What does ERR_SPDY_PROTOCOL_ERROR mean in nginx?

Question

I and a few of my colleagues got the net::ERR_SPDY_PROTOCOL_ERROR error.

We use ngnix version 1.8.0. The error is not stable (hard to replicate), and t

Answer 1

TL;DR: if you are caching assets, then check the drive space on your nginx server.

Our Scenario

I'm not sure where to post my answer to this since it might be an edge case when getting the ERR_SPDY_PROTOCOL_ERROR in Chrome (and the equivalent "failure to load resource" error in Firefox). But this post helped me narrow down the culprit. It wasn't headers, gzip, redirects, or adblock/ublock.

We have 2 web applications deployed from the machine, and both were running perfectly fine. Recently, we deployed one of the applications with changes to cached assets. Once the deploy completed, we immediately got the ERR_SPDY_PROTOCOL_ERROR from Chrome. Interestingly enough, it was receiving an HTTP 200 and if you navigated to the asset directly, Chrome would render the asset. However, loading the asset on a page would cause it to fail.

Interstingly enough, the other web application was perfectly fine. Investigating the net internals on Chrome, we discovered the server was closing the connection. After several hours, we determined that it was because our nginx server had run out drive space. I don't know why that would cause the assets to load properly when you navigate to them directly, but fail when you load a page, but clearing out space instantly fixed the problem.