The Apache Helix team would like to announce the release of Apache Helix 0.8.4.

This is the fifteenth release under the Apache umbrella, and the eleventh 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:

Key Note for Helix Release

Task Framework 2.0

Task Framework 2.0 was fully implemented in 0.8.4 including: pipeline split up from regular pipeline, runtime job DAG supporting, task assignment by producer/consumer mode and zookeeper read/write optimization. Performance improved signification compare to Task Framework 1.0.

Detailed Changes

New Features

  • [HELIX-798] HELIX: Implement auto-exit of maintenance mode
  • Check maitenanceMode rest api implementation

Bug Fixes

  • [HELIX-792] HELIX: fix typo in WorkflowDataProvider
  • [HELIX-794] TASK: Fix double-booking of tasks upon Participant disconnect
  • Fix race condition in P2P message handling that can cause long mastership handoff problem.
  • Fix race condition for purging jobs immediately after job completes
  • [HELIX-808] TASK: Fix double-booking of tasks with task CurrentStates
  • [HELIX-810] HELIX: Fix NPE in InstanceMessagesCache
  • [HELIX-811] HELIX: Only log relayMsg if it doesn't exist


  • [HELIX-793] TASK: Make TaskAssigner honor instance constraints
  • [HELIX-795] TASK: Drop tasks upon Participant reconnect
  • Batch write support for previous assignment
  • [HELIX-801] HELIX: Implement maintenance history for maintenance mode
  • [HELIX-805] Implementation on HelixAdmin to check if cluster in maintenance mode
  • Add ERROR mapping for displaying in BestPossible and Intemediate assignment. []

Cheers, -- The Apache Helix Team

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