micro/broker/nats/nats.go

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// Package nats provides a NATS broker
package nats
import (
"context"
"errors"
"net"
"net/url"
"strconv"
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"strings"
"sync"
"time"
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"github.com/micro/go-micro/broker"
"github.com/micro/go-micro/codec/json"
"github.com/micro/go-micro/registry"
"github.com/micro/go-micro/util/addr"
"github.com/micro/go-micro/util/log"
"github.com/nats-io/nats-server/v2/server"
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nats "github.com/nats-io/nats.go"
)
type natsBroker struct {
sync.Once
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sync.RWMutex
// indicate if we're connected
connected bool
addrs []string
conn *nats.Conn
opts broker.Options
nopts nats.Options
// should we drain the connection
drain bool
closeCh chan (error)
// embedded server
server *server.Server
// configure to use local server
local bool
// server exit channel
exit chan bool
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}
type subscriber struct {
s *nats.Subscription
opts broker.SubscribeOptions
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}
type publication struct {
t string
m *broker.Message
}
func (p *publication) Topic() string {
return p.t
}
func (p *publication) Message() *broker.Message {
return p.m
}
func (p *publication) Ack() error {
// nats does not support acking
return nil
}
func (s *subscriber) Options() broker.SubscribeOptions {
return s.opts
}
func (s *subscriber) Topic() string {
return s.s.Subject
}
func (s *subscriber) Unsubscribe() error {
return s.s.Unsubscribe()
}
func (n *natsBroker) Address() string {
if n.conn != nil && n.conn.IsConnected() {
return n.conn.ConnectedUrl()
}
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if len(n.addrs) > 0 {
return n.addrs[0]
}
return ""
}
func (n *natsBroker) setAddrs(addrs []string) []string {
//nolint:prealloc
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var cAddrs []string
for _, addr := range addrs {
if len(addr) == 0 {
continue
}
if !strings.HasPrefix(addr, "nats://") {
addr = "nats://" + addr
}
cAddrs = append(cAddrs, addr)
}
// if there's no address and we weren't told to
// embed a local server then use the default url
if len(cAddrs) == 0 && !n.local {
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cAddrs = []string{nats.DefaultURL}
}
return cAddrs
}
// serve stats a local nats server if needed
func (n *natsBroker) serve(exit chan bool) error {
var host string
var port int
var local bool
// with no address we just default it
// this is a local client address
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if len(n.addrs) == 0 {
// find an advertiseable ip
if h, err := addr.Extract(""); err != nil {
host = "127.0.0.1"
} else {
host = h
}
port = -1
local = true
} else {
address := n.addrs[0]
if strings.HasPrefix(address, "nats://") {
address = strings.TrimPrefix(address, "nats://")
}
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// check if its a local address and only then embed
if addr.IsLocal(address) {
h, p, err := net.SplitHostPort(address)
if err == nil {
host = h
port, _ = strconv.Atoi(p)
local = true
}
}
}
// we only setup a server for local things
if !local {
return nil
}
// 1. create new server
// 2. register the server
// 3. connect to other servers
var cOpts server.ClusterOpts
var routes []*url.URL
// get existing nats servers to connect to
services, err := n.opts.Registry.GetService("go.micro.nats.broker")
if err == nil {
for _, service := range services {
for _, node := range service.Nodes {
u, err := url.Parse("nats://" + node.Address)
if err != nil {
log.Log(err)
continue
}
// append to the cluster routes
routes = append(routes, u)
}
}
}
// try get existing server
s := n.server
// get a host address
caddr, err := addr.Extract("")
if err != nil {
caddr = "0.0.0.0"
}
// set cluster opts
cOpts = server.ClusterOpts{
Host: caddr,
Port: -1,
}
if s == nil {
var err error
s, err = server.NewServer(&server.Options{
// Specify the host
Host: host,
// Use a random port
Port: port,
// Set the cluster ops
Cluster: cOpts,
// Set the routes
Routes: routes,
NoLog: true,
NoSigs: true,
MaxControlLine: 2048,
TLSConfig: n.opts.TLSConfig,
})
if err != nil {
return err
}
// save the server
n.server = s
}
// start the server
go s.Start()
var ready bool
// wait till its ready for connections
for i := 0; i < 3; i++ {
if s.ReadyForConnections(time.Second) {
ready = true
break
}
}
if !ready {
return errors.New("server not ready")
}
// set the client address
n.addrs = []string{s.ClientURL()}
go func() {
// register the cluster address
for {
select {
case <-exit:
// deregister on exit
n.opts.Registry.Deregister(&registry.Service{
Name: "go.micro.nats.broker",
Version: "v2",
Nodes: []*registry.Node{
{Id: s.ID(), Address: s.ClusterAddr().String()},
},
})
s.Shutdown()
