scheduler(ticdc): add package keyspan

Signed-off-by: Neil Shen <overvenus@gmail.com>

cdc/scheduler/internal/v3/keyspan/reconciler.go

@@ -0,0 +1,224 @@
+// Copyright 2022 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package keyspan
+
+import (
+	"bytes"
+	"context"
+
+	"github.com/pingcap/log"
+	"github.com/pingcap/tiflow/cdc/model"
+	"github.com/pingcap/tiflow/cdc/processor/tablepb"
+	"github.com/pingcap/tiflow/cdc/scheduler/internal/v3/compat"
+	"github.com/pingcap/tiflow/cdc/scheduler/internal/v3/replication"
+	"github.com/pingcap/tiflow/pkg/config"
+	"github.com/pingcap/tiflow/pkg/spanz"
+	"github.com/tikv/client-go/v2/tikv"
+	"go.uber.org/zap"
+)
+
+// Reconciler reconciles span and table mapping, make sure spans are in
+// a desired state and covers all table ranges.
+type Reconciler struct {
+	tableSpans map[model.TableID][]tablepb.Span
+	spanCache  []tablepb.Span
+
+	regionCache      RegionCache
+	changefeedID     model.ChangeFeedID
+	maxRegionPerSpan int
+}
+
+// NewReconciler returns a Reconciler.
+func NewReconciler(
+	changefeedID model.ChangeFeedID, regionCache RegionCache,
+	cfg *config.SchedulerConfig,
+) *Reconciler {
+	return &Reconciler{
+		tableSpans:       make(map[int64][]tablepb.Span),
+		regionCache:      regionCache,
+		maxRegionPerSpan: cfg.RegionPerSpan,
+	}
+}
+
+// Reconcile spans that need to be replicated based on current cluster status.
+// It handles following cases:
+// 1. Changefeed initialization
+// 2. owner switch.
+// 3. Owner switch after some captures fail.
+// 4. Add table by DDL.
+// 5. Drop table by DDL.
+// 6. Some captures fail, does NOT affect spans.
+func (m *Reconciler) Reconcile(
+	ctx context.Context,
+	checkpointTs model.Ts,
+	currentTables []model.TableID,
+	replications *spanz.Map[*replication.ReplicationSet],
+	compat *compat.Compat,
+) []tablepb.Span {
+	tablesLenEqual := len(currentTables) == len(m.tableSpans)
+	tablesAllFind := true
+	updateCache := false
+	for _, tableID := range currentTables {
+		if _, ok := m.tableSpans[tableID]; !ok {
+			// Find a new table.
+			tablesAllFind = false
+			updateCache = true
+		}
+
+		// Reconcile spans from current replications.
+		tableStart, tableEnd := spanz.TableIDToComparableRange(tableID)
+		found, holes := replications.FindHole(tableStart, tableEnd)
+		if len(found) == 0 {
+			// No such spans in replications.
+			if _, ok := m.tableSpans[tableID]; !ok {
+				// And we have not seen such spans before, maybe:
+				// 1. it's a table being added when starting a changefeed
+				//    or after owner switch.
+				// 4. it's a new table being created by DDL when a changefeed is running.
+				tableSpan := spanz.TableIDToComparableSpan(tableID)
+				if compat.CheckSpanReplicationEnabled() {
+					m.tableSpans[tableID] = m.splitSpan(ctx, tableSpan)
+				} else {
+					// Do not split table if span replication is not enabled.
+					m.tableSpans[tableID] = []tablepb.Span{tableSpan}
+				}
+				updateCache = true
+			} else {
+				// We have seen such spans before, it is impossible.
+				log.Panic("schedulerv3: impossible spans",
+					zap.Int64("tableID", tableID),
+					zap.Stringer("spanStart", &tableStart),
+					zap.Stringer("spanEnd", &tableEnd))
+			}
+		} else if len(holes) != 0 {
+			// There are some holes in the table span, maybe:
+			// 3. owner switch after some captures failed.
+			log.Info("schedulerv3: detect owner switch after captures fail",
+				zap.Int64("tableID", tableID),
+				zap.Int("holes", len(holes)),
+				zap.Stringer("spanStart", &tableStart),
+				zap.Stringer("spanEnd", &tableEnd),
