That is a classic connection pooling/lifecycle bug, and usually one that gets caught in the first few days of having multiple people utilizing a product/service, worst case.

If someone's production site, thats been around for while, had a bug like this that can be caused by what you describe, I'd love to see how many real users they have. I'm sure its possible under certain circumstances, but its definitely bad engineering that would be caused by literally any traffic.

You can avoid triggering this in your scraper by activating a cookie jar. Pretty simple most of the time. Even commandline cURL and wget support it. I'm sure you figured that out already, but just for anyone who's wondering. ;)

That said, while obviously you want to avoid triggering the bug since it offlines your data source, this is definitely in the site's court to fix and could easily be triggered by normal usage. Some people browse with cookies disabled, especially since the EU passed its "cookie law", requiring sites to get consent before storing a cookie on visitors' machines. If you've started to notice more sites talking about cookies over the last year, that's why. [0]

[0] http://ec.europa.eu/ipg/basics/legal/cookies/index_en.htm

>Now that I think about it a bit more, I think my hypothesis was that DB connections were allocated at the session level and that without cookies enabled each request initiated a new session.

Could also be something like storing hibernates second level cache in session. Unfortunately I've seen this, a significant chunk of the database was being copied into each users session.