cluster: load regions when scanning a directory

Signed-off-by: Alejandro Mery <amery@jpi.io>

cmd/jpictl/dns.go

@@ -52,7 +52,7 @@ func populateDNSManager(mgr *dns.Manager, m *cluster.Cluster) error {
 
 	m.ForEachZone(func(z *cluster.Zone) bool {
 		z.ForEachMachine(func(p *cluster.Machine) bool {
-			err = mgr.AddHost(ctx, z.Name, p.ID, true, p.PublicAddresses...)
+			err = mgr.AddHost(ctx, z.Name, p.ID, p.IsActive(), p.PublicAddresses...)
 			return err != nil
 		})
 

go.mod

@@ -17,7 +17,6 @@ require (
 	github.com/spf13/cobra v1.7.0
 	golang.org/x/crypto v0.14.0
 	golang.org/x/net v0.17.0
-	gopkg.in/gcfg.v1 v1.2.3
 	gopkg.in/yaml.v3 v3.0.1
 )
 
@@ -48,5 +47,4 @@ require (
 	golang.org/x/text v0.13.0 // indirect
 	golang.org/x/tools v0.14.0 // indirect
 	gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c // indirect
-	gopkg.in/warnings.v0 v0.1.2 // indirect
 )

go.sum

@@ -114,10 +114,6 @@ golang.org/x/tools v0.14.0/go.mod h1:uYBEerGOWcJyEORxN+Ek8+TT266gXkNlHdJBwexUsBg
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
-gopkg.in/gcfg.v1 v1.2.3 h1:m8OOJ4ccYHnx2f4gQwpno8nAX5OGOh7RLaaz0pj3Ogs=
-gopkg.in/gcfg.v1 v1.2.3/go.mod h1:yesOnuUOFQAhST5vPY4nbZsb/huCgGGXlipJsBn0b3o=
-gopkg.in/warnings.v0 v0.1.2 h1:wFXVbFY8DY5/xOe1ECiWdKCzZlxgshcYVNkBHstARME=
-gopkg.in/warnings.v0 v0.1.2/go.mod h1:jksf8JmL6Qr/oQM2OXTHunEvvTAsrWBLb6OOjuVWRNI=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

pkg/cluster/cluster_scan.go

@@ -2,17 +2,25 @@ package cluster
 
 import (
 	"io/fs"
+	"path"
 	"sort"
 
 	"darvaza.org/core"
 )
 
+const (
+	// ZoneRegionsFileName indicates the file containing
+	// region names as references
+	ZoneRegionsFileName = "regions"
+)
+
 func (m *Cluster) scan(opts *ScanOptions) error {
 	for _, fn := range []func(*ScanOptions) error{
 		m.scanDirectory,
 		m.scanMachines,
 		m.scanZoneIDs,
 		m.scanSort,
+		m.initRegions,
 		m.scanGateways,
 		m.scanCephMonitors,
 	} {
@@ -24,7 +32,7 @@ func (m *Cluster) scan(opts *ScanOptions) error {
 	return nil
 }
 
-func (m *Cluster) scanDirectory(_ *ScanOptions) error {
+func (m *Cluster) scanDirectory(opts *ScanOptions) error {
 	// each directory is a zone
 	entries, err := fs.ReadDir(m.dir, ".")
 	if err != nil {
@@ -33,16 +41,14 @@ func (m *Cluster) scanDirectory(_ *ScanOptions) error {
 
 	for _, e := range entries {
 		if e.IsDir() {
-			z, err := m.newZone(e.Name())
+			ok, err := m.scanSubdirectory(opts, e.Name())
 			switch {
 			case err != nil:
 				return core.Wrap(err, e.Name())
-			case z.Machines.Len() == 0:
-				z.warn(nil).
-					WithField("zone", z.Name).
+			case !ok:
+				m.warn(nil).
+					WithField("zone", e.Name()).
 					Print("empty")
-			default:
-				m.Zones = append(m.Zones, z)
 			}
 		}
 	}
@@ -50,6 +56,27 @@ func (m *Cluster) scanDirectory(_ *ScanOptions) error {
 	return nil
 }
 
