[CASSANDRA-3224] LeveledCompactionStrategy is too complacent

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 1.0.0
• Labels: compaction
• Severity: Normal
• Assignee: Jonathan Ellis
• Reporter: Brandon Williams

Authors

Jonathan Ellis

Reviewers

Brandon Williams

• Created: 17/Sep/11 18:10
• Updated: 16/Apr/19 09:32
• Resolved: 20/Sep/11 13:13

Description

As the title says, it barely does anything. I inserted 50G worth of data with 1G heap and 99% overwrite ratio, and it only compacted twice:

 INFO [CompactionExecutor:1] 2011-09-16 22:29:54,572 CompactionTask.java (line 118) Compacting [SSTableReader(path='/var/lib/cassandra/data/Keyspace1/Standard1-h-1-Data.db')]
 INFO [CompactionExecutor:1] 2011-09-16 22:29:58,606 CompactionTask.java (line 220) Compacted to [/var/lib/cassandra/data/Keyspace1/Standard1-h-2-Data.db,/var/lib/cassandra/data/Keyspace1/Standard1-h-4-Data.db,/var/lib/cassandra/data/Keyspace1/Standard1-h-5-Data.db,].  12,595,811 to 12,595,811 (~100% of original) bytes for 40,501 keys at 3.058122MBPS.  Time: 3,928ms.
 INFO [CompactionExecutor:1] 2011-09-16 22:29:58,607 CompactionTask.java (line 222) CF Total Bytes Compacted: 12,595,811
 INFO [CompactionExecutor:3] 2011-09-16 22:29:58,889 CompactionTask.java (line 118) Compacting [SSTableReader(path='/var/lib/cassandra/data/Keyspace1/Standard1-h-4-Data.db'), SSTableReader(path='/var/lib/cassandra/data/Keyspace1/Standard1-h-2-Data.db'), SSTableReader(path='/var/lib/cassandra/data/Keyspace1/Standard1-h-5-Data.db'), SSTableReader(path='/var/lib/cassandra/data/Keyspace1/Standard1-h-3-Data.db')]
 INFO [CompactionExecutor:3] 2011-09-16 22:30:06,900 CompactionTask.java (line 220) Compacted to [/var/lib/cassandra/data/Keyspace1/Standard1-h-7-Data.db,/var/lib/cassandra/data/Keyspace1/Standard1-h-9-Data.db,/var/lib/cassandra/data/Keyspace1/Standard1-h-11-Data.db,/var/lib/cassandra/data/Keyspace1/Standard1-h-12-Data.db,/var/lib/cassandra/data/Keyspace1/Standard1-h-14-Data.db,/var/lib/cassandra/data/Keyspace1/Standard1-h-15-Data.db,].  28,374,396 to 28,374,396 (~100% of original) bytes for 91,236 keys at 3.380379MBPS.  Time: 8,005ms.
 INFO [CompactionExecutor:3] 2011-09-16 22:30:06,901 CompactionTask.java (line 222) CF Total Bytes Compacted: 40,970,207

Resulting in the following levels:

L0: 4965
L1: 6
L2: 0
L3: 0
L4: 0
L5: 0
L6: 0
L7: 0

This is obviously going to result in extremely poor read performance.