IsUnderPostmaster with shared_preload_libraries on Windows

Joe Conway <mail@joeconway.com> writes:

Is it expected that IsUnderPostmaster is true during postmaster startup
in an extension's _PG_init() when preloading under Windows? On Linux it
is false at this point AFAICT.

AFAIK it will be false in the *postmaster's* execution of _PG_init().
But keep in mind that on Windows each exec'd child process will have to
load the shared_preload_libraries again for itself, and those executions
should see IsUnderPostmaster = true. I think what you are seeing is
additional executions in the startup process or other background
processes, which don't happen in a forked-children environment.

You can probably duplicate this behavior for testing purposes on Unix
by compiling with EXEC_BACKEND defined, if that helps.

regards, tom lane

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On 06/13/2016 01:57 PM, Tom Lane wrote:

Joe Conway <mail@joeconway.com> writes:

Is it expected that IsUnderPostmaster is true during postmaster startup
in an extension's _PG_init() when preloading under Windows? On Linux it
is false at this point AFAICT.

AFAIK it will be false in the *postmaster's* execution of _PG_init().
But keep in mind that on Windows each exec'd child process will have to
load the shared_preload_libraries again for itself, and those executions
should see IsUnderPostmaster = true. I think what you are seeing is
additional executions in the startup process or other background
processes, which don't happen in a forked-children environment.

You can probably duplicate this behavior for testing purposes on Unix
by compiling with EXEC_BACKEND defined, if that helps.

Thanks, definitely easier to debug on Linux. It appears the best answer
is to use process_shared_preload_libraries_in_progress rather than
trying to derive that information using IsUnderPostmaster.

Joe

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