micro/registry/mdns_registry.go

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// Package mdns is a multicast dns registry
package registry
import (
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"context"
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"fmt"
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"net"
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"strconv"
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"strings"
"sync"
"time"
"github.com/google/uuid"
"github.com/micro/go-micro/v2/logger"
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"github.com/micro/mdns"
)
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var (
// use a .micro domain rather than .local
mdnsDomain = "micro"
)
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type mdnsTxt struct {
Service string
Version string
Endpoints []*Endpoint
Metadata map[string]string
}
type mdnsEntry struct {
id string
node *mdns.Server
}
type mdnsRegistry struct {
opts Options
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// the mdns domain
domain string
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sync.Mutex
services map[string][]*mdnsEntry
mtx sync.RWMutex
// watchers
watchers map[string]*mdnsWatcher
// listener
listener chan *mdns.ServiceEntry
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}
func newRegistry(opts ...Option) Registry {
options := Options{
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Context: context.Background(),
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Timeout: time.Millisecond * 100,
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}
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for _, o := range opts {
o(&options)
}
// set the domain
domain := mdnsDomain
d, ok := options.Context.Value("mdns.domain").(string)
if ok {
domain = d
}
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return &mdnsRegistry{
opts: options,
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domain: domain,
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services: make(map[string][]*mdnsEntry),
watchers: make(map[string]*mdnsWatcher),
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}
}
func (m *mdnsRegistry) Init(opts ...Option) error {
for _, o := range opts {
o(&m.opts)
}
return nil
}
func (m *mdnsRegistry) Options() Options {
return m.opts
}
func (m *mdnsRegistry) Register(service *Service, opts ...RegisterOption) error {
m.Lock()
defer m.Unlock()
entries, ok := m.services[service.Name]
// first entry, create wildcard used for list queries
if !ok {
s, err := mdns.NewMDNSService(
service.Name,
"_services",
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m.domain+".",
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"",
9999,
[]net.IP{net.ParseIP("0.0.0.0")},
nil,
)
if err != nil {
return err
}
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srv, err := mdns.NewServer(&mdns.Config{Zone: &mdns.DNSSDService{MDNSService: s}})
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if err != nil {
return err
}
// append the wildcard entry
entries = append(entries, &mdnsEntry{id: "*", node: srv})
}
var gerr error
for _, node := range service.Nodes {
var seen bool
var e *mdnsEntry
for _, entry := range entries {
if node.Id == entry.id {
seen = true
e = entry
break
}
}
// already registered, continue
if seen {
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continue
// doesn't exist
} else {
e = &mdnsEntry{}
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}
txt, err := encode(&mdnsTxt{
Service: service.Name,
Version: service.Version,
Endpoints: service.Endpoints,
Metadata: node.Metadata,
})
if err != nil {
gerr = err
continue
}
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host, pt, err := net.SplitHostPort(node.Address)
if err != nil {
gerr = err
continue
}
port, _ := strconv.Atoi(pt)
if logger.V(logger.DebugLevel, logger.DefaultLogger) {
logger.Debugf("[mdns] registry create new service with ip: %s for: %s", net.ParseIP(host).String(), host)
}
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// we got here, new node
s, err := mdns.NewMDNSService(
node.Id,
service.Name,
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m.domain+".",
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"",
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port,
[]net.IP{net.ParseIP(host)},
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txt,
)
if err != nil {
gerr = err
continue
}
srv, err := mdns.NewServer(&mdns.Config{Zone: s})
if err != nil {
gerr = err
continue
}
e.id = node.Id
e.node = srv
entries = append(entries, e)
}
// save
m.services[service.Name] = entries
return gerr
}
func (m *mdnsRegistry) Deregister(service *Service) error {
m.Lock()
defer m.Unlock()
var newEntries []*mdnsEntry
// loop existing entries, check if any match, shutdown those that do
for _, entry := range m.services[service.Name] {
var remove bool
for _, node := range service.Nodes {
if node.Id == entry.id {
entry.node.Shutdown()
remove = true
break
}
}
// keep it?
if !remove {
newEntries = append(newEntries, entry)
}
}
// last entry is the wildcard for list queries. Remove it.
