EntryCacheAppend: Assertion `cache->start_idx + cache->len == idx' failed

[aphyr]

Found another crash in 2d1cf30, with redis f88f866:

20200510T023432.000-0400.zip

147415:09 May 23:38:38.585 node:1529561842: node.c:361: NodeAddPendingResponse: id=2216, type=proxy, request_time=1589092718585
147415:09 May 23:38:38.588 node:1529561842: raft.c:479: <raftlib> recvd appendentries t:80 ci:6853 lc:6965 pli:6848 plt:79 #117
redis-server: log.c:63: EntryCacheAppend: Assertion `cache->start_idx + cache->len == idx' failed.

This one seems less frequent; first time I've seen it in about 40 runs. No observed safety impact. To reproduce (slowly), try jepsen.redis ddb68c8961a8f2b1cb0b37f263bd1eb0930ab5b8, and run:

lein run test-all --raft-version 2d1cf30 --time-limit 600 --nemesis partition,kill,pause,member --follower-proxy --test-count 50 --concurrency 4

[aphyr]

I've reproduced this with just crashes and partitions:

20200510T092833.000-0400.zip

[aphyr]

It can also occur with just partitions, or just process pauses.

20200510T151019.000-0400.zip

[aphyr]

It's... actually incredibly frequent with pauses; we're seeing it in almost every test run right now.

[aphyr]

This looks resolved as of e0123a9