"
After data segregation feature, anything that cause out-of-order writes,
like read repair, can result in small updates to past time windows.
This causes compaction to be very aggressive because whenever a past time
window is updated like that, that time window is recompacted into a
single SSTable.
Users expect that once a window is closed, it will no longer be written
to, but that has changed since the introduction of the data segregation
future. We didn't anticipate the write amplification issues that the
feature would cause. To fix this problem, let's perform size-tiered
compaction on the windows that are no longer active and were updated
because data was segregated. The current behavior where the last active
window is merged into one file is kept. But thereafter, that same
window will only be compacted using STCS.
Fixes#6928.
"
* 'fix_twcs_agressiveness_after_data_segregation_v2' of github.com:raphaelsc/scylla:
compaction/twcs: improve further debug messages
compaction/twcs: Improve debug log which shows all windows
test: Check that TWCS properly performs size-tiered compaction on past windows
compaction/twcs: Make task estimation take into account the size-tiered behavior
compaction/stcs: Export static function that estimates pending tasks
compaction/stcs: Make get_buckets() static
compact/twcs: Perform size-tiered compaction on past time windows
compaction/twcs: Make strategy easier to extend by removing duplicated knowledge
compaction/twcs: Make newest_bucket() non-static
compaction/twcs: Move TWCS implementation into source file
6f986df458