On Wed, 18 Aug 2010 11:49:01 -0400, Curtis Hovey <[email protected]> wrote: > I have seen menus show up in oopses, I have seen engineers on IRC > surprised to see a query cause by a menu, but I have not seen an outline > of the menu problem. I think I can summarise the problem and provide > some guidelines about how we want menus to behave.
I think I'm lacking some context here, like what a menu is in the Launchpad context. Let me guess a little: a Menu is a collection of Links. There is one menu per instance of a LaunchpadView subclass. Links can be disabled or enabled. The Menu itself can be rendered, and renders each link one after the other, but we don't ever do this these days. > * I recently saw Martin Pitt could not see his +participation page > because of a timeout reached querying all his uploads. This is > because a link in the person overview menu is only enabled if > the person has uploads. The page does *not* use this link. So when the Menu is constructed, all Links in the menu are checked to see if they're enabled, even if they are never rendered? That seems like a pretty clear bug. > * Many templates define an instance of a menu at the start of the > markup to avoid the cost of duplicate instances, but we know > that the menu will be reinstantiated in a portlet. Creating > reusable markup often means death by menu queries Because the menu instance is associated with the view instance, rendering a portlet, even if it's a view on the same view class, will create the menu over again? > * Even though a link is defined in the overview menu (mainsite), > and a link's view defines its facet, the menu makes the link URL > to the current host eg. we had a 404 on code.lp.net for > +downloads and we could not use the menu to get the correct > link. Doesn't the link just use morally the same code as fmt:link? If not, it should? If it does, this bug should be fixed there? facet is an obsolete idea of course. s/facet/layer/g. > I think the root problem is that our menu implementation is 5 years old. > I received a minor update 2 years ago, but they are not engineered to be > used as we use them. > > * The menus assume links are used one on a page and that the menu > is used to render a list. Only the NavigationMenu does this now. > All menus iterate over all link names in a list setup all > links. Yeah, that's stupid. > * The menus assume that they are instantiated once per request > because of the previous point. This can never have been really true. > * Most uses for a menu are like a dictionary/bag where we get the > links as needed. This often means we are doing multiple > instantiations. > * Users demand that we not show links if there is no information > on the destination page, so we are doing more writing more > "enabled" rules. > * We want to use menus to get list instead of crafting links in > the template because we want to define a link once, and test it > once. Links are certainly convenient. > Guidelines for expected behaviour > > * We build menus once per request. Getting an object's menu is > free once it is instantiated. So this means menus are associated with context objects, not with view instances? (Maybe this is already true). > * We know that at the point we start rendering, that no link can > change--once a link object is setup, we must never do it > again. Right. In fact, getting the object's menu should be trivial -- it's only getting a link out of that menu that should be non-trivial, and we should cache the link in the request once its accessed. > * Links are setup when they are accessed. There is no cost for a > link that is not used. I think this is what I just said :-) > I think we also need to ask if we really need both context menu and a > facet menu. The facet menu implies we can have separate application > concerns, but in practice, I think pages/templates cannot do that to > provide good user experience. The context menu implies there is one > massive definition of all an object's links, but they are rarely all > used. I removed a lot of links from context menus after I added a test > of the links and discovered that there is not ZCML definition of the > view any more. OK, I think this means some of my guesses above are wrong. I hope this mail still has value :-) What on earth is a facet menu? Cheers, mwh _______________________________________________ Mailing list: https://launchpad.net/~launchpad-dev Post to : [email protected] Unsubscribe : https://launchpad.net/~launchpad-dev More help : https://help.launchpad.net/ListHelp
