Hunter L created HELIX-787:
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Summary: TASK: Fix stuck tasks after Participant connection loss
Key: HELIX-787
URL: https://issues.apache.org/jira/browse/HELIX-787
Project: Apache Helix
Issue Type: Improvement
Reporter: Hunter L
Assignee: Hunter L
When Helix Participants lose ZK connection and enter a new ZK session, that
causes all task partitions on those Participants to be reset into INIT state.
This is undesirable because in reality, these tasks are considered dropped and
should be scheduled on some other instance. This is the Controller side fix for
this problem: when we detect tasks whose assigned Participants are no longer
live, we mark them as DROPPED in their parent JobContext so that
AssignableInstance will not consider them active when it is refreshed in the
next pipeline. This enables these dropped tasks to be reassigned onto other
instances.
Note that a Participant-side fix must follow so that upon reset() on task
partitions, they should be in DROPPED state, not in INIT state. This does not
inherently solve stuck INIT states on the original Participant. However, by
letting these tasks be assigned on other instances, this fix lets jobs and
workflows complete, upon which their CurrentStates will be dropped altogether.
Changelist:
1. Mark task partitions whose assigned Participants are no longer live as
DROPPED in JobContext
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