Questions about the TestSplitVote2AA test

[liiuzq-xiaobai]

Here is the difference.

I have a question about the TestSplitVote2AA test case, why is it judged to be a candidate for the Splitvote case? I refer to the relevant details in the raft paper. When a splitvote situation occurs, the two raft nodes will vote for each other, and then convert themselves to Followers, so that the two will always be in the voting process.It's right?Thanks for your answer！

[liiuzq-xiaobai]

Until a subsequent raft node times out first, for example, in this test case, 2 nodes time out, and then it is elected. Shouldn’t they return to follower after giving each other votes before that?

[Water3000]

@liiuzq-xiaobai
First of all, they don't vote for each other. A candidate only votes for itself according to the paper.
Splitting case happens when no one gets votes from the majority and therefore no one becomes the leader.
When this happens, all of the candidates will not change their state until:

0. Get any kind of RPC containing a larger term -- become a follower. (basic rules for all servers)
1. Get APrpc("heartbeat") from another peer(i.e. the new leader in this term) -- become a follower.
2. Election timeout, start a new election and win the campaign -- become a leader.

In this test case, these two candidates share the same term, so No.0 won't happen. Also, no one wins the election so no one will send out heartbeats, therefore No.1 won't happen. As for No.2, however, it will happen in a few lines below your screenshot.

Actually, I think what you've misunderstood here is how the test cases work. Try to look into the send method a few lines above your screenshot. It shows how your msgs are transferred and processed(basically it's just a single-threaded FIFO). In short, this test case uses MessageType_MsgHup to trigger leader election instead of timeout, suspends at the stage when split-vote just happens, and then triggers a new round of election using MessageType_MsgHup again. There is no tick in here, no real election timeout, everything happens under the control of msg. It's a step-by-step test.