Re: Remove non-fast promotion Re: Should we remove a fallback promotion? take 2

On 2020/04/21 10:59, Michael Paquier wrote:
> On Mon, Apr 20, 2020 at 03:26:16PM +0900, Fujii Masao wrote:
>> Patch attached. I will add this into the first CF for v14.
>
> Thanks!
>
>> - if (IsPromoteSignaled())
>> + /*
>> + * In 9.1 and 9.2 the postmaster unlinked the promote file inside the
>> + * signal handler. It now leaves the file in place and lets the
>> + * Startup process do the unlink.
>> + */
>> + if (IsPromoteSignaled() && stat(PROMOTE_SIGNAL_FILE, &stat_buf) == 0)
>> {
>> - /*
>> - * In 9.1 and 9.2 the postmaster unlinked the promote file inside the
>> - * signal handler. It now leaves the file in place and lets the
>> - * Startup process do the unlink. This allows Startup to know whether
>> - * it should create a full checkpoint before starting up (fallback
>> - * mode). Fast promotion takes precedence.
>> - */
>> - if (stat(PROMOTE_SIGNAL_FILE, &stat_buf) == 0)
>> - {
>> - unlink(PROMOTE_SIGNAL_FILE);
>> - unlink(FALLBACK_PROMOTE_SIGNAL_FILE);
>> - fast_promote = true;
>> - }
>> - else if (stat(FALLBACK_PROMOTE_SIGNAL_FILE, &stat_buf) == 0)
>> - {
>> - unlink(FALLBACK_PROMOTE_SIGNAL_FILE);
>> - fast_promote = false;
>> - }
>> -
>> ereport(LOG, (errmsg("received promote request")));
>> -
>> + unlink(PROMOTE_SIGNAL_FILE);

Thanks for reviewing the patch!

> On HEAD, this code means that it is possible to end recovery just by
> sending SIGUSR2 to the startup process.

Yes, in this case, non-fast promotion is triggered.

> With your patch, this code
> now means that in order to finish recovery you need to send SIGUSR2 to
> the startup process *and* to create the promote signal file.

Yes, but isn't this the same as the way to trigger fast promotion in HEAD?

Regards,

--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION