Ruby Agent 2.4.21 is out with a bug fix, a new configuration option, and a debug option
As reported on Issue #228, if scout_apm is disabled on a node via the configuration monitor = false, we don't intend to install any instruments, but a few snuck in anyway. Since the rest of the agent isn't running, they (slowly but steadily) built up recorded info, but didn't purge it, causing a slow memory leak that became clear over the course of a week or two. We've stopped the offending instruments from installing themselves when Scout is disabled.