This change includes basic optimizations to
locator::describe_ring, mainly caching the per-endpoint
information in an unordered_map instead of looking
them up in every inner-loop.
This yields an improvement of 20% in cpu time.
With 45 nodes organized as 3 dcs, 3 racks per dc, 5 nodes per rack, 256 tokens per
node, yielding 11520 ranges and 9 replicas per range, describe_ring took
Before: 30 milliseconds (2.6 microseconds per range)
After: 24 milliseconds (2.1 microseconds per range)
Add respective unit test of describe_ring for tablets.
A unit test for vnodes already exists in
test/nodetool/test_describering.py
Fixes#24887
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
50abeb1270