We restore a snapshot of table by streaming the sstables of
the given snapshot of the table using
`sstable_streamer::stream_sstable_mutations()` in batches. This function
reads mutations from a set of sstables, and streams them to the target
nodes. Due to the limit of this function, we are not able to track the
progress in bytes.
Previously, progress tracking used individual sstables as units, which caused
inaccuracies with tablet-distributed tables, where:
- An sstable spanning multiple tablets could be counted multiple times
- Progress reporting could become misleading (e.g., showing "40" progress
for a table with 10 sstables)
This change introduces a more robust progress tracking method:
- Use "batch" as the unit of progress instead of individual sstables.
Each batch represents a tablet when restoring a table snapshot if
the tablet being restored is distributed with tablets. When it comes
to tables distributed with vnode, each batch represents an sstable.
- Stream sstables for each tablet separately, handling both partially and
fully contained sstables
- Calculate progress based on the total number of sstables being streamed
- Skip tablet IDs with no owned tokens
For vnode-distributed tables, the number of "batches" directly corresponds
to the number of sstables, ensuring:
- Consistent progress reporting across different table distribution models
- Simplified implementation
- Accurate representation of restore progress
The new approach provides a more reliable and uniform method of tracking
restoration progress across different table distribution strategies.
Also, Corrected the use of `_sstables.size()` in
`sstable_streamer::stream_sstables()`. It addressed a review comment
from Pavel that was inadvertently overlooked during previous rebasing
the commit of 5ab4932f34.
Fixesscylladb/scylladb#21816
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#21841
d815d7013c