Re: Introduce pg_receivewal gzip compression tests

On Thu, Jul 15, 2021 at 07:48:08AM +0000, gkokolatos@pm.me wrote:
> Let us hope that it will prevent some bugs from happening.

The buildfarm has two reports.

1) bowerbird on Windows/MSVC:
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=bowerbird&dt=2021-07-15%2010%3A30%3A36
pg_receivewal: fatal: could not fsync existing write-ahead log file
"000000010000000000000002.partial": Permission denied
not ok 20 - streaming some WAL using ZLIB compression
I don't think the existing code can be blamed for that as this means a
failure with gzflush().  Likely a concurrency issue as that's an
EACCES.  If that's repeatable, that could point to an actual issue
with pg_receivewal --compress.

2) curculio:
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=curculio&dt=2021-07-15%2010%3A30%3A15
# Running: gzip --test
 /home/pgbf/buildroot/HEAD/pgsql.build/src/bin/pg_basebackup/tmp_check/t_020_pg_receivewal_primary_data/archive_wal/000000010000000000000002.gz
 /home/pgbf/buildroot/HEAD/pgsql.build/src/bin/pg_basebackup/tmp_check/t_020_pg_receivewal_primary_data/archive_wal/000000010000000000000003.gz.partial
gzip:
 /home/pgbf/buildroot/HEAD/pgsql.build/src/bin/pg_basebackup/tmp_check/t_020_pg_receivewal_primary_data/archive_wal/000000010000000000000003.gz.partial:
 unknown suffix: ignored
 not ok 24 - gzip verified the integrity of compressed WAL segments

Looking at the OpenBSD code (usr.bin/compress/main.c), long options
are supported, where --version does exit(0) without printing
anything, and --test is supported even if that's not on the man pages.
set_outfile() is doing a discard of the file suffixes it does not
recognize, and I think that their implementation bumps on .gz.partial
and generates an exit code of 512 to map with WARNING.  I still wish
to keep this test, and I'd like to think that the contents of
@zlib_wals are enough in terms of coverage.  What do you think?
--
Michael