Compaction subproperties

Enabling and disabling background compaction 

ALTER TABLE mytable WITH COMPACTION = {'class': 'SizeTieredCompactionStrategy', 'enabled': 'false' }

Disabling background compaction can be harmful: without it, Cassandra does not regain disk space, and may allow zombies to propagate. Although compaction uses I/O, it is better to leave it enabled in most cases.

Enabling extended compaction logging 

You can configure Casandra to collect in-depth information about compaction activity on a node, and write it to a dedicated log file. To enable extended compaction logging, all log-all : true to the configuration map for any table.

When extended compaction is enabled, Cassandra creates a file named compaction-%d.log (where %d is a sequential number) in $CASSANDRA_HOME/logs.

• type:enable

  Lists SSTables that have been flushed previouly

  {"type":"enable","keyspace":"test","table":"t","time":1470071098866,"strategies":
    [
      {"strategyId":"0","type":"LeveledCompactionStrategy","tables":[],"repaired":true,"folders":
        ["/home/carl/oss/cassandra/bin/../data/data"]},
      {"strategyId":"1","type":"LeveledCompactionStrategy","tables":[],"repaired":false,"folders":
        ["/home/carl/oss/cassandra/bin/../data/data"]
      }
    ]
  }

• type: flush

  Logs a flush event from a memtable to an SSTable on disk, including the CompactionStrategy for each table.

  {"type":"flush","keyspace":"test","table":"t","time":1470083335639,"tables":
    [
      {"strategyId":"1","table":
        {"generation":1,"version":"mb","size":106846362,"details":
          {"level":0,"min_token":"-9221834874718566760","max_token":"9221396997139245178"}
        }
      }
    ]
  }
  

• type: compaction

  Logs a compaction event.

  {"type":"compaction","keyspace":"test","table":"t","time":1470083660267,"start":"1470083660188","end":"1470083660267","input":
    [
      {"strategyId":"1","table":
        {"generation":1372,"version":"mb","size":1064979,"details":
          {"level":1,"min_token":"7199305267944662291","max_token":"7323434447996777057"}
        }
      }
    ],"output":
    [
      {"strategyId":"1","table":
        {"generation":1404,"version":"mb","size":1064306,"details":
          {"level":2,"min_token":"7199305267944662291","max_token":"7323434447996777057"}
        }
      }
    ]
  }
  

• type: pending

  Lists the number of pending tasks for a compaction strategy

  {"type":"pending","keyspace":"test","table":"t","time":1470083447967,"strategyId":"1","pending":200}