The Apache Helix team would like to announce the release of Apache Helix 0.6.8.

This is the eleventh release under the Apache umbrella, and the seventh 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. Helix provides the following features:

  • Automatic assignment of resource/partition to nodes
  • Node failure detection and recovery
  • Dynamic addition of Resources
  • Dynamic addition of nodes to the cluster
  • Pluggable distributed state machine to manage the state of a resource via state transitions
  • Automatic load balancing and throttling of transitions

Detailed Changes

Feature

  • [Helix-656] Support customize batch state transition thread pool.
  • Support cancel tasks with synchronized check task status.
  • Add support of setting/updating Cluster/Resource/Instance configs in ConfigAccessor.
  • Add cluster-level and resource-level config option to allow disable delayed rebalance of entire cluster or individual resource.
  • New DelayedAutoRebalancer featured with delayed partition movements during rebalancing.
  • Add support for flexible hirerachy representation of a cluster topology.
  • Add StrictMatchExternalViewVerifier that verifies whether the ExternalViews of given resources (or all resources in the cluster) match exactly as its ideal mapping (in idealstate).
  • Add Multi-round CRUSH rebalance strategy.
  • Add option to allow persisting best possible partition assignment in IdealState for semi-auto and full-auto modes.
  • Support of client's customized threadpool for state-transition message handling.
  • Support delaying jobs schedule with configurable delay time and start time

Bug

  • [HELIX-657] Fix unexpected idealstate overwrite when persist assignment is on.
  • [HELIX-631] Fix AutoRebalanceStrategy replica not assigned.
  • [HELIX-653] Fix enable/disable partition in instances for resource specific.
  • Make map in NotificationContext synchronized.
  • Fix bug in AutoRebalanceStrategy to try to assign orphan replicas to its preferred nodes instead of random nodes.
  • Fix a bug in BestPossibleExternalViewVerifier.
  • Fix BestPossibleExternalViewVerifier toString NPE.
  • Do not set MaxPartitionPerNode in IdealState if it is not greater than 0.

Improvement

  • [HELIX-660] Configurable operation timeout for Helix ZKClient.
  • Allow user to enable persisting preference list and best possible state map into IdealState in full-auto mode.
  • Expose Callbacks that can let async operation of ZkClient function.
  • Creating a separate threadpool to handle batchMessages.
  • Auto compress ZNode that are greater than 1MB.
  • Ignore instances with no instance configuration.
  • Avoid moving partitions unnecessarily when auto-rebalancing using default AutoRebalanceStrategy.
  • Move all options from IdealState to ResourceConfig, add Bulder for building ResourceConfig, and a new RebalanceConfig to hold all rebalance options for a resource.
  • Persist controller leader change history with timestamp for each leader controller.
  • Persist participant's offline timestamp in ParticipantHistory.
  • Persist session change history with timestamp for each participant.
  • Make synchronized for AsyncCallback.startTimer to avoid race condition.

Cheers, -- The Apache Helix Team

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