[Weighted Shard Routing] Fail open requests on search shard failures #5072
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,154 @@ | ||
| /* | ||
| * SPDX-License-Identifier: Apache-2.0 | ||
| * | ||
| * The OpenSearch Contributors require contributions made to | ||
| * this file be licensed under the Apache-2.0 license or a | ||
| * compatible open source license. | ||
| */ | ||
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| package org.opensearch.cluster.routing; | ||
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| import org.apache.logging.log4j.LogManager; | ||
| import org.apache.logging.log4j.Logger; | ||
| import org.apache.logging.log4j.message.ParameterizedMessage; | ||
| import org.opensearch.OpenSearchException; | ||
| import org.opensearch.action.search.SearchShardIterator; | ||
| import org.opensearch.cluster.ClusterState; | ||
| import org.opensearch.cluster.metadata.WeightedRoutingMetadata; | ||
| import org.opensearch.cluster.node.DiscoveryNode; | ||
| import org.opensearch.index.shard.ShardId; | ||
| import org.opensearch.search.SearchShardTarget; | ||
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| import java.util.List; | ||
| import java.util.Map; | ||
| import java.util.stream.Stream; | ||
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| /** | ||
| * 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 | ||
| * nodes whose attribute value weight for weighted shard routing is set to zero. | ||
| */ | ||
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| public class FailOpenRouting { | ||
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There was a problem hiding this comment. Lets write UTs for this class. There was a problem hiding this comment. nit: rename to |
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| private static final Logger logger = LogManager.getLogger(FailOpenRouting.class); | ||
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| /* exception causing failure for previous shard copy */ | ||
| private Exception exception; | ||
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| private ClusterState clusterState; | ||
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| public FailOpenRouting(Exception e, ClusterState clusterState) { | ||
| this.exception = e; | ||
| this.clusterState = clusterState; | ||
| } | ||
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| /** | ||
| * * | ||
| * @return true if exception is due to cluster availability issues | ||
| */ | ||
| private boolean isInternalFailure() { | ||
| if (exception instanceof OpenSearchException) { | ||
| return ((OpenSearchException) exception).status().getStatus() / 100 == 5; | ||
| } | ||
| return false; | ||
| } | ||
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There was a problem hiding this comment. Please lets be more specific here, prefer using something like RestStatus#INTERNAL_SERVER_ERROR |
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| /** | ||
| * This function checks if the shard is present in data node with weighted routing weight set to 0, | ||
| * In such cases we fail open, if shard search request for the shard from other shard copies fail with non | ||
| * retryable exception. | ||
| * | ||
| * @param nodeId the node with the shard copy | ||
| * @return true if the node has attribute value with shard routing weight set to zero, else false | ||
| */ | ||
| private boolean shardInNodeWithZeroWeightedRouting(String nodeId) { | ||
|
There was a problem hiding this comment. nit: Rename to |
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| DiscoveryNode node = clusterState.nodes().get(nodeId); | ||
| WeightedRoutingMetadata weightedRoutingMetadata = clusterState.metadata().weightedRoutingMetadata(); | ||
| if (weightedRoutingMetadata != null) { | ||
| WeightedRouting weightedRouting = weightedRoutingMetadata.getWeightedRouting(); | ||
| // TODO: check weighted routing has weights set after merging versioning changes | ||
| if (weightedRouting != null) { | ||
| // Fetch weighted routing attributes with weight set as zero | ||
| Stream<String> keys = weightedRouting.weights() | ||
| .entrySet() | ||
| .stream() | ||
| .filter(entry -> entry.getValue().intValue() == 0) | ||
| .map(Map.Entry::getKey); | ||
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| for (Object key : keys.toArray()) { | ||
| if (node.getAttributes().get(weightedRouting.attributeName()).equals(key.toString())) { | ||
| return true; | ||
| } | ||
| } | ||
| } | ||
| } | ||
| return false; | ||
| } | ||
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| /** | ||
| * This function returns next shard copy to retry search request in case of failure from previous copy returned | ||
| * by the iterator. It has the logic to fail open ie request shard copies present in nodes with weighted shard | ||
| * routing weight set to zero | ||
| * | ||
| * @param shardIt Shard Iterator containing order in which shard copies for a shard need to be requested | ||
| * @return the next shard copy | ||
| */ | ||
| public SearchShardTarget findNext(final SearchShardIterator shardIt) { | ||
| SearchShardTarget next = shardIt.nextOrNull(); | ||
| while (next != null && shardInNodeWithZeroWeightedRouting(next.getNodeId())) { | ||
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| if (canFailOpen(next.getShardId())) { | ||
| logFailOpen(next.getShardId()); | ||
| break; | ||
| } | ||
| next = shardIt.nextOrNull(); | ||
| } | ||
| return next; | ||
| } | ||
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| /** | ||
| * This function returns next shard copy to retry search request in case of failure from previous copy returned | ||
| * by the iterator. It has the logic to fail open ie request shard copies present in nodes with weighted shard | ||
| * routing weight set to zero | ||
| * | ||
| * @param shardsIt Shard Iterator containing order in which shard copies for a shard need to be requested | ||
| * @return the next shard copy | ||
| */ | ||
| public ShardRouting findNext(final ShardsIterator shardsIt) { | ||
| ShardRouting next = shardsIt.nextOrNull(); | ||
