eolivelli commented on code in PR #16603:
URL: https://github.com/apache/pulsar/pull/16603#discussion_r921893502
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pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentDispatcherMultipleConsumers.java:
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@@ -520,10 +521,19 @@ public synchronized void readEntriesComplete(List<Entry>
entries, Object ctx) {
log.debug("[{}] Distributing {} messages to {} consumers", name,
entries.size(), consumerList.size());
}
- sendMessagesToConsumers(readType, entries);
+ if (serviceConfig.isDispatcherDispatchMessagesInSubscriptionThread()) {
+ // dispatch messages to a separate thread, but still in order for
this subscription
+ // sendMessagesToConsumers is responsible for running broker-side
filters
+ // that may be quite expensive
+ topic.getBrokerService().getTopicOrderedExecutor()
+ .executeOrdered(name,
Review Comment:
`do we care about potential (unchecked) RejectedExecutionException here?`
we usually don't deal with RejectedExecutionException in Dispatcher code.
in any case even if the execution is rejected the Dispatcher will read more
entries for some other reasons
`we may need to prevent this code from submitting unlimited amount of
runnables into that executor / handle long backlog.`
This shouldn't be a problem because there is a "natural" backpressure
mechanism here, we trigger this code when new entries are read from storage
(BK/Offloaders) but we request new entries after dispatching them to Consumers.
So usually there is only one of this tasks that is pending for the
subscription.
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