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Andrew Kyle Purtell updated HBASE-25726: ---------------------------------------- Fix Version/s: 2.3.6 2.4.3 2.5.0 1.7.0 3.0.0-alpha-1 Hadoop Flags: Reviewed Resolution: Fixed Status: Resolved (was: Patch Available) Merged back to branch-1. Some minor changes to the new unit test required along the way. Thanks for the fix [~dmanning] . > MoveCostFunction is not included in the list of cost functions for > StochasticLoadBalancer > ----------------------------------------------------------------------------------------- > > Key: HBASE-25726 > URL: https://issues.apache.org/jira/browse/HBASE-25726 > Project: HBase > Issue Type: Bug > Components: Balancer > Affects Versions: 3.0.0-alpha-1, 2.3.1, 1.7.0, 2.4.0 > Reporter: David Manning > Assignee: David Manning > Priority: Major > Fix For: 3.0.0-alpha-1, 1.7.0, 2.5.0, 2.4.3, 2.3.6 > > > After OffPeakHours fix for MoveCostFunction (HBASE-24709), MoveCostFunction > is no longer included in costFunctions list. {{addCostFunction}} expects > multiplier to be non-zero, but multiplier is now only set in {{cost}} > function. > As a result, {{hbase.master.balancer.stochastic.maxMovePercent}} is not > respected, and there is no cost function to oppose a move. Any move that > decreases total cost at all will be accepted, causing more churn and > disruption from balancer executions. > We noticed this when investigating a case where the balancer would run after > a regionserver was restarted without use of region_mover script. The > regionserver comes online with 0 regions, leading to a shortcut in > {{needsBalance}} for {{idleRegionServerExist}}. The balancer runs to move > regions to that newly restarted regionserver. However, it moves a large > number of regions in the cluster, hyper-optimizing the other cost variables. > There were ~4300 regions in the cluster at the time, so moving 25% of the > regions should have had a final cost of at least 7 (default moveCostFunction > weight.) MoveCostFunction is also not listed in the functions contributing to > the initial cost. > {{2021-03-30 15:47:43,396 INFO [49187_ChoreService_3] > balancer.StochasticLoadBalancer - start StochasticLoadBalancer.balancer, > initCost=12.91377229840024, functionCost=RegionCountSkewCostFunction : > (500.0, 0.014878672009326464); TableSkewCostFunction : (35.0, > 0.013600280177445717); RegionReplicaHostCostFunction : (100000.0, 0.0); > RegionReplicaRackCostFunction : (10000.0, 0.0); ReadRequestCostFunction : > (5.0, 0.8296332203204705); WriteRequestCostFunction : (5.0, > 0.06818455421617946); MemstoreSizeCostFunction : (5.0, 0.08132131691669181); > StoreFileCostFunction : (5.0, 0.02054620605193966); computedMaxSteps: > 1000000}} > {{2021-03-30 15:48:13,385 DEBUG [49187_ChoreService_3] > balancer.StochasticLoadBalancer - Finished computing new load balance plan. > Computation took 30004ms to try 6571 different iterations. Found a solution > that moves 1095 regions; Going from a computed cost of 12.91377229840024 to a > new cost of 4.804625730746651}} -- This message was sent by Atlassian Jira (v8.3.4#803005)