allocation: create separate limit for frozen tier concurrent rebalance #135243
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -20,13 +20,15 @@ | |
| /** | ||
| * Similar to the {@link ClusterRebalanceAllocationDecider} this | ||
| * {@link AllocationDecider} controls the number of currently in-progress | ||
| * re-balance (shard relocation) operations and restricts node allocations | ||
| * if the configured threshold is reached. Frozen and non-frozen shards are | ||
| * considered separately. The default number of concurrent rebalance operations | ||
| * is set to {@code 2} for non-frozen shards, and {@code 10} for frozen shards. | ||
| * <p> | ||
| * Re-balance operations can be controlled in real-time via the cluster update API using | ||
| * {@code cluster.routing.allocation.cluster_concurrent_rebalance} and | ||
| * {@code cluster.routing.allocation.cluster_concurrent_frozen_rebalance}. | ||
| * Iff either setting is set to {@code -1} the number of concurrent re-balance operations | ||
| * are unlimited. | ||
| */ | ||
| public class ConcurrentRebalanceAllocationDecider extends AllocationDecider { | ||
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@@ -44,21 +46,91 @@ public class ConcurrentRebalanceAllocationDecider extends AllocationDecider { | |
| ); | ||
| private volatile int clusterConcurrentRebalance; | ||
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| /** | ||
| * Same as cluster_concurrent_rebalance, but applies separately to frozen tier shards | ||
| * | ||
| * Defaults to the same value as normal concurrent rebalance, if unspecified | ||
| */ | ||
| public static final Setting<Integer> CLUSTER_ROUTING_ALLOCATION_CLUSTER_CONCURRENT_FROZEN_REBALANCE_SETTING = Setting.intSetting( | ||
| "cluster.routing.allocation.cluster_concurrent_frozen_rebalance", | ||
| CLUSTER_ROUTING_ALLOCATION_CLUSTER_CONCURRENT_REBALANCE_SETTING, | ||
| -1, | ||
| Property.Dynamic, | ||
| Property.NodeScope | ||
| ); | ||
| private volatile int clusterConcurrentFrozenRebalance; | ||
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| public ConcurrentRebalanceAllocationDecider(ClusterSettings clusterSettings) { | ||
| clusterSettings.initializeAndWatch( | ||
| CLUSTER_ROUTING_ALLOCATION_CLUSTER_CONCURRENT_REBALANCE_SETTING, | ||
| this::setClusterConcurrentRebalance | ||
| ); | ||
| clusterSettings.initializeAndWatch( | ||
| CLUSTER_ROUTING_ALLOCATION_CLUSTER_CONCURRENT_FROZEN_REBALANCE_SETTING, | ||
| this::setClusterConcurrentFrozenRebalance | ||
| ); | ||
| logger.debug( | ||
| "using [cluster_concurrent_rebalance] with [concurrent_rebalance={}, concurrent_frozen_rebalance={}]", | ||
| clusterConcurrentRebalance, | ||
| clusterConcurrentFrozenRebalance | ||
| ); | ||
| } | ||
|
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||
| private void setClusterConcurrentRebalance(int concurrentRebalance) { | ||
| clusterConcurrentRebalance = concurrentRebalance; | ||
| } | ||
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| private void setClusterConcurrentFrozenRebalance(int concurrentFrozenRebalance) { | ||
| clusterConcurrentFrozenRebalance = concurrentFrozenRebalance; | ||
| } | ||
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||
| @Override | ||
| public Decision canRebalance(ShardRouting shardRouting, RoutingAllocation allocation) { | ||
| int relocatingFrozenShards = allocation.routingNodes().getRelocatingFrozenShardCount(); | ||
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| if (allocation.routingNodes().isDedicatedFrozenNode(shardRouting.currentNodeId())) { | ||
| if (clusterConcurrentFrozenRebalance == -1) { | ||
| return allocation.decision(Decision.YES, NAME, "unlimited concurrent frozen rebalances are allowed"); | ||
| } | ||
| if (relocatingFrozenShards >= clusterConcurrentFrozenRebalance) { | ||
| return allocation.decision( | ||
| Decision.THROTTLE, | ||
| NAME, | ||
| "reached the limit of concurrently rebalancing frozen shards [%d], cluster setting [%s=%d]", | ||
| relocatingFrozenShards, | ||
| CLUSTER_ROUTING_ALLOCATION_CLUSTER_CONCURRENT_FROZEN_REBALANCE_SETTING.getKey(), | ||
| clusterConcurrentFrozenRebalance | ||
| ); | ||
| } | ||
| return allocation.decision( | ||
| Decision.YES, | ||
| NAME, | ||
| "below threshold [%d] for concurrent frozen rebalances, current frozen rebalance shard count [%d]", | ||
| clusterConcurrentFrozenRebalance, | ||
| relocatingFrozenShards | ||
| ); | ||
| } else { | ||