+				zap.Stringer("foundStart", &found[0]),
+				zap.Stringer("foundEnd", &found[len(found)-1]))
+			for i := range holes {
+				holes[i].TableID = tableID
+				m.tableSpans[tableID] = append(found, holes[i])
+				// TODO: maybe we should split holes too.
+			}
+			updateCache = true
+		} else {
+			// Found and no hole, maybe:
+			// 2. owner switch and no capture fails.
+			m.tableSpans[tableID] = found
+		}
+	}
+
+	// 4. Drop table by DDL.
+	// For most of the time, remove tables are unlikely to happen.
+	//
+	// Fast path for check whether two sets are identical:
+	// If the length of currentTables and tableSpan are equal,
+	// and for all tables in currentTables have a record in tableSpan.
+	if !tablesLenEqual || !tablesAllFind {
+		// The two sets are not identical. We need to find removed tables.
+		intersectionTable := make(map[model.TableID]struct{}, len(currentTables))
+		for _, tableID := range currentTables {
+			_, ok := m.tableSpans[tableID]
+			if !ok {
+				continue
+			}
+			intersectionTable[tableID] = struct{}{}
+		}
+		for tableID := range m.tableSpans {
+			_, ok := intersectionTable[tableID]
+			if !ok {
+				// Found dropped table.
+				delete(m.tableSpans, tableID)
+				updateCache = true
+			}
+		}
+	}
+
+	if updateCache {
+		m.spanCache = make([]tablepb.Span, 0)
+		for _, spans := range m.tableSpans {
+			m.spanCache = append(m.spanCache, spans...)
+		}
+	}
+	return m.spanCache
+}
+
+func (m *Reconciler) splitSpan(ctx context.Context, span tablepb.Span) []tablepb.Span {
+	bo := tikv.NewBackoffer(ctx, 500)
+	regions, err := m.regionCache.ListRegionIDsInKeyRange(bo, span.StartKey, span.EndKey)
+	if err != nil {
+		log.Warn("schedulerv3: list regions failed, skip split span",
+			zap.String("namespace", m.changefeedID.Namespace),
+			zap.String("changefeed", m.changefeedID.ID),
+			zap.Error(err))
+		return []tablepb.Span{span}
+	}
+	if len(regions) <= m.maxRegionPerSpan {
+		return []tablepb.Span{span}
+	}
+
+	spans := make([]tablepb.Span, 0, len(regions)/m.maxRegionPerSpan+1)
+	start, end := 0, m.maxRegionPerSpan
+	for {
+		startRegion, err := m.regionCache.LocateRegionByID(bo, regions[start])
+		if err != nil {
+			log.Warn("schedulerv3: get regions failed, skip split span",
+				zap.String("namespace", m.changefeedID.Namespace),
+				zap.String("changefeed", m.changefeedID.ID),
+				zap.Error(err))
+			return []tablepb.Span{span}
+		}
+		endRegion, err := m.regionCache.LocateRegionByID(bo, regions[end-1])
+		if err != nil {
+			log.Warn("schedulerv3: get regions failed, skip split span",
+				zap.String("namespace", m.changefeedID.Namespace),
+				zap.String("changefeed", m.changefeedID.ID),
+				zap.Error(err))
+			return []tablepb.Span{span}
+		}
+		if len(spans) > 0 &&
+			bytes.Compare(spans[len(spans)-1].EndKey, startRegion.StartKey) > 0 {
+			log.Warn("schedulerv3: list region out of order detected",
+				zap.String("namespace", m.changefeedID.Namespace),
+				zap.String("changefeed", m.changefeedID.ID),
+				zap.Stringer("lastSpan", &spans[len(spans)-1]),
+				zap.Stringer("region", startRegion))
+			return []tablepb.Span{span}
+		}
+		spans = append(spans, tablepb.Span{
+			TableID:  span.TableID,
+			StartKey: startRegion.StartKey,
+			EndKey:   endRegion.EndKey,
+		})
+
+		if end == len(regions) {
+			break
+		}
+		start = end
+		if end+m.maxRegionPerSpan < len(regions) {
+			end = end + m.maxRegionPerSpan
+		} else {
+			end = len(regions)
+		}
+	}
+	// Make sure spans does not exceed [startKey, endKey).
+	spans[0].StartKey = span.StartKey
+	spans[len(spans)-1].EndKey = span.EndKey
+	return spans
+}