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    Same thing happens with SSL error warnings in Mozilla, when the certificate chain is missing in a new installation due to a fresh cache.

    https://superuser.com/a/524234

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      Great lesson in cache management…I think?

      It does remind me of a problem the sysadmin and myself were working on this morning where PDO was throwing exceptions over an unknown hostname, and the inability to get an IP from it. Turns out when he cycled the instances, the Redis session was never switched up, so it had all the cached data it needed - but PHP didn’t know how to properly unserialize the data. Flush the cache, back to normal!

      Probably shouldn’t be storing configuration in Redis, but man parsing XML is pretty heavy.

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        Yeah, I think the lesson is that users don’t have a good mental model for the behavior of caches, and they might be a bad idea in a system that users have to debug themselves.

        The SSL comparison that cnst mentioned is a great example. I don’t immediately see a case where that behavior would lead users to being less secure than they expect they are, but it’s clear that the cache is part of the security properties and, even being aware of that, I doubt I could reliably anticipate when it’s important in practice.

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        Fun story but man lighten up on the exclamation points.