*: last bound source is prior to other source when pick for bound

dm/common/common.go

@@ -38,6 +38,10 @@ var (
 	// UpstreamBoundWorkerKeyAdapter used to store address of worker in which MySQL-tasks which are running.
 	// k/v: Encode(name) -> the bound relationship.
 	UpstreamBoundWorkerKeyAdapter KeyAdapter = keyHexEncoderDecoder("/dm-master/bound-worker/")
+	// UpstreamLastBoundWorkerKeyAdapter used to store address of worker in which MySQL-tasks which are running.
+	// different with UpstreamBoundWorkerKeyAdapter, this kv should not be deleted when unbound, to provide a priority
+	// k/v: Encode(name) -> the bound relationship.
+	UpstreamLastBoundWorkerKeyAdapter KeyAdapter = keyHexEncoderDecoder("/dm-master/last-bound-worker/")
 	// TaskConfigKeyAdapter used to store task config string.
 	// k/v: Encode(task-name) -> task-config-string
 	TaskConfigKeyAdapter KeyAdapter = keyHexEncoderDecoder("/dm-master/task/")
@@ -77,7 +81,8 @@ var (
 func keyAdapterKeysLen(s KeyAdapter) int {
 	switch s {
 	case WorkerRegisterKeyAdapter, UpstreamConfigKeyAdapter, UpstreamBoundWorkerKeyAdapter,
-		WorkerKeepAliveKeyAdapter, StageRelayKeyAdapter, TaskConfigKeyAdapter:
+		WorkerKeepAliveKeyAdapter, StageRelayKeyAdapter, TaskConfigKeyAdapter,
+		UpstreamLastBoundWorkerKeyAdapter:
 		return 1
 	case UpstreamSubTaskKeyAdapter, StageSubTaskKeyAdapter,
 		ShardDDLPessimismInfoKeyAdapter, ShardDDLPessimismOperationKeyAdapter,

dm/master/scheduler/scheduler.go

@@ -111,6 +111,9 @@ type Scheduler struct {
 	// - when bounded the source to a worker.
 	unbounds map[string]struct{}
 
+	// a mirror of bounds whose element is not deleted when worker unbound. worker -> SourceBound
+	lastBound map[string]ha.SourceBound
+
 	// expectant relay stages for sources, source ID -> stage.
 	// add:
 	// - bound the source to a worker (at first time).
@@ -143,6 +146,7 @@ func NewScheduler(pLogger *log.Logger, securityCfg config.Security) *Scheduler {
 		workers:             make(map[string]*Worker),
 		bounds:              make(map[string]*Worker),
 		unbounds:            make(map[string]struct{}),
+		lastBound:           make(map[string]ha.SourceBound),
 		expectRelayStages:   make(map[string]ha.Stage),
 		expectSubTaskStages: make(map[string]map[string]ha.Stage),
 		securityCfg:         securityCfg,
@@ -906,6 +910,11 @@ func (s *Scheduler) recoverWorkersBounds(cli *clientv3.Client) (int64, error) {
 	if err != nil {
 		return 0, err
 	}
+	lastSourceBoundM, _, err := ha.GetLastSourceBounds(cli)
+	if err != nil {
+		return 0, err
+	}
+	s.lastBound = lastSourceBoundM
 
 	// 3. get all history offline status.
 	kam, rev, err := ha.GetKeepAliveWorkers(cli)
@@ -1164,14 +1173,22 @@ func (s *Scheduler) handleWorkerOffline(ev ha.WorkerEvent, toLock bool) error {
 	return nil
 }
 
-// tryBoundForWorker tries to bound a random unbounded source to the worker.
+// tryBoundForWorker tries to bound a source to the worker. first try last source of this worker, then randomly pick one
 // returns (true, nil) after bounded.
 func (s *Scheduler) tryBoundForWorker(w *Worker) (bounded bool, err error) {
-	// 1. check whether any unbound source exists.
-	var source string
-	for source = range s.unbounds {
-		break // got a source.
+	// 1. check if last bound is still available.
+	// if lastBound not found, or this source has been bounded to another worker (we also check that source still exists
+	// here), randomly pick one from unbounds.
+	// NOTE: if worker isn't in lastBound, we'll get "zero" SourceBound and it's OK, because "zero" string is not in
+	// unbounds
+	source := s.lastBound[w.baseInfo.Name].Source
+	if _, ok := s.unbounds[source]; !ok {
+		source = ""
+		for source = range s.unbounds {
+			break // got a source.
+		}
 	}
+
 	if source == "" {
 		s.logger.Info("no unbound sources need to bound", zap.Stringer("worker", w.BaseInfo()))
 		return false, nil
@@ -1198,14 +1215,31 @@ func (s *Scheduler) tryBoundForWorker(w *Worker) (bounded bool, err error) {
 // tryBoundForSource tries to bound a source to a random Free worker.
 // returns (true, nil) after bounded.
 func (s *Scheduler) tryBoundForSource(source string) (bool, error) {
-	// 1. try to find a random Free worker.
+	// 1. try to find history workers, then random Free worker.
 	var worker *Worker
-	for _, w := range s.workers {
-		if w.Stage() == WorkerFree {
-			worker = w
-			break
+	for workerName, bound := range s.lastBound {
+		if bound.Source == source {
+			w, ok := s.workers[workerName]
+			if !ok {
+				// a not found worker
+				continue
+			}
+			if w.Stage() == WorkerFree {
+				worker = w
+				break
+			}
 		}
 	}
+
+	if worker == nil {
+		for _, w := range s.workers {
+			if w.Stage() == WorkerFree {
+				worker = w
+				break
+			}
+		}
+	}
+
 	if worker == nil {
 		s.logger.Info("no free worker exists for bound", zap.String("source", source))
 		return false, nil
@@ -1280,14 +1314,15 @@ func (s *Scheduler) deleteWorker(name string) {
 
