Enable deprecation checks for removed settings

x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/DeprecationChecks.java

@@ -33,7 +33,7 @@ private DeprecationChecks() {
     static List<Function<ClusterState, DeprecationIssue>> CLUSTER_SETTINGS_CHECKS =
         Collections.emptyList();
 
-    static List<BiFunction<Settings, PluginsAndModules, DeprecationIssue>> NODE_SETTINGS_CHECKS = Collections.emptyList();
+    static List<BiFunction<Settings, PluginsAndModules, DeprecationIssue>> NODE_SETTINGS_CHECKS = List.of();
 
     static List<Function<IndexMetaData, DeprecationIssue>> INDEX_SETTINGS_CHECKS =
             List.of(IndexDeprecationChecks::oldIndicesCheck, IndexDeprecationChecks::translogRetentionSettingCheck);

x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/NodeDeprecationChecks.java

@@ -0,0 +1,30 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+package org.elasticsearch.xpack.deprecation;
+
+import org.elasticsearch.common.settings.Setting;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.xpack.core.deprecation.DeprecationIssue;
+
+import java.util.Locale;
+
+public class NodeDeprecationChecks {
+
+    static DeprecationIssue checkRemovedSetting(final Settings settings, final Setting<?> removedSetting, final String url) {
+        if (removedSetting.exists(settings) == false) {
+            return null;
+        }
+        final String removedSettingKey = removedSetting.getKey();
+        final String value = removedSetting.get(settings).toString();
+        final String message =
+            String.format(Locale.ROOT, "setting [%s] is deprecated and will be removed in the next major version", removedSettingKey);
+        final String details =
+            String.format(Locale.ROOT, "the setting [%s] is currently set to [%s], remove this setting", removedSettingKey, value);
+        return new DeprecationIssue(DeprecationIssue.Level.CRITICAL, message, url, details);
+    }
+
+}

x-pack/plugin/deprecation/src/test/java/org/elasticsearch/xpack/deprecation/NodeDeprecationChecksTests.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+package org.elasticsearch.xpack.deprecation;
+
+import org.elasticsearch.common.settings.Setting;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.test.ESTestCase;
+import org.elasticsearch.xpack.core.deprecation.DeprecationIssue;
+
+import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.not;
+import static org.hamcrest.Matchers.nullValue;
+
+public class NodeDeprecationChecksTests extends ESTestCase {
+
+    public void testRemovedSettingNotSet() {
+        final Settings settings = Settings.EMPTY;
+        final Setting<?> removedSetting = Setting.simpleString("node.removed_setting");
+        final DeprecationIssue issue =
+            NodeDeprecationChecks.checkRemovedSetting(settings, removedSetting, "http://removed-setting.example.com");
+        assertThat(issue, nullValue());
+    }
+
+    public void testRemovedSetting() {
+        final Settings settings = Settings.builder().put("node.removed_setting", "value").build();
+        final Setting<?> removedSetting = Setting.simpleString("node.removed_setting");
+        final DeprecationIssue issue =
+            NodeDeprecationChecks.checkRemovedSetting(settings, removedSetting, "https://removed-setting.example.com");
+        assertThat(issue, not(nullValue()));
+        assertThat(issue.getLevel(), equalTo(DeprecationIssue.Level.CRITICAL));
+        assertThat(
+            issue.getMessage(),
+            equalTo("setting [node.removed_setting] is deprecated and will be removed in the next major version"));
+        assertThat(
+            issue.getDetails(),
+            equalTo("the setting [node.removed_setting] is currently set to [value], remove this setting"));
+        assertThat(issue.getUrl(), equalTo("https://removed-setting.example.com"));
+    }
+
+}