Don't omit default values when updating routing exclusions (#33638)

Exclusion setting `cluster.routing.allocation.exclude._host` default value
is an empty string.

When an exclusion setting is sent with a null value the
o.e.c.s.Setting#innerGetRaw API return an empty string (probably to
avoid a NullPointerException to be raised).

The o.e.c.r.a.d.FilterAllocationDecider class is developed to omit
updates of default values for exclusion setting.

That's why a null exclusion setting value is translated to an empty
string which is equals to the exclusion default value which is
configured to be ignored.

A simple fix would be to not omit default values for exclusion setting
and keep the NullPointerException guard. This is the purpose of this
commit.

Closes #32721

Author: cbismuth

server/src/main/java/org/elasticsearch/cluster/routing/allocation/decider/FilterAllocationDecider.java

@@ -101,9 +101,9 @@ public FilterAllocationDecider(Settings settings, ClusterSettings clusterSetting
         setClusterRequireFilters(CLUSTER_ROUTING_REQUIRE_GROUP_SETTING.getAsMap(settings));
         setClusterExcludeFilters(CLUSTER_ROUTING_EXCLUDE_GROUP_SETTING.getAsMap(settings));
         setClusterIncludeFilters(CLUSTER_ROUTING_INCLUDE_GROUP_SETTING.getAsMap(settings));
-        clusterSettings.addAffixMapUpdateConsumer(CLUSTER_ROUTING_REQUIRE_GROUP_SETTING, this::setClusterRequireFilters, (a,b)-> {}, true);
-        clusterSettings.addAffixMapUpdateConsumer(CLUSTER_ROUTING_EXCLUDE_GROUP_SETTING, this::setClusterExcludeFilters, (a,b)-> {}, true);
-        clusterSettings.addAffixMapUpdateConsumer(CLUSTER_ROUTING_INCLUDE_GROUP_SETTING, this::setClusterIncludeFilters, (a,b)-> {}, true);
+        clusterSettings.addAffixMapUpdateConsumer(CLUSTER_ROUTING_REQUIRE_GROUP_SETTING, this::setClusterRequireFilters, (a, b) -> {});
+        clusterSettings.addAffixMapUpdateConsumer(CLUSTER_ROUTING_EXCLUDE_GROUP_SETTING, this::setClusterExcludeFilters, (a, b) -> {});
+        clusterSettings.addAffixMapUpdateConsumer(CLUSTER_ROUTING_INCLUDE_GROUP_SETTING, this::setClusterIncludeFilters, (a, b) -> {});
     }
 
     @Override

server/src/main/java/org/elasticsearch/common/settings/AbstractScopedSettings.java

@@ -301,13 +301,13 @@ private void ensureSettingIsRegistered(Setting.AffixSetting<?> setting) {
      * consumer in order to be processed correctly. This consumer will get a namespace to value map instead of each individual namespace
      * and value as in {@link #addAffixUpdateConsumer(Setting.AffixSetting, BiConsumer, BiConsumer)}
      */
-    public synchronized <T> void addAffixMapUpdateConsumer(Setting.AffixSetting<T> setting,  Consumer<Map<String, T>> consumer,
-                                                        BiConsumer<String, T> validator, boolean omitDefaults) {
+    public synchronized <T> void addAffixMapUpdateConsumer(Setting.AffixSetting<T> setting, Consumer<Map<String, T>> consumer,
+                                                           BiConsumer<String, T> validator) {
         final Setting<?> registeredSetting = this.complexMatchers.get(setting.getKey());
         if (setting != registeredSetting) {
             throw new IllegalArgumentException("Setting is not registered for key [" + setting.getKey() + "]");
         }
-        addSettingsUpdater(setting.newAffixMapUpdater(consumer, logger, validator, omitDefaults));
+        addSettingsUpdater(setting.newAffixMapUpdater(consumer, logger, validator));
     }
 
     synchronized void addSettingsUpdater(SettingUpdater<?> updater) {

server/src/main/java/org/elasticsearch/common/settings/Setting.java

@@ -700,7 +700,7 @@ public void apply(Map<AbstractScopedSettings.SettingUpdater<T>, T> value, Settin
         }
 
         AbstractScopedSettings.SettingUpdater<Map<String, T>> newAffixMapUpdater(Consumer<Map<String, T>> consumer, Logger logger,
-                                                                                 BiConsumer<String, T> validator, boolean omitDefaults) {
+                                                                                 BiConsumer<String, T> validator) {
             return new AbstractScopedSettings.SettingUpdater<Map<String, T>>() {
 
