Even though there are many thousands of components, I don't think it should take more than a couple of seconds. I timed it at 15 seconds and I think sometimes it takes longer. Fedora/Fedora is a good one to test since it has the most components. My guess is there is some code in here [1] that is slower than is should be. [1] https://bugzilla.redhat.com/js/productform.js
It also tends to lock up Firefox completely, and trigger it's warning to kill errant scripts.
It takes a minimum of 20 seconds on my system (with a Core i7) to load the Fedora component list and Firefox is completely unusable during that time. I've also had an warning pop-up saying my extensions (e.g., It's All Text) are taking too long to run while waiting for the component list. Please bring back the "Refresh Components" button from Bugzilla 3.x
Preferably the script would just be better at not locking up the browser while it works. A busy indicator would also be nice.
*** Bug 823402 has been marked as a duplicate of this bug. ***
*** Bug 826878 has been marked as a duplicate of this bug. ***
*** Bug 826839 has been marked as a duplicate of this bug. ***
*** Bug 826669 has been marked as a duplicate of this bug. ***
*** Bug 834155 has been marked as a duplicate of this bug. ***
I've marked a lot of bugs as a duplicate of this one because they will have a common fix. Because RHBZ have some products that have thousand of components I feel we're going to need to go back to the old style of 'click here to reload the components' when a product or classification is selected. For those reporting the 'list of X doesn't show valid value' bugs, this will be fixed a side effect on introducing this change. For browers that have Javascript enabled, the components select box will be changed with a link to reload the component list (which does a page reload). For non Javascript browsers, there will be a permanent button that does the same thing.
I still think that js should be able to finish whatever it's doing in a sensible amount of time.
*** Bug 847738 has been marked as a duplicate of this bug. ***
*** Bug 847628 has been marked as a duplicate of this bug. ***
*** Bug 844887 has been marked as a duplicate of this bug. ***
*** Bug 844890 has been marked as a duplicate of this bug. ***
*** Bug 842266 has been marked as a duplicate of this bug. ***
*** Bug 842004 has been marked as a duplicate of this bug. ***
*** Bug 828646 has been marked as a duplicate of this bug. ***
*** Bug 823341 has been marked as a duplicate of this bug. ***
*** Bug 823519 has been marked as a duplicate of this bug. ***
*** Bug 829951 has been marked as a duplicate of this bug. ***
*** Bug 831696 has been marked as a duplicate of this bug. ***
It went back to the old style of 'click here to reload the components' when a product or classification is selected, we can click the refresh button. Verified.