Date: Thu, 15 Jul 2021 09:47:37 -0500
From: Justin Pryzby <pryzby@telsasoft.com>
To: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Cc: pgsql-hackers@lists.postgresql.org,
	Alvaro Herrera <alvherre@alvh.no-ip.org>
Subject: Re: What are exactly bootstrap processes, auxiliary processes,
 standalone backends, normal backends(user sessions)?
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On Fri, Jul 09, 2021 at 09:24:19PM +0530, Bharath Rupireddy wrote:
> I've always had a hard time distinguishing various types of
> processes/terms used in postgres. I look at the source code every time
> to understand them, yet I don't feel satisfied with my understanding.
> I request any hacker (having a better idea than me) to help me with
> what each different process does and how they are different from each
> other? Of course, I'm clear with normal backends (user sessions), bg
> workers, but the others need a bit more understanding.

It sounds like something that should be in the glossary, which currently refers
to but doesn't define "auxiliary processes".

 * Background writer, checkpointer, WAL writer and archiver run during normal
 * operation.  Startup process and WAL receiver also consume 2 slots, but WAL
 * writer is launched only after startup has exited, so we only need 5 slots.
 */
#define NUM_AUXILIARY_PROCS             5

Bootstrap is run by initdb:
src/bin/initdb/initdb.c:                                 "\"%s\" --boot -x0 %s %s "

Standalone backend is run by --single, right ?

-- 
Justin