[jira] [Created] (CARBONDATA-484) LRU cache for B-Tree to ensure to avoid out memory, when too many number of tables exits and all are not frequently used.

["Mohammad Shahid Khan (JIRA)" <ji...@apache.org>]

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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