and alias...
-        assertAcked(client().admin().indices().prepareAliases().removeAlias(PRIMARY_INDEX_NAME, INDEX_NAME).get());
-        assertAcked(client().admin().indices().prepareDelete(PRIMARY_INDEX_NAME));
+        assertAcked(client().admin().indices().prepareAliases().removeAlias(concreteIndex, INDEX_NAME).get());
+        assertAcked(client().admin().indices().prepareDelete(concreteIndex));
 
         // ...so that we can check that the they will still be auto-created again,
         // but this time with updated settings
@@ -101,26 +111,26 @@ private void doCreateTest(Runnable runnable) {
         runnable.run();
         ensureGreen(INDEX_NAME);
 
-        assertMappingsAndSettings(TestSystemIndexDescriptor.getNewMappings());
+        assertMappingsAndSettings(TestSystemIndexDescriptor.getNewMappings(), concreteIndex);
     }
 
     /**
      * Fetch the mappings and settings for {@link TestSystemIndexDescriptor#INDEX_NAME} and verify that they match the expected values.
      * Note that in the case of the mappings, this is just a dumb string comparison, so order of keys matters.
      */
-    private void assertMappingsAndSettings(String expectedMappings) {
+    private void assertMappingsAndSettings(String expectedMappings, String concreteIndex) {
         final GetMappingsResponse getMappingsResponse = client().admin()
             .indices()
             .getMappings(new GetMappingsRequest().indices(INDEX_NAME))
             .actionGet();
 
         final ImmutableOpenMap<String, MappingMetadata> mappings = getMappingsResponse.getMappings();
         assertThat(
-            "Expected mappings to contain a key for [" + PRIMARY_INDEX_NAME + "], but found: " + mappings.toString(),
-            mappings.containsKey(PRIMARY_INDEX_NAME),
+            "Expected mappings to contain a key for [" + concreteIndex + "], but found: " + mappings.toString(),
+            mappings.containsKey(concreteIndex),
             equalTo(true)
         );
-        final Map<String, Object> sourceAsMap = mappings.get(PRIMARY_INDEX_NAME).getSourceAsMap();
+        final Map<String, Object> sourceAsMap = mappings.get(concreteIndex).getSourceAsMap();
 
         try {
             assertThat(convertToXContent(sourceAsMap, XContentType.JSON).utf8ToString(), equalTo(expectedMappings));
@@ -133,7 +143,7 @@ private void assertMappingsAndSettings(String expectedMappings) {
             .getSettings(new GetSettingsRequest().indices(INDEX_NAME))
             .actionGet();
 
-        final Settings actual = getSettingsResponse.getIndexToSettings().get(PRIMARY_INDEX_NAME);
+        final Settings actual = getSettingsResponse.getIndexToSettings().get(concreteIndex);
 
         for (String settingName : TestSystemIndexDescriptor.SETTINGS.keySet()) {
             assertThat(actual.get(settingName), equalTo(TestSystemIndexDescriptor.SETTINGS.get(settingName)));

server/src/main/java/org/elasticsearch/action/admin/indices/create/AutoCreateAction.java

@@ -169,7 +169,7 @@ public ClusterState execute(ClusterState currentState) throws Exception {
                                 throw new IllegalStateException(message);
                             }
 
-                            updateRequest = buildSystemIndexUpdateRequest(descriptor);
+                            updateRequest = buildSystemIndexUpdateRequest(indexName, descriptor);
                         } else {
                             updateRequest = buildUpdateRequest(indexName);
                         }
@@ -187,11 +187,14 @@ private CreateIndexClusterStateUpdateRequest buildUpdateRequest(String indexName
                     return updateRequest;
                 }
 
-                private CreateIndexClusterStateUpdateRequest buildSystemIndexUpdateRequest(SystemIndexDescriptor descriptor) {
+                private CreateIndexClusterStateUpdateRequest buildSystemIndexUpdateRequest(
+                    String indexName, SystemIndexDescriptor descriptor) {
                     String mappings = descriptor.getMappings();
                     Settings settings = descriptor.getSettings();
                     String aliasName = descriptor.getAliasName();
-                    String concreteIndexName = descriptor.getPrimaryIndex();
+
+                    // if we are writing to the alias name, we should create the primary index here
+                    String concreteIndexName = indexName.equals(aliasName) ? descriptor.getPrimaryIndex() : indexName;
 
                     CreateIndexClusterStateUpdateRequest updateRequest =
                         new CreateIndexClusterStateUpdateRequest(request.cause(), concreteIndexName, request.index())
@@ -210,7 +213,13 @@ private CreateIndexClusterStateUpdateRequest buildSystemIndexUpdateRequest(Syste
                         updateRequest.aliases(Set.of(new Alias(aliasName)));
                     }
 
-                    logger.debug("Auto-creating system index {}", concreteIndexName);
+                    if (logger.isDebugEnabled()) {
+                        if (concreteIndexName.equals(indexName) == false) {
+                            logger.debug("Auto-creating backing system index {} for alias {}", concreteIndexName, indexName);
+                        } else {
+                            logger.debug("Auto-creating system index {}", concreteIndexName);
+                        }
+                    }
 
                     return updateRequest;
                 }