implement snapshot pruning feature

cmd/prune.go

@@ -0,0 +1,97 @@
+package main
+
+import (
+	"fmt"
+	"github.com/zrepl/zrepl/util"
+	"github.com/zrepl/zrepl/zfs"
+	"sort"
+	"time"
+)
+
+type PruneContext struct {
+	Prune  Prune
+	Now    time.Time
+	DryRun bool
+}
+
+type retentionGridAdaptor struct {
+	zfs.FilesystemVersion
+}
+
+func (a retentionGridAdaptor) Date() time.Time {
+	return a.Creation
+}
+
+func (a retentionGridAdaptor) LessThan(b util.RetentionGridEntry) bool {
+	return a.CreateTXG < b.(retentionGridAdaptor).CreateTXG
+}
+
+func doPrune(ctx PruneContext, log Logger) error {
+
+	if ctx.DryRun {
+		log.Printf("doing dry run")
+	}
+
+	prune := ctx.Prune
+
+	// ZFSListSnapsFiltered --> todo can extend fsfilter or need new? Have already something per fs
+	// Dedicated snapshot object? Adaptor object to FilesystemVersion?
+
+	filesystems, err := zfs.ZFSListMapping(prune.DatasetFilter)
+	if err != nil {
+		return fmt.Errorf("error applying filesystem filter: %s", err)
+	}
+
+	for _, fs := range filesystems {
+
+		fsversions, err := zfs.ZFSListFilesystemVersions(fs, prune.SnapshotFilter)
+		if err != nil {
+			return fmt.Errorf("error listing filesytem versions of %s: %s", fs, err)
+		}
+
+		if len(fsversions) == 0 {
+			continue
+		}
+
+		adaptors := make([]util.RetentionGridEntry, len(fsversions))
+		for fsv := range fsversions {
+			adaptors[fsv] = retentionGridAdaptor{fsversions[fsv]}
+		}
+
+		sort.SliceStable(adaptors, func(i, j int) bool {
+			return adaptors[i].LessThan(adaptors[j])
+		})
+		ctx.Now = adaptors[len(adaptors)-1].Date()
+
+		describe := func(a retentionGridAdaptor) string {
+			timeSince := a.Creation.Sub(ctx.Now)
+			const day time.Duration = 24 * time.Hour
+			days := timeSince / day
+			remainder := timeSince % day
+			return fmt.Sprintf("%s@%dd%s from now", a.ToAbsPath(fs), days, remainder)
+		}
+
+		keep, remove := prune.RetentionPolicy.FitEntries(ctx.Now, adaptors)
+		for _, a := range remove {
+			r := a.(retentionGridAdaptor)
+			log.Printf("remove %s", describe(r))
+			// do echo what we'll do and exec zfs destroy if not dry run
+			// special handling for EBUSY (zfs hold)
+			// error handling for clones? just echo to cli, skip over, and exit with non-zero status code (we're idempotent)
+			if !ctx.DryRun {
+				err := zfs.ZFSDestroy(r.ToAbsPath(fs))
+				if err != nil {
+					// handle
+					log.Printf("error: %s", err)
+				}
+			}
+		}
+		for _, a := range keep {
+			r := a.(retentionGridAdaptor)
+			log.Printf("would keep %s", describe(r))
+		}
+	}
+
+	return nil
+
+}