Multiple tabs lead to errors and duplications

[stianr]

A fellow lecturer found this, and I've just replicated it setting up my own quiz. Seems to be if I am logged in to Quodl across two or more tabs, when setting up a quiz, either the quiz fails to save (I think it was a 400 error), or multiple instances of the quiz are created - see below for two spurious versions of the Week 4 quiz:

[stianr]

Just to add to this, another user has found themselves stuck on a loading page, which meant they had to delete cookies in order to access the app:

They also report a blank screen on Internet Explorer.

[stianr]

Adding this to LTI milestone (though it's not LTI related), though will leave it to your judgement as to whether you think it's worth starting to look at this in the remaining time. It's high priority, so if there's time to review the current way in which sessions are handled and any potential issues that may lead to problems like the one above, that would be great. But understand if there's not time to do this in this sprint.

[iteles]

@stianr We did actually take a look at this but couldn't replicate it on a Mac.

@Danwhy Correct me if I'm wrong but we haven't tested this on IE yet?

[stianr]

One more data point: Trying to load the app page https://app.quodl.co.uk gave a blank screen which wouldn't disappear with a refresh. Found this with both Win10 Firefox and Android Firefox. Fully closing and reopening the browser brought it back.

On the Win10 system the login page appeared, but it was impossible to log in - login credentials were clearly checked - an incorrect user/pass combination gave the correct error message, but if a legitimate login was attempted, it redirected to the login page again.

After deleting cookies and logging in (successfully), clicking on several of the modules (e.g., MULT), gave 404 errors. A few minutes later, they came back.