reset.css doesn't load sometimes

[chadwhitacre]

@clone1018 saw this when we first started caching static assets. It's why I turned off static caching initially. Now static caching is back with #1245 and indeed we're seeing this again. :(

[chadwhitacre]

This is tricky to debug because by the time you open the network tab of the debug console and refresh, the bug goes away.

[clone1018]

I'm gonna assume that's because chrome forces a cache clear when dev tools is opened. No idea how to reproduce though.

[chadwhitacre]

I am definitely hitting this "often." I wrote a script to smash at reset.css a little bit:

https://gist.github.com/whit537/18046310e4c6db689741

Here's the result of running that for a while:

https://gist.github.com/whit537/91dafe2a6239a44a88c5

It looks like we're alternating between Content-Length: 867 and transfer-encoding: chunked. I don't really trust Cheroot's chunked encoding implementation, because of AspenWeb/pando.py#140. Perhaps the failures are when we send reset.css chunked? But why in that case does this only show up now that we've started caching? Somehow that has to play in. The script above doesn't sent any caching headers. Maybe it should send If-Modified-Since.

[chadwhitacre]

I looked at a sniffer:

• Fiddler - http://fiddler2.com/ - Win
• HTTPScoop - http://www.tuffcode.com/ - Mac
• Wireshark - http://www.wireshark.org/ - cross-platform

HTTPScoop works great but it can't read SSL. They recommend setting up a reverse proxy:

http://www.tuffcode.com/support.html#support7

[chadwhitacre]

Apparently Wireshark can be used to decrypt SSL:

http://wiki.wireshark.org/SSL

[clone1018]

I use Fiddler normally, it just installs a certificate proxy so you can decrypt and view.

[chadwhitacre]

Windows only. :(

[chadwhitacre]

@clone1018 Next time you see this can you grab a capture with Fiddler? I find that a simple refresh gives me the same missing-reset behavior.

[chadwhitacre]

We could probably fix this by moving reset.css to the CDN but it'd be better to get to the bottom of this if we can.

[chadwhitacre]

Eureka!

For 304 the content-type is text/html!

IRC

Found using http://www.charlesproxy.com/, per @greggles.

[chadwhitacre]

Here's where Tornado dealt with this:

https://groups.google.com/forum/#!topic/python-tornado/-P_enYKAwrY

Looks like it's safe to simply unset Content-Type for 304 (we're already not sending Content-Length).

My apologies to Cheroot. :-)