Add nats broker as a default

broker/nats/nats.go

@@ -0,0 +1,245 @@
+// Package nats provides a NATS broker
+package nats
+
+import (
+	"context"
+	"errors"
+	"strings"
+	"sync"
+
+	"github.com/micro/go-micro/broker"
+	"github.com/micro/go-micro/codec/json"
+	nats "github.com/nats-io/nats.go"
+)
+
+type natsBroker struct {
+	sync.RWMutex
+	addrs []string
+	conn  *nats.Conn
+	opts  broker.Options
+	nopts nats.Options
+	drain bool
+}
+
+type subscriber struct {
+	s     *nats.Subscription
+	opts  broker.SubscribeOptions
+	drain bool
+}
+
+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 {
+	if s.drain {
+		return s.s.Drain()
+	}
+	return s.s.Unsubscribe()
+}
+
+func (n *natsBroker) Address() string {
+	if n.conn != nil && n.conn.IsConnected() {
+		return n.conn.ConnectedUrl()
+	}
+	if len(n.addrs) > 0 {
+		return n.addrs[0]
+	}
+
+	return ""
+}
+
+func setAddrs(addrs []string) []string {
+	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 len(cAddrs) == 0 {
+		cAddrs = []string{nats.DefaultURL}
+	}
+	return cAddrs
+}
+
+func (n *natsBroker) Connect() error {
+	n.Lock()
+	defer n.Unlock()
+
+	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()
+	if n.drain {
+		n.conn.Drain()
+	} else {
+		n.conn.Close()
+	}
+	n.RUnlock()
+	return nil
+}
+
+func (n *natsBroker) Init(opts ...broker.Option) error {
+	for _, o := range opts {
+		o(&n.opts)
+	}
+	n.addrs = setAddrs(n.opts.Addrs)
+	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)
+	}
+
+	var drain bool
+	if _, ok := opt.Context.Value(drainSubscriptionKey{}).(bool); ok {
+		drain = true
+	}
+
+	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, drain: drain}, nil
+}
+
+func (n *natsBroker) String() string {
+	return "nats"
+}
+
+func NewBroker(opts ...broker.Option) broker.Broker {
+	options := broker.Options{
+		// Default codec
+		Codec:   json.Marshaler{},
+		Context: context.Background(),
+	}
+
+	for _, o := range opts {
+		o(&options)
+	}
+
+	natsOpts := nats.GetDefaultOptions()
+	if n, ok := options.Context.Value(optionsKey{}).(nats.Options); ok {
+		natsOpts = n
+	}
+
+	var drain bool
+	if _, ok := options.Context.Value(drainSubscriptionKey{}).(bool); ok {
+		drain = true
+	}
+
+	// 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(options.Addrs) == 0 {
+		options.Addrs = natsOpts.Servers
+	}
+
+	if !options.Secure {
+		options.Secure = natsOpts.Secure
+	}
+
+	if options.TLSConfig == nil {
+		options.TLSConfig = natsOpts.TLSConfig
+	}
+
+	return &natsBroker{
+		opts:  options,
+		nopts: natsOpts,
+		addrs: setAddrs(options.Addrs),
+		drain: drain,
+	}
+}