On 2020/10/28 20:50, Bharath Rupireddy wrote:
On Wed, Oct 21, 2020 at 6:43 PM Magnus Hagander <mag...@hagander.net> wrote:
I think it would be nicer to have a pg_terminate_backend(pid, wait=false), so a
function with a second parameter which defaults to the current behaviour of not
waiting. And it might be a good idea to also give it a timeout parameter?
Done.
2. pg_wait_backend() -- which waits for a given backend process. Note that this
function has to be used carefully after pg_terminate_backend(), if used on a
backend that's not ternmited it simply keeps waiting in a loop.
It seems this one also very much would need a timeout value.
Done.
And surely we should show some sort of wait event when it's waiting.
Added two wait events.
If the backend is terminated within the user specified timeout then
the function returns true, otherwise false.
I’m suggesting an option for the second case to fail instead of returning false.
Done.
I prefer that false is returned when the timeout happens,
like pg_promote() does.
I could imagine, in theory at least, wanting to wait for a backend to go idle
as well as for it disappearing. Scope creep in terms of this patch's goal but
worth at least considering now.
IIUC, do we need a new option, something like pg_wait_backend(pid,
timeout, waituntil) where "waituntil" if specified "idle" waits until
the given backend goes to idle mode, or "termination" waits until
termination?
Isn't this wait-for-idle mode fragile? Because there is no guarantee
that the backend is still in idle state when pg_wait_backend(idle) returns.
Done.
Attaching a v2 patch herewith.
Thoughts and feedback are welcome.
Thanks for the patch!
When the specified timeout is negative, the following error is thrown *after*
SIGTERM is signaled to the target backend. This seems strange to me.
The timeout value should be verified at the beginning of the function, instead.
ERROR: timeout cannot be negative
pg_terminate_backend(xxx, false) failed with the following error. I think
it's more helpful if the function can work even without the timeout value.
That is, what about redefining the function in
src/backend/catalog/system_views.sql
and specifying the DEFAULT values for the arguments "wait" and "timeout"?
The similar function "pg_promote" would be good reference to you.
ERROR: function pg_terminate_backend(integer, boolean) does not exist at
character 8
Regards,
--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION
