When do Symfony's user attributes get written to session?

Question

I have a Symfony app that populates the "widgets" of a portal application and I'm noticing something (that seems) odd. The portal app has iframes that make calls to the Symfony app. On each of those calls, a random user key is passed on the query string. The Symfony app stores that key its session using myUser->setAttribute(). If the incoming value is different from what it has in session, it overwrites the session value.

In pseudo-code (and applying a synchronous nature for clarity even though it may not exist):

# Widget request arrives with ?foo=bar
if the user attribute 'foo' does not equal 'bar'
  overwrite the user attribute 'foo' with 'bar'
end

What I'm noticing is that, on a portal page with multiple widgets (read: multiple requests coming in more or less simultaneously) where the value needs to be overwritten, each request is trying to overwrite. Is this a timing problem? When I look at the log prints, I'd expect the first request that arrives to overwrite and subsequent requests to see that the user attribute they received matches what was just put into cache by the initial request.

In this scenario, it could be that subsequent requests begin (and are checked) even before the first one--the one that should overwrite the cached value--has completely finished. Are session values not really available to subsequent requests until one request has completed entirely or could there be something else that I'm missing?

Thanks.

Answer 1

Attributes of the user do not get written to storage until the end of the request (in sfUser::shutdown). Attributes get loaded into sfUser at the beginning of a request. So in this case, the second request would have to be initiated after the first request is finished. Your best options are probably

• Add hardRead and hardWrite methods to sfUser (look at what sfUser::initialize and sfUser::shutdown do respectively).
• Use another method of storing the information that has better support for concurrency. The database or potentially the caching system you're using could work. For example, I think this could be done using APC cache.

Note that depending on what class you're using for storage, user attributes may not get written to $_SESSION at all. Symfony supports using many methods for storing user attributes (e.g. database, cache).