This is an automated cherry-pick of tikv#15124

close tikv#15122

Signed-off-by: ti-chi-bot <ti-community-prow-bot@tidb.io>

components/snap_recovery/Cargo.toml

@@ -13,6 +13,7 @@ engine_rocks = { workspace = true }
 engine_traits = { workspace = true }
 futures = { version = "0.3", features = ["executor"] }
 grpcio = { workspace = true }
+itertools = "0.10"
 keys = { workspace = true }
 kvproto = { git = "https://github.com/pingcap/kvproto.git", branch = "release-6.5" }
 log = { version = "0.4", features = ["max_level_trace", "release_max_level_debug"] }
@@ -28,5 +29,6 @@ thiserror = "1.0"
 tikv = { workspace = true }
 tikv_alloc = { workspace = true }
 tikv_util = { workspace = true }
+tokio = { version = "1.17", features = ["rt"] }
 toml = "0.5"
 txn_types = { workspace = true }

components/snap_recovery/src/leader_keeper.rs

@@ -0,0 +1,260 @@
+// Copyright 2022 TiKV Project Authors. Licensed under Apache-2.0.
+
+use std::{
+    collections::HashSet,
+    marker::PhantomData,
+    sync::Mutex,
+    time::{Duration, Instant},
+};
+
+use engine_traits::KvEngine;
+use futures::compat::Future01CompatExt;
+use itertools::Itertools;
+use raftstore::{
+    errors::{Error, Result},
+    store::{Callback, CasualMessage, CasualRouter, SignificantMsg, SignificantRouter},
+};
+use tikv_util::{future::paired_future_callback, timer::GLOBAL_TIMER_HANDLE};
+
+pub struct LeaderKeeper<EK, Router> {
+    router: Router,
+    not_leader: HashSet<u64>,
+
+    _ek: PhantomData<EK>,
+}
+
+#[derive(Default)]
+pub struct StepResult {
+    pub failed_leader: Vec<(u64, Error)>,
+    pub campaign_failed: Vec<(u64, Error)>,
+}
+
+fn ellipse<T: std::fmt::Debug>(ts: &[T], max_len: usize) -> String {
+    if ts.len() < max_len {
+        return format!("{:?}", &ts);
+    }
+    format!("{:?} (and {} more)", &ts[..max_len], ts.len() - max_len)
+}
+
+impl std::fmt::Debug for StepResult {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("StepResult")
+            .field(
+                "failed_leader",
+                &format_args!("{}", ellipse(&self.failed_leader, 8)),
+            )
+            .field(
+                "campaign_failed",
+                &format_args!("{}", ellipse(&self.campaign_failed, 8)),
+            )
+            .finish()
+    }
+}
+
+impl<EK, Router> LeaderKeeper<EK, Router>
+where
+    EK: KvEngine,
+    Router: CasualRouter<EK> + SignificantRouter<EK> + 'static,
+{
+    pub fn new(router: Router, to_keep: impl IntoIterator<Item = u64>) -> Self {
+        Self {
+            router,
+
+            not_leader: to_keep.into_iter().collect(),
+            _ek: PhantomData,
+        }
+    }
+
+    pub async fn elect_and_wait_all_ready(&mut self) {
+        loop {
+            let now = Instant::now();
+            let res = self.step().await;
+            info!("finished leader keeper stepping."; "result" => ?res, "take" => ?now.elapsed());
+            GLOBAL_TIMER_HANDLE
+                .delay(now + Duration::from_secs(10))
+                .compat()
+                .await
+                .expect("wrong with global timer, cannot stepping.");
+            if res.failed_leader.is_empty() {
+                return;
+            }
+        }
+    }
+
+    pub async fn step(&mut self) -> StepResult {
+        const CONCURRENCY: usize = 256;
+        let r = Mutex::new(StepResult::default());
+        let success = Mutex::new(HashSet::new());
+        for batch in &self.not_leader.iter().chunks(CONCURRENCY) {
+            let tasks = batch.map(|region_id| async {
+                match self.check_leader(*region_id).await {
+                    Ok(_) => {
+                        success.lock().unwrap().insert(*region_id);
+                        return;
+                    }
+                    Err(err) => r.lock().unwrap().failed_leader.push((*region_id, err)),
+                };
+
+                if let Err(err) = self.force_leader(*region_id) {
+                    r.lock().unwrap().campaign_failed.push((*region_id, err));
+                }
+            });
+            futures::future::join_all(tasks).await;
+        }
+        success.lock().unwrap().iter().for_each(|i| {
+            debug_assert!(self.not_leader.remove(i));
+        });
+        r.into_inner().unwrap()
+    }
+
+    async fn check_leader(&self, region_id: u64) -> Result<()> {
+        let (cb, fut) = paired_future_callback();
+        let msg = SignificantMsg::LeaderCallback(Callback::<EK::Snapshot>::read(cb));
+        self.router.significant_send(region_id, msg)?;
+        let resp = fut
+            .await
+            .map_err(|_err| Error::Other("canceled by store".into()))?;
+        let header = resp.response.get_header();
+        if header.has_error() {
+            return Err(Error::Other(box_err!(
+                "got error: {:?}",
+                header.get_error()
+            )));
