Stale analysis keys lead to infinite reload loop

[jhpedemonte]

After upgrading server, Zazl kept returning the same analysis keys for code which had changed, resulting in the browser using cached pages and sending invalid "exclude" key to Zazl. Zazl then returned "location.reload(true)", repeating the process and leading to infinite reload loop.

Here's a breakdown of the requests:

---

old app

1. host/_javascript?modules=ModuleA&...
   • size: 676767
   • analysis key: fb0995befcb079aa3d9e9e000fc54bc0
2. host/_javascript?modules=ModuleB&...&exclude=fb0995befcb079aa3d9e9e000fc54bc0
   • size: 12039
   • analysis key: e6c99d5c231848e11a40cfb98563c057

login to web app

1. host/_javascript?modules=ModuleA&... (cache)
2. host/_javascript?modules=ModuleB&...&exclude=fb0995befcb079aa3d9e9e000fc54bc0 (cache)
3. host/_javascript?modules=ModuleC&...&exclude=fb0995befcb079aa3d9e9e000fc54bc0,e6c99d5c231848e11a40cfb98563c057
   • size: 553734
   • analysis key: 30958c95b80d4286189baade86e4954

---

updated app

Running new web app on browser with cached files. Since server was restarted, Zazl has an empty server-side cache.

1. host/_javascript?modules=ModuleA&...
   • size: _678045_
   • analysis key: fb0995befcb079aa3d9e9e000fc54bc0
2. host/_javascript?modules=ModuleB&...&exclude=fb0995befcb079aa3d9e9e000fc54bc0 (cache)
3. host/_javascript?modules=ModuleC&...&exclude=fb0995befcb079aa3d9e9e000fc54bc0,e6c99d5c231848e11a40cfb98563c057
   • _content: "location.reload(true);"_

---

With the updated app, the first module returned a different artifact (due to changes in the code) but with the same analysis key. The URL for the 2nd module, then, contained the same exclude string and matched the previously cached URL, so the cached content was returned.

Then, when loading the 3rd module, Zazl failed because the key e6c99d5c231848e11a40cfb98563c057 was not known to it. The failure fallback in this case is for Zazl to try to force the browser to reload the page. However, this just results in the exact same sequence of events, leading to an infinite loop.

[rbackhouse]

Javier,

I'm having trouble figuring out the exact scenario you have, particularly around the changes you are making to the module(s) between server restarts. Can you breakdown the module interaction better or if you have a simple test case that would be even better.

[rbackhouse]

I'm guessing the location.reload(true) is not working in your particular browser. Can you provide the details of what it is

[jhpedemonte]

Saw this happen on latest versions of Chrome and Firefox (and Safari, I think). So not browser dependent.

I don't have a simple test case. In fact, we've been running with Zazl between version updates just fine. It seems like the latest JS/HTML updates somehow exposed a bug in Zazl that we caught this particular time.

I can do some debugging on my end of things, if you point me in the right direction.

[rbackhouse]

I can recreate now. The scenario is making a modification to a module while the server is stopped that affects its dependencies. If a another module is lazy loaded via another js request that contains an exclude of this one that has been modified it will fail to find it and thus cause the loop. I'll work on a fix.

[rbackhouse]

I have a fix. I've put it into the optimizer-release repo. If you can try it when you get a chance that would be great