Hi Rajan,
Even we don't persistent NonPersistentSubscription's state, but it has a
`isDurable` field
```
public NonPersistentSubscription(NonPersistentTopic topic, String
subscriptionName, boolean isDurable,
Map<String, String> properties) {
this.topic = topic;
this.topicName = topic.getName();
this.subName = subscriptionName;
this.fullName = MoreObjects.toStringHelper(this).add("topic",
topicName).add("name", subName).toString();
IS_FENCED_UPDATER.set(this, FALSE);
this.lastActive = System.currentTimeMillis();
this.isDurable = isDurable;
this.subscriptionProperties = properties != null
? Collections.unmodifiableMap(properties) :
Collections.emptyMap();
}
```
When users create a `Consumer`, the `durable` will set to be `true`.
And in `removeConsumer` method of `NonPersistentSubscription`, after
consumers disconnected, we can remove the `durable` subscription
automatically.
```
public synchronized void removeConsumer(Consumer consumer, boolean
isResetCursor) throws BrokerServiceException {
updateLastActive();
if (dispatcher != null) {
dispatcher.removeConsumer(consumer);
}
// preserve accumulative stats form removed consumer
ConsumerStatsImpl stats = consumer.getStats();
bytesOutFromRemovedConsumers.add(stats.bytesOutCounter);
msgOutFromRemovedConsumer.add(stats.msgOutCounter);
if (!isDurable) {
topic.unsubscribe(subName);
}
// invalid consumer remove will throw an exception
// decrement usage is triggered only for valid consumer close
topic.decrementUsageCount();
if (log.isDebugEnabled()) {
log.debug("[{}] [{}] [{}] Removed consumer -- count: {}",
topic.getName(), subName, consumer.consumerName(),
topic.currentUsageCount());
}
}
```
The PIP is for the purpose of deprecate `durable` subscriptions on
NonPersistentTopic for the following reasons:
1. We don't persistent NonPersistentSubscription's state, it's totally
in-memory state, keep the `isDurable` field is meaningless and may takes
misunderstanding
2. The expired subscriptions auto clean like wrote in the PIP.
Thanks,
Tao Jiuming
Rajan Dhabalia <rdhaba...@apache.org> 于2023年2月23日周四 12:33写道：
> > But for NonPersistentTopic, creating a Durable subscription is
> meaningless, NonPersistentSubscription doesn't have a ManagedCursor to
> persistent its data. After its consumer disconnected, the subscription
> couldn't be removed automatically if we didn't set the value of
> subscriptionExpirationTimeMinutes greater than 0.
> This is not correct. Non-Persistent topics don't create durable
> subscriptions but It creates NonPersistent Subscription without storing its
> state.
>
> > if we set the value of subscriptionExpirationTimeMinutes greater than 0,
> it may lead to data loss(The durable subscriptions of PersistentTopic also
> can be removed).
> Non-Persistent topics don't provide data persistent or dispatch guarantee
> and it's by design so, let's not try to change semantics of non-persistent
> topic and there could be data loss in non-persistent topic.
>
> > And the Non-durable subscriptions will be removed automatically after all
> the consumers disconnected, it's the existing logic.
> Why can't we do this in the existing NonPersistent Subscription? I really
> don't understand the purpose of this PIP?
>
> Thanks,
> Rajan
>
> On Sun, Feb 12, 2023 at 10:56 PM Jiuming Tao <jm...@streamnative.io.invalid
> >
> wrote:
>
> > Hi all,
> >
> > I would like to start a VOTE on `PIP-245: Make subscriptions of
> > non-persistent topic non-durable`.
> >
> > Motivation:
> >
> > There are two types of subscriptions for a topic: Durable and
> Non-durable.
> >
> > We create a Consumer with a Durable subscription and a Reader with a
> > Non-durable subscription.
> >
> > But for NonPersistentTopic, creating a Durable subscription is
> > meaningless, NonPersistentSubscription doesn't have a ManagedCursor to
> > persistent its data. After its consumer disconnected, the subscription
> > couldn't be removed automatically if we didn't set the value of
> > subscriptionExpirationTimeMinutes greater than 0.
> >
> > For subscriptionExpirationTimeMinutes, it controls the subscription
> > expiration of NonPersistentTopic and PersistentTopic, if we set the value
> > of subscriptionExpirationTimeMinutes greater than 0, it may lead to data
> > loss(The durable subscriptions of PersistentTopic also can be removed).
> >
> > And the Non-durable subscriptions will be removed automatically after all
> > the consumers disconnected, it's the existing logic.
> >
> > For the purpose of removing the subscriptions which have no active
> > consumers of NonPersistentTopic and the above reasons, we can make all
> the
> > subscriptions of a NonPersistentTopic Non-durable.
> >
> >
> >
> > For more details, you can read:
> > https://github.com/apache/pulsar/issues/19448 <
> > https://github.com/apache/pulsar/issues/19448>
> >
> > And the discuss thread is available at:
> > https://lists.apache.org/thread/2ltmyglnb25jy8nk58twkwbglws43bst <
> > https://lists.apache.org/thread/2ltmyglnb25jy8nk58twkwbglws43bst>
> >
> > Thanks,
> > Tao Jiuming
>
