Additional Compaction Logging

Currently, viewing the results of past compactions requires parsing the log and looking at the compaction history system table, which doesn't have information about, for example, flushed sstables not previously compacted.

This is a proposal to extend the information captured for compaction. Initially, this would be done through a JMX call, but if it proves to be useful and not much overhead, it might be a feature that could be enabled for the compaction strategy all the time.

Initial log information would include:

• The compaction strategy type controlling each column family
• The set of sstables included in each compaction strategy
• Information about flushes and compactions, including times and all involved sstables
• Information about sstables, including generation, size, and tokens
• Any additional metadata the strategy wishes to add to a compaction or an sstable, like the level of an sstable or the type of compaction being performed