Note that this is a lazy property, and will only be generated when you first access it.If you call Forms may subclass other forms as needed.Two general constraints apply to usage of selective cache invalidation: A production site publishing agent can be configured to exclude specific repositories and item descriptors from selective cache invalidation—in other words, require that item caches be fully invalidated on each deployment.To do so, set the property If no item descriptors are supplied, all item caches in the repository are invalidated.For now, someone who understands this better needs to decide what's the best approach. As soon as one of the anonymous users submits such a form, the record gets removed from cache. Here is what happens: When page caching is turned on and if we grab the form for user login, we always get a form for each anonymous user with the same form_build_id.The next visitor who is submitting the same form will potentially run into trouble because of the missing form record in cache. This issue arrises always when page caching for anonymous users and form submission via Drupal's own ajax mechanism get used in combination. This can be reproduced when you use two different browsers on the same PC and call the same page Only those cached items that change as a result of the deployment are invalidated. Because selective invalidation increases deployment overhead, you might want to configure a threshold for the number of invalidated items.
Another check, if you turn off Ajax submission for that form, the exact same scenario will not cause that problem. In the firebug,the unsuccessful login attempts record a "200 OK" response.
Item caches of all deployed repositories are invalidated.
This can result in slow response time to initial requests, as fresh data is obtained directly from the database.
They contain your field definitions, delegate validation, take input, aggregate errors, and in general function as the glue holding everything together. This is usually done in the context of a view/controller in your application.
When a Form is constructed, the fields populate their input based on the formdata, obj, and kwargs.The function drupal_get_form() which is used without Ajax is not deleting the record from cache after having loaded it and that's why the behaviour is different. View Just came across the very same problem and looked around on how I could fix it.