Re: Throttling WAL inserts when the standby falls behind more than the configured replica_lag_in_bytes

On Fri, Dec 24, 2021 at 3:13 AM Dilip Kumar <dilipbalaut@gmail.com> wrote:

On Fri, Dec 24, 2021 at 3:27 AM SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com> wrote:

XLogInsert in my opinion is the best place to call it and the hook can be something like this "void xlog_insert_hook(NULL)" as all the throttling logic required is the current flush position which can be obtained from GetFlushRecPtr and the ReplicationSlotCtl. Attached a draft patch.

IMHO, it is not a good idea to call an external hook function inside a critical section.  Generally, we ensure that we do not call any code path within a critical section which can throw an error and if we start calling the external hook then we lose that control. 

Thank you for the comment. XLogInsertRecord is inside a critical section but not XLogInsert. Am I missing something?