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Perl also changed its behavior, but in the other direction: a random seed was used per interpreter start after 5.18. https://www.perlmonks.org/?node_id=1005122

• masklinn 2y ago
  That's actually the first python transition I mentioned, per-process hash randomisation had the effect of making map iteration non-deterministic. I believe in both cases this was in response to the hashdos concern / attacks.
  • zbentley 2y ago
    Ah, sorry I didn't read that closely. One minor nit (which the Perl press releases also mess up): the randomisation is per-interpreter, not per-process. That's not a pedantic distinction. I've seen a couple of bugs/bad behaviors caused by forking servers forgetting to call srand(3)/re-randomize the hash seed after fork(2) and then relying on more randomness than they actually have. Suddenly (for example) hashing rate limiters or bloom filters all operate in near-lockstep, which can cause significant issues at high volumes. Forking has also caused randomness-related issues (though not necessarily specifically re: hashing) for Rust[1] and Ruby[2], and probably many other platforms. OpenSSL seems to sidestep[3] the issue by using the PID as part of its salt internally. 1: https://github.com/rust-lang/rust/issues/16799 https://github.com/rust-lang/rust/issues/16799 2: https://bugs.ruby-lang.org/issues/4579 https://bugs.ruby-lang.org/issues/4579 3: https://wiki.openssl.org/index.php/Random_fork-safety https://wiki.openssl.org/index.php/Random_fork-safety