In real usage the likelihood is low. But I can't guarantee there will never be a problem caused by network latency, either.
I don't use file-based sessions because I have several applications that work together, as in 'cooperating applications.' Though I suppose I could have one repository for session files and softlink to it. I'll have to read up on that. By the way, thanks. Your contributions here are a real benefit. I bookmark a lot of them. On Dec 9, 11:58 am, Anthony <[email protected]> wrote: > In real usage, is a user likely to be able to update the date field and > then quickly click the view link so fast that the view query happens before > the update query? If so, then your client side feedback idea is probably > the way to go. > > Actually, if both the update and view requests use the session (or rather, > do not do session.forget), and you are using file based sessions, then the > first request should block the second request until the first request > completes. In that case, you could only get a race condition if the view > request actually arrives at the server before the update request. > > Anthony > > > > > > > > On Friday, December 9, 2011 11:43:37 AM UTC-5, Cliff wrote: > > > The problem occurs in many-to-many relations, as in this example > > model: > > > db.define_table('owners', Field('name')) > > db.define_table('dogs', Field('name')) > > db.define_table(dog_owners', > > Field('owner_id', db.owners), > > Field('dog_id', 'db.dogs'), > > Field('date_owner_got_dog', 'date') #This is important! > > ) > > > When an owner record is edited, I would also put on the page a table > > of all dogs owned by the owner. With each dog there is a field for > > editing date_owner_got_dog. The change event for that field triggers > > a jQuery script. The script uses Ajax to tell the server to update > > the value. > > > When an owner record is viewed, I would put up the same table without > > capability to edit date_owner_got_dog. > > > Here is how to get the race condition: > > 1. Open an owner record for editing. > > 2. Update one of date_owner_got_dog fields. > > 3. Quickly click the 'view' link. > > 4. Observe old value in the updated field because the server fetched > > the dog record before it was updated. > > > The server can fetch the owner and dog records before finishing the > > update triggered by step 2. > > > I didn't see this in manual testing but Selenium found it right away. > > > I'm going to put up a 'please wait' flash message before kicking off > > the ajax call and change it to a 'done' message when the server has > > done its piece. > > > Anybody have any better ideas? > > > How does smartgrid handle this?
