If there's a token metadata for a given table, and it is in split mode,
it will be registered such that split monitor can look at it, for
example, to start split work, or do nothing if table completed it.
during topology change, e.g. drain, split is stalled since it cannot
take over the state machine.
It was noticed that the log is being spammed with a message saying the
table completed split work, since every tablet metadata update, means
waking up the monitor on behalf of a table. So it makes sense to
demote the logging level to debug. That persists until drain completes
and split can finally complete.
Another thing that was noticed is that during drain, a table can be
submitted for processing faster than the monitor can handle, so the
candidate queue may end up with multiple duplicated entries for same
table, which means unnecessary work. That is fixed by using a
sequenced set, which keeps the current FIFO behavior.
Fixes#20339.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closesscylladb/scylladb#20029
26facd807e