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 for vnode keyspace
and for tablets.
Fixes#24887
* backport up to 2025.1 as describe_ring slowness was hit in the field with large clusters
Closesscylladb/scylladb#24889
* github.com:scylladb/scylladb:
locator: util: optimize describe_ring
locator: util: construct_range_to_endpoint_map: pass is_vnode=true to get_natural_replicas
vnode_effective_replication_map: do_get_replicas: throw internal error if token not found in map
locator: effective_replication_map: get_natural_replicas: get is_vnode param
test: cluster: test_repair: add test_vnode_keyspace_describe_ring
fe6e1071d3