[RATIS-1909] Fix Decreasing Next Index When GrpcLogAppender Reset Client

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.0.0
• Component/s: gRPC
• Assignee: Anpu Lu
• Reporter: Anpu Lu
• Created: 16/Oct/23 18:19
• Updated: 18/Oct/23 16:50
• Resolved: 18/Oct/23 16:50

Description

GrpcLogAppender call `resetClient` when error accors in appending entries.

In `resetClient`,  the new next index `nextIndex` may be match index + 1 when `request` is null.

This will make `getFollower().decreaseNextIndex(nextIndex);` have chance to decrease next index to the value of match index, which is against that Next index should be larger than match index.

 

// GrpcLogAppender.java:resetClient() line 134
final long nextIndex = 1 + Optional.ofNullable(request)
    .map(AppendEntriesRequest::getPreviousLog)
    .map(TermIndex::getIndex)
    .orElseGet(f::getMatchIndex);
if (onError && request == null) {
    LOG.warn("{}: Follower failed and request == null, " +
        " keep nextIndex ({}) unchanged and retry.", this, f.getNextIndex());
    return;
}
if (request != null && request.isHeartbeat()) {
    return;
}

// new next index will be min(old-1, nextIndex)
getFollower().decreaseNextIndex(nextIndex);

 

 

Issue Links

• links to: GitHub Pull Request #939