GitHub user mohammadshahidkhan opened a pull request:
https://github.com/apache/incubator-carbondata/pull/454
[CARBONDATA-484] Implement LRU cache for B-Tree
LRU Cache for B-Tree is proposed to ensure to avoid out memory, when too
many number of tables exits and all are not frequently used.
**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.
4. Compacted segments driver and executor cache should be invalidated
## Below things are as part of this PR:
1. Implemented Block B-Tree LRU cache at the executor side.
2. Implemented Segment B-Tree LRU cache at Driver side.
3. Implemented mechanism to clear the compacted segment cache from the
segment cache.
4. Implemented mechanism to clear to blocks from the executor cache.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/mohammadshahidkhan/incubator-carbondata
LRU_Cache_ForB-Tree
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/incubator-carbondata/pull/454.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #454
----
commit 2455544b6cd710d4fef6494e41739529b1c6b3df
Author: mohammadshahidkhan <[email protected]>
Date: 2016-10-05T04:45:09Z
[CARBONDATA-484] Implement LRU cache for B-Tree
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