Archive for April, 2014

Cache invaldiation, naming things, and vertically aligning the damn checkboxes

Thursday, April 24th, 2014

One of the two three hard things in computer science solved:

Use “the big E” for quick and clean monitoring

Thursday, April 3rd, 2014

Despite all the great tools out there these days for monitoring, it’s difficult to get away without writing a custom monitoring script or two. Spools, various types of cache, multi-server indexing. So many things that can go wrong.

Once upon a time I used to write quick and dirty complex scripts that would email in one case, otherwise do some-such-thing, etc. They were brittle with questionable reliability. Talk about a false sense of security.

These days I like to use an untouted feature of mail to keep things simpler. The idea is to only make noise when there is a problem. If all is well, keep silent.

Take this cron job for example:

*/5 * * * * root /somedir/ | mail -E -s 'Spool Monitor' will do just that: Check a spool each time it is run. If everything is fine, no output. If it finds a problem then it outputs what it finds. The “big E” (-E) switch tells mail to ignore any body-less input, and will therefore only spam us when there is some panic-worthy output.

Thanks big E.