+func (m *Cluster) scanSubdirectory(_ *ScanOptions, name string) (bool, error) {
+	z, err := m.newZone(name)
+	switch {
+	case err != nil:
+		// somewhere went wrong scanning the subdirectory
+		return false, err
+	case z.Machines.Len() > 0:
+		// zones have machines and the regions they belong
+		m.Zones = append(m.Zones, z)
+		return true, nil
+	case len(z.Regions) > 0:
+		// regions have no machines but can include
+		// other regions
+		m.appendRegionRegions(name, z.Regions...)
+		return true, nil
+	default:
+		// empty
+		return false, nil
+	}
+}
+
 func (m *Cluster) newZone(name string) (*Zone, error) {
 	z := &Zone{
 		zones:  m,
@@ -154,34 +181,68 @@ func (z *Zone) scan() error {
 	}
 
 	for _, e := range entries {
-		if e.IsDir() {
-			m := &Machine{
-				zone:   z,
-				logger: z,
-				Name:   e.Name(),
-			}
+		name := e.Name()
 
-			m.debug().
-				WithField("node", m.Name).
+		switch {
+		case name == ZoneRegionsFileName:
+			err = z.loadRegions()
+		case e.IsDir():
+			err = z.scanSubdirectory(name)
+		default:
+			z.warn(nil).
 				WithField("zone", z.Name).
-				Print("found")
+				WithField("filename", name).
+				Print("unknown")
+		}
 
-			if err := m.init(); err != nil {
-				m.error(err).
-					WithField("node", m.Name).
-					WithField("zone", z.Name).
-					Print()
-
-				return err
-			}
-
-			z.Machines = append(z.Machines, m)
+		if err != nil {
+			return err
 		}
 	}
 
 	return nil
 }
 
+func (z *Zone) loadRegions() error {
+	filename := path.Join(z.Name, ZoneRegionsFileName)
+	regions, err := z.zones.ReadLines(filename)
+
+	if err == nil {
+		// parsed
+		err = z.appendRegions(regions...)
+		if err != nil {
+			err = core.Wrap(err, filename)
+		}
+	}
+
+	return err
+}
+
+func (z *Zone) scanSubdirectory(name string) error {
+	m := &Machine{
+		zone:   z,
+		logger: z,
+		Name:   name,
+	}
+
+	m.debug().
+		WithField("node", m.Name).
+		WithField("zone", z.Name).
+		Print("found")
+
+	if err := m.init(); err != nil {
+		m.error(err).
+			WithField("node", m.Name).
+			WithField("zone", z.Name).
+			Print()
+
+		return err
+	}
+
+	z.Machines = append(z.Machines, m)
+	return nil
+}
+
 // GetGateway returns the first gateway found, if none
 // files will be created to enable the first [Machine] to
 // be one

pkg/cluster/machine.go

@@ -15,6 +15,7 @@ type Machine struct {
 	ID   int
 	Name string `json:"-" yaml:"-"`
 
+	Inactive        bool         `json:"inactive,omitempty"     yaml:"inactive,omitempty"`
 	CephMonitor     bool         `json:"ceph_monitor,omitempty" yaml:"ceph_monitor,omitempty"`
 	PublicAddresses []netip.Addr `json:"public,omitempty"       yaml:"public,omitempty"`
 	Rings           []*RingInfo  `json:"rings,omitempty"        yaml:"rings,omitempty"`
@@ -43,6 +44,11 @@ func (m *Machine) FullName() string {
 	return strings.Join(name, ".")
 }
 
+// IsActive indicates the machine is to be included in regions' DNS entries
+func (m *Machine) IsActive() bool {
+	return !m.Inactive
+}
+
 // IsGateway tells if the Machine is a ring0 gateway
 func (m *Machine) IsGateway() bool {
 	_, ok := m.getRingInfo(0)

pkg/cluster/machine_scan.go

@@ -3,6 +3,7 @@ package cluster
 import (
 	"context"
 	"net/netip"
+	"os"
 	"strconv"
 	"strings"
 	"time"
@@ -81,7 +82,30 @@ func (m *Machine) scan(_ *ScanOptions) error {
 		}
 	}
 
