static files are sometimes not delivered via fastly

[tripodsan]

see https://github.com/adobe/developer.adobe.com/issues/133

I think the main problem is, that the 404 from the html action is cached, and then the vlc_hit doesn't restart the request for invoking the static action.

I believe that the improvements of adobe/helix-publish#7 would address this issue. in the mean time, a quick workaround is to ensure the 404 is not cacheable:

sub vlc_fetch {
...
  } elseif ((beresp.status == 404 || beresp.status == 204) && !req.http.X-Disable-Static) {
    # That was a miss. Let's try to restart.
    set beresp.http.X-Status = beresp.status + "-Restart " + req.restarts;
    set beresp.status = 404;
    # ensure that 404 from the backends are not cached. otherwise the a potential vlc_hit will not re-fetch the static files.
    set beresp.cacheable = false;    
...