+        }
+        Ok(())
+    }
+
+    fn force_leader(&self, region_id: u64) -> Result<()> {
+        let msg = CasualMessage::Campaign;
+        self.router.send(region_id, msg)?;
+        // We have nothing to do...
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use std::{cell::RefCell, collections::HashSet};
+
+    use engine_rocks::RocksEngine;
+    use engine_traits::KvEngine;
+    use futures::executor::block_on;
+    use kvproto::raft_cmdpb;
+    use raftstore::store::{CasualRouter, SignificantRouter};
+
+    use super::LeaderKeeper;
+
+    #[derive(Default)]
+    struct MockStore {
+        regions: HashSet<u64>,
+        leaders: RefCell<HashSet<u64>>,
+    }
+
+    impl<EK, Router> LeaderKeeper<EK, Router> {
+        fn mut_router(&mut self) -> &mut Router {
+            &mut self.router
+        }
+    }
+
+    // impl SignificantRouter for MockStore, which only handles `LeaderCallback`,
+    // return success when source region is leader, otherwise fill the error in
+    // header.
+    impl<EK: KvEngine> SignificantRouter<EK> for MockStore {
+        fn significant_send(
+            &self,
+            region_id: u64,
+            msg: raftstore::store::SignificantMsg<EK::Snapshot>,
+        ) -> raftstore::errors::Result<()> {
+            match msg {
+                raftstore::store::SignificantMsg::LeaderCallback(cb) => {
+                    let mut resp = raft_cmdpb::RaftCmdResponse::default();
+                    let mut header = raft_cmdpb::RaftResponseHeader::default();
+                    if !self.leaders.borrow().contains(&region_id) {
+                        let mut err = kvproto::errorpb::Error::new();
+                        err.set_not_leader(kvproto::errorpb::NotLeader::new());
+                        header.set_error(err);
+                    }
+                    resp.set_header(header);
+                    cb.invoke_with_response(resp);
+                    Ok(())
+                }
+                _ => panic!("unexpected msg"),
+            }
+        }
+    }
+
+    // impl CasualRouter for MockStore, which only handles `Campaign`,
+    // add the region to leaders list when handling it.
+    impl<EK: KvEngine> CasualRouter<EK> for MockStore {
+        fn send(
+            &self,
+            region_id: u64,
+            msg: raftstore::store::CasualMessage<EK>,
+        ) -> raftstore::errors::Result<()> {
+            match msg {
+                raftstore::store::CasualMessage::Campaign => {
+                    if !self.regions.contains(&region_id) {
+                        return Err(raftstore::Error::RegionNotFound(region_id));
+                    }
+                    self.leaders.borrow_mut().insert(region_id);
+                    Ok(())
+                }
+                _ => panic!("unexpected msg"),
+            }
+        }
+    }
+
+    #[test]
+    fn test_basic() {
+        let leaders = vec![1, 2, 3];
+        let mut store = MockStore::default();
+        store.regions = leaders.iter().copied().collect();
+        let mut lk = LeaderKeeper::<RocksEngine, _>::new(store, leaders);
+        let res = block_on(lk.step());
+        assert_eq!(res.failed_leader.len(), 3);
+        assert_eq!(res.campaign_failed.len(), 0);
+    }
+
+    #[test]
+    fn test_failure() {
+        let leaders = vec![1, 2, 3];
+        let mut store = MockStore::default();
+        store.regions = leaders.iter().copied().collect();
+        let mut lk = LeaderKeeper::<RocksEngine, _>::new(store, vec![1, 2, 3, 4]);
+        let res = block_on(lk.step());
+        assert_eq!(res.failed_leader.len(), 4);
+        assert_eq!(res.campaign_failed.len(), 1);
+        let res = block_on(lk.step());
+        assert_eq!(res.failed_leader.len(), 1);
+        assert_eq!(res.campaign_failed.len(), 1);
+        lk.mut_router().regions.insert(4);
+        let res = block_on(lk.step());
+        assert_eq!(res.failed_leader.len(), 1);
+        assert_eq!(res.campaign_failed.len(), 0);
+        let res = block_on(lk.step());
+        assert_eq!(res.failed_leader.len(), 0);
+        assert_eq!(res.campaign_failed.len(), 0);
+    }
+
+    #[test]
+    fn test_many_regions() {
+        let leaders = std::iter::repeat_with({
+            let mut x = 0;
+            move || {
+                x += 1;
+                x
+            }
+        })
+        .take(2049)
+        .collect::<Vec<_>>();
+        let mut store = MockStore::default();
+        store.regions = leaders.iter().copied().collect();
+        let mut lk = LeaderKeeper::<RocksEngine, _>::new(store, leaders);
+        let res = block_on(lk.step());
+        assert_eq!(res.failed_leader.len(), 2049);
+        assert_eq!(res.campaign_failed.len(), 0);
+        let res = block_on(lk.step());
+        assert_eq!(res.failed_leader.len(), 0);
+        assert_eq!(res.campaign_failed.len(), 0);
+    }
+}

