rc1

recovery/advisor.go

@@ -0,0 +1,255 @@
+package recovery
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strconv"
+)
+
+var (
+	reChanges  = regexp.MustCompile(`(\d+)\.changes`)
+	reSnapshot = regexp.MustCompile(`(\d+)\.snapshot`)
+)
+
+func joinChangesFileName(dir string, logNumber int) string {
+	return filepath.Join(dir, fmt.Sprintf("%d.changes", logNumber))
+}
+
+type RecoveryRecipe struct {
+	Snapshot         string
+	Changes          []string
+	LogNumber        int
+	ToDelete         []string
+	CompleteSnapshot bool // флаг - что нужно завершить создание снапшота
+}
+
+type RecoveryAdvisor struct {
+	dir            string
+	verifySnapshot func(string) (bool, error) // (fileName) isVerified, error
+}
+
+type RecoveryAdvisorOptions struct {
+	Dir            string
+	VerifySnapshot func(string) (bool, error)
+}
+
+func NewRecoveryAdvisor(opt RecoveryAdvisorOptions) (*RecoveryAdvisor, error) {
+	if opt.Dir == "" {
+		return nil, errors.New("Dir option is required")
+	}
+	if opt.VerifySnapshot == nil {
+		return nil, errors.New("VerifySnapshot option is required")
+	}
+	return &RecoveryAdvisor{
+		dir:            opt.Dir,
+		verifySnapshot: opt.VerifySnapshot,
+	}, nil
+}
+
+type SnapshotChangesPair struct {
+	SnapshotFileName string
+	ChangesFileName  string
+	LogNumber        int
+}
+
+func (s *RecoveryAdvisor) getSnapshotChangesPairs() (*SnapshotChangesPair, *SnapshotChangesPair, error) {
+	var (
+		numSet       = make(map[int]bool)
+		changesSet   = make(map[int]bool)
+		snapshotsSet = make(map[int]bool)
+		pairs        []SnapshotChangesPair
+	)
+
+	entries, err := os.ReadDir(s.dir)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	for _, entry := range entries {
+		if entry.Type().IsRegular() {
+			baseName := entry.Name()
+			groups := reChanges.FindStringSubmatch(baseName)
+			if len(groups) == 2 {
+				num, _ := strconv.Atoi(groups[1])
+
+				numSet[num] = true
+				changesSet[num] = true
+			}
+			groups = reSnapshot.FindStringSubmatch(baseName)
+			if len(groups) == 2 {
+				num, _ := strconv.Atoi(groups[1])
+
+				numSet[num] = true
+				snapshotsSet[num] = true
+			}
+		}
+	}
+
+	for logNumber := range numSet {
+		var (
+			snapshotFileName string
+			changesFileName  string
+		)
+		if changesSet[logNumber] {
+			changesFileName = joinChangesFileName(s.dir, logNumber)
+		}
+		if snapshotsSet[logNumber] {
+			snapshotFileName = filepath.Join(s.dir, fmt.Sprintf("%d.snapshot", logNumber))
+		}
+		pairs = append(pairs, SnapshotChangesPair{
+			ChangesFileName:  changesFileName,
+			SnapshotFileName: snapshotFileName,
+			LogNumber:        logNumber,
+		})
+	}
+
+	if len(pairs) == 0 {
+		return nil, nil, nil
+	}
+
+	sort.Slice(pairs, func(i, j int) bool {
+		return pairs[i].LogNumber > pairs[j].LogNumber
+	})
+
+	pair := pairs[0]
+	if pair.ChangesFileName == "" {
+		return nil, nil, fmt.Errorf("has %d.shapshot file, but %d.changes file not found",
+			pair.LogNumber, pair.LogNumber)
+	}
+
+	if len(pairs) > 1 {
+		prevPair := pairs[1]
+		if prevPair.SnapshotFileName == "" && prevPair.LogNumber != 1 {
+			return &pair, nil, nil
+		}
+
+		if prevPair.ChangesFileName == "" && pair.SnapshotFileName == "" {
