sankalp kohli created CASSANDRA-4310:
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Summary: Make Level Compaction go faster(multiple independant
compactions in parallel) for insert heavy workload
Key: CASSANDRA-4310
URL: https://issues.apache.org/jira/browse/CASSANDRA-4310
Project: Cassandra
Issue Type: Improvement
Reporter: sankalp kohli
Priority: Minor
Problem: If you are inserting data into cassandra and level compaction cannot
catchup, you will create lot of files in L0. This will starve compactions in
the lower levels and make things worse.
There is a comment about this problem in the code as well.
Here is a solution which will help here and also increase the performance of
level compaction.
We can do many compactions in parallel for unrelated data.
1) For no over lapping levels. Ex: when L0 stable is compacting with L1, we can
do compactions in other levels like L2 and L3 if they are eligible.
2) We can also do compactions with files in L1 which are not participating in
L0 compactions.
This is specially useful if you are using SSD and is not bottlenecked by IO.
I am seeing this issue in my cluster. The compactions pending are more than 50k.
I am doing multithreaded to true and also not throttling the IO by putting the
value as 0.
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