On Sat, 28 Jan 2023 21:11:06 -0000 (UTC) Stuart Henderson <[email protected]> wrote:
> Thanks for the detailed report, thinking about what information > might be useful, and including it directly in your email. > > On 2023-01-28, Roger Marsh <[email protected]> wrote: > > Package lmdb-0.9.29 was installed; and py-lmdb, as a --user install, from > > PyPi so lmdb can be used from Python3.9. > > py-lmdb bundles its own copy of LMDB and uses it by default, or you > can set extra flags to use the system version. > > Normally the bundled one is ok, but the LMDB library assumes an OS with > coherent file and mmap access (often referred to as 'unified buffer > cache') which OpenBSD lacks. The LMDB port (and OpenLDAP) are patched to > force MDB_WRITEMAP so all io goes through mmap. This has some drawbacks > (and some advantages in certain circumstances) but as far as we know > it's the only way we can run it. Obviously the copy bundled in py-lmdb > doesn't have this patch. > > "Use a writeable memory map unless MDB_RDONLY is set. This is > faster and uses fewer mallocs, but loses protection from application > bugs like wild pointer writes and other bad updates into the database. > Incompatible with nested transactions. Do not mix processes with and > without MDB_WRITEMAP on the same environment. This can defeat durability > (mdb_env_sync etc)." > > (If I understand correctly, LMDB normally writes through file access, > reads through mmap). > > > Behaviour seemed erratic, including segmentation faults, but for a > > while it seemed possible to avoid these by using alternative methods > > supported by py-lmdb. > > Yes this sounds about the expected behaviour for the UBC problem. > > You can try the port I've just posted to ports@ which uses the system > lmdb library. https://marc.info/?l=openbsd-ports&m=167493896320807&w=2 > Alternatively set the flags from MAKE_ENV in that port while building > py-lmdb manually. > > Thanks for the explanation and the port.
