GUI charm does not handle browser cache properly

[Gary Poster]

jujucharms.com is deployed per
https://wiki.canonical.com/InformationInfrastructure/WebOps/CDO/JujuGui

A close approximation of this is to use PyJuju, deploy the GUI, expose it, and use the following configuration.

juju set jgui-app juju-gui-source=0.8.0 staging=false sandbox=true secure=false show-get-juju-button=true default-viewmode='fullscreen'

Last week, we deployed 0.8.0 on Monday, and then we deployed 0.8.1 on Friday morning.

I visited jujucharms.com several times and browsed a number of charms before Friday. After the Friday deployment, I saw a number of unpleasant visual artifacts. They generally seemed to have the characteristic that the CSS was out of sync with the HTML, JS and image files. Specifically, a number of images, like the header Juju image, were incorrect; and the tabs in the charm detail view had blue bars in them that were not at all what we intend.

My impression was that the JS had been changed--that is, I believe that the bugs we expected to have fixed were fixed--but the CSS was old.

A hard refresh corrected the issue. Others confirmed my experience.

Quick investigation revealed that we were using ETags, as I had expected, but they seemed to change on every request.

We need to resolve this issue ASAP in order to make deployments smooth. I have two possible avenues of exploration at the moment.

1) deploy 0.8.0. Visit it in a browser. deploy 0.8.1. Visit it in a browser. Can we dupe? If so, fix locally. Note that this fix should go in the ~juju-gui-charmers gui charm ideally without merging the ~juju-gui charm. the ~juju-gui charm is undergoing a lot of changes, and qaing all of them will be a much bigger job than simply qaing this change.

2) if the first idea does not allow us to dupe the problem, perhaps the problem is in the Apache that IS uses to front the GUI. The configuration does not look problematic to me, but maybe I am missing something.

See https://bazaar.launchpad.net/~prodstack-cdo/canonical-is-charm-configs/srv-prodstack-cdo-configs/files and in particular these files:

https://bazaar.launchpad.net/~prodstack-cdo/canonical-is-charm-configs/srv-prodstack-cdo-configs/view/head:/jgui.cfg
https://bazaar.launchpad.net/~prodstack-cdo/canonical-is-charm-configs/srv-prodstack-cdo-configs/view/head:/jgui-vhost-https.tmpl