[MESOS-7973] Non-leading VOTING replica catch-up

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.5.0
• Component/s: replicated log
• Target Version/s: 1.5.0
• Assignee: Ilya
• Reporter: Ilya
• Shepherd: Jie Yu
• Created: 13/Sep/17 16:22
• Updated: 03/Jan/18 19:19
• Resolved: 21/Dec/17 22:32

Description

Currently it is not possible to perform consistent reads from non-leading replicas due to the fact that if a non-leading replica is partitioned it may miss some log positions and will not make any attempt to “fill” those holes.

If a non-leading replica could catch-up missing log positions it would be able to serve eventually consistent reads to the framework. This would make it possible to do additional work on non-leading framework replicas (e.g. offload some reading from a leader to standbys or reduce failover time by keeping in-memory storage represented by the log “hot”).

Design doc: https://docs.google.com/document/d/1dERXJeAsi3Lnq9Akt82JGWK4pKNeJ6k7PTVCpM9ic_8/edit?usp=sharing