Last week in scylla.git master (issue #83; 2021-06-20)

[Avi Kivity]

This short report brings to light some interesting commits to scylla.git master from the last week. Commits in the 7521301b7..055bc33f0f range are covered.

There were 122 non-merge commits from 17 authors in that period. Some notable commits:

The internal representation of range tombstones is changing. Instead of a {start, end} pair, after which rows that may be affected by the range tombstone (and rows that are not) are emitted, we emit a {start} marker, then all affected rows, then the {end} marker. This fits well with 'm' format sstables, and once the work is complete will improve workloads which have many range tombstones.

It's now possible to prevent users from using SimpleReplicationStrategy. The goal is to first default to warning and then default to actual prevention. SimpleReplicationStrategy can make it hard to later grow the cluster by adding datacenters.

Speculative retry will now no longer consider failed responses when calculating the 99th percentile of a request. Doing so let to the latency threshold being continuously raised, since failed (timed out) requests have very long latency; so the effectiveness of the feature is much reduced. Now it will only consider successful responses.

The read path has been optimized to remove unnecessary work, leading to a small performance increase.

See you in the next issue of last week in scylla.git master!