Nishant Bangarwa created HIVE-20349:
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Summary: Implement Retry Logic in HiveDruidSplit for Scan Queries
Key: HIVE-20349
URL: https://issues.apache.org/jira/browse/HIVE-20349
Project: Hive
Issue Type: Bug
Reporter: Nishant Bangarwa
Assignee: Nishant Bangarwa
while distributing druid scan query we check where the segments are loaded and
then each HiveDruidSplit directly queries the historical node.
There are few cases when we need to retry and refetch the segments.
# The segment is loaded on multiple historical nodes and one of them went down.
in this case when we do not get response from one segment, we query the next
replica.
# The segment was loaded onto a realtime task and was handed over, when we
query the realtime task has already finished. In this case there is no replica.
The Split needs to query the broker again for the location of the segment and
then send the query to correct historical node.
This is also the root cause of failure of druidkafkamini_basic.q test, where
the segment handover happens before the scan query is executed.
Note: This is not a problem when we are directly querying Druid brokers as the
broker handles the retry logic.
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