Make default value for _tier_preference be "data_frozen" for frozen SBIs

Author: dakrone

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/cluster/routing/allocation/DataTierAllocationDecider.java

@@ -32,6 +32,7 @@
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
+import java.util.function.Function;
 import java.util.stream.Collectors;
 
 import static org.elasticsearch.xpack.core.DataTier.DATA_FROZEN;
@@ -66,8 +67,8 @@ public class DataTierAllocationDecider extends AllocationDecider {
         VALIDATOR, Setting.Property.Dynamic, Setting.Property.IndexScope);
     public static final Setting<String> INDEX_ROUTING_EXCLUDE_SETTING = Setting.simpleString(INDEX_ROUTING_EXCLUDE,
         VALIDATOR, Setting.Property.Dynamic, Setting.Property.IndexScope);
-    public static final Setting<String> INDEX_ROUTING_PREFER_SETTING = Setting.simpleString(INDEX_ROUTING_PREFER,
-        VALIDATOR, Setting.Property.Dynamic, Setting.Property.IndexScope);
+    public static final Setting<String> INDEX_ROUTING_PREFER_SETTING = new Setting<>(new Setting.SimpleKey(INDEX_ROUTING_PREFER),
+        DataTierValidator::getDefaultTierPreference, Function.identity(), VALIDATOR, Setting.Property.Dynamic, Setting.Property.IndexScope);
 
     private static void validateTierSetting(String setting) {
         if (Strings.hasText(setting)) {
@@ -84,6 +85,14 @@ private static class DataTierValidator implements Setting.Validator<String> {
         private static final Collection<Setting<?>> dependencies = List.of(IndexModule.INDEX_STORE_TYPE_SETTING,
             SearchableSnapshotsConstants.SNAPSHOT_PARTIAL_SETTING);
 
+        public static String getDefaultTierPreference(Settings settings) {
+            if (SearchableSnapshotsConstants.isPartialSearchableSnapshotIndex(settings)) {
+                return DATA_FROZEN;
+            } else {
+                return "";
+            }
+        }
+
         @Override
         public void validate(String value) {
             validateTierSetting(value);

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/searchablesnapshots/SearchableSnapshotsConstants.java

@@ -42,6 +42,11 @@ public static boolean isPartialSearchableSnapshotIndex(Map<Setting<?>, Object> i
             && (boolean) indexSettings.get(SNAPSHOT_PARTIAL_SETTING);
     }
 
+    public static boolean isPartialSearchableSnapshotIndex(Settings indexSettings) {
+        return SNAPSHOT_DIRECTORY_FACTORY_KEY.equals(INDEX_STORE_TYPE_SETTING.get(indexSettings))
+            && SNAPSHOT_PARTIAL_SETTING.get(indexSettings);
+    }
+
     public static final String CACHE_FETCH_ASYNC_THREAD_POOL_NAME = "searchable_snapshots_cache_fetch_async";
     public static final String CACHE_FETCH_ASYNC_THREAD_POOL_SETTING = "xpack.searchable_snapshots.cache_fetch_async_thread_pool";
 

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/cluster/routing/allocation/DataTierAllocationDeciderTests.java

@@ -752,7 +752,6 @@ public void testNonFrozenIllegalForPartialSnapshot() {
         Randomness.shuffle(tierList);
 
         String value = Strings.join(tierList, ",");
-        logger.info("--> value: {}", value);
         Settings.Builder builder = Settings.builder().put(DataTierAllocationDecider.INDEX_ROUTING_PREFER, value);
         builder.put(IndexModule.INDEX_STORE_TYPE_SETTING.getKey(), SearchableSnapshotsConstants.SNAPSHOT_DIRECTORY_FACTORY_KEY);
         builder.put(SearchableSnapshotsConstants.SNAPSHOT_PARTIAL_SETTING.getKey(), true);
@@ -764,6 +763,17 @@ public void testNonFrozenIllegalForPartialSnapshot() {
         assertThat(e.getMessage(), containsString("only the [data_frozen] tier preference may be used for partial searchable snapshots"));
     }
 
+    public void testDefaultValueForPreference() {
+        assertThat(DataTierAllocationDecider.INDEX_ROUTING_PREFER_SETTING.get(Settings.EMPTY), equalTo(""));
+
+        Settings.Builder builder = Settings.builder();
+        builder.put(IndexModule.INDEX_STORE_TYPE_SETTING.getKey(), SearchableSnapshotsConstants.SNAPSHOT_DIRECTORY_FACTORY_KEY);
+        builder.put(SearchableSnapshotsConstants.SNAPSHOT_PARTIAL_SETTING.getKey(), true);
+
+        Settings settings = builder.build();
+        assertThat(DataTierAllocationDecider.INDEX_ROUTING_PREFER_SETTING.get(settings), equalTo(DATA_FROZEN));
+    }
+
     public Setting<String> randomTierSetting() {
         //noinspection unchecked
         return randomFrom(