Re: fsync error handling in pg_receivewal, pg_recvlogical

Hi,

Tried out this patch and it applies, compiles, and passes check-world. Also flipped things around in pg_recvlogical.c to exit-on-success to ensure it's actually being called and that worked too. Outside of a more complicated harness that simulates fsync errors not sure how else to test this further.

I did some searching and found a FUSE based on that looks interesting: CharybdeFS[1]. Rather than being fixed at mount time, it has a client/server interface so you can change the handling of syscalls on the fly[2]. For example you can error out fsync calls halfway through a test rather than always or randomly. Haven't tried it out but leaving it here as it seems relevant.

[1]: https://github.com/scylladb/charybdefs
[2]: https://www.scylladb.com/2016/05/02/fault-injection-filesystem-cookbook/