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Add request snapshot #243

Merged
merged 27 commits into from
Jul 1, 2019
Merged

Add request snapshot #243

merged 27 commits into from
Jul 1, 2019

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overvenus
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This adds a feature that allows follower/learner request snapshot actively.

Impls tikv/rfcs#26

@overvenus overvenus requested review from BusyJay and hicqu June 10, 2019 07:12
BusyJay
BusyJay reviewed Jun 13, 2019
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@overvenus overvenus mentioned this pull request Jun 19, 2019
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BusyJay
BusyJay reviewed Jun 19, 2019
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BusyJay reviewed Jun 19, 2019
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BusyJay reviewed Jun 19, 2019
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BusyJay reviewed Jun 19, 2019
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BusyJay reviewed Jun 21, 2019
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BusyJay
BusyJay previously approved these changes Jun 27, 2019
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hicqu
hicqu reviewed Jun 27, 2019
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hicqu
hicqu reviewed Jun 27, 2019
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src/progress.rs
if self.next_idx < 1 {
self.next_idx = 1;
}
} else if self.pending_request_snapshot == INVALID_INDEX {
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Why else if instead of else?

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We don't want to update pending request snapshot if there is one already, let's keep it simple.

hicqu
hicqu reviewed Jun 27, 2019
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src/raft.rs
// TODO: revoke pub when there is a better way to test.
/// For a given message, append the entries to the log.
pub fn handle_append_entries(&mut self, m: &Message) {
if self.pending_request_snapshot != INVALID_INDEX {
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what if the entries is more new than pending_request_snapshot?

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It should be dropped if a follower is requesting a snapshot. After applying a snapshot, the follower will receive raft log entries again.

hicqu
hicqu reviewed Jun 27, 2019
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src/raft.rs
@@ -1794,7 +1849,10 @@ impl<T: Storage> Raft<T> {

fn restore_raft(&mut self, snap: &Snapshot) -> Option<bool> {
let meta = snap.get_metadata();
if self.raft_log.match_term(meta.get_index(), meta.get_term()) {
// Do not fast-forward commit if we are requesting snapshot.
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Why?

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Because the snapshot may be dropped if there is no further proposal after requesting a snapshot.

zhangjinpeng87
zhangjinpeng87 reviewed Jun 29, 2019
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src/progress.rs
if self.state == ProgressState::Replicate {
// the rejection must be stale if the progress has matched and "rejected"
// is smaller than "match".
if rejected <= self.matched {
// Or rejected equals to matched and request_snapshot is the INVALID_INDEX.
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Can you give more explanation for this condition?

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Got it.

zhangjinpeng87
zhangjinpeng87 reviewed Jun 29, 2019
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zhangjinpeng87
zhangjinpeng87 reviewed Jun 29, 2019
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src/raft.rs
let mut m = Message::new();
m.set_msg_type(MessageType::MsgAppendResponse);
m.set_index(self.raft_log.committed);
m.set_reject(true);
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Why set reject?

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It needs to be rejected, so it can enter requesting snapshot state in leader's view. See more at handle_append_response.

zhangjinpeng87
zhangjinpeng87 reviewed Jun 29, 2019
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src/raft.rs
// TODO: revoke pub when there is a better way to test.
/// For a given message, append the entries to the log.
pub fn handle_append_entries(&mut self, m: &Message) {
if self.pending_request_snapshot != INVALID_INDEX {
self.send_request_snapshot();
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Does the leader can tolerant follower send_request_snapshot multiple times with the same pending_request_snapshot?

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Yes, because request snapshot message may be dropped on the network, it needs to be able to send the same message multiple times.

zhangjinpeng87
zhangjinpeng87 reviewed Jun 29, 2019
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@overvenus
Address comments
a2a5c53 
Signed-off-by: Neil Shen <[email protected]>
zhangjinpeng87
zhangjinpeng87 approved these changes Jun 29, 2019
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LGTM

@overvenus
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PTAL @hicqu @BusyJay Thanks!

@overvenus overvenus merged commit fe10576 into 0.4.x Jul 1, 2019
nrc added a commit to nrc/raft-rs that referenced this pull request Jul 11, 2019
@nrc
Port tikv#243 to the Prost branch
da05916 
Signed-off-by: Nick Cameron <[email protected]>
nrc added a commit to nrc/raft-rs that referenced this pull request Jul 11, 2019
@nrc
Port tikv#243 to the Prost branch
fa03acc 
Signed-off-by: Nick Cameron <[email protected]>
@nrc nrc mentioned this pull request Jul 11, 2019
Merged
nrc added a commit to nrc/raft-rs that referenced this pull request Jul 11, 2019
@nrc
Port tikv#243 to the Prost branch
66c9c1e 
Signed-off-by: Nick Cameron <[email protected]>
nrc added a commit that referenced this pull request Jul 12, 2019
@nrc
Port #243 to the Prost branch (#259)
eeaee89 
Signed-off-by: Nick Cameron <[email protected]>
hicqu pushed a commit to hicqu/raft-rs that referenced this pull request Jul 17, 2019
@overvenus @hicqu
Request snapshot (tikv#243)
e6d98a4 
Signed-off-by: Neil Shen <[email protected]>
Hoverbear pushed a commit that referenced this pull request Jul 19, 2019
@hicqu @Hoverbear
Cherry pick all 0.4.x (#263)
1377cb6 
* Check pending conf change before campaign (#225)

Fix #221.

* Add more convenient lite-weight interfaces (#227)

This PR introduces two simple and lite weight interfaces:
- ping to trigger heartbeats without ticking,
- status_ref to borrow the progress set instead of cloning.

* *: bump to 0.4.2 (#228)

* Bump to v0.4.3 (#231)

* raft: leader respond to learner read index message (#220)

Signed-off-by: nolouch <[email protected]>

* Bump to v0.4.3

Signed-off-by: Neil Shen <[email protected]>

* Request snapshot (#243)

Signed-off-by: Neil Shen <[email protected]>

* fix tests

* cargo fmt

* address comments.
@BusyJay BusyJay mentioned this pull request Mar 3, 2020
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@overvenus overvenus deleted the request-snapshot branch October 15, 2023 10:43
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@zhangjinpeng87 zhangjinpeng87 zhangjinpeng87 approved these changes

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4 participants
@overvenus @BusyJay @hicqu @zhangjinpeng87