return
default:
// register the broker
n.opts.Registry.Register(&registry.Service{
Name: "go.micro.nats.broker",
Version: "v2",
Nodes: []*registry.Node{
{Id: s.ID(), Address: s.ClusterAddr().String()},
},
}, registry.RegisterTTL(time.Minute))
time.Sleep(time.Minute)
}
}
}()
return nil
}
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func (n *natsBroker) Connect() error {
n.Lock()
defer n.Unlock()
if !n.connected {
// create exit chan
n.exit = make(chan bool)
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// start embedded server if asked to
if n.local {
if err := n.serve(n.exit); err != nil {
return err
}
}
// set to connected
n.connected = true
}
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status := nats.CLOSED
if n.conn != nil {
status = n.conn.Status()
}
switch status {
case nats.CONNECTED, nats.RECONNECTING, nats.CONNECTING:
return nil
default: // DISCONNECTED or CLOSED or DRAINING
opts := n.nopts
opts.Servers = n.addrs
opts.Secure = n.opts.Secure
opts.TLSConfig = n.opts.TLSConfig
// secure might not be set
if n.opts.TLSConfig != nil {
opts.Secure = true
}
c, err := opts.Connect()
if err != nil {
return err
}
n.conn = c
return nil
}
}
func (n *natsBroker) Disconnect() error {
n.RLock()
defer n.RUnlock()
// drain the connection if specified
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if n.drain {
n.conn.Drain()
return <-n.closeCh
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}
// close the client connection
n.conn.Close()
// shutdown the local server
// and deregister
if n.server != nil {
select {
case <-n.exit:
default:
close(n.exit)
}
}
// set not connected
n.connected = false
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return nil
}
func (n *natsBroker) Init(opts ...broker.Option) error {
n.setOption(opts...)
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return nil
}
func (n *natsBroker) Options() broker.Options {
return n.opts
}
func (n *natsBroker) Publish(topic string, msg *broker.Message, opts ...broker.PublishOption) error {
b, err := n.opts.Codec.Marshal(msg)
if err != nil {
return err
}
n.RLock()
defer n.RUnlock()
return n.conn.Publish(topic, b)
}
func (n *natsBroker) Subscribe(topic string, handler broker.Handler, opts ...broker.SubscribeOption) (broker.Subscriber, error) {
if n.conn == nil {
return nil, errors.New("not connected")
}
opt := broker.SubscribeOptions{
AutoAck: true,
Context: context.Background(),
}
for _, o := range opts {
o(&opt)
}
fn := func(msg *nats.Msg) {
var m broker.Message
if err := n.opts.Codec.Unmarshal(msg.Data, &m); err != nil {
return
}
handler(&publication{m: &m, t: msg.Subject})
}
var sub *nats.Subscription
var err error
n.RLock()
if len(opt.Queue) > 0 {
sub, err = n.conn.QueueSubscribe(topic, opt.Queue, fn)
} else {
sub, err = n.conn.Subscribe(topic, fn)
}
n.RUnlock()
if err != nil {
return nil, err
}
return &subscriber{s: sub, opts: opt}, nil
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}
func (n *natsBroker) String() string {
return "nats"
}
func (n *natsBroker) setOption(opts ...broker.Option) {
for _, o := range opts {
o(&n.opts)
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}
n.Once.Do(func() {
n.nopts = nats.GetDefaultOptions()
})
if nopts, ok := n.opts.Context.Value(optionsKey{}).(nats.Options); ok {
n.nopts = nopts
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}
local, ok := n.opts.Context.Value(localServerKey{}).(bool)
if ok {
n.local = local
}
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// broker.Options have higher priority than nats.Options
// only if Addrs, Secure or TLSConfig were not set through a broker.Option
// we read them from nats.Option
if len(n.opts.Addrs) == 0 && !n.local {
n.opts.Addrs = n.nopts.Servers
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}
if !n.opts.Secure {
n.opts.Secure = n.nopts.Secure
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}
if n.opts.TLSConfig == nil {
n.opts.TLSConfig = n.nopts.TLSConfig
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}
n.addrs = n.setAddrs(n.opts.Addrs)
if n.opts.Context.Value(drainConnectionKey{}) != nil {
n.drain = true
n.closeCh = make(chan error)
n.nopts.ClosedCB = n.onClose
n.nopts.AsyncErrorCB = n.onAsyncError
}
}
func (n *natsBroker) onClose(conn *nats.Conn) {
n.closeCh <- nil
}
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func (n *natsBroker) onAsyncError(conn *nats.Conn, sub *nats.Subscription, err error) {
// There are kinds of different async error nats might callback, but we are interested
// in ErrDrainTimeout only here.
if err == nats.ErrDrainTimeout {
n.closeCh <- err
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}
}
func NewBroker(opts ...broker.Option) broker.Broker {
options := broker.Options{
// Default codec
Codec: json.Marshaler{},
Context: context.Background(),
Registry: registry.DefaultRegistry,
}
n := &natsBroker{
opts: options,
}
n.setOption(opts...)
return n
}