Hi Penghui, Thanks for your question.
One case is failure recovery for a windowing function. A windowing function will ack message until its window is emitted. If the window function fails due to issues such as OOM and restarts, it has a massive backlog to catch up. And the function will never be able to recover itself since the backlog keeps growing and it keeps OOM. Our user prefers an automatic way for recovery, given they are okay with skipping some backlog data. (This is acceptable in IoT cases). Also, Users may deploy hundreds of functions in their environment. Manually resetting the cursor is not scalable and is a heavy burden for the on-call person in such cases. Hope the above use case can help provide some more context regarding the change. On 2023/03/03 03:51:35 PengHui Li wrote: > Hi Neng, > > Thanks for raising up the discussion > > > In certain failure cases, the function needs to skip all the content > between the last successfully acked message and the latest message in the > topic in order to skip the huge backlog and quick recovery. > > Do you have some real cases that can help us to understand it > is necessary to introduce a new flag? Another possibility is users > can use pulsar admin to reset the cursor to the latest position, > Why will it not work for users? > > Regards, > Penghui > > > On Mar 1, 2023, at 10:16, Neng Lu <nl...@apache.org> wrote: > > > > In certain failure cases, the function needs to skip all the content > > between the last successfully acked message and the latest message in the > > topic in order to skip the huge backlog and quick recovery. > >
