[RATIS-662] Watch request should watch on metadata entry corresponding to a commit

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Target Version/s: 0.5.0
• Assignee: Lokesh Jain
• Reporter: Lokesh Jain
• Created: 19/Aug/19 11:47
• Updated: 20/Aug/19 06:07

Description

For any commit index c1 there is a corresponding metadata entry which is added to the log. This metadata entry signifies that c1 has been replicated by majority nodes in the quorum. 

Currently watch requests watch on the log entry itself. It should rather watch the metadata entry corresponding to the commit.

Let us take a majority commit c1 with servers s1(leader) and s2 in the majority. s1 and s2 were able to commit c1 in the log. Now s1 fails and s2 may not have received metadata entry for c1. In such a scenario if s2 restarts it will not be able to apply c1 on the state machine.

Issue Links

• relates to: RATIS-663 Watch requests should watch follower's log flush index