Adding upstream version 2.5.1.

Signed-off-by: Daniel Baumann <daniel@debian.org>

index/scorch/rollback.go

@@ -0,0 +1,216 @@
+//  Copyright (c) 2017 Couchbase, 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,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package scorch
+
+import (
+	"fmt"
+	"log"
+	"os"
+
+	bolt "go.etcd.io/bbolt"
+)
+
+type RollbackPoint struct {
+	epoch uint64
+	meta  map[string][]byte
+}
+
+func (r *RollbackPoint) GetInternal(key []byte) []byte {
+	return r.meta[string(key)]
+}
+
+// RollbackPoints returns an array of rollback points available for
+// the application to rollback to, with more recent rollback points
+// (higher epochs) coming first.
+func RollbackPoints(path string) ([]*RollbackPoint, error) {
+	if len(path) == 0 {
+		return nil, fmt.Errorf("RollbackPoints: invalid path")
+	}
+
+	rootBoltPath := path + string(os.PathSeparator) + "root.bolt"
+	rootBoltOpt := &bolt.Options{
+		ReadOnly: true,
+	}
+	rootBolt, err := bolt.Open(rootBoltPath, 0600, rootBoltOpt)
+	if err != nil || rootBolt == nil {
+		return nil, err
+	}
+
+	// start a read-only bolt transaction
+	tx, err := rootBolt.Begin(false)
+	if err != nil {
+		return nil, fmt.Errorf("RollbackPoints: failed to start" +
+			" read-only transaction")
+	}
+
+	// read-only bolt transactions to be rolled back
+	defer func() {
+		_ = tx.Rollback()
+		_ = rootBolt.Close()
+	}()
+
+	snapshots := tx.Bucket(boltSnapshotsBucket)
+	if snapshots == nil {
+		return nil, nil
+	}
+
+	rollbackPoints := []*RollbackPoint{}
+
+	c1 := snapshots.Cursor()
+	for k, _ := c1.Last(); k != nil; k, _ = c1.Prev() {
+		_, snapshotEpoch, err := decodeUvarintAscending(k)
+		if err != nil {
+			log.Printf("RollbackPoints:"+
+				" unable to parse segment epoch %x, continuing", k)
+			continue
+		}
+
+		snapshot := snapshots.Bucket(k)
+		if snapshot == nil {
+			log.Printf("RollbackPoints:"+
+				" snapshot key, but bucket missing %x, continuing", k)
+			continue
+		}
+
+		meta := map[string][]byte{}
+		c2 := snapshot.Cursor()
+		for j, _ := c2.First(); j != nil; j, _ = c2.Next() {
+			if j[0] == boltInternalKey[0] {
+				internalBucket := snapshot.Bucket(j)
+				if internalBucket == nil {
+					err = fmt.Errorf("internal bucket missing")
+					break
+				}
+				err = internalBucket.ForEach(func(key []byte, val []byte) error {
+					copiedVal := append([]byte(nil), val...)
+					meta[string(key)] = copiedVal
+					return nil
+				})
+				if err != nil {
+					break
+				}
+			}
+		}
+
+		if err != nil {
+			log.Printf("RollbackPoints:"+
+				" failed in fetching internal data: %v", err)
+			continue
+		}
+
+		rollbackPoints = append(rollbackPoints, &RollbackPoint{
+			epoch: snapshotEpoch,
+			meta:  meta,
+		})
+	}
+
+	return rollbackPoints, nil
+}
+
+// Rollback atomically and durably brings the store back to the point
+// in time as represented by the RollbackPoint.
+// Rollback() should only be passed a RollbackPoint that came from the
+// same store using the RollbackPoints() API along with the index path.
+func Rollback(path string, to *RollbackPoint) error {
+	if to == nil {
+		return fmt.Errorf("Rollback: RollbackPoint is nil")
+	}
+	if len(path) == 0 {
+		return fmt.Errorf("Rollback: index path is empty")
+	}
+
+	rootBoltPath := path + string(os.PathSeparator) + "root.bolt"
+	rootBoltOpt := &bolt.Options{
+		ReadOnly: false,
+	}
+	rootBolt, err := bolt.Open(rootBoltPath, 0600, rootBoltOpt)
+	if err != nil || rootBolt == nil {
+		return err
+	}
+	defer func() {
+		err1 := rootBolt.Close()
+		if err1 != nil && err == nil {
+			err = err1
+		}
+	}()
+
+	// pick all the younger persisted epochs in bolt store
+	// including the target one.
+	var found bool
+	var eligibleEpochs []uint64
+	err = rootBolt.View(func(tx *bolt.Tx) error {
+		snapshots := tx.Bucket(boltSnapshotsBucket)
+		if snapshots == nil {
+			return nil
+		}
+		sc := snapshots.Cursor()
+		for sk, _ := sc.Last(); sk != nil && !found; sk, _ = sc.Prev() {
+			_, snapshotEpoch, err := decodeUvarintAscending(sk)
+			if err != nil {
+				continue
+			}
+			if snapshotEpoch == to.epoch {
+				found = true
+			}
+			eligibleEpochs = append(eligibleEpochs, snapshotEpoch)
+		}
+		return nil
+	})
+
+	if len(eligibleEpochs) == 0 {
+		return fmt.Errorf("Rollback: no persisted epochs found in bolt")
+	}
+	if !found {
+		return fmt.Errorf("Rollback: target epoch %d not found in bolt", to.epoch)
+	}
+
+	// start a write transaction
+	tx, err := rootBolt.Begin(true)
+	if err != nil {
+		return err
+	}
+
+	defer func() {
+		if err == nil {
+			err = tx.Commit()
+		} else {
+			_ = tx.Rollback()
+		}
+		if err == nil {
+			err = rootBolt.Sync()
+		}
+	}()
+
+	snapshots := tx.Bucket(boltSnapshotsBucket)
+	if snapshots == nil {
+		return nil
+	}
+	for _, epoch := range eligibleEpochs {
+		k := encodeUvarintAscending(nil, epoch)
+		if err != nil {
+			continue
+		}
+		if epoch == to.epoch {
+			// return here as it already processed until the given epoch
+			return nil
+		}
+		err = snapshots.DeleteBucket(k)
+		if err == bolt.ErrBucketNotFound {
+			err = nil
+		}
+	}
+
+	return err
+}