-	return nil
+	return m.loadInactive()
+}
+
+func (m *Machine) loadInactive() error {
+	data, err := m.ReadLines("region")
+	switch {
+	case os.IsNotExist(err):
+		// no file
+		return nil
+	case err != nil:
+		// read error
+		return err
+	default:
+		// look for "none"
+		for _, r := range data {
+			switch r {
+			case "none":
+				m.Inactive = true
+			default:
+				m.Inactive = false
+			}
+		}
+		return nil
+	}
 }
 
 // scanWrapUp is called once all machines have been scanned

pkg/cluster/regions.go

@@ -1,5 +1,10 @@
 package cluster
 
+import (
+	"bytes"
+	"path/filepath"
+)
+
 var (
 	_ MachineIterator = (*Region)(nil)
 	_ ZoneIterator    = (*Region)(nil)
@@ -32,7 +37,9 @@ func (r *Region) ForEachMachine(fn func(*Machine) bool) {
 		var term bool
 
 		z.ForEachMachine(func(p *Machine) bool {
-			term = fn(p)
+			if p.IsActive() {
+				term = fn(p)
+			}
 			return term
 		})
 
@@ -66,7 +73,7 @@ func (m *Cluster) initRegions(_ *ScanOptions) error {
 
 	// bind first level regions and their zones
 	for name, zones := range regions {
-		m.syncRegions(name, zones...)
+		m.setRegionZones(name, zones...)
 	}
 
 	// and combine zones to produce larger regions
@@ -79,8 +86,10 @@ func (m *Cluster) initRegions(_ *ScanOptions) error {
 	return nil
 }
 
-func (m *Cluster) syncRegions(name string, zones ...*Zone) {
-	for _, r := range m.Regions {
+func (m *Cluster) setRegionZones(name string, zones ...*Zone) {
+	for i := range m.Regions {
+		r := &m.Regions[i]
+
 		if r.Name == name {
 			// found
 			r.m = m
@@ -97,6 +106,38 @@ func (m *Cluster) syncRegions(name string, zones ...*Zone) {
 	})
 }
 
+func (m *Cluster) appendRegionRegions(name string, subs ...string) {
+	for i := range m.Regions {
+		r := &m.Regions[i]
+
+		if name == r.Name {
+			// found
+			r.Regions = append(r.Regions, subs...)
+			return
+		}
+	}
+
+	// new
+	m.Regions = append(m.Regions, Region{
+		Name:    name,
+		Regions: subs,
+	})
+}
+
+func (z *Zone) appendRegions(regions ...string) error {
+	for _, s := range regions {
+		// TODO: validate
+		z.debug().
+			WithField("zone", z.Name).
+			WithField("region", s).
+			Print("attached")
+
+		z.Regions = append(z.Regions, s)
+	}
+
+	return nil
+}
+
 func (m *Cluster) finishRegion(r *Region) {
 	if r.m != nil {
 		// ready
@@ -130,3 +171,61 @@ func (m *Cluster) getRegion(name string) (*Region, bool) {
 
 	return nil, false
 }
+
+// SyncRegions writes to the file system the regions this [Zone]
+// belongs to.
+func (z *Zone) SyncRegions() error {
+	err := z.syncZoneRegions()
+	if err == nil {
+		z.ForEachMachine(func(p *Machine) bool {
+			if p.IsActive() {
+				err = p.RemoveFile("region")
+			} else {
+				err = p.WriteStringFile("none\n", "region")
+			}
+			return err != nil
+		})
+	}
+
+	return err
+}
+
+func (z *Zone) syncZoneRegions() error {
+	name := filepath.Join(z.Name, "regions")
+
+	if len(z.Regions) > 0 {
+		var buf bytes.Buffer
+
+		for _, s := range z.Regions {
+			_, _ = buf.WriteString(s)
+			_, _ = buf.WriteRune('\n')
+		}
+
+		return z.zones.WriteStringFile(buf.String(), name)
+	}
+
+	return z.zones.RemoveFile(name)
+}
+
+// SyncRegions writes to the file system the regions covered
+// by this meta-region
+func (r *Region) SyncRegions() error {
+	name := filepath.Join(r.Name, "regions")
+
+	if len(r.Regions) > 0 {
+		var buf bytes.Buffer
+
+		for _, s := range r.Regions {
+			_, _ = buf.WriteString(s)
+			_, _ = buf.WriteRune('\n')
+		}
+
+		if err := r.m.MkdirAll(r.Name); err != nil {
+			return err
+		}
+
+		return r.m.WriteStringFile(buf.String(), name)
+	}
+
+	return r.m.RemoveFile(name)
+}

