pruning: implement 'grid' keep rule

pruning/keep_grid.go

@@ -0,0 +1,102 @@
+package pruning
+
+import (
+	"fmt"
+	"github.com/pkg/errors"
+	"github.com/zrepl/zrepl/config"
+	"github.com/zrepl/zrepl/pruning/retentiongrid"
+	"regexp"
+	"sort"
+	"time"
+)
+
+// KeepGrid fits snapshots that match a given regex into a retentiongrid.Grid,
+// uses the most recent snapshot among those that match the regex as 'now',
+// and deletes all snapshots that do not fit the grid specification.
+type KeepGrid struct {
+	retentionGrid *retentiongrid.Grid
+	re *regexp.Regexp
+}
+
+func NewKeepGrid(in *config.PruneGrid) (p *KeepGrid, err error) {
+
+	if in.Regex == "" {
+		return nil, fmt.Errorf("Regex must not be empty")
+	}
+	re, err := regexp.Compile(in.Regex)
+	if err != nil {
+		return nil, errors.Wrap(err, "Regex is invalid")
+	}
+
+	// Assert intervals are of increasing length (not necessarily required, but indicates config mistake)
+	lastDuration := time.Duration(0)
+	for i := range in.Grid {
+
+		if in.Grid[i].Length() < lastDuration {
+			// If all intervals before were keep=all, this is ok
+			allPrevKeepCountAll := true
+			for j := i - 1; allPrevKeepCountAll && j >= 0; j-- {
+				allPrevKeepCountAll = in.Grid[j].KeepCount() == config.RetentionGridKeepCountAll
+			}
+			if allPrevKeepCountAll {
+				goto isMonotonicIncrease
+			}
+			err = errors.New("retention grid interval length must be monotonically increasing")
+			return
+		}
+	isMonotonicIncrease:
+		lastDuration = in.Grid[i].Length()
+
+	}
+
+	retentionIntervals := make([]retentiongrid.Interval, len(in.Grid))
+	for i := range in.Grid {
+		retentionIntervals[i] = &in.Grid[i]
+	}
+
+	return &KeepGrid{
+		retentiongrid.NewGrid(retentionIntervals),
+		re,
+	}, nil
+}
+
+type retentionGridAdaptor struct {
+	Snapshot
+}
+
+func (a retentionGridAdaptor) LessThan(b retentiongrid.Entry) bool {
+	return a.Date().Before(b.Date())
+}
+
+// Prune filters snapshots with the retention grid.
+func (p *KeepGrid) KeepRule(snaps []Snapshot) (destroyList []Snapshot) {
+
+	snaps = filterSnapList(snaps, func(snapshot Snapshot) bool {
+		return p.re.MatchString(snapshot.Name())
+	})
+	if len(snaps) == 0 {
+		return nil
+	}
+
+	// Build adaptors for retention grid
+	adaptors := make([]retentiongrid.Entry, 0)
+	for i := range snaps {
+		adaptors = append(adaptors, retentionGridAdaptor{snaps[i]})
+	}
+
+	// determine 'now' edge
+	sort.SliceStable(adaptors, func(i, j int) bool {
+		return adaptors[i].LessThan(adaptors[j])
+	})
+	now := adaptors[len(adaptors)-1].Date()
+
+	// Evaluate retention grid
+	_, removea := p.retentionGrid.FitEntries(now, adaptors)
+
+	// Revert adaptors
+	destroyList = make([]Snapshot, len(removea))
+	for i := range removea {
+		destroyList[i] = removea[i].(retentionGridAdaptor).Snapshot
+	}
+	return destroyList
+}