Ah-ha, the Wi-Fi controller needed to update the version of MongoDB that my server had installed, and the old version's repository was no longer signed, so apt-get update was failing silently, and that led to my weather graph generator library being linked against an old version of glibc.

@futzle it’s only MongoDB if it’s a RDBMS from the Steppes Of Mongolia, otherwise it’s just sparkling data corruption

@jpm @futzle “Conan! What is best in life?”
“Crush your DB admins, see data driven into shards, and hear the lamentation of the web-scalers”