Suppose you have a system with nodes and work items. You have to assignwork items to nodes somehow; one way to do it is to randomly distributework items around the nodes, but another is to assign them based onsome sort of fixed-outcome affinity function (like 'is topologicallynearest'). Now consider what happens when a node overloads or fails (oris just taken out of service) and its work has to be reassigned to newnodes.

In a random-assignment system, the failed

This used to be widely understood around Unix, but it's evidentlyslipped from common knowledge over time:

It's a mistake to log nonexistent usernames on bad logins .

(Corollary: it is an especially bad mistake to log them by default.)

To illustrate why I say this, let me tell you what happened tome recently. I normally leave myself logged in to my officeworkstation with the screen locked and blanked. This weekend, my officeworkstation crashed and rebooted because of some ongoing issues ; as

Here is a core principle of how and when programs should show error andwarning messages of all sorts:

Error messages should only go to the people who can do somethingabout them.

This goes double for warning messages.

(Sometimes you don't have a choice, at least in theory; if your programsuffers a fatal error and you have nowhere else to log it, dumping it onthe user does some moderate amount of good. Maybe.)

There's two reasons to be careful where your error messages