+			return &pair, nil, nil
+		}
+		return &pair, &prevPair, nil
+	} else {
+		return &pair, nil, nil
+	}
+}
+
+func (s *RecoveryAdvisor) GetRecipe() (*RecoveryRecipe, error) {
+	pair, prevPair, err := s.getSnapshotChangesPairs()
+	if err != nil {
+		return nil, err
+	}
+
+	if pair == nil {
+		return nil, nil
+	}
+
+	if pair.SnapshotFileName != "" {
+		isVerified, err := s.verifySnapshot(pair.SnapshotFileName)
+		if err != nil {
+			return nil, fmt.Errorf("verifySnapshot %s: %s",
+				pair.SnapshotFileName, err)
+		}
+
+		if isVerified {
+			recipe := &RecoveryRecipe{
+				Snapshot: pair.SnapshotFileName,
+				Changes: []string{
+					pair.ChangesFileName,
+				},
+				LogNumber: pair.LogNumber,
+			}
+
+			if prevPair != nil {
+				if prevPair.ChangesFileName != "" {
+					recipe.ToDelete = append(recipe.ToDelete, prevPair.ChangesFileName)
+				}
+				if prevPair.SnapshotFileName != "" {
+					recipe.ToDelete = append(recipe.ToDelete, prevPair.SnapshotFileName)
+				}
+			}
+			return recipe, nil
+		}
+		if prevPair != nil {
+			return s.tryPrevPair(pair, prevPair)
+		}
+		return nil, fmt.Errorf("%d.shapshot is corrupted", pair.LogNumber)
+	} else {
+		if prevPair != nil {
+			return s.tryPrevPair(pair, prevPair)
+		} else {
+			if pair.LogNumber == 1 {
+				return &RecoveryRecipe{
+					Changes: []string{
+						pair.ChangesFileName,
+					},
+					LogNumber: pair.LogNumber,
+				}, nil
+			} else {
+				return nil, fmt.Errorf("%d.snapshot not found", pair.LogNumber)
+			}
+		}
+	}
+}
+
+func (s *RecoveryAdvisor) tryPrevPair(pair, prevPair *SnapshotChangesPair) (*RecoveryRecipe, error) {
+	if prevPair.ChangesFileName == "" {
+		if pair.SnapshotFileName != "" {
+			return nil, fmt.Errorf("%d.shapshot is corrupted and %d.changes not found",
+				pair.LogNumber, prevPair.LogNumber)
+		} else {
+			return nil, fmt.Errorf("%d.changes not found", prevPair.LogNumber)
+		}
+	}
+
+	if prevPair.SnapshotFileName == "" {
+		if prevPair.LogNumber == 1 {
+			recipe := &RecoveryRecipe{
+				Changes: []string{
+					prevPair.ChangesFileName,
+					pair.ChangesFileName,
+				},
+				LogNumber:        pair.LogNumber,
+				CompleteSnapshot: true,
+				ToDelete: []string{
+					prevPair.ChangesFileName,
+				},
+			}
+			return recipe, nil
+		} else {
+			if pair.SnapshotFileName != "" {
+				return nil, fmt.Errorf("%d.shapshot is corrupted and %d.snapshot not found",
+					pair.LogNumber, prevPair.LogNumber)
+			} else {
+				return nil, fmt.Errorf("%d.snapshot not found", pair.LogNumber)
+			}
+		}
+	}
+
+	isVerified, err := s.verifySnapshot(prevPair.SnapshotFileName)
+	if err != nil {
+		return nil, fmt.Errorf("verifySnapshot %s: %s",
+			prevPair.SnapshotFileName, err)
+	}
+
+	if !isVerified {
+		return nil, fmt.Errorf("%d.shapshot is corrupted", prevPair.LogNumber)
+	}
+
+	recipe := &RecoveryRecipe{
+		Snapshot: prevPair.SnapshotFileName,
+		Changes: []string{
+			prevPair.ChangesFileName,
+			pair.ChangesFileName,
+		},
+		LogNumber:        pair.LogNumber,
+		CompleteSnapshot: true,
+		ToDelete: []string{
+			prevPair.ChangesFileName,
+			prevPair.SnapshotFileName,
+		},
+	}
+	return recipe, nil
+}