dns: introduce initial DNS Manager

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

go.mod

@@ -16,6 +16,7 @@ require (
 	github.com/mgechev/revive v1.3.3
 	github.com/spf13/cobra v1.7.0
 	golang.org/x/crypto v0.12.0
+	golang.org/x/net v0.14.0
 	gopkg.in/gcfg.v1 v1.2.3
 	gopkg.in/yaml.v3 v3.0.1
 )
@@ -41,7 +42,6 @@ require (
 	github.com/rs/zerolog v1.30.0 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
 	golang.org/x/mod v0.12.0 // indirect
-	golang.org/x/net v0.14.0 // indirect
 	golang.org/x/sys v0.12.0 // indirect
 	golang.org/x/text v0.13.0 // indirect
 	golang.org/x/tools v0.12.0 // indirect

pkg/dns/dns.go

@@ -1,2 +1,38 @@
 // Package dns manages DNS entries for the cluster
 package dns
+
+import (
+	"fmt"
+	"net/netip"
+)
+
+// Zone represents a set of hosts with high affinity
+type Zone struct {
+	Name string
+
+	Hosts map[int]*Host
+}
+
+func (z *Zone) String() string {
+	if z == nil {
+		return "undetermined"
+	}
+	return z.Name
+}
+
+// Host represents a member of the cluster
+type Host struct {
+	zone *Zone
+
+	ID     int
+	Active bool
+	Addrs  []netip.Addr
+}
+
+func (p *Host) String() string {
+	if p == nil {
+		return "undetermined"
+	}
+
+	return fmt.Sprintf("%s-%v", p.zone, p.ID)
+}

pkg/dns/manager.go

@@ -0,0 +1,173 @@
+package dns
+
+import (
+	"context"
+	"errors"
+	"io/fs"
+	"net/netip"
+	"strings"
+
+	"darvaza.org/core"
+	"darvaza.org/slog"
+	"git.jpi.io/amery/jpictl/pkg/cluster"
+	"golang.org/x/net/publicsuffix"
+)
+
+// Manager is a DNS Manager instance
+type Manager struct {
+	domain  string
+	suffix  string
+	zones   map[string]*Zone
+	regions map[string][]string
+
+	p Provider
+	l slog.Logger
+}
+
+// ManagerOption configures a Manager
+type ManagerOption func(*Manager) error
+
+func newErrorManagerOption(err error, hint string) ManagerOption {
+	return func(*Manager) error {
+		return core.Wrap(err, hint)
+	}
+}
+
+// WithProvider attaches a libdns Provider to the Manager
+func WithProvider(p Provider) ManagerOption {
+	var err error
+
+	if p == nil {
+		p, err = DefaultDNSProvider()
+	}
+
+	if err != nil {
+		return newErrorManagerOption(err, "WithProvider")
+	}
+
+	return func(mgr *Manager) error {
+		mgr.p = p
+		return nil
+	}
+}
+
+// WithLogger attaches a logger to the Manager
+func WithLogger(log slog.Logger) ManagerOption {
+	if log == nil {
+		log = cluster.DefaultLogger()
+	}
+
+	return func(mgr *Manager) error {
+		mgr.l = log
+		return nil
+	}
+}
+
+func (mgr *Manager) setDefaults() error {
+	var opts []ManagerOption
+
+	if mgr.l == nil {
+		opts = append(opts, WithLogger(nil))
+	}
+
+	if mgr.domain == "" || mgr.suffix == "" {
+		return errors.New("domain not specified")
+	}
+
+	for _, opt := range opts {
+		if err := opt(mgr); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// WithDomain specifies where the manager operates
+func WithDomain(domain string) ManagerOption {
+	base, err := publicsuffix.EffectiveTLDPlusOne(domain)
+	if err != nil {
+		return newErrorManagerOption(err, "publicsuffix")
+	}
+
+	suffix := strings.TrimSuffix(domain, base)
+	if suffix != "" {
+		suffix = "." + suffix[:len(suffix)-1]
+	}
+
+	return func(mgr *Manager) error {
+		mgr.domain = base
+		mgr.suffix = suffix
+		return nil
+	}
+}
+
+// NewManager creates a DNS manager with the
+func NewManager(opts ...ManagerOption) (*Manager, error) {
+	mgr := &Manager{
+		zones:   make(map[string]*Zone),
+		regions: make(map[string][]string),
+	}
+
+	for _, opt := range opts {
+		if err := opt(mgr); err != nil {
+			return nil, err
+		}
+	}
+
+	if err := mgr.setDefaults(); err != nil {
+		return nil, err
+	}
+	return mgr, nil
+}
+
+// AddHost registers a host
+func (mgr *Manager) AddHost(_ context.Context, zone string, id int,
+	active bool, addrs ...netip.Addr) error {
+	//
+	if zone == "" || id <= 0 {
+		return fs.ErrInvalid
+	}
+
+	z, ok := mgr.zones[zone]
+	if !ok {
+		z = &Zone{
+			Name:  zone,
+			Hosts: make(map[int]*Host),
+		}
+
+		mgr.zones[zone] = z
+	}
+
+	p := &Host{
+		zone:   z,
+		ID:     id,
+		Active: active,
+		Addrs:  SortAddrSlice(addrs),
+	}
+	z.Hosts[id] = p
+
+	if log, ok := mgr.l.Debug().WithEnabled(); ok {
+		log.WithField("subsystem", "dns").
+			WithField("zone", zone).
+			WithField("host", p.String()).
+			WithField("active", active).
+			Print()
+	}
+
+	return nil
+}
+
+// AddRegion specifies a new region and the zones it contains
+func (mgr *Manager) AddRegion(_ context.Context, region string, zones ...string) error {
+	mgr.regions[region] = append(mgr.regions[region], zones...)
+
+	if log, ok := mgr.l.Debug().WithEnabled(); ok {
+		for _, zoneName := range zones {
+			log.WithField("subsystem", "dns").
+				WithField("region", region).
+				WithField("zone", zoneName).Print()
+		}
+	}
+
+	return nil
+}

