Enhance search preference based routing for WRR

CHANGELOG.md

@@ -87,6 +87,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - [Segment Replication] Add new cluster setting to set replication strategy by default for all indices in cluster. ([#6791](https:/opensearch-project/OpenSearch/pull/6791))
 - Enable sort optimization for all NumericTypes ([#6464](https:/opensearch-project/OpenSearch/pull/6464)
 - Remove 'cluster_manager' role attachment when using 'node.master' deprecated setting ([#6331](https:/opensearch-project/OpenSearch/pull/6331))
+- Add new cluster settings to ignore weighted round-robin routing and fallback to default behaviour. ([#6834](https:/opensearch-project/OpenSearch/pull/6834))
 
 ### Dependencies
 - Bump `org.apache.logging.log4j:log4j-core` from 2.18.0 to 2.20.0 ([#6490](https:/opensearch-project/OpenSearch/pull/6490))

server/src/main/java/org/opensearch/cluster/routing/FailAwareWeightedRouting.java

@@ -20,6 +20,8 @@
 
 import java.util.List;
 
+import static org.opensearch.cluster.routing.OperationRouting.IGNORE_WEIGHTED_SHARD_ROUTING;
+
 /**
  * This class contains logic to find next shard to retry search request in case of failure from other shard copy.
  * This decides if retryable shard search requests can be tried on shard copies present in data
@@ -72,9 +74,13 @@ public SearchShardTarget findNext(
  Runnable onShardSkipped
  ) {
  SearchShardTarget next = shardIt.nextOrNull();
+ if (ignoreWeightedRouting(clusterState)) {
+ return next;
+ }
+
  while (next != null && WeightedRoutingUtils.isWeighedAway(next.getNodeId(), clusterState)) {
  SearchShardTarget nextShard = next;
- if (canFailOpen(nextShard.getShardId(), exception, clusterState)) {
+ if (canFailOpen(nextShard.getShardId(), shardIt.size(), exception, clusterState)) {
  logger.info(() -> new ParameterizedMessage("{}: Fail open executed due to exception", nextShard.getShardId()), exception);
  getWeightedRoutingStats().updateFailOpenCount();
  break;
@@ -98,10 +104,13 @@ public SearchShardTarget findNext(
  */
  public ShardRouting findNext(final ShardsIterator shardsIt, ClusterState clusterState, Exception exception, Runnable onShardSkipped) {
  ShardRouting next = shardsIt.nextOrNull();
+ if (ignoreWeightedRouting(clusterState)) {
+ return next;
+ }
 
  while (next != null && WeightedRoutingUtils.isWeighedAway(next.currentNodeId(), clusterState)) {
  ShardRouting nextShard = next;
- if (canFailOpen(nextShard.shardId(), exception, clusterState)) {
+ if (canFailOpen(nextShard.shardId(), shardsIt.size(), exception, clusterState)) {
  logger.info(() -> new ParameterizedMessage("{}: Fail open executed due to exception", nextShard.shardId()), exception);
  getWeightedRoutingStats().updateFailOpenCount();
  break;
@@ -117,8 +126,8 @@ public ShardRouting findNext(final ShardsIterator shardsIt, ClusterState cluster
  * @return true if can fail open ie request shard copies present in nodes with weighted shard
  * routing weight set to zero
  */
- private boolean canFailOpen(ShardId shardId, Exception exception, ClusterState clusterState) {
- return isInternalFailure(exception) || hasInActiveShardCopies(clusterState, shardId);
+ private boolean canFailOpen(ShardId shardId, int shardItSize, Exception exception, ClusterState clusterState) {
+ return shardItSize == 1 || isInternalFailure(exception) || hasInActiveShardCopies(clusterState, shardId);
  }
 
  private boolean hasInActiveShardCopies(ClusterState clusterState, ShardId shardId) {
@@ -131,6 +140,10 @@ private boolean hasInActiveShardCopies(ClusterState clusterState, ShardId shardI
  return false;
  }
 
+ private boolean ignoreWeightedRouting(ClusterState clusterState) {
+ return IGNORE_WEIGHTED_SHARD_ROUTING.get(clusterState.getMetadata().settings());
+ }
+
  public WeightedRoutingStats getWeightedRoutingStats() {
  return WeightedRoutingStats.getInstance();
  }

server/src/main/java/org/opensearch/cluster/routing/IndexShardRoutingTable.java

@@ -324,9 +324,12 @@ public ShardIterator activeInitializingShardsWeightedIt(
  WeightedRouting weightedRouting,
  DiscoveryNodes nodes,
  double defaultWeight,
- boolean isFailOpenEnabled
+ boolean isFailOpenEnabled,
+ @Nullable Integer seed
  ) {
- final int seed = shufflerForWeightedRouting.nextSeed();
+ if (seed == null) {
+ seed = shufflerForWeightedRouting.nextSeed();
+ }
  List<ShardRouting> ordered = activeInitializingShardsWithWeights(weightedRouting, nodes, defaultWeight, seed);
 
