97 Things Every Programmer Should Know

(Chris Devlin) #1

(^180) 97 Things Every Programmer Should Know

Verbose Logging Will Disturb Your Sleep ...............

Verbose Logging Will Disturb Your Sleep ...............

Johannes Brodwall

WHEN i ENCOUNTER A SYSTEM that has already been in development or pro-
duction for a while, the first sign of real trouble is always a dirty log. You know
what I’m talking about: when clicking a single link on a normal flow on a web
page results in a deluge of messages in the only log that the system provides.
Too much logging can be as useless as none at all.

If your systems are like mine, when your job is done, someone else’s job is
just starting. After the system has been developed, it will hopefully live a long
and prosperous life serving customers (if you’re lucky). How will you know if
something goes wrong when the system is in production, and how will you
deal with it?

Maybe someone monitors your system for you, or maybe you will monitor it
yourself. Either way, the logs will probably be part of the monitoring. If some-
thing shows up and you have to be woken up to deal with it, you want to make
sure there’s a good reason for it. If my system is dying, I want to know. But if
there’s just a hiccup, I’d rather enjoy my beauty sleep.

For many systems, the first indication that something is wrong is a log mes-
sage being written to some log. Mostly, this will be the error log. So do yourself
a favor: make sure from day one that if something is logged in the error log,
you’re willing to have someone call and wake you in the middle of the night
about it. If you can simulate load on your system during system testing, look-
ing at a noise-free error log is also a good first indication that your system is
reasonably robust—or an early warning if it’s not.

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