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Question

Every time a user logs in to the application, I want to perform a certain task, say, record the time of login. So I wanted to know if a hook is fired on login by default? If yes, how can I make my module respond to it.

Edit - Assume there are multiple entry points in the application to login.

Answer 1

While there may well be multiple points of entry, it's crucial that your auth/session code conform to the DRY principle.

Once/if you're down to a single code path for logging in, you should be able to find an appropriate place in that code path to do something as simple as this:

user.last_login = time
user.num_logins++
user.save()

Additionally, you could use a memcache cooldown to make sure this only happens once every, say, 30 minutes:

cooldown_memcache_key = "login_cooldown_%s" % user.id
cooldown = memcache.get(cooldown_memcache_key)
if cooldown is None:
    user.last_login = time
    user.num_logins++
    user.save()
    memcache.add(cooldown_key, True, 1800)

Answer 2

I'm using Python on GAE (so it may be different for Java) but have seen no documentation about such a hook for a user logging in. If you used one of the session management frameworks you'd probably get some indication for that, but otherwise I do this kind of house keeping on my opening page itself which requires login. (What do you want to do about an already logged in user returning to your site a few days later... that is, do you really want to record logins or the start time of a visit/session??)

If I wanted to do this but with multiple landing pages, and without using a session framework, I'd use memcache to do a quick check on every page request and then only write to the datastore when a new visit starts.