Question

We’re using sessions in our GAE/J application. Over the weekend, we had a large spike in our datastore writes that appears to have been caused by a large number of _ah_SESSION entities being created (about 100-200 every minute). Near as we can tell, there was a rogue task queue creating them because they stopped when we purged the queue. The task was part of a mapper process we run hourly.

We don’t need sessions in that hourly mapper (or indeed in any of our task queues or cron jobs or many other requests). Is there a way to disable creating a session for selected URLs?

Answer 1

Unfortunately that can not be done.

This is particularly nasty when you have a non-browser clients (devices via REST or mapreduce jobs) where every request generates a new _ah_SESSION entity in the database.

The only way to avoid this is to write your own session handler: e.g. a servlet filter that sets/checks cookies and set it so that it ignores certain paths.

EDIT:

I just realized that there could be another way: make sure your client (mapreduce job) sets a dummy cookie with a proper name. GAE uses cookies named ACSID in production and dev_appserver_login on dev server. Just use always the same cookie value, so all requests will be treated as one user/session.

There will still be overhead of looking-up/saving session objects, but at least it will not create countless _ah_SESSION entities.