 // updateStatusForBound updates the in-memory status for bound, including:
 // - update the stage of worker to `Bound`.
-// - record the bound relationship in the scheduler.
+// - record the bound relationship and last bound relationship in the scheduler.
 // this func is called after the bound relationship existed in etcd.
 func (s *Scheduler) updateStatusForBound(w *Worker, b ha.SourceBound) error {
 	err := w.ToBound(b)
 	if err != nil {
 		return err
 	}
 	s.bounds[b.Source] = w
+	s.lastBound[b.Worker] = b
 	return nil
 }
 

dm/master/scheduler/scheduler_test.go

@@ -944,3 +944,77 @@ func (t *testScheduler) TestWatchWorkerEventEtcdCompact(c *C) {
 	cancel3()
 	wg.Wait()
 }
+
+func (t *testScheduler) TestLastBound(c *C) {
+	defer clearTestInfoOperation(c)
+
+	var (
+		logger      = log.L()
+		s           = NewScheduler(&logger, config.Security{})
+		sourceID1   = "mysql-replica-1"
+		sourceID2   = "mysql-replica-2"
+		workerName1 = "dm-worker-1"
+		workerName2 = "dm-worker-2"
+		workerName3 = "dm-worker-3"
+		workerName4 = "dm-worker-4"
+		sourceCfg1  config.SourceConfig
+	)
+
+	c.Assert(sourceCfg1.LoadFromFile(sourceSampleFile), IsNil)
+	sourceCfg1.SourceID = sourceID1
+	sourceCfg2 := sourceCfg1
+	sourceCfg2.SourceID = sourceID2
+	worker1 := &Worker{baseInfo: ha.WorkerInfo{Name: workerName1}}
+	worker2 := &Worker{baseInfo: ha.WorkerInfo{Name: workerName2}}
+	worker3 := &Worker{baseInfo: ha.WorkerInfo{Name: workerName3}}
+	worker4 := &Worker{baseInfo: ha.WorkerInfo{Name: workerName4}}
+
+	// step 1: start an empty scheduler without listening the worker event
+	s.started = true
+	s.etcdCli = etcdTestCli
+	s.workers[workerName1] = worker1
+	s.workers[workerName2] = worker2
+	s.workers[workerName3] = worker3
+	s.workers[workerName4] = worker4
+
+	s.lastBound[workerName1] = ha.SourceBound{Source: sourceID1}
+	s.lastBound[workerName2] = ha.SourceBound{Source: sourceID2}
+	s.unbounds[sourceID1] = struct{}{}
+	s.unbounds[sourceID2] = struct{}{}
+
+	// worker1 goes to last bounded source
+	worker1.ToFree()
+	bounded, err := s.tryBoundForWorker(worker1)
+	c.Assert(err, IsNil)
+	c.Assert(bounded, IsTrue)
+	c.Assert(s.bounds[sourceID1], DeepEquals, worker1)
+
+	// worker3 has to bounded to source2
+	worker3.ToFree()
+	bounded, err = s.tryBoundForWorker(worker3)
+	c.Assert(err, IsNil)
+	c.Assert(bounded, IsTrue)
+	c.Assert(s.bounds[sourceID2], DeepEquals, worker3)
+
+	// though worker2 has a previous source, that source is not available, so not bound
+	worker2.ToFree()
+	bounded, err = s.tryBoundForWorker(worker2)
+	c.Assert(err, IsNil)
+	c.Assert(bounded, IsFalse)
+
+	// worker4 is used to test whether source2 should be bounded to worker2 rather than a new worker
+	worker4.ToFree()
+	bounded, err = s.tryBoundForWorker(worker4)
+	c.Assert(err, IsNil)
+	c.Assert(bounded, IsFalse)
+
+	// after worker3 become offline, worker2 should be bounded to worker2
+	s.updateStatusForUnbound(sourceID2)
+	_, ok := s.bounds[sourceID2]
+	c.Assert(ok, IsFalse)
+	worker3.ToOffline()
+	bounded, err = s.tryBoundForSource(sourceID2)
+	c.Assert(err, IsNil)
+	c.Assert(bounded, IsTrue)
+	c.Assert(s.bounds[sourceID2], DeepEquals, worker2)
+}

