Re: fix bgworkers in EXEC_BACKEND

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> schrieb:

>Andres Freund <andres(at)2ndquadrant(dot)com> writes:
>> I am still worried about the following scenario in the EXEC_BACKEND
>case:
>
>> 1) postmaster starts
>> 2) reads config
>> 3) executes _PG_init for shared_preload_libraries
>> 4) library 'abc' gets config value 'abc.num_workers = 2' and
>registers as many workers
>> 5) some time goes by, workers, backends start
>> 6) abc.num_workers gets changed to 3, SIGHUP
>
>This is broken whether it's EXEC_BACKEND or not: you don't get to
>change
>anything that determines the number of workers post-startup.
>num_workers should have been declared PGC_POSTMASTER.

BTW, I think it happens not to be broken in the non EXEC_BACKEND case because the registration point for bgworkers is _PG_init which will only be called once without EXEC_BACKEND, so config changes to SIGHUP'able variables won't change a thing dangerous as the bgworker stuff is all set up.

Andres

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Please excuse the brevity and formatting - I am writing this on my mobile phone.