I'm a new developer to moodle and i'm still learning its architecture.
What's the best place to put some code that I want to run in every page request? (some custom logging / other systems integration)
Any sugestions, following the good practices of moodle?
For stuff that gets printed to user, I'd put it in the theme. For strictly server-side things, like you're talking about, I might actually put that in config.php (see here and here for more info). If it's more than a couple of lines of code, I'd put it in a file in /local which I then call from config.php.