The previous logic was erroneously setting Ready.MustSync to true when
the hard state had not changed because we were comparing an empty hard
state to the previous hard state. In combination with another misfeature
in CockroachDB (unnecessary writing of empty batches), this was causing
a steady stream of synchronous writes to disk.
The MaxSizePerMsg setting is now used to limit the size of
Ready.CommittedEntries. This prevents out-of-memory errors if the raft
log has become very large and commits all at once.
Scanning the uncommitted portion of the raft log to determine whether
there are any pending config changes can be expensive. In
cockroachdb/cockroach#18601, we've seen that a new leader can spend so
much time scanning its log post-election that it fails to send
its first heartbeats in time to prevent a second election from
starting immediately.
Instead of tracking whether a pending config change exists with a
boolean, this commit tracks the latest log index at which a pending
config change *could* exist. This is a less expensive solution to
the problem, and the impact of false positives should be minimal since
a newly-elected leader should be able to quickly commit the tail of
its log.
If the node is stopped, then Status can hang forever because there is no
event loop to answer. So, just return empty status to avoid deadlocks.
Fix#6855
Signed-off-by: Alexander Morozov <lk4d4math@gmail.com>
The relevant structures are properly aligned, however, there is no comment
highlighting the need to keep it aligned as is present elsewhere in the
codebase.
Adding note to keep alignment, in line with similar comments in the codebase.
Those three log statements in node.go have not been using the logger that was passed via `raft.Config`, but instead the default raft logger. This changes it to use the proper logger.
raft node should set initial prev hard state to empty.
Or it will not send the first hard coded state to application
until the state changes again.
This commit fixs the issue. It introduce a small overhead, that
the same tate might send to application twice when restarting.
But this is fine.
raft relies on the link layer to report the status of the sent snapshot.
If the snapshot is still sending, the replication to that remote peer will
be paused. If the snapshot finish sending, the replication will begin
optimistically after electionTimeout. If the snapshot fails, raft will
try to resend it.
If we cannot find the `m.from` from current peers in the raft and it is a response
message, we should filter it out or raft panics. We are not targetting to avoid
malicious peers.
It has to be done in the raft node layer syncchronously. Although we can check
it at the application layer asynchronously, but after the checking and before
the message going into raft, the raft state machine might make progress and
unfortunately remove the `m.from` peer.
