The Apache Helix team would like to announce the release of Apache Helix 0.8.2.

This is the fourteenth release under the Apache umbrella, and the tenth as a top-level project.

Helix is a generic cluster management framework used for the automatic management of partitioned, replicated and distributed resources hosted on a cluster of nodes.

In this release, Helix provides several performance improvements for rebalance pipeline:

Detailed Changes

New Features

  • [ROUTER] Expose ExternalViews in RoutingTable and RoutingTableSnapshot
  • [TASK] Expose UserContentStore in TaskDriver
  • [TASK] Add ThreadCountBasedAssignmentCalculator and integrate with Workflow/JobRebalancer and fix rebalancing logic
  • Should not start periodical refresh in RoutingTableProvider if helixmanager is not set.
  • Allow downward state transition during recovery and add recovery threshold
  • Support batch add jobs to JobQueue
  • Add periodic refresh to RoutingTableProvider

Bug Fixes

  • Make swap instance more robust and idempotent
  • Fix the issue that resource MBean may not be cleaned up when the resource is dropped.
  • Check NPE in getInstancesInClusterWithTag and throw more meaningful exception
  • Fix GroupCommit issue for adding back current state
  • Fix zkclient state related check and some potential bugs.
  • Fix race condition in Helix messaging service.
  • Fix bugs in ClusterStateVerifier and StrictMatchExternalViewVerifier.
  • Verify downward load balance and fix TestPartitionMovementThrottle

Improvements

  • Adding RoutingTableProvider monitor for tracking refresh actions and routing table update callbacks.
  • Helix manager should support getting metadata store connection string
  • Add missing replica partition metric into ClusterStatus.
  • Improve BestPossibleExternalViewVerifier by avoid fully refreshing entire cluster data everytime and avoid to calulate bestpossible states for not required resources.
  • Support event differentiated logging
  • Helix job should fail immediately if the target resource is disabled
  • Make ZkClient keep retrying connect on expiring.
  • DelayedAutoRebalancer should calculate assignment based on full partition list.
  • Change RoutingDataCache to use zk version based selective update when reading the ExternalViews and TargetExternalView.
  • Change migration strategy to N -> N+1 -> N model
  • Add ThreadPoolExecutor purge and shutdown to avoid memory leak in RoutingTableProvider

Cheers, -- The Apache Helix Team

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