pkg/cluster/sync.go

@@ -6,6 +6,7 @@ func (m *Cluster) SyncAll() error {
 		m.SyncMkdirAll,
 		m.SyncAllWireguard,
 		m.SyncAllCeph,
+		m.SyncAllRegions,
 		m.WriteHosts,
 	} {
 		if err := fn(); err != nil {
@@ -58,3 +59,24 @@ func (m *Cluster) SyncAllCeph() error {
 
 	return m.WriteCephConfig(cfg)
 }
+
+// SyncAllRegions rewrites all region data
+func (m *Cluster) SyncAllRegions() error {
+	var err error
+
+	m.ForEachZone(func(z *Zone) bool {
+		err := z.SyncRegions()
+		return err != nil
+	})
+
+	if err != nil {
+		return err
+	}
+
+	m.ForEachRegion(func(r *Region) bool {
+		err = r.SyncRegions()
+		return err != nil
+	})
+
+	return err
+}

pkg/wireguard/config.go

@@ -2,7 +2,6 @@ package wireguard
 
 import (
 	"bytes"
-	"errors"
 	"fmt"
 	"io"
 	"net/netip"
@@ -10,8 +9,8 @@ import (
 	"strings"
 	"text/template"
 
+	"asciigoat.org/ini/basic"
 	"darvaza.org/core"
-	"gopkg.in/gcfg.v1"
 )
 
 var configTemplate = template.Must(template.New("config").Funcs(template.FuncMap{
@@ -107,6 +106,11 @@ func (ep EndpointAddress) String() string {
 	}
 }
 
+// UnmarshalText loads an endpoint address from text data
+func (ep *EndpointAddress) UnmarshalText(b []byte) error {
+	return ep.FromString(string(b))
+}
+
 // FromString sets the EndpointAddress from a given "[host]:port"
 func (ep *EndpointAddress) FromString(s string) error {
 	host, port, err := core.SplitHostPort(s)
@@ -127,100 +131,6 @@ func (ep *EndpointAddress) FromString(s string) error {
 	return nil
 }
 
-type intermediateConfig struct {
-	Interface interfaceConfig
-	Peer      peersConfig
-}
-
-func (v *intermediateConfig) Export() (*Config, error) {
-	var out Config
-	var err error
-
-	// Interface
-	out.Interface, err = v.Interface.Export()
-	if err != nil {
-		return nil, err
-	}
-
-	// Peers
-	peers, ok := v.PeersCount()
-	if !ok {
-		return nil, errors.New("inconsistent Peer data")
-	}
-
-	for i := 0; i < peers; i++ {
-		p, err := v.ExportPeer(i)
-		if err != nil {
-			err = core.Wrap(err, "Peer[%v]:", i)
-			return nil, err
-		}
-
-		out.Peer = append(out.Peer, p)
-	}
-
-	return &out, nil
-}
-
-type interfaceConfig struct {
-	Address    netip.Addr
-	PrivateKey string
-	ListenPort uint16
-}
-
-func (p interfaceConfig) Export() (InterfaceConfig, error) {
-	var err error
-
-	out := InterfaceConfig{
-		Address:    p.Address,
-		ListenPort: p.ListenPort,
-	}
-
-	if p.PrivateKey != "" {
-		out.PrivateKey, err = PrivateKeyFromBase64(p.PrivateKey)
-		if err != nil {
-			err = core.Wrap(err, "PrivateKey")
-			return InterfaceConfig{}, err
-		}
-	}
-
-	return out, nil
-}
-
-type peersConfig struct {
-	PublicKey  []string
-	Endpoint   []string
-	AllowedIPs []string
-}
-
-func (v *intermediateConfig) ExportPeer(i int) (PeerConfig, error) {
-	var out PeerConfig
-
-	// Endpoint
-	s := v.Peer.Endpoint[i]
-	err := out.Endpoint.FromString(s)
-	if err != nil {
-		err = core.Wrap(err, "Endpoint")
-		return out, err
-	}
-
-	// PublicKey
-	out.PublicKey, err = PublicKeyFromBase64(v.Peer.PublicKey[i])
-	if err != nil {
-		err = core.Wrap(err, "PublicKey")
-		return out, err
-	}
-
-	// AllowedIPs
-	s = v.Peer.AllowedIPs[i]
-	out.AllowedIPs, err = parseAllowedIPs(s)
-	if err != nil {
-		err = core.Wrap(err, "AllowedIPs")
-		return out, err
-	}
-
-	return out, nil
-}
-
 func parseAllowedIPs(data string) ([]netip.Prefix, error) {
 	var out []netip.Prefix
 
