Memcache sharing between different OSes

[brownp2k]

Given two Apache proxies running on two different OSes using the OS-level repo-provided mod_auth_openidc (Ubuntu 22 uses 2.4.11, Ubuntu 24 uses 2.4.15.1), should it be possible for them to share a single memcached server?

I know that 2.4.19 introduced session format changes, and 2.4.20 introduced session encryption key changes, so I would expect "crossing" those boundaries to not be able to use a single memcached server, but I didn't see anything claiming session incompatibility between 2.4.11 and 2.4.15.1.

[brownp2k]

Ah, thanks for pointing those out. I knew about them a while back but when writing up the issue I was just looking at the italicized comment at the top of each release version.

I also read somewhere that the encryption logic delegates to system libraries, so I assumed any difference in system encryption libraries between Ubuntu 22 and 24 would also cause sessions to not be sharable.