components/snap_recovery/src/lib.rs

@@ -9,4 +9,9 @@ pub use init_cluster::{enter_snap_recovery_mode, start_recovery};
 pub use services::RecoveryService;
 
 mod data_resolver;
+<<<<<<< HEAD
+=======
+mod leader_keeper;
+mod metrics;
+>>>>>>> 4e3102e82a (snap_recovery: added keep leader (#15124))
 mod region_meta_collector;

components/snap_recovery/src/services.rs

@@ -27,15 +27,24 @@ use raftstore::{
     router::RaftStoreRouter,
     store::{
         fsm::RaftRouter,
-        msg::{Callback, CasualMessage, PeerMsg, SignificantMsg},
+        msg::{PeerMsg, SignificantMsg},
         transport::SignificantRouter,
         SnapshotRecoveryWaitApplySyncer,
     },
 };
 use thiserror::Error;
 use tikv_util::sys::thread::{StdThreadBuildWrapper, ThreadBuildWrapper};
 
+<<<<<<< HEAD
 use crate::{data_resolver::DataResolverManager, region_meta_collector::RegionMetaCollector};
+=======
+use crate::{
+    data_resolver::DataResolverManager,
+    leader_keeper::LeaderKeeper,
+    metrics::{CURRENT_WAIT_APPLY_LEADER, REGION_EVENT_COUNTER},
+    region_meta_collector::RegionMetaCollector,
+};
+>>>>>>> 4e3102e82a (snap_recovery: added keep leader (#15124))
 
 pub type Result<T> = result::Result<T, Error>;
 
@@ -233,6 +242,7 @@ impl<ER: RaftEngine> RecoverData for RecoveryService<ER> {
                 }
             }
 
+<<<<<<< HEAD
             let mut rxs = Vec::with_capacity(leaders.len());
             for &region_id in &leaders {
                 if let Err(e) = raft_router.send_casual_msg(region_id, CasualMessage::Campaign) {
@@ -275,6 +285,19 @@ impl<ER: RaftEngine> RecoverData for RecoveryService<ER> {
             }
 
             info!("all region leader assigned done");
+=======
+            let mut lk = LeaderKeeper::new(raft_router.clone(), leaders.clone());
+            // We must use the tokio runtime here because there isn't a `block_in_place`
+            // like thing in the futures executor. It simply panics when block
+            // on the block_on context.
+            // It is also impossible to directly `await` here, because that will make
+            // borrowing to the raft router crosses the await point.
+            tokio::runtime::Builder::new_current_thread()
+                .build()
+                .expect("failed to build temporary tokio runtime.")
+                .block_on(lk.elect_and_wait_all_ready());
+            info!("all region leader assigned done"; "count" => %leaders.len());
+>>>>>>> 4e3102e82a (snap_recovery: added keep leader (#15124))
 
             let now = Instant::now();
             // wait apply to the last log