zitadel/apps/api/internal/eventstore/subscription.go

package eventstore

import (
	"slices"
	"sync"

	"github.com/zitadel/logging"
)

var (
	subscriptions = map[AggregateType][]*Subscription{}
	subsMutex     sync.RWMutex
)

type Subscription struct {
	Events chan Event
	types  map[AggregateType][]EventType
}

// SubscribeAggregates subscribes for all events on the given aggregates
func SubscribeAggregates(eventQueue chan Event, aggregates ...AggregateType) *Subscription {
	types := make(map[AggregateType][]EventType, len(aggregates))
	for _, aggregate := range aggregates {
		types[aggregate] = nil
	}
	sub := &Subscription{
		Events: eventQueue,
		types:  types,
	}

	subsMutex.Lock()
	defer subsMutex.Unlock()

	for _, aggregate := range aggregates {
		subscriptions[aggregate] = append(subscriptions[aggregate], sub)
	}

	return sub
}

// SubscribeEventTypes subscribes for the given event types
// if no event types are provided the subscription is for all events of the aggregate
func SubscribeEventTypes(eventQueue chan Event, types map[AggregateType][]EventType) *Subscription {
	sub := &Subscription{
		Events: eventQueue,
		types:  types,
	}

	subsMutex.Lock()
	defer subsMutex.Unlock()

	for aggregate := range types {
		subscriptions[aggregate] = append(subscriptions[aggregate], sub)
	}

	return sub
}

func (es *Eventstore) notify(events []Event) {
	subsMutex.RLock()
	defer subsMutex.RUnlock()
	for _, event := range events {
		subs, ok := subscriptions[event.Aggregate().Type]
		if !ok {
			continue
		}
		for _, sub := range subs {
			eventTypes := sub.types[event.Aggregate().Type]
			//subscription for all events
			if len(eventTypes) == 0 {
				sub.Events <- event
				continue
			}
			//subscription for certain events
			if slices.Contains(eventTypes, event.Type()) {
				select {
				case sub.Events <- event:
				default:
					logging.Debug("unable to push event")
				}
			}
		}
	}
}

func (s *Subscription) Unsubscribe() {
	subsMutex.Lock()
	defer subsMutex.Unlock()
	for aggregate := range s.types {
		subs, ok := subscriptions[aggregate]
		if !ok {
			continue
		}
		for i := len(subs) - 1; i >= 0; i-- {
			if subs[i] == s {
				subs[i] = subs[len(subs)-1]
				subs[len(subs)-1] = nil
				subs = subs[:len(subs)-1]
			}
		}
	}
	_, ok := <-s.Events
	if ok {
		close(s.Events)
	}
}