@@ -237,25 +147,17 @@ func parseAllowedIPs(data string) ([]netip.Prefix, error) {
 	return out, nil
 }
 
-func (v *intermediateConfig) PeersCount() (int, bool) {
-	c0 := len(v.Peer.Endpoint)
-	c1 := len(v.Peer.PublicKey)
-	c2 := len(v.Peer.AllowedIPs)
-
-	if c0 != c1 || c1 != c2 {
-		return 0, false
-	}
-
-	return c0, true
-}
-
 // NewConfigFromReader parses a wgN.conf file
 func NewConfigFromReader(r io.Reader) (*Config, error) {
-	temp := &intermediateConfig{}
-
-	if err := gcfg.ReadInto(temp, r); err != nil {
+	doc, err := basic.Decode(r)
+	if err != nil {
 		return nil, err
 	}
 
-	return temp.Export()
+	cfg, err := newConfigFromDocument(doc)
+	if err != nil {
+		return nil, err
+	}
+
+	return cfg, nil
 }

pkg/wireguard/config_parser.go

@@ -0,0 +1,169 @@
+package wireguard
+
+import (
+	"io/fs"
+	"strconv"
+
+	"asciigoat.org/ini/basic"
+	"darvaza.org/core"
+)
+
+type sectionHandler func(*Config, *basic.Section) error
+
+var sectionMap = map[string]func(*Config, *basic.Section) error{
+	"Interface": loadInterfaceConfSection,
+	"Peer":      loadPeerConfSection,
+}
+
+func loadConfSection(out *Config, src *basic.Section) error {
+	h, ok := sectionMap[src.Key]
+	if !ok {
+		return core.Wrap(fs.ErrInvalid, "unknown section %q", src.Key)
+	}
+
+	return h(out, src)
+}
+
+func loadInterfaceConfSection(out *Config, src *basic.Section) error {
+	var cfg InterfaceConfig
+
+	for _, field := range src.Fields {
+		if err := loadInterfaceConfField(&cfg, field); err != nil {
+			return core.Wrap(err, "Interface")
+		}
+	}
+
+	out.Interface = cfg
+	return nil
+}
+
+func loadPeerConfSection(out *Config, src *basic.Section) error {
+	var cfg PeerConfig
+
+	for _, field := range src.Fields {
+		if err := loadPeerConfField(&cfg, field); err != nil {
+			return core.Wrap(err, "Peer[%v]", len(out.Peer))
+		}
+	}
+
+	out.Peer = append(out.Peer, cfg)
+	return nil
+}
+
+// revive:disable:cyclomatic
+// revive:disable:cognitive-complexity
+
+func loadInterfaceConfField(cfg *InterfaceConfig, field basic.Field) error {
+	// revive:enable:cyclomatic
+	// revive:enable:cognitive-complexity
+
+	// TODO: refactor when asciigoat's ini parser learns to do reflection
+	switch field.Key {
+	case "Address":
+		if !core.IsZero(cfg.Address) {
+			return core.Wrap(fs.ErrInvalid, "duplicate field %q", field.Key)
+		}
+
+		err := cfg.Address.UnmarshalText([]byte(field.Value))
+		switch {
+		case err != nil:
+			return core.Wrap(err, field.Key)
+		default:
+			return nil
+		}
+	case "PrivateKey":
+		if !core.IsZero(cfg.PrivateKey) {
+			return core.Wrap(fs.ErrInvalid, "duplicate field %q", field.Key)
+		}
+
+		err := cfg.PrivateKey.UnmarshalText([]byte(field.Value))
+		switch {
+		case err != nil:
