Re: Why are wait events not reported even though it reads/writes a timeline history file?

On Tue, Apr 28, 2020 at 02:49:00PM +0900, Fujii Masao wrote:
> Isn't it safer to report the wait event during fgets() rather than putting
> those calls around the whole loop, like other code does? For example,
> writeTimeLineHistory() reports the wait event during read() rather than
> whole loop.

Yeah, I/O wait events should be taken only during the duration of the
system calls.  Particularly here, you may finish with an elog() that
causes the wait event to be set longer than it should, leading to a
rather incorrect state if a snapshot of pg_stat_activity is taken.
--
Michael