Part of the vnodes-to-tablets migration is to reshard the SSTables of
each node on vnode boundaries. Resharding is a heavy operation that
runs on startup while the node is offline. Since nodes can restart
for unexpected reasons, we need a flag to do it in a controllable way.
We also need the ability to roll back the migration, which requires
resharding in the opposite direction. This means a node must be aware of
the intended migration direction.
To address both requirements, this patch introduces a new column,
intended_storage_mode, in system.topology. A non-null value indicates
that a node should perform a migration and specifies the migration
direction.
Signed-off-by: Nikos Dragazis <nikolaos.dragazis@scylladb.com>
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