TestNodeWithSmallerTermCanCompleteElection tests the scenario where a
node that has been partitioned away (and fallen behind) rejoins the
cluster at about the same time the leader node gets partitioned away.
Previously the cluster would come to a standstill when run with PreVote
enabled.
When responding to Msg{Pre,}Vote messages we now include the term from
the message, not the local term. To see why consider the case where a
single node was previously partitioned away and it's local term is now
of date. If we include the local term (recall that for pre-votes we
don't update the local term), the (pre-)campaigning node on the other
end will proceed to ignore the message (it ignores all out of date
messages).
The term in the original message and current local term are the same in
the case of regular votes, but different for pre-votes.
NB: Had to change TestRecvMsgVote to include pb.Message.Term when
sending MsgVote messages. The new sanity checks on MsgVoteResp
(m.Term != 0) would panic with the old test as raft.Term would be equal
to 0 when responding with MsgVoteResp messages.
This test verifies that adding a node does not cause the leader to step
down until at least one full ElectionTick cycle elapses.
Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
advance() should use rs.req.Entries[0].Data as the context instead of
req.Context for deletion. Since req.Context is never set, there won't be
any context being deleted from pendingReadIndex; results mem leak.
FIXES#7571
The "logs converge" case in TestLeaderElectionPreVote was incorrectly
passing because some nodes were not actually using the preVoteConfig.
This test case was more complex than its siblings and it was not
verifying what it wanted to verify, so pull it out into a separate test
where everything can be tested more explicitly.
Fixes#6895
If MsgTimeoutNow arrived after a node was removed, the node could start
and win an election, then panic in becomeLeader (see
cockroachdb/cockroach#8535)
Move all vote handling from the per-state step functions to the
top-level Step(). This wasn't necessary before because MsgVote would
cause us to become a follower, but MsgPreVote needs to be handled
without changing the node's current state.
Some tests were starting nodes with a non-empty log but a term of zero,
which cannot happen in the real world. This was affecting the final term
being tested in TestLeaderElection.
Previously, the checkQuorum flag required an election timeout to
expire before a node could cast its first vote. This change permits
the node to cast a vote at any time when the leader is not known,
including immediately after startup.
Follower has already set its leader ID from
previous append messages from the leader, but
to be consistent, this adds a line to set its
leader id from leader snapshot message.
removeNode reduces the required quorum size, so some pending entries may
be able to commit after it is applied.
Discovered in cockroachdb/cockroach#3642
