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Fix multi subscribes handling for the same single topic #10

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393464e
Fix multi subscribe handling for single topic
tymonx Apr 12, 2022
d05a48b
Add more proper msg distribution for N subscribers
Apr 13, 2022
c232938
Add channel index in logs.
Apr 13, 2022
65176fe
Merge branch 'master' into fix/multi-subscribe-one-topic
m110 Aug 26, 2025
c95139a
fmt
m110 Aug 26, 2025
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70 changes: 48 additions & 22 deletions pkg/http/subscriber.go
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Original file line number Diff line number Diff line change
Expand Up @@ -66,7 +66,7 @@ type Subscriber struct {

logger watermill.LoggerAdapter

outputChannels []chan *message.Message
outputChannels map[string][]chan *message.Message
outputChannelsLock sync.Locker

closed bool
Expand All @@ -89,7 +89,7 @@ func NewSubscriber(addr string, config SubscriberConfig, logger watermill.Logger
config: config,
server: s,
logger: logger,
outputChannels: make([]chan *message.Message, 0),
outputChannels: make(map[string][]chan *message.Message),
outputChannelsLock: &sync.Mutex{},
}, nil
}
Expand All @@ -104,7 +104,8 @@ func (s *Subscriber) Subscribe(ctx context.Context, url string) (<-chan *message
messages := make(chan *message.Message)

s.outputChannelsLock.Lock()
s.outputChannels = append(s.outputChannels, messages)
s.outputChannels[url] = append(s.outputChannels[url], messages)
channels := s.outputChannels[url]
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@m110 m110 Aug 26, 2025

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I'm not sure if it's fine to call s.config.Router.Post below for each Subscribe separately. Perhaps it should be cached in some way.

s.outputChannelsLock.Unlock()

baseLogFields := watermill.LogFields{"url": url, "provider": ProviderName}
Expand Down Expand Up @@ -133,24 +134,47 @@ func (s *Subscriber) Subscribe(ctx context.Context, url string) (<-chan *message

logFields := baseLogFields.Add(watermill.LogFields{"message_uuid": msg.UUID})

s.logger.Trace("Sending msg", logFields)
messages <- msg

s.logger.Trace("Waiting for ACK", logFields)
select {
case <-msg.Acked():
code := StatusCodeFromContext(msg.Context(), http.StatusOK)
s.logger.Trace("Message acknowledged", logFields.Add(watermill.LogFields{"err": err, "http_status_code": code}))
w.WriteHeader(code)
case <-msg.Nacked():
code := StatusCodeFromContext(msg.Context(), http.StatusInternalServerError)
s.logger.Trace("Message nacked", logFields.Add(watermill.LogFields{"err": err, "http_status_code": code}))
w.WriteHeader(code)
case <-r.Context().Done():
code := StatusCodeFromContext(msg.Context(), http.StatusInternalServerError)
s.logger.Info("Request stopped without ACK received", logFields.Add(watermill.LogFields{"http_status_code": code}))
w.WriteHeader(code)
var acked, nacked, cancelled int

for index, channel := range channels {
m := msg.Copy()

m.SetContext(ctx)

s.logger.Trace("Sending msg", logFields.Add(watermill.LogFields{"index": index}))
channel <- m
s.logger.Trace("Waiting for ACK", logFields.Add(watermill.LogFields{"index": index}))

select {
case <-m.Acked():
s.logger.Trace("Message acknowledged", logFields.Add(watermill.LogFields{"index": index}))
acked++
case <-m.Nacked():
s.logger.Trace("Message nacked", logFields.Add(watermill.LogFields{"index": index}))
nacked++
case <-r.Context().Done():
s.logger.Info("Request stopped without ACK received", logFields.Add(watermill.LogFields{"index": index}))
cancelled++
}
}

var code int

if cancelled != 0 || nacked != 0 || acked == 0 {
code = StatusCodeFromContext(msg.Context(), http.StatusInternalServerError)
} else {
code = StatusCodeFromContext(msg.Context(), http.StatusOK)
}

s.logger.Trace("Messages processed", logFields.Add(watermill.LogFields{
"total": len(channels),
"nacked": nacked,
"acked": acked,
"cancelled": cancelled,
"http_status_code": code,
}))

w.WriteHeader(code)
})

return messages, nil
Expand Down Expand Up @@ -190,8 +214,10 @@ func (s *Subscriber) Close() error {
return err
}

for _, ch := range s.outputChannels {
close(ch)
for _, channels := range s.outputChannels {
for _, ch := range channels {
close(ch)
}
}

return nil
Expand Down