Deprecate unused index.ttl.disable_purge setting (#29526)

This setting does nothing. This change deprecates it, for the 6.x series, and
#29527 removes it entirely for the 7.x series.

Author: DaveCTurner

server/src/main/java/org/elasticsearch/index/IndexSettings.java

@@ -80,8 +80,9 @@ public final class IndexSettings {
             (value) -> Translog.Durability.valueOf(value.toUpperCase(Locale.ROOT)), Property.Dynamic, Property.IndexScope);
     public static final Setting<Boolean> INDEX_WARMER_ENABLED_SETTING =
         Setting.boolSetting("index.warmer.enabled", true, Property.Dynamic, Property.IndexScope);
+    @Deprecated
     public static final Setting<Boolean> INDEX_TTL_DISABLE_PURGE_SETTING =
-        Setting.boolSetting("index.ttl.disable_purge", false, Property.Dynamic, Property.IndexScope);
+        Setting.boolSetting("index.ttl.disable_purge", false, Property.Dynamic, Property.IndexScope, Property.Deprecated);
     public static final Setting<String> INDEX_CHECK_ON_STARTUP = new Setting<>("index.shard.check_on_startup", "false", (s) -> {
         switch(s) {
             case "false":
@@ -302,7 +303,6 @@ public final class IndexSettings {
     private volatile int maxScriptFields;
     private volatile int maxNgramDiff;
     private volatile int maxShingleDiff;
-    private volatile boolean TTLPurgeDisabled;
     private volatile int maxAnalyzedOffset;
     private volatile int maxTermsCount;
 
@@ -410,7 +410,6 @@ public IndexSettings(final IndexMetaData indexMetaData, final Settings nodeSetti
         maxScriptFields = scopedSettings.get(MAX_SCRIPT_FIELDS_SETTING);
         maxNgramDiff = scopedSettings.get(MAX_NGRAM_DIFF_SETTING);
         maxShingleDiff = scopedSettings.get(MAX_SHINGLE_DIFF_SETTING);
-        TTLPurgeDisabled = scopedSettings.get(INDEX_TTL_DISABLE_PURGE_SETTING);
         maxRefreshListeners = scopedSettings.get(MAX_REFRESH_LISTENERS_PER_SHARD);
         maxSlicesPerScroll = scopedSettings.get(MAX_SLICES_PER_SCROLL);
         maxAnalyzedOffset = scopedSettings.get(MAX_ANALYZED_OFFSET_SETTING);
@@ -436,7 +435,6 @@ public IndexSettings(final IndexMetaData indexMetaData, final Settings nodeSetti
             mergeSchedulerConfig::setMaxThreadAndMergeCount);
         scopedSettings.addSettingsUpdateConsumer(MergeSchedulerConfig.AUTO_THROTTLE_SETTING, mergeSchedulerConfig::setAutoThrottle);
         scopedSettings.addSettingsUpdateConsumer(INDEX_TRANSLOG_DURABILITY_SETTING, this::setTranslogDurability);
-        scopedSettings.addSettingsUpdateConsumer(INDEX_TTL_DISABLE_PURGE_SETTING, this::setTTLPurgeDisabled);
         scopedSettings.addSettingsUpdateConsumer(MAX_RESULT_WINDOW_SETTING, this::setMaxResultWindow);
         scopedSettings.addSettingsUpdateConsumer(MAX_INNER_RESULT_WINDOW_SETTING, this::setMaxInnerResultWindow);
         scopedSettings.addSettingsUpdateConsumer(MAX_ADJACENCY_MATRIX_FILTERS_SETTING, this::setMaxAdjacencyMatrixFilters);
@@ -774,18 +772,6 @@ public MergePolicy getMergePolicy() {
         return mergePolicyConfig.getMergePolicy();
     }
 
-    /**
-     * Returns <code>true</code> if the TTL purge is disabled for this index. Default is <code>false</code>
-     */
-    public boolean isTTLPurgeDisabled() {
-        return TTLPurgeDisabled;
-    }
-
-    private  void setTTLPurgeDisabled(boolean ttlPurgeDisabled) {
-        this.TTLPurgeDisabled = ttlPurgeDisabled;
-    }
-
-
     public <T> T getValue(Setting<T> setting) {
         return scopedSettings.get(setting);
     }

server/src/test/java/org/elasticsearch/index/IndexSettingsTests.java

@@ -386,24 +386,12 @@ public void testGCDeletesSetting() {
     }
 
     public void testIsTTLPurgeDisabled() {
-        IndexMetaData metaData = newIndexMeta("index", Settings.builder()
+        final Settings settings = Settings.builder()
             .put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT)
-            .put(IndexSettings.INDEX_TTL_DISABLE_PURGE_SETTING.getKey(), false)
-            .build());
-        IndexSettings settings = new IndexSettings(metaData, Settings.EMPTY);
-        assertFalse(settings.isTTLPurgeDisabled());
-        settings.updateIndexMetaData(newIndexMeta("index", Settings.builder().put(IndexSettings.INDEX_TTL_DISABLE_PURGE_SETTING.getKey(),
-            "true").build()));
-        assertTrue(settings.isTTLPurgeDisabled());
-
-        settings.updateIndexMetaData(newIndexMeta("index", Settings.EMPTY));
-        assertFalse("reset to default", settings.isTTLPurgeDisabled());
-
-        metaData = newIndexMeta("index", Settings.builder()
-            .put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT)
-            .build());
-        settings = new IndexSettings(metaData, Settings.EMPTY);
-        assertFalse(settings.isTTLPurgeDisabled());
+            .put(IndexSettings.INDEX_TTL_DISABLE_PURGE_SETTING.getKey(), true)
+            .build();
+        assertTrue(IndexSettings.INDEX_TTL_DISABLE_PURGE_SETTING.get(settings));
+        assertSettingDeprecationsAndWarnings(new Setting<?>[]{IndexSettings.INDEX_TTL_DISABLE_PURGE_SETTING});
     }
 
     public void testTranslogFlushSizeThreshold() {