pkg/ha/bound.go

@@ -86,11 +86,11 @@ func sourceBoundFromJSON(s string) (b SourceBound, err error) {
 func PutSourceBound(cli *clientv3.Client, bounds ...SourceBound) (int64, error) {
 	ops := make([]clientv3.Op, 0, len(bounds))
 	for _, bound := range bounds {
-		op, err := putSourceBoundOp(bound)
+		boundOps, err := putSourceBoundOp(bound)
 		if err != nil {
 			return 0, err
 		}
-		ops = append(ops, op)
+		ops = append(ops, boundOps...)
 	}
 	_, rev, err := etcdutil.DoOpsInOneTxnWithRetry(cli, ops...)
 	return rev, err
@@ -137,6 +137,29 @@ func GetSourceBound(cli *clientv3.Client, worker string) (map[string]SourceBound
 	return sbm, resp.Header.Revision, nil
 }
 
+// GetLastSourceBounds gets all last source bound relationship. Different with GetSourceBound, "last source bound" will
+// not be deleted when worker offline
+func GetLastSourceBounds(cli *clientv3.Client) (map[string]SourceBound, int64, error) {
+	ctx, cancel := context.WithTimeout(cli.Ctx(), etcdutil.DefaultRequestTimeout)
+	defer cancel()
+
+	var (
+		sbm = make(map[string]SourceBound)
+	)
+	resp, err := cli.Get(ctx, common.UpstreamLastBoundWorkerKeyAdapter.Path(), clientv3.WithPrefix())
+
+	if err != nil {
+		return sbm, 0, err
+	}
+
+	sbm, err = sourceBoundFromResp("", resp)
+	if err != nil {
+		return sbm, 0, err
+	}
+
+	return sbm, resp.Header.Revision, nil
+}
+
 // GetSourceBoundConfig gets the source bound relationship and relative source config at the same time
 // for the specified DM-worker. The index worker **must not be empty**:
 // if source bound is empty, will return an empty sourceBound and an empty source config
@@ -310,14 +333,22 @@ func deleteSourceBoundOp(worker string) clientv3.Op {
 	return clientv3.OpDelete(common.UpstreamBoundWorkerKeyAdapter.Encode(worker))
 }
 
-// putSourceBoundOp returns a PUT etcd operation for the bound relationship.
+// deleteLastSourceBoundOp returns a DELETE ectd operation for the last bound relationship of the specified DM-worker.
+func deleteLastSourceBoundOp(worker string) clientv3.Op {
+	return clientv3.OpDelete(common.UpstreamLastBoundWorkerKeyAdapter.Encode(worker))
+}
+
+// putSourceBoundOp returns PUT etcd operations for the bound relationship.
 // k/v: worker-name -> bound relationship.
-func putSourceBoundOp(bound SourceBound) (clientv3.Op, error) {
+func putSourceBoundOp(bound SourceBound) ([]clientv3.Op, error) {
 	value, err := bound.toJSON()
 	if err != nil {
-		return clientv3.Op{}, err
+		return []clientv3.Op{}, err
 	}
-	key := common.UpstreamBoundWorkerKeyAdapter.Encode(bound.Worker)
+	key1 := common.UpstreamBoundWorkerKeyAdapter.Encode(bound.Worker)
+	op1 := clientv3.OpPut(key1, value)
+	key2 := common.UpstreamLastBoundWorkerKeyAdapter.Encode(bound.Worker)
+	op2 := clientv3.OpPut(key2, value)
 