  // append shards for attribute value with weight zero, so that shard search requests can be tried on
@@ -350,6 +353,7 @@ public ShardIterator activeInitializingShardsWeightedIt(
  logger.debug("no shard copies found for shard id [{}] for node attribute with weight zero", shardId);
  }
  }
+
  return new PlainShardIterator(shardId, ordered);
  }
 
@@ -371,21 +375,6 @@ private List<ShardRouting> activeInitializingShardsWithWeights(
  return orderedListWithDistinctShards;
  }
 
- /**
- * Returns an iterator over active and initializing shards, shards are ordered by weighted
- * round-robin scheduling policy. Uses the passed seed to shuffle the shards.
- *
- */
- public ShardIterator activeInitializingShardsSimpleWeightedIt(
- WeightedRouting weightedRouting,
- DiscoveryNodes nodes,
- double defaultWeight,
- int seed
- ) {
- List<ShardRouting> ordered = activeInitializingShardsWithWeights(weightedRouting, nodes, defaultWeight, seed);
- return new PlainShardIterator(shardId, ordered);
- }
-
  /**
  * Returns a list containing shard routings ordered using weighted round-robin scheduling.
  */

server/src/main/java/org/opensearch/cluster/routing/OperationRouting.java

@@ -93,16 +93,30 @@ public class OperationRouting {
 
  public static final Setting<Boolean> STRICT_WEIGHTED_SHARD_ROUTING_ENABLED = Setting.boolSetting(
  "cluster.routing.weighted.strict",
+ true,
+ Setting.Property.Dynamic,
+ Setting.Property.NodeScope
+ );
+
+ public static final Setting<Boolean> IGNORE_WEIGHTED_SHARD_ROUTING = Setting.boolSetting(
+ "cluster.routing.ignore_weighted_routing",
  false,
  Setting.Property.Dynamic,
  Setting.Property.NodeScope
  );
+
+ private static final List<Preference> WEIGHTED_ROUTING_RESTRICTED_PREFERENCES = Arrays.asList(
+ Preference.ONLY_NODES,
+ Preference.PREFER_NODES
+ );
+
  private volatile List<String> awarenessAttributes;
  private volatile boolean useAdaptiveReplicaSelection;
  private volatile boolean ignoreAwarenessAttr;
  private volatile double weightedRoutingDefaultWeight;
  private volatile boolean isFailOpenEnabled;
  private volatile boolean isStrictWeightedShardRouting;
+ private volatile boolean ignoreWeightedRouting;
 
  public OperationRouting(Settings settings, ClusterSettings clusterSettings) {
  // whether to ignore awareness attributes when routing requests
@@ -116,11 +130,13 @@ public OperationRouting(Settings settings, ClusterSettings clusterSettings) {
  this.weightedRoutingDefaultWeight = WEIGHTED_ROUTING_DEFAULT_WEIGHT.get(settings);
  this.isFailOpenEnabled = WEIGHTED_ROUTING_FAILOPEN_ENABLED.get(settings);
  this.isStrictWeightedShardRouting = STRICT_WEIGHTED_SHARD_ROUTING_ENABLED.get(settings);
+ this.ignoreWeightedRouting = IGNORE_WEIGHTED_SHARD_ROUTING.get(settings);
  clusterSettings.addSettingsUpdateConsumer(USE_ADAPTIVE_REPLICA_SELECTION_SETTING, this::setUseAdaptiveReplicaSelection);
  clusterSettings.addSettingsUpdateConsumer(IGNORE_AWARENESS_ATTRIBUTES_SETTING, this::setIgnoreAwarenessAttributes);
  clusterSettings.addSettingsUpdateConsumer(WEIGHTED_ROUTING_DEFAULT_WEIGHT, this::setWeightedRoutingDefaultWeight);
  clusterSettings.addSettingsUpdateConsumer(WEIGHTED_ROUTING_FAILOPEN_ENABLED, this::setFailOpenEnabled);
  clusterSettings.addSettingsUpdateConsumer(STRICT_WEIGHTED_SHARD_ROUTING_ENABLED, this::setStrictWeightedShardRouting);
+ clusterSettings.addSettingsUpdateConsumer(IGNORE_WEIGHTED_SHARD_ROUTING, this::setIgnoreWeightedRouting);
  }
 
  void setUseAdaptiveReplicaSelection(boolean useAdaptiveReplicaSelection) {
@@ -143,6 +159,10 @@ void setStrictWeightedShardRouting(boolean strictWeightedShardRouting) {
  this.isStrictWeightedShardRouting = strictWeightedShardRouting;
  }
 