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| while (next != null && shardInNodeWithZeroWeightedRouting(next.currentNodeId())) { | ||
| if (canFailOpen(next.shardId())) { | ||
| logFailOpen(next.shardId()); | ||
| break; | ||
| } | ||
| next = shardsIt.nextOrNull(); | ||
| } | ||
| return next; | ||
| } | ||
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| private void logFailOpen(ShardId shardID) { | ||
| logger.info(() -> new ParameterizedMessage("{}: Fail open executed", shardID)); | ||
| } | ||
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There was a problem hiding this comment. nit : do we need a function here or can inline it directly in There was a problem hiding this comment. since this is used at multiple place, I think its better to make a function |
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| /** | ||
| * * | ||
| * @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) { | ||
| return isInternalFailure() || hasInActiveShardCopies(shardId); | ||
| } | ||
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| private boolean hasInActiveShardCopies(ShardId shardId) { | ||
| List<ShardRouting> shards = clusterState.routingTable().shardRoutingTable(shardId).shards(); | ||
| for (ShardRouting shardRouting : shards) { | ||
| if (!shardRouting.active()) { | ||
| return true; | ||
| } | ||
| } | ||
| return false; | ||
| } | ||
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| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -32,6 +32,8 @@ | |
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| package org.opensearch.cluster.routing; | ||
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| import org.apache.logging.log4j.LogManager; | ||
| import org.apache.logging.log4j.Logger; | ||
| import org.opensearch.cluster.node.DiscoveryNode; | ||
| import org.opensearch.cluster.node.DiscoveryNodes; | ||
| import org.opensearch.common.Nullable; | ||
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@@ -57,6 +59,7 @@ | |
| import java.util.Optional; | ||
| import java.util.Set; | ||
| import java.util.function.Predicate; | ||
| import java.util.stream.Stream; | ||
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| import static java.util.Collections.emptyMap; | ||
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@@ -89,6 +92,8 @@ public class IndexShardRoutingTable implements Iterable<ShardRouting> { | |
| private volatile Map<WeightedRoutingKey, List<ShardRouting>> activeShardsByWeight = emptyMap(); | ||
| private volatile Map<WeightedRoutingKey, List<ShardRouting>> initializingShardsByWeight = emptyMap(); | ||
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| private static final Logger logger = LogManager.getLogger(IndexShardRoutingTable.class); | ||
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| /** | ||
| * The initializing list, including ones that are initializing on a target node because of relocation. | ||
| * If we can come up with a better variable name, it would be nice... | ||
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@@ -305,10 +310,17 @@ public ShardIterator activeInitializingShardsRankedIt( | |
| * | ||
| * @param weightedRouting entity | ||
| * @param nodes discovered nodes in the cluster | ||
| * @param isFailOpenEnabled if true, shards search requests in case of failures are tried on shard copies present | ||
| * in node attribute value with weight zero | ||
| * @return an iterator over active and initializing shards, ordered by weighted round-robin | ||
| * scheduling policy. Making sure that initializing shards are the last to iterate through. | ||
| */ | ||
| public ShardIterator activeInitializingShardsWeightedIt( | ||
| WeightedRouting weightedRouting, | ||
| DiscoveryNodes nodes, | ||
| double defaultWeight, | ||
| boolean isFailOpenEnabled | ||
| ) { | ||
| final int seed = shuffler.nextSeed(); | ||
| List<ShardRouting> ordered = new ArrayList<>(); | ||
| List<ShardRouting> orderedActiveShards = getActiveShardsByWeight(weightedRouting, nodes, defaultWeight); | ||
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@@ -317,6 +329,29 @@ public ShardIterator activeInitializingShardsWeightedIt(WeightedRouting weighted | |
| List<ShardRouting> orderedInitializingShards = getInitializingShardsByWeight(weightedRouting, nodes, defaultWeight); | ||
| ordered.addAll(orderedInitializingShards); | ||
| } | ||
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| // append shards for attribute value with weight zero, so that shard search requests can be tried on | ||
| // shard copies in case of request failure from other attribute values. | ||
| if (isFailOpenEnabled) { | ||
| try { | ||
| Stream<String> keys = weightedRouting.weights() | ||
| .entrySet() | ||
| .stream() | ||
| .filter(entry -> entry.getValue().intValue() == 0) | ||
| .map(Map.Entry::getKey); | ||
| keys.forEach(key -> { | ||
| ShardIterator iterator = onlyNodeSelectorActiveInitializingShardsIt(weightedRouting.attributeName() + ":" + key, nodes); | ||
| while (iterator.remaining() > 0) { | ||
| ordered.add(iterator.nextOrNull()); | ||
| } | ||
| }); | ||
| } catch (IllegalArgumentException e) { | ||
| // this exception is thrown by {@link onlyNodeSelectorActiveInitializingShardsIt} in case count of shard | ||
| // copies found is zero | ||
| logger.debug("no shard copies found for shard id [{}] for node attribute with weight zero", shardId); | ||
| } | ||
| } | ||
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There was a problem hiding this comment. I just realised we aren't maintaining any state across request and hence we might just be implementing an incorrect version of weighted routing. There was a problem hiding this comment. State is maintained across requests using seed https://github.com/opensearch-project/OpenSearch/blob/main/server/src/main/java/org/opensearch/cluster/routing/IndexShardRoutingTable.java#L312 But since the shuffler sits in the IndexShardRoutingTable class, the state would be lost in case of modifications to Created a follow up task for this #5754 |
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| return new PlainShardIterator(shardId, ordered); | ||
| } | ||
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Please reword this as