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pubsub_localbus_adapter.go
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pubsub_localbus_adapter.go
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package pubsub
import (
"cloud.google.com/go/pubsub"
"context"
"fmt"
"github.com/AltScore/gothic/pkg/eventbus"
"github.com/AltScore/gothic/pkg/logger"
"github.com/AltScore/gothic/pkg/xerrors"
"github.com/google/uuid"
"github.com/modernice/goes/codec"
"github.com/modernice/goes/event"
"go.uber.org/zap"
"strconv"
"time"
)
type PullAdapterConfig struct {
ProjectID string
SubscriptionName string
Debug bool
}
// PullAdapter pulls events from a PubSub topic and publishes them to a local event bus
type PullAdapter struct {
client *pubsub.Client
logger logger.Logger
config PullAdapterConfig
publisher eventbus.Publisher
encoding codec.Encoding
sub *pubsub.Subscription
ctx context.Context
cancel context.CancelFunc
}
// NewPullAdapter creates a new PullAdapter that pulls events from a PubSub topic and publishes them to another publisher
//
// The provided enconder should have all the event types registered before processing events.
//
// To authenticate with PubSub, the GOOGLE_APPLICATION_CREDENTIALS environment variable must be set
// See https://cloud.google.com/docs/authentication/getting-started for more information
func NewPullAdapter(client *pubsub.Client, publisher eventbus.Publisher, encoder codec.Encoding, log logger.Logger, config PullAdapterConfig) *PullAdapter {
xerrors.EnsureNotEmpty(client, "client")
xerrors.EnsureNotEmpty(encoder, "encoder")
xerrors.EnsureNotEmpty(encoder, "encoder")
log.Info("Connected to PubSub", zap.String("project_id", config.ProjectID), zap.String("subscription", config.SubscriptionName))
sub := client.Subscription(config.SubscriptionName)
pa := &PullAdapter{
client: client,
logger: log,
config: config,
publisher: publisher,
encoding: encoder,
sub: sub,
}
if lp, ok := publisher.(eventbus.LifeCycleProvider); ok {
lp.AddLifecycleListener(lifeCycleListener{pa})
}
return pa
}
// Start starts the adapter
func (a *PullAdapter) start(ctx context.Context) error {
a.ctx, a.cancel = context.WithCancel(ctx)
go func() {
err := a.sub.Receive(a.ctx, func(ctx context.Context, m *pubsub.Message) {
if err := a.publish(ctx, m); err != nil {
m.Nack()
} else {
m.Ack() // Acknowledge that we've consumed the message.
}
})
if err != nil {
a.logger.Error("Failed to receive from PubSub", zap.Error(err))
}
}()
return nil
}
func (a *PullAdapter) stop() {
if a.cancel != nil {
a.logger.Info("Stopping PubSub adapter, canceling context")
a.cancel()
a.cancel = nil
a.ctx = nil
}
}
func (a *PullAdapter) publish(ctx context.Context, m *pubsub.Message) error {
ev, err := a.unmarshalEvent(m)
if err != nil {
return err
}
aggID, _, _ := ev.Aggregate()
a.logger.Info("Received event from PubSub", zap.String("event", ev.Name()), zap.Any("id", ev.ID()), zap.Any("agg_id", aggID))
errCh := make(chan error)
err = a.publisher.Publish(ev, eventbus.WithAckChan(errCh), eventbus.WithContext(ctx))
if err != nil {
return err
}
return <-errCh // Wait for the response to be received
}
func (a *PullAdapter) unmarshalEvent(msg *pubsub.Message) (event.Event, error) {
evIDStr := msg.Attributes[EventIDMessageAttributeKey]
evID, err := uuid.Parse(evIDStr)
if err != nil {
return nil, fmt.Errorf("failed to parse event ID '%s': %w", evIDStr, err)
}
evName := msg.Attributes[EventNameMessageAttributeKey]
aggIDStr := msg.Attributes[AggregateIDMessageAttributeKey]
aggID, err := uuid.Parse(aggIDStr)
if err != nil {
return nil, fmt.Errorf("failed to parse aggregate ID '%s': %w", aggIDStr, err)
}
aggName := msg.Attributes[AggregateNameMessageAttributeKey]
aggVersionStr := msg.Attributes[AggregateVersionMessageAttributeKey]
aggVersion, err := strconv.Atoi(aggVersionStr)
if err != nil {
return nil, fmt.Errorf("failed to parse aggregate version '%s': %w", aggVersionStr, err)
}
evTime, err := time.Parse(EventTimeFormat, msg.Attributes[EventTimeMessageAttributeKey])
if err != nil {
return nil, fmt.Errorf("failed to parse event time '%s': %w", msg.Attributes[EventTimeMessageAttributeKey], err)
}
eventName := msg.Attributes[EventNameMessageAttributeKey]
data, err := a.encoding.Unmarshal(msg.Data, evName)
if err != nil {
if a.config.Debug {
a.logger.Error("Failed to unmarshal event data", zap.Error(err), zap.String("event", eventName), zap.String("data", string(msg.Data)))
}
return nil, fmt.Errorf("failed to unmarshal event data: %w", err)
}
ev := event.New(
eventName,
data,
event.Aggregate(aggID, aggName, aggVersion),
event.ID(evID),
event.Time(evTime),
)
return &ev, nil
}
type lifeCycleListener struct {
adapter *PullAdapter
}
func (l lifeCycleListener) OnStart(ctx context.Context) {
err := l.adapter.start(ctx)
if err != nil {
l.adapter.logger.Error("Failed to start PubSub adapter", zap.Error(err))
panic(err)
}
}
func (l lifeCycleListener) OnStop() {
l.adapter.stop()
}