Use binary search in ShardBoundaries#getShardForToken

[michaeljmarshall]

What is the issue

There is not an issue yet. I am submitting this PR to run tests and to start a discussion about the implementation.

What does this PR fix and why was it fixed

We currently scan shards in the getShardForToken method. Given that we have a sorted array and that this method is called multiple times for writes and reads, it seems worth considering a switch from an O(n) operation to an O(n log(n)) operation. This would like need further performance testing. I am just submitting to start a discussion.

[github-actions]

Checklist before you submit for review

• Make sure there is a PR in the CNDB project updating the Converged Cassandra version
• Use NoSpamLogger for log lines that may appear frequently in the logs
• Verify test results on Butler
• Test coverage for new/modified code is > 80%
• Proper code formatting
• Proper title for each commit staring with the project-issue number, like CNDB-1234
• Each commit has a meaningful description
• Each commit is not very long and contains related changes
• Renames, moves and reformatting are in distinct commits
• All new files should contain the DataStax copyright header instead of the Apache License one

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[cassci-bot]

✔️ Build ds-cassandra-pr-gate/PR-1792 approved by Butler

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Approved by Butler
See build details here

[pkolaczk]

Overall I like this change and binary search should be in general better.

However binary search might not be faster when n is very small or when tokens are not spaced very uniformly (I guess it's not the problem here). I agree we might need a microbenchmark here. But if this method doesn't appear heavily in the profile, I'd say let's not spend too much time on that.

[michaeljmarshall]

@blambov suggested we could branch based on number of shards, but that would only really make a difference if we performance tested it to find a meaningful inflection point.