Support to compaction strategy options was recently added.
Previously, we were using default values in compaction strategy for
options, but now we can use the options defined in the schema.
Currently, we only support size-tiered strategy, so let's start
with it.
Signed-off-by: Raphael S. Carvalho <raphaelsc@cloudius-systems.com>
Size-tired strategy basically consists of creating buckets with sstables
of nearly the same size.
Afterwards, it will find the most interesting bucket, which size must be
between min threshold and max threshold. Bucket with the smallest average
size is the most interesting one.
Bucket hotness is also considered when finding the most interesting bucket,
but we don't support this yet.
We are also missing some code that discards sstable based on its coldness,
i.e. hardly read.
Signed-off-by: Raphael S. Carvalho <raphaelsc@cloudius-systems.com>
As the name implies, this patch introduces the concept of automatic
compaction for sstables.
Compaction task is triggered whenever a new sstable is written.
Concurrent compaction on the same column family isn't supported, so
compaction may be postponed if there is an ongoing compression.
In addition, seastar::gate is used both to prevent a new compaction
from starting and to wait for an ongoing compaction to finish, when
the system is asked for a shutdown.
This patch also introduces an abstract class for compaction strategy,
which is really useful for supporting multiple strategies.
Currently, null and major compaction strategies are supported.
As the name implies, null compaction strategy does nothing.
Major compaction strategy is about compacting all sstables into one.
This strategy may end up being helpful when adding support to major
compaction via nodetool.
Signed-off-by: Raphael S. Carvalho <raphaelsc@cloudius-systems.com>
