Hi, I'm the maintainer of flink-connector-pulsar. I would like to start a survey on a function change proposal in flink-connector-pulsar.
I have created a ticket <https://issues.apache.org/jira/browse/FLINK-30413> on JIRA and paste its description here: A lot of Pulsar connector test unstable issues are related to Shared and Key_Shared subscription. Because this two subscription is designed to consume the records in an unordered way. And we can support multiple consumers in same topic partition. But this feature lead to some drawbacks in connector. 1. Performance Flink is a true stream processor with high correctness support. But support multiple consumer will require higher correctness which depends on Pulsar transaction. But the internal implementation of Pulsar transaction on source is record the message one by one and stores all the pending ack status in client side. Which is slow and memory inefficient. This means that we can only use Shared and Key_Shared on Flink with low throughput. This against our intention to support these two subscription. Because adding multiple consumer to same partition can increase the consuming speed. 2. Unstable Pulsar transaction acknowledge the messages one by one in an internal Pulsar's topic. But it's not stable enough to get it works. A lot of pending issues in Flink JIRA are related to Pulsar transaction and we don't have any workaround. 3. Complex Support Shared and Key_Shared subscription make the connector's code more complex than we expect. We have to make every part of code into ordered and unordered way. Which is hard to understand for the maintainer. 4. Necessary The current implementation on Shared and Key_Shared is completely unusable to use in Production environment. For the user, this function is not necessary. Because there is no bottleneck in consuming data from Pulsar, the bottleneck is in processing the data, which we can achieve by increasing the parallelism of the processing operator.
