A Long Story about how I dug into the PostgreSQL source code to write my own WAL receiver, and what came out of it

Some thoughts are unpredictable. For example: "I wonder how pg_receivewal works internally?" From the outside, it sounds almost innocent. Really, what could possibly be wrong with that? Just ordinary engineering curiosity. I will take a quick look, understand the general structure, satisfy my curiosity, and then go on living peacefully. But then, for some reason, this happens: you are already building PostgreSQL from source, digging into receivelog.c , comparing the behavior of your little creat