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pubsub.go
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pubsub.go
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package run
import (
"container/list"
"context"
"errors"
"reflect"
"sync"
)
type PublisherFanOut[W AbstractEnvelopeWriter, P AbstractPublisher[W]] struct {
Publishers []P
}
func (p PublisherFanOut[W, P]) Send(ctx context.Context, envelopes ...W) error {
// TODO: use FanOut everywhere here
if len(p.Publishers) == 1 {
return p.Publishers[0].Send(ctx, envelopes...)
}
pool := NewErrorPool()
for i := 0; i < len(p.Publishers); i++ {
i := i
pool.Go(func() error {
return p.Publishers[i].Send(ctx, envelopes...)
})
}
return pool.Wait()
}
func (p PublisherFanOut[W, P]) Close() (err error) {
for _, pub := range p.Publishers {
err = errors.Join(pub.Close())
}
return
}
type SubscriberFanIn[R AbstractEnvelopeReader, S AbstractSubscriber[R]] struct {
Subscribers []S
}
func (s SubscriberFanIn[R, S]) Receive(ctx context.Context, cb func(envelope R)) error {
if len(s.Subscribers) == 1 {
return s.Subscribers[0].Receive(ctx, cb)
}
poolCtx, cancel := context.WithCancel(ctx)
defer cancel()
pool := NewErrorPool()
for i := 0; i < len(s.Subscribers); i++ {
i := i
pool.Go(func() error {
return s.Subscribers[i].Receive(poolCtx, cb)
})
}
return pool.Wait()
}
func (s SubscriberFanIn[R, S]) Close() (err error) {
for _, sub := range s.Subscribers {
err = errors.Join(sub.Close())
}
return
}
func GatherPublishers[W AbstractEnvelopeWriter, PUB AbstractPublisher[W], B any, PRD AbstractProducer[B, W, PUB]](
ctx context.Context,
chName ParamString,
channelBindings *B,
producers []PRD,
) ([]PUB, error) {
pubsCh := make(chan PUB, len(producers))
pool := NewErrorPool()
for _, prod := range producers {
prod := prod
pool.Go(func() error {
p, e := prod.Publisher(ctx, chName.String(), channelBindings)
pubsCh <- p
return e
})
}
err := pool.Wait()
close(pubsCh)
pubs := make([]PUB, 0, len(producers))
var zero PUB
for pub := range pubsCh {
pubs = append(pubs, pub)
if err != nil && !reflect.DeepEqual(pub, zero) {
err = errors.Join(err, pub.Close()) // Close subscribers on error to avoid resource leak
}
}
return pubs, err
}
func GatherSubscribers[R AbstractEnvelopeReader, SUB AbstractSubscriber[R], B any, C AbstractConsumer[B, R, SUB]](
ctx context.Context,
chName ParamString,
channelBindings *B,
consumers []C,
) ([]SUB, error) {
subsCh := make(chan SUB, len(consumers))
pool := NewErrorPool()
for _, cons := range consumers {
cons := cons
pool.Go(func() error {
s, e := cons.Subscriber(ctx, chName.String(), channelBindings)
subsCh <- s
return e
})
}
err := pool.Wait()
close(subsCh)
subs := make([]SUB, 0, len(consumers))
var zero SUB
for sub := range subsCh {
subs = append(subs, sub)
if err != nil && !reflect.DeepEqual(sub, zero) {
err = errors.Join(err, sub.Close()) // Close subscribers on error to avoid resource leak
}
}
return subs, err
}
func NewFanOut[MessageT any]() *FanOut[MessageT] {
mu := &sync.RWMutex{}
return &FanOut[MessageT]{
receivers: list.New(),
mu: mu,
cnd: sync.NewCond(mu),
}
}
type FanOut[MessageT any] struct {
receivers *list.List
mu *sync.RWMutex
cnd *sync.Cond
}
func (cm *FanOut[MessageT]) Add(cb func(msg MessageT)) *list.Element {
cm.cnd.L.Lock()
defer cm.cnd.L.Unlock()
res := cm.receivers.PushBack(cb)
cm.cnd.Broadcast()
return res
}
func (cm *FanOut[MessageT]) Remove(el *list.Element) {
cm.cnd.L.Lock()
defer cm.cnd.L.Unlock()
cm.cnd.Broadcast()
cm.receivers.Remove(el)
}
func (cm *FanOut[MessageT]) Put(newItem func() MessageT) {
cm.cnd.L.Lock()
defer cm.cnd.L.Unlock()
for cm.receivers.Len() == 0 {
cm.cnd.Wait()
}
for item := cm.receivers.Front(); item != nil; item = item.Next() {
item.Value.(func(msg MessageT))(newItem())
}
}