initial working command

main.go

@@ -0,0 +1,192 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"os/exec"
+	"strconv"
+	"strings"
+	"time"
+)
+
+type Snapshot struct {
+	SnapshotName string // Name sans dataset (the part after the '@')
+	Name         string // Full dataset@snapname
+	Dataset      string
+	Creation     time.Time
+	GUID         int64
+}
+
+func zfsCmd(ctx context.Context, arg string, a ...any) ([]byte, error) {
+	if len(a) > 0 {
+		arg = fmt.Sprintf(arg, a...)
+	}
+
+	cmd := exec.CommandContext(ctx, "/bin/sh", "-c", arg)
+
+	fmt.Printf("zfs: %+v\n", arg)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		return out, err
+	}
+	return out, err
+}
+
+func (j *BackupJob) listSnapshots(ctx context.Context) ([]Snapshot, error) {
+	out, err := zfsCmd(ctx, "zfs list -Hp -o name,creation -t snapshot -s creation %s | grep '%s'", j.Source, j.Prefix)
+	if err != nil {
+		execErr, ok := err.(*exec.ExitError)
+		if !ok {
+			log.Printf("%s\n", out)
+			return nil, err
+		}
+
+		if execErr.ExitCode() == 1 {
+			return nil, nil
+		}
+	}
+
+	snapList := strings.Split(string(out), "\n")
+	snaps := make([]Snapshot, len(snapList)-1)
+
+	for i, snap := range snapList {
+		params := strings.Split(snap, "\t") // "zroot@foo\tTIME" -> ["zroot@foo", "TIME"]
+		if len(params) != 2 {
+			continue
+		}
+		log.Printf("%+v\n", params)
+		t, err := strconv.ParseInt(params[1], 10, 64)
+		if err != nil {
+			log.Fatalf("invalid time %s", params[1])
+		}
+
+		identifier := strings.Split(params[0], "@") // zroot@foo -> ["zroot", "foo"]
+
+		snaps[i] = Snapshot{
+			SnapshotName: identifier[1],
+			Dataset:      identifier[0],
+			Name:         params[0],
+			Creation:     time.Unix(t, 0),
+		}
+	}
+
+	return snaps, nil
+}
+
+func (j *BackupJob) snapName() string {
+	// ts := time.Now().Format(time.RFC3339)
+	ts := time.Now().UnixMicro()
+	if j.Prefix == "" {
+		return fmt.Sprintf("%d", ts)
+	} else {
+		return fmt.Sprintf("%s%d", j.Prefix, ts)
+	}
+}
+
+func (j *BackupJob) Snapshot(ctx context.Context) (string, error) {
+	snapName := j.snapName()
+	snap := fmt.Sprintf("%s@%s", j.Source, snapName)
+
+	out, err := zfsCmd(
+		ctx,
+		"zfs snapshot %s",
+		snap,
+	)
+	if err != nil {
+		log.Printf("zfs-snapshot: error: %s", out)
+		return snapName, nil
+	}
+	return snap, err
+}
+
+func (j *BackupJob) FullSend(ctx context.Context, snap string) {
+	out, err := zfsCmd(ctx, "zfs send -Lec %s | ssh %s zfs recv -Fu %s", snap, j.TargetHost, j.Target)
+	if err != nil {
+		log.Fatalf("zfs-send: error: %s", out)
+	}
+}
+
+func (j *BackupJob) IncrementalSend(ctx context.Context, prevSnap *Snapshot, newSnap string) {
+	out, err := zfsCmd(
+		ctx,
+		"zfs send -I@%s %s | ssh %s zfs recv %s",
+		prevSnap.SnapshotName,
+		newSnap,
+		j.TargetHost,
+		j.Target,
+	)
+	if err != nil {
+		// FIXME: return an error so we can cleanup
+		log.Fatalf("zfs-send: error: %s", out)
+	}
+}
+
+type BackupJob struct {
+	Source     string // the source dataset (e.g., zroot)
+	TargetHost string // SSH-compatible host
+	Target     string // the target dataset
+	Keep       int    // number of snapshots to keep
+	Prefix     string // name each snapshot with this prefix
+	Recursive  bool   // create recursive snapshots
+}
+
+func (j *BackupJob) Do(ctx context.Context) {
+	currentSnaps, err := j.listSnapshots(ctx)
+	if err != nil {
+		log.Fatal("failed to list existing snapshots")
+	}
+	var prev *Snapshot
+
+	if len(currentSnaps) > 0 {
+		prev = &currentSnaps[len(currentSnaps)-1]
+	}
+
+	newSnapshot, err := j.Snapshot(ctx)
+	if err != nil {
+		log.Fatalf("error creating new snapshot: %s", err.Error())
+	}
+
+	if prev == nil {
+		// Full Send
+		j.FullSend(ctx, newSnapshot)
+	} else {
+		// Inc send
+		j.IncrementalSend(ctx, prev, newSnapshot)
+	}
+}
+
+type ZProperty struct {
+	Value string
+}
+
+type ZDataset struct {
+	Name         string
+	Type         string
+	SnapshotName string
+	Properties   map[string]ZProperty
+}
+
+type ZJSON struct {
+	Datasets map[string]ZDataset
+}
+
+// func (j *BackupJob) getBaseSnap() {
+// 	params := "zfs get -j -d 1 -t snapshot guid,creation %s"
+// 	srcCmd := fmt.Sprintf(params, j.Source)
+// 	dstCmd := fmt.Sprintf(params, j.Target)
+// }
+
+func main() {
+	myJob := BackupJob{
+		Source:     "zroot/home/sam/thanks",
+		Target:     "zrust/backup/weller/thanks",
+		TargetHost: "backup@woodford.gentoo.party",
+		Keep:       30,
+		Prefix:     "thanks-",
+		Recursive:  false,
+	}
+
+	ctx := context.Background()
+	myJob.Do(ctx)
+}