From 5ecd0183fb6afa4a07aad71ea0e08c70f64a42a9 Mon Sep 17 00:00:00 2001 From: Michael Paquier Date: Sat, 29 Jan 2022 10:47:36 +0900 Subject: [PATCH] Fix comments about bgworker registration before MaxBackends initialization Since 6bc8ef0b, InitializeMaxBackends() has used max_worker_processes instead of adapting MaxBackends to the number of background workers registered by modules loaded in shared_preload_libraries (at this time, bgworkers were only static, but gained dynamic capabilities as a matter of supporting parallel queries meaning that a control cap was necessary). Some comments referred to the past registration logic, making them confusing and incorrect, so fix these. Some of the out-of-core modules that could be loaded in this path sometimes like to manipulate dynamically some of the resource-related GUCs for their own needs, this commit adds a note about that. Author: Nathan Bossart Discussion: https://postgr.es/m/20220127181815.GA551692@nathanxps13 --- src/backend/postmaster/postmaster.c | 10 ++++------ src/backend/utils/init/postinit.c | 5 ++--- 2 files changed, 6 insertions(+), 9 deletions(-) diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c index dc4afdd75a..ac0ec0986a 100644 --- a/src/backend/postmaster/postmaster.c +++ b/src/backend/postmaster/postmaster.c @@ -1014,10 +1014,8 @@ PostmasterMain(int argc, char *argv[]) LocalProcessControlFile(false); /* - * Register the apply launcher. Since it registers a background worker, - * it needs to be called before InitializeMaxBackends(), and it's probably - * a good idea to call it before any modules had chance to take the - * background worker slots. + * Register the apply launcher. It's probably a good idea to call this + * before any modules had a chance to take the background worker slots. */ ApplyLauncherRegister(); @@ -1038,8 +1036,8 @@ PostmasterMain(int argc, char *argv[]) #endif /* - * Now that loadable modules have had their chance to register background - * workers, calculate MaxBackends. + * Now that loadable modules have had their chance to alter any GUCs, + * calculate MaxBackends. */ InitializeMaxBackends(); diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c index d046caabd7..cd7c829ff5 100644 --- a/src/backend/utils/init/postinit.c +++ b/src/backend/utils/init/postinit.c @@ -483,9 +483,8 @@ pg_split_opts(char **argv, int *argcp, const char *optstr) /* * Initialize MaxBackends value from config options. * - * This must be called after modules have had the chance to register background - * workers in shared_preload_libraries, and before shared memory size is - * determined. + * This must be called after modules have had the chance to alter GUCs in + * shared_preload_libraries and before shared memory size is determined. * * Note that in EXEC_BACKEND environment, the value is passed down from * postmaster to subprocesses via BackendParameters in SubPostmasterMain; only