+ void setIgnoreWeightedRouting(boolean isWeightedRoundRobinEnabled) {
+ this.ignoreWeightedRouting = isWeightedRoundRobinEnabled;
+ }
+
  public boolean isIgnoreAwarenessAttr() {
  return ignoreAwarenessAttr;
  }
@@ -314,11 +334,7 @@ private ShardIterator preferenceActiveShardIterator(
  }
  }
  preferenceType = Preference.parse(preference);
- if (weightedRoutingMetadata != null && weightedRoutingMetadata.getWeightedRouting().isSet() && isStrictWeightedShardRouting) {
- throw new PreferenceBasedSearchNotAllowedException(
- "Preference type based routing not allowed with strict weighted shard routing enabled"
- );
- }
+ checkPreferenceBasedRoutingAllowed(preferenceType, weightedRoutingMetadata);
  switch (preferenceType) {
  case PREFER_NODES:
  final Set<String> nodesIds = Arrays.stream(preference.substring(Preference.PREFER_NODES.type().length() + 1).split(","))
@@ -344,11 +360,16 @@ private ShardIterator preferenceActiveShardIterator(
  // for a different element in the list by also incorporating the
  // shard ID into the hash of the user-supplied preference key.
  routingHash = 31 * routingHash + indexShard.shardId.hashCode();
- if (weightedRoutingMetadata != null && weightedRoutingMetadata.getWeightedRouting().isSet() && isStrictWeightedShardRouting) {
- return indexShard.activeInitializingShardsSimpleWeightedIt(
+ if (WeightedRoutingUtils.shouldPerformStrictWeightedRouting(
+ isStrictWeightedShardRouting,
+ ignoreWeightedRouting,
+ weightedRoutingMetadata
+ )) {
+ return indexShard.activeInitializingShardsWeightedIt(
  weightedRoutingMetadata.getWeightedRouting(),
  nodes,
  getWeightedRoutingDefaultWeight(),
+ isFailOpenEnabled,
  routingHash
  );
  } else if (ignoreAwarenessAttributes()) {
@@ -365,12 +386,13 @@ private ShardIterator shardRoutings(
  @Nullable Map<String, Long> nodeCounts,
  @Nullable WeightedRoutingMetadata weightedRoutingMetadata
  ) {
- if (weightedRoutingMetadata != null && weightedRoutingMetadata.getWeightedRouting().isSet()) {
+ if (WeightedRoutingUtils.shouldPerformWeightedRouting(ignoreWeightedRouting, weightedRoutingMetadata)) {
  return indexShard.activeInitializingShardsWeightedIt(
  weightedRoutingMetadata.getWeightedRouting(),
  nodes,
  getWeightedRoutingDefaultWeight(),
- isFailOpenEnabled
+ isFailOpenEnabled,
+ null
  );
  } else if (ignoreAwarenessAttributes()) {
  if (useAdaptiveReplicaSelection) {
@@ -438,4 +460,15 @@ private static int calculateScaledShardId(IndexMetadata indexMetadata, String ef
  return Math.floorMod(hash, indexMetadata.getRoutingNumShards()) / indexMetadata.getRoutingFactor();
  }
 
+ private void checkPreferenceBasedRoutingAllowed(Preference preference, @Nullable WeightedRoutingMetadata weightedRoutingMetadata) {
+ if (WeightedRoutingUtils.shouldPerformStrictWeightedRouting(
+ isStrictWeightedShardRouting,
+ ignoreWeightedRouting,
+ weightedRoutingMetadata
+ ) && WEIGHTED_ROUTING_RESTRICTED_PREFERENCES.contains(preference)) {
+ throw new PreferenceBasedSearchNotAllowedException(
+ "Preference type based routing not allowed with strict weighted shard routing enabled"
+ );
+ }
+ }
 }

server/src/main/java/org/opensearch/cluster/routing/WeightedRoutingUtils.java

@@ -53,4 +53,16 @@ public static boolean isWeighedAway(String nodeId, ClusterState clusterState) {
  }
  return false;
  }
+
+ public static boolean shouldPerformWeightedRouting(boolean ignoreWeightedRouting, WeightedRoutingMetadata weightedRoutingMetadata) {
+ return !ignoreWeightedRouting && weightedRoutingMetadata != null && weightedRoutingMetadata.getWeightedRouting().isSet();
+ }
+
+ public static boolean shouldPerformStrictWeightedRouting(
+ boolean isStrictWeightedShardRouting,
+ boolean ignoreWeightedRouting,
+ WeightedRoutingMetadata weightedRoutingMetadata
+ ) {
+ return isStrictWeightedShardRouting && shouldPerformWeightedRouting(ignoreWeightedRouting, weightedRoutingMetadata);
+ }
 }

server/src/main/java/org/opensearch/common/settings/ClusterSettings.java

@@ -546,6 +546,7 @@ public void apply(Settings value, Settings current, Settings previous) {
  OperationRouting.WEIGHTED_ROUTING_DEFAULT_WEIGHT,
  OperationRouting.WEIGHTED_ROUTING_FAILOPEN_ENABLED,
  OperationRouting.STRICT_WEIGHTED_SHARD_ROUTING_ENABLED,
+ OperationRouting.IGNORE_WEIGHTED_SHARD_ROUTING,
  IndexGraveyard.SETTING_MAX_TOMBSTONES,
  PersistentTasksClusterService.CLUSTER_TASKS_ALLOCATION_RECHECK_INTERVAL_SETTING,
  EnableAssignmentDecider.CLUSTER_TASKS_ALLOCATION_ENABLE_SETTING,