Peng Zhang created YARN-3414:
--------------------------------
Summary: FairScheduler's preemption may cause livelock
Key: YARN-3414
URL: https://issues.apache.org/jira/browse/YARN-3414
Project: Hadoop YARN
Issue Type: Bug
Components: fairscheduler
Affects Versions: 2.6.0
Reporter: Peng Zhang
I met this problem in our cluster, it cause livelock during preemption and
scheduling.
Queue hierarchy described as below:
{noformat}
root
/ | \
queue-1 queue-2 queue-3
/ \
queue-1-1 queue-1-2
{noformat}
# Assume cluster resource is 100G in memory
# Assume queue-1 has max resource limit 20G
# queue-1-1 is active and it will get max 20G memory(equal to its fairshare)
# queue-2 is active then, and it require 30G memory(less than its fairshare)
# queue-3 is active, and it can be assigned with all other resources, 50G
memory(larger than its fairshare). At here three queues' fair share is (20, 40,
40), and usage is (20, 30, 50)
# queue-1-2 is active, it will cause new preemption request(10G memory and
intuitively it can only preempt from its sibling queue-1-1)
# Actually preemption starts from root, and it will find queue-3 is most over
fairshare, and preempt some resources form queue-3.
# But during scheduling, it will find queue-1 itself arrived it's max
fairshare, and cannot assign resource to it. Then resource's again assigned to
queue-3
And then it repeats between last two steps.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