+			return core.Wrap(err, field.Key)
+		default:
+			return nil
+		}
+	case "ListenPort":
+		if cfg.ListenPort > 0 {
+			return core.Wrap(fs.ErrInvalid, "duplicate field %q", field.Key)
+		}
+
+		u64, err := strconv.ParseUint(field.Value, 10, 16)
+		switch {
+		case err != nil:
+			return core.Wrap(err, field.Key)
+		case u64 == 0:
+			return core.Wrap(fs.ErrInvalid, "invalid %q value", field.Key)
+		default:
+			cfg.ListenPort = uint16(u64)
+			return nil
+		}
+	default:
+		return core.Wrap(fs.ErrInvalid, "unknown field %q", field.Key)
+	}
+}
+
+// revive:disable:cyclomatic
+// revive:disable:cognitive-complexity
+
+func loadPeerConfField(cfg *PeerConfig, field basic.Field) error {
+	// revive:enable:cyclomatic
+	// revive:enable:cognitive-complexity
+
+	switch field.Key {
+	case "PublicKey":
+		if !core.IsZero(cfg.PublicKey) {
+			return core.Wrap(fs.ErrInvalid, "duplicate field %q", field.Key)
+		}
+
+		err := cfg.PublicKey.UnmarshalText([]byte(field.Value))
+		switch {
+		case err != nil:
+			return core.Wrap(err, field.Key)
+		default:
+			return nil
+		}
+	case "Endpoint":
+		if cfg.Endpoint.String() != "" {
+			return core.Wrap(fs.ErrInvalid, "duplicate field %q", field.Key)
+		}
+
+		err := cfg.Endpoint.UnmarshalText([]byte(field.Value))
+		switch {
+		case err != nil:
+			return core.Wrap(err, field.Key)
+		default:
+			return nil
+		}
+	case "AllowedIPs":
+		s, err := parseAllowedIPs(field.Value)
+		switch {
+		case err != nil:
+			return core.Wrap(err, field.Key)
+		case len(s) > 0:
+			cfg.AllowedIPs = append(cfg.AllowedIPs, s...)
+			return nil
+		}
+	default:
+		return core.Wrap(fs.ErrInvalid, "unknown field %q", field.Key)
+	}
+	return nil
+}
+
+func newConfigFromDocument(doc *basic.Document) (*Config, error) {
+	var out Config
+
+	if len(doc.Global) > 0 {
+		err := core.Wrap(fs.ErrInvalid, "fields before the first section")
+		return nil, err
+	}
+
+	for i := range doc.Sections {
+		src := &doc.Sections[i]
+		if err := loadConfSection(&out, src); err != nil {
+			return nil, err
+		}
+	}
+
+	return &out, nil
+}

pkg/wireguard/keys.go

@@ -51,6 +51,28 @@ func (pub PublicKey) String() string {
 	}
 }
 
+// UnmarshalText loads the value from base64
+func (key *PrivateKey) UnmarshalText(b []byte) error {
+	v, err := PrivateKeyFromBase64(string(b))
+	if err != nil {
+		return err
+	}
+
+	*key = v
+	return nil
+}
+
+// UnmarshalText loads the value from base64
+func (pub *PublicKey) UnmarshalText(b []byte) error {
+	v, err := PublicKeyFromBase64(string(b))
+	if err != nil {
+		return err
+	}
+
+	*pub = v
+	return nil
+}
+
 // MarshalJSON encodes the key for JSON, omitting empty.
 func (key PrivateKey) MarshalJSON() ([]byte, error) {
 	return encodeKeyJSON(key.String())