| int relocatingShards = allocation.routingNodes().getRelocatingShardCount() - relocatingFrozenShards; | ||
| if (clusterConcurrentRebalance == -1) { | ||
| return allocation.decision(Decision.YES, NAME, "unlimited concurrent rebalances are allowed"); | ||
| } | ||
| if (relocatingShards >= clusterConcurrentRebalance) { | ||
| return allocation.decision( | ||
| Decision.THROTTLE, | ||
| NAME, | ||
| "reached the limit of concurrently rebalancing shards [%d], cluster setting [%s=%d]", | ||
| relocatingShards, | ||
| CLUSTER_ROUTING_ALLOCATION_CLUSTER_CONCURRENT_REBALANCE_SETTING.getKey(), | ||
| clusterConcurrentRebalance | ||
| ); | ||
| } | ||
| return allocation.decision( | ||
| Decision.YES, | ||
| NAME, | ||
| "below threshold [%d] for concurrent rebalances, current rebalance shard count [%d]", | ||
| clusterConcurrentRebalance, | ||
| relocatingShards | ||
| ); | ||
| } | ||
| } | ||
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| /** | ||
|
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@@ -68,33 +140,52 @@ public Decision canRebalance(ShardRouting shardRouting, RoutingAllocation alloca | |
| */ | ||
| @Override | ||
| public Decision canRebalance(RoutingAllocation allocation) { | ||
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| int relocatingFrozenShards = allocation.routingNodes().getRelocatingFrozenShardCount(); | ||
| int relocatingShards = allocation.routingNodes().getRelocatingShardCount(); | ||
| if (allocation.isSimulating() && relocatingShards >= 2) { | ||
| // BalancedShardAllocator is prone to perform unnecessary moves when cluster_concurrent_rebalance is set to high values (>2). | ||
| // (See https://github.com/elastic/elasticsearch/issues/87279) | ||
| // Above allocator is used in DesiredBalanceComputer. Since we do not move actual shard data during calculation | ||
| // it is possible to artificially set above setting to 2 to avoid unnecessary moves in desired balance. | ||
| // Separately: keep overall limit in simulation to two including frozen shards | ||
| return allocation.decision(Decision.THROTTLE, NAME, "allocation should move one shard at the time when simulating"); | ||
|
There was a problem hiding this comment. As discussed, this whole branch might be redundant (?) since #134786 There was a problem hiding this comment. This is helpful -- can we leave this to a separate PR? This may not be the only decider that needs to change. |
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| } | ||
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| // separate into frozen/non-frozen counts | ||
| relocatingShards = relocatingShards - relocatingFrozenShards; | ||
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| // either frozen or non-frozen having some allowance before their limit means the allocator has room to rebalance | ||
| if (clusterConcurrentRebalance == -1 || relocatingShards < clusterConcurrentRebalance) { | ||
| return allocation.decision( | ||
| Decision.YES, | ||
| NAME, | ||
| "below threshold [%s=%d] for concurrent rebalances, current rebalance shard count [%d]", | ||
| CLUSTER_ROUTING_ALLOCATION_CLUSTER_CONCURRENT_REBALANCE_SETTING.getKey(), | ||
| clusterConcurrentRebalance, | ||
| relocatingShards | ||
| ); | ||
| } | ||
| if (clusterConcurrentFrozenRebalance == -1 || relocatingFrozenShards < clusterConcurrentFrozenRebalance) { | ||
| return allocation.decision( | ||
| Decision.YES, | ||
| NAME, | ||
| "below threshold [%s=%d] for concurrent frozen rebalances, current frozen rebalance shard count [%d]", | ||
| CLUSTER_ROUTING_ALLOCATION_CLUSTER_CONCURRENT_FROZEN_REBALANCE_SETTING.getKey(), | ||
| clusterConcurrentFrozenRebalance, | ||
| relocatingFrozenShards | ||
| ); | ||
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|
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| } | ||
| return allocation.decision( | ||
| Decision.THROTTLE, | ||
| NAME, | ||
| "reached the limit of concurrently rebalancing shards [%d] for concurrent rebalances, cluster setting [%s=%d], " | ||
| + "and [%d] for concurrent frozen rebalances, frozen cluster setting [%s=%d]", | ||
| relocatingShards, | ||
| CLUSTER_ROUTING_ALLOCATION_CLUSTER_CONCURRENT_REBALANCE_SETTING.getKey(), | ||
| clusterConcurrentRebalance, | ||
| relocatingFrozenShards, | ||
| CLUSTER_ROUTING_ALLOCATION_CLUSTER_CONCURRENT_FROZEN_REBALANCE_SETTING.getKey(), | ||
| clusterConcurrentFrozenRebalance | ||
| ); | ||
| } | ||
| } | ||
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This doc is out of date with the implementation.