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FIXED: MQTT retained message consumer creation #5048

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merged 3 commits into from
Feb 7, 2024
Merged

FIXED: MQTT retained message consumer creation #5048

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1ba4e9e
fix: cleanup the RMS consumer name
levb Feb 7, 2024
df61cce
change: do not use a durable consumer for RMS
levb Feb 7, 2024
ac44715
nit: Intention-revealing function names
levb Feb 7, 2024
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38 changes: 19 additions & 19 deletions server/mqtt.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1451,21 +1451,12 @@ func (s *Server) mqttCreateAccountSessionManager(acc *Account, quitCh chan struc
rmLegacyDurName := mqttRetainedMsgsStreamName + "_" + jsa.id
jsa.deleteConsumer(mqttRetainedMsgsStreamName, rmLegacyDurName)

// Using ephemeral consumer is too risky because if this server were to be
// disconnected from the rest for few seconds, then the leader would remove
// the consumer, so even after a reconnect, we would no longer receive
// retained messages.
//
// So we use a durable consumer, and create a new one each time we start.
// The old one should expire and get deleted due to inactivity. The name for
// the durable is $MQTT_rmsgs_{uuid}_{server-name}, the server name is just
// for readability.
rmDurName := mqttRetainedMsgsStreamName + "_" + nuid.Next() + "_" + s.String()

// Create a new, uniquely names consumer for retained messages for this
// server. The prior one will expire eventually.
ccfg := &CreateConsumerRequest{
Stream: mqttRetainedMsgsStreamName,
Config: ConsumerConfig{
Durable: rmDurName,
Name: mqttRetainedMsgsStreamName + "_" + nuid.Next(),
FilterSubject: mqttRetainedMsgsStreamSubject + ">",
DeliverSubject: rmsubj,
ReplayPolicy: ReplayInstant,
Expand Down Expand Up @@ -1658,12 +1649,21 @@ func (jsa *mqttJSA) createConsumer(cfg *CreateConsumerRequest) (*JSApiConsumerCr
if err != nil {
return nil, err
}
var subj string
if cfg.Config.Durable != _EMPTY_ {
subj = fmt.Sprintf(JSApiDurableCreateT, cfg.Stream, cfg.Config.Durable)
} else {
subj = fmt.Sprintf(JSApiConsumerCreateT, cfg.Stream)
subj := fmt.Sprintf(JSApiConsumerCreateT, cfg.Stream)
ccri, err := jsa.newRequest(mqttJSAConsumerCreate, subj, 0, cfgb)
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if err != nil {
return nil, err
}
ccr := ccri.(*JSApiConsumerCreateResponse)
return ccr, ccr.ToError()
}

func (jsa *mqttJSA) createDurableConsumer(cfg *CreateConsumerRequest) (*JSApiConsumerCreateResponse, error) {
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How is this materially different from createConsumer above?

cfgb, err := json.Marshal(cfg)
if err != nil {
return nil, err
}
subj := fmt.Sprintf(JSApiDurableCreateT, cfg.Stream, cfg.Config.Durable)
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Why is this durable and one above is not?

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I broke out the function into 2 to make it more explicit. Do you prefer to keep it exactly as before, 1 function triggering which API to use based on .Durable set?

ccri, err := jsa.newRequest(mqttJSAConsumerCreate, subj, 0, cfgb)
if err != nil {
return nil, err
Expand Down Expand Up @@ -4941,7 +4941,7 @@ func (sess *mqttSession) ensurePubRelConsumerSubscription(c *client) error {
if opts.MQTT.ConsumerInactiveThreshold > 0 {
ccr.Config.InactiveThreshold = opts.MQTT.ConsumerInactiveThreshold
}
if _, err := sess.jsa.createConsumer(ccr); err != nil {
if _, err := sess.jsa.createDurableConsumer(ccr); err != nil {
c.Errorf("Unable to add JetStream consumer for PUBREL for client %q: err=%v", id, err)
return err
}
Expand Down Expand Up @@ -5047,7 +5047,7 @@ func (sess *mqttSession) processJSConsumer(c *client, subject, sid string,
if opts.MQTT.ConsumerInactiveThreshold > 0 {
ccr.Config.InactiveThreshold = opts.MQTT.ConsumerInactiveThreshold
}
if _, err := sess.jsa.createConsumer(ccr); err != nil {
if _, err := sess.jsa.createDurableConsumer(ccr); err != nil {
c.Errorf("Unable to add JetStream consumer for subscription on %q: err=%v", subject, err)
return nil, nil, err
}
Expand Down