Dead Canary In a Coal Mine.
Little bird in a cage in the mine. Bird sings happily (or whatever). Oxygen level sinks due to methane rising silently from a hidden source. Bird stops singing and falls asleep. Why? The bird is such a small one, he is much more "hit" by the methane level than a human (needs less methane in the air to die). Today there are machines for that, but, no happy bird-tunes down there anymore. Just buzzers. A shame, really, for the musical coalminer of nowadays.
In geek talk, the canary is like an EventListener?, or perhaps closer to a WatchdogTimer?.
I once set up a little app at a client's site that periodically runs a bunch of test queries against some databases, and sends out warning emails if any of those queries turns up something strange. It gives us a heads up on problem data that has somehow made its way into the system. We called it the Canary. :-) -- KevinMcConnellThat sounds more like an inverse-canary :) -- AnonymousCoward
Maybe you should use a framework for that, like NagiosMonitor?.
Mentioned on StackOverflow Q&A: http://stackoverflow.com/questions/1906590/good-name-for-the-opposite-of-a-canary. Maybe someone here could lend their insight. What would be the name for the opposite pattern, i.e., some "magic" that is placed in a data area to detect that it has been (correctly) overwritten? An InverseCanary? of sorts. -- ClaesWallin