Implement DatasetMapping + basic ZFS list functionality.

zfs/zfs.go

@@ -1,13 +1,111 @@
 package zfs
 
-func InitialSend(snapshot string) (io.Read, error) {
+import (
+	"github.com/zrepl/zrepl/model"
+	"os/exec"
+	"bufio"
+	"strings"
+	"errors"
+	"io"
+	"fmt"
+	"io/ioutil"
+)
+
+func InitialSend(snapshot string) (io.Reader, error) {
+	return nil, nil
+}
+
+func IncrementalSend(from, to string) (io.Reader, error) {
+	return nil, nil
+}
+
+func FilesystemsAtRoot(root string) (fs model.Filesystem, err error) {
+
+	_, _ = zfsList("zroot", func(path DatasetPath) bool {
+		return true
+	})
+
+	return
 
 }
 
-func IncrementalSend(from, to string) (io.Read, error) {
+type DatasetPath []string
 
+func (p DatasetPath) ToString() string {
+	return strings.Join(p, "/")
 }
 
-func FilesystemsAtRoot(root string) (model.Filesystem, error) {
+func toDatasetPath(s string) DatasetPath {
+	return strings.Split(s, "/")
+}
 
-}
+type DatasetFilter func(path DatasetPath) bool
+
+type ZFSError struct {
+	Stderr  []byte
+	WaitErr error
+}
+
+func (e ZFSError) Error() string {
+	return fmt.Sprintf("zfs exited with error: %s", e.WaitErr.Error())
+}
+
+var ZFS_BINARY string = "zfs"
+
+func zfsList(root string, filter DatasetFilter) (datasets []DatasetPath, err error) {
+
+	const ZFS_LIST_FIELD_COUNT = 1
+
+	cmd := exec.Command(ZFS_BINARY, "list", "-H", "-r",
+						"-t", "filesystem,volume",
+						"-o", "name",
+						root)
+
+	var stdout io.Reader
+	var stderr io.Reader
+
+	if stdout, err = cmd.StdoutPipe(); err != nil {
+		return
+	}
+
+	if stderr, err = cmd.StderrPipe(); err != nil {
+		return
+	}
+
+	if err = cmd.Start(); err != nil {
+		return
+	}
+
+	s := bufio.NewScanner(stdout)
+	buf := make([]byte, 1024)
+	s.Buffer(buf, 0)
+
+	datasets = make([]DatasetPath, 0)
+
+	for s.Scan() {
+		fields := strings.SplitN(s.Text(), "\t", ZFS_LIST_FIELD_COUNT)
+		if len(fields) != ZFS_LIST_FIELD_COUNT {
+			err = errors.New("unexpected output")
+			return
+		}
+
+		dp := toDatasetPath(fields[0])
+
+		if filter(dp) {
+			datasets = append(datasets, dp)
+		}
+	}
+
+	stderrOutput, err := ioutil.ReadAll(stderr)
+
+	if waitErr:= cmd.Wait(); waitErr != nil {
+		err := ZFSError{
+			Stderr: stderrOutput,
+			WaitErr: waitErr,
+		}
+		return nil, err
+	}
+
+	return
+
+}