Make legacy template noop updates not change cluster state (elastic#6…

…4493)

When a legacy template does not change, there is no need to create and publish a new cluster state,
rather the update should be a noop.

Relates to elastic#57851
Resolves elastic#57662

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

@@ -176,7 +176,8 @@ public boolean equals(Object o) {
  if (!settings.equals(that.settings)) return false;
  if (!patterns.equals(that.patterns)) return false;
 
- return Objects.equals(version, that.version);
+ return Objects.equals(aliases, that.aliases) &&
+ Objects.equals(version, that.version);
  }
 
  @Override
@@ -187,6 +188,7 @@ public int hashCode() {
  result = 31 * result + patterns.hashCode();
  result = 31 * result + settings.hashCode();
  result = 31 * result + mappings.hashCode();
+ result = 31 * result + aliases.hashCode();
  return result;
  }
 

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

@@ -780,6 +780,11 @@ static ClusterState innerPutTemplate(final ClusterState currentState, PutRequest
  templateBuilder.putAlias(aliasMetadata);
  }
  IndexTemplateMetadata template = templateBuilder.build();
+ IndexTemplateMetadata existingTemplate = currentState.metadata().templates().get(request.name);
+ if (template.equals(existingTemplate)) {
+ // The template is unchanged, therefore there is no need for a cluster state update
+ return currentState;
+ }
 
  Metadata.Builder builder = Metadata.builder(currentState.metadata()).put(template);
 

server/src/test/java/org/elasticsearch/cluster/metadata/MetadataIndexTemplateServiceTests.java

@@ -98,6 +98,28 @@ protected Collection<Class<? extends Plugin>> getPlugins() {
  return Collections.singletonList(DummyPlugin.class);
  }
 
+ public void testLegacyNoopUpdate() {
+ ClusterState state = ClusterState.EMPTY_STATE;
+ PutRequest pr = new PutRequest("api", "id");
+ pr.patterns(Arrays.asList("foo", "bar"));
+ if (randomBoolean()) {
+ pr.settings(Settings.builder()
+ .put(IndexMetadata.SETTING_NUMBER_OF_SHARDS, 3).build());
+ }
+ if (randomBoolean()) {
+ pr.mappings("{}");
+ }
+ if (randomBoolean()) {
+ pr.aliases(Collections.singleton(new Alias("alias")));
+ }
+ pr.order(randomIntBetween(0, 10));
+ state = MetadataIndexTemplateService.innerPutTemplate(state, pr, new IndexTemplateMetadata.Builder("id"));
+
+ assertNotNull(state.metadata().templates().get("id"));
+
+ assertThat(MetadataIndexTemplateService.innerPutTemplate(state, pr, new IndexTemplateMetadata.Builder("id")), equalTo(state));
+ }
+
  public void testIndexTemplateInvalidNumberOfShards() {
  PutRequest request = new PutRequest("test", "test_shards");
  request.patterns(singletonList("test_shards*"));
@@ -730,7 +752,6 @@ public void testFindV2InvalidGlobalTemplate() {
  }
  }
 
- @AwaitsFix(bugUrl = "https:/elastic/elasticsearch/pull/57393")
  public void testResolveConflictingMappings() throws Exception {
  final MetadataIndexTemplateService service = getMetadataIndexTemplateService();
  ClusterState state = ClusterState.EMPTY_STATE;