cli: add 'test placeholder' subcommand for placeholder debugging

cli/cli.go

@@ -42,6 +42,7 @@ func init() {
 type Subcommand struct {
 	Use             string
 	Short           string
+	Example 		string
 	NoRequireConfig bool
 	Run             func(subcommand *Subcommand, args []string) error
 	SetupFlags      func(f *pflag.FlagSet)
@@ -94,6 +95,7 @@ func addSubcommandToCobraCmd(c *cobra.Command, s *Subcommand) {
 	cmd := cobra.Command{
 		Use: s.Use,
 		Short: s.Short,
+		Example: s.Example,
 	}
 	if s.SetupSubcommands == nil {
 		cmd.Run = s.run

client/testcmd.go

@@ -2,6 +2,7 @@ package client
 
 import (
 	"fmt"
+	"github.com/pkg/errors"
 	"github.com/spf13/pflag"
 	"github.com/zrepl/zrepl/cli"
 	"github.com/zrepl/zrepl/config"
@@ -12,7 +13,7 @@ import (
 var TestCmd = &cli.Subcommand {
 	Use: "test",
 	SetupSubcommands: func() []*cli.Subcommand {
-		return []*cli.Subcommand{testFilter}
+		return []*cli.Subcommand{testFilter, testPlaceholder}
 	},
 }
 
@@ -106,3 +107,85 @@ func runTestFilterCmd(subcommand *cli.Subcommand, args []string) error {
 	}
 	return nil
 }
+
+var testPlaceholderArgs struct {
+	action string
+	ds     string
+	plv    string
+	all    bool
+}
+
+var testPlaceholder = &cli.Subcommand{
+	Use:   "placeholder [--all | --dataset DATASET --action [compute | check [--placeholder PROP_VALUE]]]",
+	Short: fmt.Sprintf("list received placeholder filesystems & compute the ZFS property %q", zfs.ZREPL_PLACEHOLDER_PROPERTY_NAME),
+	Example: `
+	placeholder --all
+	placeholder --dataset path/to/sink/clientident/fs --action compute
+	placeholder --dataset path/to/sink/clientident/fs --action check --placeholder 1671a61be44d32d1f3f047c5f124b06f98f54143d82900545ee529165060b859`,
+	NoRequireConfig: true,
+	SetupFlags: func(f *pflag.FlagSet) {
+		f.StringVar(&testPlaceholderArgs.action, "action", "", "check | compute")
+		f.StringVar(&testPlaceholderArgs.ds, "dataset", "", "dataset path (not required to exist)")
+		f.StringVar(&testPlaceholderArgs.plv, "placeholder", "", "existing placeholder value to check against DATASET path")
+		f.BoolVar(&testPlaceholderArgs.all, "all", false, "list tab-separated placeholder status of all filesystems")
+	},
+	Run: runTestPlaceholder,
+}
+
+func runTestPlaceholder(subcommand *cli.Subcommand, args []string) error {
+
+	// all actions first
+	if testPlaceholderArgs.all {
+		out, err := zfs.ZFSList([]string{"name", zfs.ZREPL_PLACEHOLDER_PROPERTY_NAME})
+		if err != nil {
+			return errors.Wrap(err, "could not list ZFS filesystems")
+		}
+		fmt.Printf("IS_PLACEHOLDER\tDATASET\tPROPVALUE\tCOMPUTED\n")
+		for _, row := range out {
+			dp, err := zfs.NewDatasetPath(row[0])
+			if err != nil {
+				panic(err)
+			}
+			computedProp := zfs.PlaceholderPropertyValue(dp)
+			is := "yes"
+			if computedProp != row[1] {
+				is = "no"
+			}
+			fmt.Printf("%s\t%s\t%q\t%q\n", is, dp.ToString(), row[1], computedProp)
+		}
+		return nil
+	}
+
+	// other actions
+
+	dp, err := zfs.NewDatasetPath(testPlaceholderArgs.ds)
+	if err != nil {
+		return err
+	}
+
+	computedProp := zfs.PlaceholderPropertyValue(dp)
+
+	switch testPlaceholderArgs.action {
+	case "check":
+		var isPlaceholder bool
+		if testPlaceholderArgs.plv != "" {
+			isPlaceholder = computedProp == testPlaceholderArgs.plv
+		} else {
+			isPlaceholder, err = zfs.ZFSIsPlaceholderFilesystem(dp)
+			if err != nil {
+				return err
+			}
+		}
+		if isPlaceholder {
+			fmt.Printf("%s is placeholder\n", dp.ToString())
+			return nil
+		} else {
+			return fmt.Errorf("%s is not a placeholder", dp.ToString())
+		}
+	case "compute":
+		fmt.Printf("%s\n", computedProp)
+		return nil
+	}
+
+	return fmt.Errorf("unknown --action %q", testPlaceholderArgs.action)
+}