Mohammad Shahid Khan created CARBONDATA-484:
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Summary: LRU cache for B-Tree to ensure to avoid out memory, when
too many number of tables exits and all are not frequently used.
Key: CARBONDATA-484
URL: https://issues.apache.org/jira/browse/CARBONDATA-484
Project: CarbonData
Issue Type: Bug
Reporter: Mohammad Shahid Khan
Assignee: Mohammad Shahid Khan
*LRU Cache for B-Tree*
Problem:
CarbonData is maintaining two level of B-Tree cache, one at the driver level
and another at executor level. Currently CarbonData has the mechanism to
invalidate the segments and blocks cache for the invalid table segments, but
there is no eviction policy for the unused cached object. So the instance at
which complete memory is utilized then the system will not be able to process
any new requests.
Solution:
In the cache maintained at the driver level and at the executor there must be
objects in cache currently not in use. Therefore system should have the
mechanism to below mechanism.
1. Set the max memory limit till which objects could be hold in the
memory.
2. When configured memory limit reached then identify the cached objects
currently not in use so that the required memory could be freed without
impacting the existing process.
3. Eviction should be done only till the required memory is not meet.
For details please refer to attachments.
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