                 @Override
@@ -721,9 +721,7 @@ public Map<String, T> getValue(Settings current, Settings previous) {
                             // only the ones that have changed otherwise we might get too many updates
                             // the hasChanged above checks only if there are any changes
                             T value = updater.getValue(current, previous);
-                            if ((omitDefaults && value.equals(concreteSetting.getDefault(current))) == false) {
-                                result.put(namespace, value);
-                            }
+                            result.put(namespace, value);
                         }
                     });
                     return result;

server/src/test/java/org/elasticsearch/common/settings/ScopedSettingsTests.java

@@ -371,9 +371,8 @@ public void testAddConsumerAffixMap() {
             listResults.clear();
             listResults.putAll(map);
         };
-        boolean omitDefaults = randomBoolean();
-        service.addAffixMapUpdateConsumer(listSetting, listConsumer, (s, k) -> {}, omitDefaults);
-        service.addAffixMapUpdateConsumer(intSetting, intConsumer, (s, k) -> {}, omitDefaults);
+        service.addAffixMapUpdateConsumer(listSetting, listConsumer, (s, k) -> {});
+        service.addAffixMapUpdateConsumer(intSetting, intConsumer, (s, k) -> {});
         assertEquals(0, listResults.size());
         assertEquals(0, intResults.size());
         service.applySettings(Settings.builder()
@@ -403,7 +402,6 @@ public void testAddConsumerAffixMap() {
         assertEquals(2, listResults.size());
         assertEquals(2, intResults.size());
 
-
         listResults.clear();
         intResults.clear();
 
@@ -416,17 +414,9 @@ public void testAddConsumerAffixMap() {
         assertNull("test wasn't changed", intResults.get("test"));
         assertEquals(8, intResults.get("test_1").intValue());
         assertNull("test_list wasn't changed", listResults.get("test_list"));
-        if (omitDefaults) {
-            assertNull(listResults.get("test_list_1"));
-            assertFalse(listResults.containsKey("test_list_1"));
-            assertEquals(0, listResults.size());
-            assertEquals(1, intResults.size());
-        } else {
-            assertEquals(Arrays.asList(1), listResults.get("test_list_1")); // reset to default
-            assertEquals(1, listResults.size());
-            assertEquals(1, intResults.size());
-        }
-
+        assertEquals(Arrays.asList(1), listResults.get("test_list_1")); // reset to default
+        assertEquals(1, listResults.size());
+        assertEquals(1, intResults.size());
     }
 
     public void testAffixMapConsumerNotCalledWithNull() {
@@ -442,7 +432,7 @@ public void testAffixMapConsumerNotCalledWithNull() {
             affixResults.clear();
             affixResults.putAll(map);
         };
-        service.addAffixMapUpdateConsumer(prefixSetting, consumer, (s, k) -> {}, randomBoolean());
+        service.addAffixMapUpdateConsumer(prefixSetting, consumer, (s, k) -> {});
         assertEquals(0, affixResults.size());
         service.applySettings(Settings.builder()
                 .put("eggplant._name", 2)

server/src/test/java/org/elasticsearch/common/settings/SettingTests.java

@@ -19,6 +19,7 @@
 package org.elasticsearch.common.settings;
 
 import org.elasticsearch.common.collect.Tuple;
+import org.elasticsearch.common.settings.AbstractScopedSettings.SettingUpdater;
 import org.elasticsearch.common.settings.Setting.Property;
 import org.elasticsearch.common.unit.ByteSizeUnit;
 import org.elasticsearch.common.unit.ByteSizeValue;
@@ -33,6 +34,8 @@
 import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.BiConsumer;
+import java.util.function.Consumer;
 import java.util.function.Function;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
@@ -890,4 +893,39 @@ public void testExistsWithFallback() {
         }
     }
 
+    public void testAffixMapUpdateWithNullSettingValue() {
+        // GIVEN an affix setting changed from "prefix._foo"="bar" to "prefix._foo"=null
+        final Settings current = Settings.builder()
+            .put("prefix._foo", (String) null)
+            .build();
+
+        final Settings previous = Settings.builder()
+            .put("prefix._foo", "bar")
+            .build();
+
+        final Setting.AffixSetting<String> affixSetting =
+            Setting.prefixKeySetting("prefix" + ".",
+                (key) -> Setting.simpleString(key, (value, map) -> {}, Property.Dynamic, Property.NodeScope));
+
+        final Consumer<Map<String, String>> consumer = (map) -> {};
+        final BiConsumer<String, String> validator = (s1, s2) -> {};
+
+        // WHEN creating an affix updater
+        final SettingUpdater<Map<String, String>> updater = affixSetting.newAffixMapUpdater(consumer, logger, validator);
+
+        // THEN affix updater is always expected to have changed (even when defaults are omitted)
+        assertTrue(updater.hasChanged(current, previous));
+
+        // THEN changes are expected when defaults aren't omitted
+        final Map<String, String> updatedSettings = updater.getValue(current, previous);
+        assertNotNull(updatedSettings);
+        assertEquals(1, updatedSettings.size());
+
+        // THEN changes are reported when defaults aren't omitted
+        final String key = updatedSettings.keySet().iterator().next();
+        final String value = updatedSettings.get(key);
+        assertEquals("_foo", key);
+        assertEquals("", value);
+    }
+
 }