-	return clientv3.OpPut(key, value), nil
+	return []clientv3.Op{op1, op2}, nil
 }

pkg/ha/ops.go

@@ -33,9 +33,9 @@ func PutRelayStageSourceBound(cli *clientv3.Client, stage Stage, bound SourceBou
 	if err != nil {
 		return 0, err
 	}
-	ops := make([]clientv3.Op, 0, 2)
+	ops := make([]clientv3.Op, 0, 3)
 	ops = append(ops, ops1...)
-	ops = append(ops, op2)
+	ops = append(ops, op2...)
 	_, rev, err := etcdutil.DoOpsInOneTxnWithRetry(cli, ops...)
 	return rev, err
 }
@@ -48,7 +48,8 @@ func DeleteSourceCfgRelayStageSourceBound(cli *clientv3.Client, source, worker s
 	sourceCfgOp := deleteSourceCfgOp(source)
 	relayStageOp := deleteRelayStageOp(source)
 	sourceBoundOp := deleteSourceBoundOp(worker)
-	_, rev, err := etcdutil.DoOpsInOneTxnWithRetry(cli, sourceCfgOp, relayStageOp, sourceBoundOp)
+	lastBoundOp := deleteLastSourceBoundOp(worker)
+	_, rev, err := etcdutil.DoOpsInOneTxnWithRetry(cli, sourceCfgOp, relayStageOp, sourceBoundOp, lastBoundOp)
 	return rev, err
 }
 

pkg/ha/source.go

@@ -102,9 +102,10 @@ func ClearTestInfoOperation(cli *clientv3.Client) error {
 	clearWorkerInfo := clientv3.OpDelete(common.WorkerRegisterKeyAdapter.Path(), clientv3.WithPrefix())
 	clearWorkerKeepAlive := clientv3.OpDelete(common.WorkerKeepAliveKeyAdapter.Path(), clientv3.WithPrefix())
 	clearBound := clientv3.OpDelete(common.UpstreamBoundWorkerKeyAdapter.Path(), clientv3.WithPrefix())
+	clearLastBound := clientv3.OpDelete(common.UpstreamLastBoundWorkerKeyAdapter.Path(), clientv3.WithPrefix())
 	clearRelayStage := clientv3.OpDelete(common.StageRelayKeyAdapter.Path(), clientv3.WithPrefix())
 	clearSubTaskStage := clientv3.OpDelete(common.StageSubTaskKeyAdapter.Path(), clientv3.WithPrefix())
 	_, _, err := etcdutil.DoOpsInOneTxnWithRetry(cli, clearSource, clearTask, clearSubTask, clearWorkerInfo, clearBound,
-		clearWorkerKeepAlive, clearRelayStage, clearSubTaskStage)
+		clearLastBound, clearWorkerKeepAlive, clearRelayStage, clearSubTaskStage)
 	return err
 }

tests/ha_cases/lib.sh

@@ -186,3 +186,40 @@ function isolate_worker() {
     run_dm_worker $WORK_DIR/worker$1 $port $cur/conf/dm-worker$1.toml
     export GO_FAILPOINTS=''
 }
+
+function check_bound() {
+    bound1=$($PWD/bin/dmctl.test DEVEL --master-addr "127.0.0.1:$MASTER_PORT1" list-member --name worker1 \
+        | grep 'source' | awk -F: '{print $2}')
+    bound2=$($PWD/bin/dmctl.test DEVEL --master-addr "127.0.0.1:$MASTER_PORT1" list-member --name worker2 \
+        | grep 'source' | awk -F: '{print $2}')
+    if [[ $worker1bound != $bound1 || $worker2bound != $bound2 ]]; then
+        echo "worker1bound $worker1bound bound1 $bound1"
+        echo "worker2bound $worker2bound bound2 $bound2"
+        exit 1
+    fi
+}
+
+function start_2_worker_ensure_bound() {
+    worker_ports_2=(0 $WORKER1_PORT $WORKER2_PORT $WORKER3_PORT $WORKER4_PORT $WORKER5_PORT)
+
+    echo "start worker$1"
+    run_dm_worker $WORK_DIR/worker$1 ${worker_ports_2[$1]} $cur/conf/dm-worker$1.toml
+    check_rpc_alive $cur/../bin/check_worker_online 127.0.0.1:${worker_ports_2[$1]}
+    echo "start worker$2"
+    run_dm_worker $WORK_DIR/worker$2 ${worker_ports_2[$2]} $cur/conf/dm-worker$2.toml
+    check_rpc_alive $cur/../bin/check_worker_online 127.0.0.1:${worker_ports_2[$2]}
+    run_dm_ctl_with_retry $WORK_DIR "127.0.0.1:$MASTER_PORT1" \
+        "list-member --name worker$1 --name worker$2" \
+        "\"source\": \"mysql-replica-01\"" 1 \
+        "\"source\": \"mysql-replica-02\"" 1
+}
+
+function kill_2_worker_ensure_unbound() {
+    echo "kill dm-worker$1"
+    ps aux | grep dm-worker$1 |awk '{print $2}'|xargs kill || true
+    echo "kill dm-worker$2"
+    ps aux | grep dm-worker$2 |awk '{print $2}'|xargs kill || true
+    run_dm_ctl_with_retry $WORK_DIR "127.0.0.1:$MASTER_PORT1" \
+        "list-member --name worker$1 --name worker$2" \
+        "\"source\": \"\"" 2
+}