pg_restore causing ENOSPACE on the WAL partition. Fundamental issue?

Hello list,

I have previously raised an issue on pgsql-general, where PostgreSQL is
logging without any boundaries to the WAL directory, even if other writer
processes can't catch up with it. It ends up with WAL partition becoming
full and a bad crash. Read more at the thread at:

https://www.postgresql.org/message-id/flat/076464ad-3d70-dd25-9e8f-e84f27decfba%40gmx.net

If it's true, I consider this a critical and under-documented issue, thus
I'm bringing it up here. Otherwise please let me know if any of my
assumptions are wrong.

In short, this is how it can easily happen, but in principle it's much
more generic:

+ The WAL is on a dedicated high-perf drive

+ pg_restore is writing to a slow tablespace on a network drive

+ data is logged to the WAL faster than what can be written to that
   tablespace

+ it eventually ends up with the WAL filling up, regardless of
   max_wal_size...


In other words, I'm surprised that there is no mechanism for the backends
to block while the WAL is overflowing. Am I wrong here?


Thank in advance,
Dimitris