Remove the 'template' field in index templates. (#49460)

The `template` field was deprecated in 6.0 in favor of `index_patterns`, and can
now be removed.

Relates to #21009.

Author: jtibshirani

client/rest-high-level/src/main/java/org/elasticsearch/client/indices/PutIndexTemplateRequest.java

@@ -278,18 +278,14 @@ public PutIndexTemplateRequest source(Map<String, Object> templateSource) {
         Map<String, Object> source = templateSource;
         for (Map.Entry<String, Object> entry : source.entrySet()) {
             String name = entry.getKey();
-            if (name.equals("template")) {
-                if(entry.getValue() instanceof String) {
-                    patterns(Collections.singletonList((String) entry.getValue()));
-                }
-            } else if (name.equals("index_patterns")) {
+            if (name.equals("index_patterns")) {
                 if(entry.getValue() instanceof String) {
                     patterns(Collections.singletonList((String) entry.getValue()));
                 } else if (entry.getValue() instanceof List) {
                     List<String> elements = ((List<?>) entry.getValue()).stream().map(Object::toString).collect(Collectors.toList());
                     patterns(elements);
                 } else {
-                    throw new IllegalArgumentException("Malformed [template] value, should be a string or a list of strings");
+                    throw new IllegalArgumentException("Malformed [index_patterns] value, should be a string or a list of strings");
                 }
             } else if (name.equals("order")) {
                 order(XContentMapValues.nodeIntegerValue(entry.getValue(), order()));

docs/reference/migration/migrate_8_0/indices.asciidoc

@@ -20,3 +20,10 @@ The `index.force_memory_term_dictionary` setting was introduced in 7.0 as a
 temporary measure to allow users to opt-out of the optimization that leaves the
 term dictionary on disk when appropriate. This optimization is now mandatory
 and the setting is removed.
+
+[float]
+==== Remove support for `template` in put index template requests
+
+In 6.0, we deprecated the `template` field in put index template requests
+in favor of using `index_patterns`. Support for the `template` field is now
+removed in 8.0.

server/src/main/java/org/elasticsearch/action/admin/indices/template/put/PutIndexTemplateRequest.java

@@ -323,14 +323,8 @@ public PutIndexTemplateRequest source(Map<String, Object> templateSource) {
         Map<String, Object> source = templateSource;
         for (Map.Entry<String, Object> entry : source.entrySet()) {
             String name = entry.getKey();
-            if (name.equals("template")) {
-                // This is needed to allow for bwc (beats, logstash) with pre-5.0 templates (#21009)
-                if(entry.getValue() instanceof String) {
-                    deprecationLogger.deprecated("Deprecated field [template] used, replaced by [index_patterns]");
-                    patterns(Collections.singletonList((String) entry.getValue()));
-                }
-            } else if (name.equals("index_patterns")) {
-                if(entry.getValue() instanceof String) {
+            if (name.equals("index_patterns")) {
+                if (entry.getValue() instanceof String) {
                     patterns(Collections.singletonList((String) entry.getValue()));
                 } else if (entry.getValue() instanceof List) {
                     List<String> elements = ((List<?>) entry.getValue()).stream().map(Object::toString).collect(Collectors.toList());

server/src/main/java/org/elasticsearch/rest/action/admin/indices/RestPutIndexTemplateAction.java

@@ -19,11 +19,9 @@
 
 package org.elasticsearch.rest.action.admin.indices;
 
-import org.apache.logging.log4j.LogManager;
 import org.elasticsearch.action.admin.indices.template.put.PutIndexTemplateRequest;
 import org.elasticsearch.client.node.NodeClient;
 import org.elasticsearch.common.Strings;
-import org.elasticsearch.common.logging.DeprecationLogger;
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.rest.BaseRestHandler;
 import org.elasticsearch.rest.RestController;
@@ -32,14 +30,10 @@
 
 import java.io.IOException;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.Map;
 
 public class RestPutIndexTemplateAction extends BaseRestHandler {
 
-    private static final DeprecationLogger deprecationLogger = new DeprecationLogger(
-            LogManager.getLogger(RestPutIndexTemplateAction.class));
-
     public RestPutIndexTemplateAction(RestController controller) {
         controller.registerHandler(RestRequest.Method.PUT, "/_template/{name}", this);
         controller.registerHandler(RestRequest.Method.POST, "/_template/{name}", this);
@@ -54,12 +48,7 @@ public String getName() {
     public RestChannelConsumer prepareRequest(final RestRequest request, final NodeClient client) throws IOException {
 
         PutIndexTemplateRequest putRequest = new PutIndexTemplateRequest(request.param("name"));
-        if (request.hasParam("template")) {
-            deprecationLogger.deprecated("Deprecated parameter[template] used, replaced by [index_patterns]");
-            putRequest.patterns(Collections.singletonList(request.param("template")));
-        } else {
-            putRequest.patterns(Arrays.asList(request.paramAsStringArray("index_patterns", Strings.EMPTY_ARRAY)));
-        }
+        putRequest.patterns(Arrays.asList(request.paramAsStringArray("index_patterns", Strings.EMPTY_ARRAY)));
         putRequest.order(request.paramAsInt("order", putRequest.order()));
         putRequest.masterNodeTimeout(request.paramAsTime("master_timeout", putRequest.masterNodeTimeout()));
         putRequest.create(request.paramAsBoolean("create", false));

server/src/test/java/org/elasticsearch/indices/template/SimpleIndexTemplateIT.java

@@ -433,7 +433,7 @@ public void testIndexTemplateWithAliases() throws Exception {
     public void testIndexTemplateWithAliasesInSource() {
         client().admin().indices().preparePutTemplate("template_1")
                 .setSource(new BytesArray("{\n" +
-                        "    \"template\" : \"*\",\n" +
+                        "    \"index_patterns\" : \"*\",\n" +
                         "    \"aliases\" : {\n" +
                         "        \"my_alias\" : {\n" +
                         "            \"filter\" : {\n" +