Kuhu Shukla created TEZ-3972:
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Summary: Tez DAG can hang when a single task fails to fetch
Key: TEZ-3972
URL: https://issues.apache.org/jira/browse/TEZ-3972
Project: Apache Tez
Issue Type: Bug
Affects Versions: 0.9.1
Reporter: Kuhu Shukla
Assignee: Kuhu Shukla
Description of the hung DAG:
A DAG with 2 vertices. {{Map}} Vertex has 22k maps, downstream vertex
{{Reduce}} has 1009 tasks. All tasks succeed but one, which hangs. This one
task (attempt) is doing a local fetch from a node that (now) has a bad disk. It
fails to fetch and reports to the AM for the offending input attempt
identifiers. However the AM does not schedule a re-run as
{{uniquefailedOutputReports}} size is 1 (since only this task attempt failed to
fetch) and failure fraction is not met. The denominator for this fraction is
the total number of tasks. That causes the re-run to never occur. This JIRA
tracks the AM side of the change to alleviate this problem.
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