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gcp_pubsub.go
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gcp_pubsub.go
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package adapter
import (
"cloud.google.com/go/pubsub"
"context"
"encoding/json"
cmap "github.com/orcaman/concurrent-map"
"github.com/rs/xid"
"github.com/stanlry/gopolling"
"sync"
)
func NewGCPPubSubAdapter(client *pubsub.Client) *GCPPubSub {
p := &GCPPubSub{
client: client,
log: &gopolling.NoOpLog{},
subscribers: cmap.New(),
listenMap: make(map[string]context.CancelFunc),
}
p.start()
return p
}
type GCPPubSub struct {
client *pubsub.Client
log gopolling.Log
subscribers cmap.ConcurrentMap
listenMap map[string]context.CancelFunc
m sync.RWMutex
}
func (g *GCPPubSub) start() {
ctx, cf := context.WithCancel(context.Background())
ctx2, cf2 := context.WithCancel(context.Background())
g.m.Lock()
g.listenMap[pubSubName] = cf
g.listenMap[queueName] = cf2
g.m.Unlock()
go g.listenToSubscription(ctx, pubSubName, false, g.handleMessage)
go g.listenToSubscription(ctx2, queueName, true, g.handleEvent)
}
func (g *GCPPubSub) Shutdown() {
g.m.RLock()
// invoke two cancel functions
cf := g.listenMap[pubSubName]
cf()
cf = g.listenMap[queueName]
cf()
g.m.RUnlock()
}
func (g *GCPPubSub) getTopic(name string) (*pubsub.Topic, error) {
ctx := context.Background()
topic := g.client.Topic(name)
exist, err := topic.Exists(ctx)
if err != nil {
return nil, err
}
if !exist {
topic, err = g.client.CreateTopic(ctx, name)
if err != nil {
return nil, err
}
}
return topic, nil
}
func (g *GCPPubSub) Publish(_ string, msg gopolling.Message) error {
topic, err := g.getTopic(pubSubName)
if err != nil {
return err
}
defer topic.Stop()
data, _ := json.Marshal(msg)
ctx := context.Background()
r := topic.Publish(ctx, &pubsub.Message{
Data: data,
})
_, err = r.Get(ctx)
return err
}
func (g *GCPPubSub) handleMessage(ctx context.Context, m *pubsub.Message) {
var msg gopolling.Message
if err := json.Unmarshal(m.Data, &msg); err != nil {
g.log.Errorf("fail to unmarshal message, error: %v", err)
return
}
if val, ok := g.subscribers.Get(msg.Channel); ok {
subMap := val.(*cmap.ConcurrentMap)
subMap.IterCb(func(_ string, v interface{}) {
ch := v.(chan gopolling.Message)
ch <- msg
})
}
m.Ack()
}
func (g *GCPPubSub) handleEvent(ctx context.Context, m *pubsub.Message) {
var ev gopolling.Event
if err := json.Unmarshal(m.Data, &ev); err != nil {
g.log.Errorf("fail to unmarshal message, error: %v", err)
return
}
if val, ok := g.subscribers.Get(ev.Channel); ok {
ch := val.(chan gopolling.Event)
ch <- ev
}
m.Ack()
}
type pubsubHandler func(context.Context, *pubsub.Message)
func (g *GCPPubSub) listenToSubscription(ctx context.Context, topicName string, exact bool, handler pubsubHandler) {
subID := subPrefix + topicName
if !exact {
subID = subPrefix + xid.New().String()
}
sub := g.client.Subscription(subID)
exist, err := sub.Exists(ctx)
if err != nil {
g.log.Errorf("fail to check subscription existence, error: %v", err)
return
}
if !exist {
topic, err := g.getTopic(topicName)
if err != nil {
g.log.Errorf("fail to get topic, error: %v", err)
return
}
sub, err = g.client.CreateSubscription(ctx, subID, pubsub.SubscriptionConfig{Topic: topic})
if err != nil {
g.log.Errorf("fail to create subscription, error: %v", err)
return
}
if !exact {
defer func() {
if err := sub.Delete(ctx); err != nil {
g.log.Errorf("fail to delete subscription, error: %v", err)
}
}()
}
}
for {
err := sub.Receive(ctx, handler)
if err == context.Canceled {
break
}
if err != nil {
g.log.Errorf("error receiving from subscription %v, error :%v", subID, err)
break
}
}
}
func (g *GCPPubSub) Subscribe(channel string) (gopolling.Subscription, error) {
id := xid.New().String()
ch := make(chan gopolling.Message)
if val, ok := g.subscribers.Get(channel); ok {
subMap := val.(*cmap.ConcurrentMap)
subMap.Set(id, ch)
} else {
ss := cmap.New()
ss.Set(id, ch)
g.subscribers.Set(channel, &ss)
}
return gopolling.NewDefaultSubscription(channel, id, ch), nil
}
func (g *GCPPubSub) Unsubscribe(sub gopolling.Subscription) error {
rsub := sub.(*gopolling.DefaultSubscription)
if val, ok := g.subscribers.Get(rsub.Channel); ok {
subMap := val.(*cmap.ConcurrentMap)
subMap.Remove(rsub.ID)
}
return nil
}
func (g *GCPPubSub) Enqueue(_ string, event gopolling.Event) {
topic, err := g.getTopic(queueName)
if err != nil {
g.log.Errorf("fail to get topic, error: %v", err)
return
}
defer topic.Stop()
data, _ := json.Marshal(event)
ctx := context.Background()
r := topic.Publish(ctx, &pubsub.Message{
Data: data,
})
if _, err = r.Get(ctx); err != nil {
g.log.Errorf("fail deliver enqueue message, error: %v", err)
}
}
func (g *GCPPubSub) Dequeue(channel string) <-chan gopolling.Event {
ch := make(chan gopolling.Event)
g.subscribers.Set(channel, ch)
return ch
}
func (g *GCPPubSub) SetLog(log gopolling.Log) {
g.log = log
}