> if we add the new field in CommandSubscribe, we should ensure > the synchronization between consumer reconnection and user > calling receive and redeliverUnack method. it will affect the performance > of receive. expose synchronization to hot paths it not a good idea.
I don't think this is a valid objection. I am pretty sure we already synchronize in the relevant places in the consumer to solve the exact race condition you're concerned about: [0] [1]. My proposed operation is to keep track of the latest message id that the application has seen, and then tell the broker that id when sending the Subscribe command. We already do similar logic here [2] [3], but instead of getting the first message id the consumer hasn't seen, we'll get the latest message id seen. Regarding performance, the PIP doesn't touch on how it will filter out messages. What is the planned approach? In my understanding, the client will keep track of the latest message id that the application has seen and then will need to compare that message id against every new mess. As such, it seems like telling the broker where to start instead of naively checking a filter on every message would be cheaper. > As described in Compatibility in PIP. Client consumer doesn't know > Pulsar Admin reset cursor. The problem of "the consumer doesn't know" seems like something that is reasonably within the protocol's responsibilities. In this case, an event happens on the broker, and the broker can tell the consumer. > * <p>Consumers should close when the server resets the cursor, > * when the cursor reset success, and then restart. Otherwise, > * the consumer will not receive the history messages. This is introducing a confusing edge case that requires reading a Javadoc in order to understand. That seems risky to me, and I do not think we should add such an edge case. A new protocol message would easily handle it and make it transparent to the application. Thanks, Michael [0] https://github.com/apache/pulsar/blob/af1360fb167c1f9484fda5771df3ea9b21d1440b/pulsar-client/src/main/java/org/apache/pulsar/client/impl/ConsumerImpl.java#L826-L912 [1] https://github.com/apache/pulsar/blob/af1360fb167c1f9484fda5771df3ea9b21d1440b/pulsar-client/src/main/java/org/apache/pulsar/client/impl/ConsumerImpl.java#L1870-L1876 [2] https://github.com/apache/pulsar/blob/af1360fb167c1f9484fda5771df3ea9b21d1440b/pulsar-client/src/main/java/org/apache/pulsar/client/impl/ConsumerImpl.java#L789-L795 [3] https://github.com/apache/pulsar/blob/af1360fb167c1f9484fda5771df3ea9b21d1440b/pulsar-client/src/main/java/org/apache/pulsar/client/impl/ConsumerImpl.java#L922-L960 On Tue, Mar 21, 2023 at 8:58 AM Yubiao Feng <yubiao.f...@streamnative.io.invalid> wrote: > > +1 > > Hi, Bo : > > Thanks for your explanation. That makes sense to me. > > Thanks, > Yubiao Feng > > On Mon, Mar 20, 2023 at 10:21 PM 丛搏 <congbobo...@gmail.com> wrote: > > > Hi, pulsar community: > > > > I started a PIP about `Client consumer filter received messages`. > > > > PIP: https://github.com/apache/pulsar/issues/19864 > > > > Thanks, > > Bo > >
