forked from st3v/go-plugins
/
gocloud.go
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/
gocloud.go
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// Package gocloud provides a pubsub broker for Go Cloud.
// Go Cloud offers cloud-agnostic interface for a variety of common cloud APIs.
// See https://github.com/google/go-cloud.
package gocloud
import (
"context"
"errors"
"log"
"sync"
"time"
"github.com/micro/go-micro/broker"
"github.com/micro/go-micro/cmd"
"github.com/streadway/amqp"
"gocloud.dev/gcp"
"gocloud.dev/pubsub"
"gocloud.dev/pubsub/gcppubsub"
"gocloud.dev/pubsub/mempubsub"
"gocloud.dev/pubsub/rabbitpubsub"
)
func init() {
cmd.DefaultBrokers["gocloud"] = NewBroker
}
type (
topicOpener func(string) *pubsub.Topic
subOpener func(*pubsub.Topic, string) *pubsub.Subscription
)
type pubsubBroker struct {
options broker.Options
openTopic topicOpener
openSub subOpener
err error
mu sync.Mutex
topics map[string]*pubsub.Topic
subs map[string]*pubsub.Subscription
}
// NewBroker creates a new gocloud pubsubBroker.
// If the GCPProjectID option is set, Go Cloud uses its Google Cloud PubSub implementation.
// If the RabbitURL option is set, Go Cloud uses its RabbitMQ implementation.
// Otherwise, Go Cloud uses its in-memory implementation.
func NewBroker(opts ...broker.Option) broker.Broker {
options := broker.Options{
Context: context.Background(),
}
for _, o := range opts {
o(&options)
}
var openTopic topicOpener
var openSub subOpener
var err error
if projID, ok := options.Context.Value(gcpProjectIDKey{}).(gcp.ProjectID); ok {
ts := options.Context.Value(gcpTokenSourceKey{}).(gcp.TokenSource)
openTopic, openSub, err = setupGCP(options.Context, projID, ts)
} else if rurl, ok := options.Context.Value(rabbitURLKey{}).(string); ok {
openTopic, openSub, err = setupRabbit(options.Context, rurl)
} else {
openTopic, openSub, err = setupMem()
}
if err != nil {
return &pubsubBroker{err: err}
}
return &pubsubBroker{
options: options,
openTopic: openTopic,
openSub: openSub,
topics: map[string]*pubsub.Topic{},
subs: map[string]*pubsub.Subscription{},
}
}
func setupGCP(ctx context.Context, projectID gcp.ProjectID, ts gcp.TokenSource) (topicOpener, subOpener, error) {
conn, _, err := gcppubsub.Dial(ctx, ts) // ignore closer; no way to close
if err != nil {
return nil, nil, err
}
pc, err := gcppubsub.PublisherClient(ctx, conn)
if err != nil {
return nil, nil, err
}
sc, err := gcppubsub.SubscriberClient(ctx, conn)
if err != nil {
return nil, nil, err
}
return func(name string) *pubsub.Topic {
return gcppubsub.OpenTopic(ctx, pc, projectID, name, nil)
},
func(t *pubsub.Topic, name string) *pubsub.Subscription {
return gcppubsub.OpenSubscription(ctx, sc, projectID, name, nil)
},
nil
}
func setupRabbit(ctx context.Context, url string) (topicOpener, subOpener, error) {
conn, err := amqp.Dial(url)
if err != nil {
return nil, nil, err
}
return func(name string) *pubsub.Topic { return rabbitpubsub.OpenTopic(conn, name) },
func(_ *pubsub.Topic, name string) *pubsub.Subscription {
return rabbitpubsub.OpenSubscription(conn, name)
},
nil
}
func setupMem() (topicOpener, subOpener, error) {
return func(string) *pubsub.Topic { return mempubsub.NewTopic() },
func(t *pubsub.Topic, _ string) *pubsub.Subscription {
return mempubsub.NewSubscription(t, 10*time.Second)
},
nil
}
func (b *pubsubBroker) String() string { return "gocloud" }
func (b *pubsubBroker) Address() string { return "" }
func (b *pubsubBroker) Connect() error { return nil }
func (b *pubsubBroker) Disconnect() error { return nil }
func (b *pubsubBroker) Options() broker.Options { return b.options }
func (b *pubsubBroker) Init(opts ...broker.Option) error {
return errors.New("unimplemented; pass options to NewBroker instead")
}
// Publish opens the topic if it hasn't been already, then publishes the message.
func (b *pubsubBroker) Publish(topic string, msg *broker.Message, opts ...broker.PublishOption) error {
if b.err != nil {
return b.err
}
t := b.topic(topic)
return t.Send(context.Background(), &pubsub.Message{Metadata: msg.Header, Body: msg.Body})
}
// Subscribe opens a subscription to the given topic and begins receiving messages and passing
// them to handler in a separate goroutine.
//
// The Queue SubscribeOption is required. Subscribe never creates new subscriptions on the backend (except
// for mempubsub, but you still need a queue name).
func (b *pubsubBroker) Subscribe(topic string, h broker.Handler, opts ...broker.SubscribeOption) (broker.Subscriber, error) {
if b.err != nil {
return nil, b.err
}
options := broker.SubscribeOptions{
AutoAck: false,
Context: b.options.Context,
}
for _, o := range opts {
o(&options)
}
if options.Queue == "" {
return nil, errors.New("gocloud.Subscribe: need Queue option")
}
t := b.topic(topic)
b.mu.Lock()
defer b.mu.Unlock()
s := b.subs[options.Queue]
if s == nil {
// TODO(jba): how to configure ack deadline?
s = b.openSub(t, options.Queue)
b.subs[options.Queue] = s
}
// TODO(jba): how can we verify that an existing subscription's topic matches?
ctx, cancel := context.WithCancel(context.Background())
sub := &subscriber{
options: options,
topic: topic,
sub: s,
cancel: cancel,
}
go sub.run(ctx, h)
return sub, nil
}
// topic returns the topic with the given name if this broker has
// seen it before. Otherwise it opens a new topic.
func (b *pubsubBroker) topic(name string) *pubsub.Topic {
b.mu.Lock()
defer b.mu.Unlock()
t := b.topics[name]
if t == nil {
t = b.openTopic(name)
b.topics[name] = t
}
return t
}
// A pubsub subscriber that manages handling of messages.
type subscriber struct {
options broker.SubscribeOptions
topic string
sub *pubsub.Subscription
cancel func()
}
func (s *subscriber) Options() broker.SubscribeOptions { return s.options }
func (s *subscriber) Topic() string { return s.topic }
func (s *subscriber) Unsubscribe() error {
s.cancel()
return s.sub.Shutdown(context.Background())
}
func (s *subscriber) run(ctx context.Context, h broker.Handler) {
for {
m, err := s.sub.Receive(ctx)
if err != nil {
log.Printf("Receive returned %v; stopping", err)
break
}
p := &publication{
msg: &broker.Message{
Header: m.Metadata,
Body: m.Body,
},
topic: s.topic,
ack: m.Ack,
}
if err := h(p); err != nil {
log.Printf("handler returned %v; continuing", err)
continue
}
if s.options.AutoAck {
p.Ack()
}
}
}
// A single publication received by a handler.
type publication struct {
msg *broker.Message
topic string
ack func()
}
func (p *publication) Topic() string { return p.topic }
func (p *publication) Message() *broker.Message { return p.msg }
func (p *publication) Ack() error { p.ack(); return nil }