if len(newEntries) == 1 && newEntries[0].id == "*" {
newEntries[0].node.Shutdown()
delete(m.services, service.Name)
} else {
m.services[service.Name] = newEntries
}
return nil
}
func (m *mdnsRegistry) GetService(service string) ([]*Service, error) {
serviceMap := make(map[string]*Service)
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entries := make(chan *mdns.ServiceEntry, 10)
done := make(chan bool)
p := mdns.DefaultParams(service)
// set context with timeout
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var cancel context.CancelFunc
p.Context, cancel = context.WithTimeout(context.Background(), m.opts.Timeout)
defer cancel()
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// set entries channel
p.Entries = entries
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// set the domain
p.Domain = m.domain
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go func() {
for {
select {
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case e := <-entries:
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// list record so skip
if p.Service == "_services" {
continue
}
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if p.Domain != m.domain {
continue
}
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if e.TTL == 0 {
continue
}
txt, err := decode(e.InfoFields)
if err != nil {
continue
}
if txt.Service != service {
continue
}
s, ok := serviceMap[txt.Version]
if !ok {
s = &Service{
Name: txt.Service,
Version: txt.Version,
Endpoints: txt.Endpoints,
}
}
addr := ""
// prefer ipv4 addrs
if e.AddrV4 != nil {
addr = e.AddrV4.String()
// else use ipv6
} else if e.AddrV6 != nil {
addr = "[" + e.AddrV6.String() + "]"
} else {
if logger.V(logger.InfoLevel, logger.DefaultLogger) {
logger.Infof("[mdns]: invalid endpoint received: %v", e)
}
continue
}
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s.Nodes = append(s.Nodes, &Node{
Id: strings.TrimSuffix(e.Name, "."+p.Service+"."+p.Domain+"."),
Address: fmt.Sprintf("%s:%d", addr, e.Port),
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Metadata: txt.Metadata,
})
serviceMap[txt.Version] = s
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case <-p.Context.Done():
close(done)
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return
}
}
}()
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// execute the query
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if err := mdns.Query(p); err != nil {
return nil, err
}
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// wait for completion
<-done
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// create list and return
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services := make([]*Service, 0, len(serviceMap))
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for _, service := range serviceMap {
services = append(services, service)
}
return services, nil
}
func (m *mdnsRegistry) ListServices() ([]*Service, error) {
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serviceMap := make(map[string]bool)
entries := make(chan *mdns.ServiceEntry, 10)
done := make(chan bool)
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p := mdns.DefaultParams("_services")
// set context with timeout
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var cancel context.CancelFunc
p.Context, cancel = context.WithTimeout(context.Background(), m.opts.Timeout)
defer cancel()
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// set entries channel
p.Entries = entries
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// set domain
p.Domain = m.domain
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var services []*Service
go func() {
for {
select {
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case e := <-entries:
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if e.TTL == 0 {
continue
}
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if !strings.HasSuffix(e.Name, p.Domain+".") {
continue
}
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name := strings.TrimSuffix(e.Name, "."+p.Service+"."+p.Domain+".")
if !serviceMap[name] {
serviceMap[name] = true
services = append(services, &Service{Name: name})
}
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case <-p.Context.Done():
close(done)
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return
}
}
}()
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// execute query
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if err := mdns.Query(p); err != nil {
return nil, err
}
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// wait till done
<-done
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return services, nil
}
func (m *mdnsRegistry) Watch(opts ...WatchOption) (Watcher, error) {
var wo WatchOptions
for _, o := range opts {
o(&wo)
}
md := &mdnsWatcher{
id: uuid.New().String(),
wo: wo,
ch: make(chan *mdns.ServiceEntry, 32),
exit: make(chan struct{}),
domain: m.domain,
registry: m,
}
m.mtx.Lock()
defer m.mtx.Unlock()
// save the watcher
m.watchers[md.id] = md
// check of the listener exists
if m.listener != nil {
return md, nil
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}
// start the listener
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go func() {
// go to infinity
for {
m.mtx.Lock()
// just return if there are no watchers
if len(m.watchers) == 0 {
m.listener = nil
m.mtx.Unlock()
return
}
// check existing listener
if m.listener != nil {
m.mtx.Unlock()
return
}
// reset the listener
exit := make(chan struct{})
ch := make(chan *mdns.ServiceEntry, 32)
m.listener = ch
m.mtx.Unlock()
// send messages to the watchers
go func() {
send := func(w *mdnsWatcher, e *mdns.ServiceEntry) {
select {
case w.ch <- e:
default:
}
}
for {
select {
case <-exit:
return
case e, ok := <-ch:
if !ok {
return
}
m.mtx.RLock()
// send service entry to all watchers
for _, w := range m.watchers {
send(w, e)
}
m.mtx.RUnlock()
}
}
}()
// start listening, blocking call
mdns.Listen(ch, exit)
// mdns.Listen has unblocked
// kill the saved listener
m.mtx.Lock()
m.listener = nil
close(ch)
m.mtx.Unlock()
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}
}()
return md, nil
}
func (m *mdnsRegistry) String() string {
return "mdns"
}
// NewRegistry returns a new default registry which is mdns
func NewRegistry(opts ...Option) Registry {
return newRegistry(opts...)
}