[CASSANDRA-6507] counters++ get rid of logical clock in global shards

• Type: Improvement
• Status: Resolved
• Priority: Low
• Resolution: Not A Problem
• Fix Version/s: 2.1 beta1
• Assignee: Aleksey Yeschenko
• Reporter: Aleksey Yeschenko

Authors

Aleksey Yeschenko

Reviewers

Sylvain Lebresne

• Created: 19/Dec/13 02:11
• Updated: 16/Apr/19 09:31
• Resolved: 19/Dec/13 11:36

Description

In CASSANDRA-6504 the global shards still follow the

{count, logical clock}

pattern of the legacy shards. We could store the

{increments, decrements}

tuple in the shard instead, and for reconcile, instead of relying on the logical clock, pick the largest value of `increments` and `decrements` of the two shards, and use that.

E.g., shard1:

{2000, 1001}

(total 999), shard2:

{2001, 1000}

(total 1001). reconciled =

{max(2000, 2001), max(1001, 1000)}

=

{2001, 1001}

(total 1000).

While scenarios like this generally shouldn't happen post CASSANDRA-6504, this change costs us nothing, and makes issues like CASSANDRA-4417 theoretically impossible . This also makes our new implementation directly follow the http://hal.inria.fr/docs/00/55/55/88/PDF/techreport.pdf white paper.