pkg/dns/record.go

@@ -113,3 +113,83 @@ func (rr *AddrRecord) String() string {
 	_, _ = rr.WriteTo(&buf)
 	return buf.String()
 }
+
+func (mgr *Manager) genRegionsSorted() []string {
+	regions := make([]string, 0, len(mgr.regions))
+	for name := range mgr.regions {
+		regions = append(regions, name)
+	}
+
+	return SortRegions(regions)
+}
+
+func (mgr *Manager) genAllAddrRecords() []AddrRecord {
+	var out []AddrRecord
+
+	cache := make(map[string][]netip.Addr)
+
+	// zones
+	for _, z := range mgr.zones {
+		// hosts
+		s := mgr.genZoneHostRecords(z)
+		out = append(out, s...)
+
+		// zone alias
+		addrs := mgr.genZoneAddresses(z)
+		name := z.Name
+
+		out = append(out, AddrRecord{
+			Name: name + mgr.suffix,
+			Addr: addrs,
+		})
+
+		// and cache for regions
+		cache[name] = addrs
+	}
+
+	for _, name := range mgr.genRegionsSorted() {
+		var addrs []netip.Addr
+
+		for _, z := range mgr.regions[name] {
+			addrs = append(addrs, cache[z]...)
+		}
+
+		rec := AddrRecord{
+			Name: name + mgr.suffix,
+			Addr: addrs,
+		}
+		rec.Sort()
+
+		out = append(out, rec)
+	}
+
+	return out
+}
+
+func (*Manager) genZoneAddresses(z *Zone) []netip.Addr {
+	var out []netip.Addr
+
+	for _, p := range z.Hosts {
+		if p.Active {
+			out = append(out, p.Addrs...)
+		}
+	}
+
+	SortAddrSlice(out)
+	return out
+}
+
+func (mgr *Manager) genZoneHostRecords(z *Zone) []AddrRecord {
+	out := make([]AddrRecord, 0, len(z.Hosts))
+
+	for _, p := range z.Hosts {
+		rec := AddrRecord{
+			Name: p.String() + mgr.suffix,
+			Addr: p.Addrs,
+		}
+		out = append(out, rec)
+	}
+
+	SortAddrRecords(out)
+	return out
+}