Shrink should not touch max_retries (elastic#47719)

Shrink would set `max_retries=1` in order to avoid retrying. This
however sticks to the shrunk index afterwards, causing issues when a
shard copy later fails to allocate just once.

Avoiding a retry of a shrink makes sense since there is no new node
to allocate to and a retry will likely fail again. However, the downside of
having max_retries=1 afterwards outweigh the benefit of not retrying
the failed shrink a few times. This change ensures shrink no longer
sets max_retries and also makes all resize operations (shrink, clone,
split) leave the setting at default value rather than copy it from source.

server/src/main/java/org/elasticsearch/cluster/metadata/MetaDataCreateIndexService.java

@@ -785,10 +785,7 @@ static void prepareResizeIndexSettings(
         if (type == ResizeType.SHRINK) {
             final List<String> nodesToAllocateOn = validateShrinkIndex(currentState, resizeSourceIndex.getName(),
                 mappingKeys, resizeIntoName, indexSettingsBuilder.build());
-            indexSettingsBuilder
-                .put(initialRecoveryIdFilter, Strings.arrayToCommaDelimitedString(nodesToAllocateOn.toArray()))
-                // we only try once and then give up with a shrink index
-                .put("index.allocation.max_retries", 1);
+            indexSettingsBuilder.put(initialRecoveryIdFilter, Strings.arrayToCommaDelimitedString(nodesToAllocateOn.toArray()));
         } else if (type == ResizeType.SPLIT) {
             validateSplitIndex(currentState, resizeSourceIndex.getName(), mappingKeys, resizeIntoName, indexSettingsBuilder.build());
             indexSettingsBuilder.putNull(initialRecoveryIdFilter);

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

@@ -37,7 +37,7 @@
 public class MaxRetryAllocationDecider extends AllocationDecider {
 
     public static final Setting<Integer> SETTING_ALLOCATION_MAX_RETRY = Setting.intSetting("index.allocation.max_retries", 5, 0,
-        Setting.Property.Dynamic, Setting.Property.IndexScope);
+        Setting.Property.Dynamic, Setting.Property.IndexScope, Setting.Property.NotCopyableOnResize);
 
     public static final String NAME = "max_retry";
 

server/src/test/java/org/elasticsearch/cluster/metadata/MetaDataCreateIndexServiceTests.java

@@ -69,6 +69,7 @@
 import static org.hamcrest.Matchers.endsWith;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.hasToString;
+import static org.hamcrest.Matchers.nullValue;
 
 public class MetaDataCreateIndexServiceTests extends ESTestCase {
 
@@ -263,16 +264,18 @@ public void testPrepareResizeIndexSettings() {
         versions.sort(Comparator.comparingLong(l -> l.id));
         final Version version = versions.get(0);
         final Version upgraded = versions.get(1);
-        final Settings indexSettings =
+        final Settings.Builder indexSettingsBuilder =
                 Settings.builder()
                         .put("index.version.created", version)
                         .put("index.version.upgraded", upgraded)
                         .put("index.similarity.default.type", "BM25")
                         .put("index.analysis.analyzer.default.tokenizer", "keyword")
-                        .put("index.soft_deletes.enabled", "true")
-                        .build();
+                        .put("index.soft_deletes.enabled", "true");
+        if (randomBoolean()) {
+            indexSettingsBuilder.put("index.allocation.max_retries", randomIntBetween(1, 1000));
+        }
         runPrepareResizeIndexSettingsTest(
-                indexSettings,
+                indexSettingsBuilder.build(),
                 Settings.EMPTY,
                 Collections.emptyList(),
                 randomBoolean(),
@@ -283,7 +286,7 @@ public void testPrepareResizeIndexSettings() {
                             settings.get("index.analysis.analyzer.default.tokenizer"),
                             equalTo("keyword"));
                     assertThat(settings.get("index.routing.allocation.initial_recovery._id"), equalTo("node1"));
-                    assertThat(settings.get("index.allocation.max_retries"), equalTo("1"));
+                    assertThat(settings.get("index.allocation.max_retries"), nullValue());
                     assertThat(settings.getAsVersion("index.version.created", null), equalTo(version));
                     assertThat(settings.getAsVersion("index.version.upgraded", null), equalTo(upgraded));
                     assertThat(settings.get("index.soft_deletes.enabled"), equalTo("true"));