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Reverse proxying a Tide application with Nginx 16 Feb 2021
nginx rust

Every now and again I’ll encounter a silly problem, fix it, forget about it, and then later run into the exact same problem again. Today’s example is a confusing error I encountered when reverse-proxying a Tide application with Nginx. In the Tide application, I was greeted with an ever-so-descriptive error:

ERROR tide::listener::tcp_listener > async-h1 error

I knew that I had hit this before, because I remember discussing with jbr the need for async-h1 to be a bit more verbose in its error messages. Try as I might however, I was not able to remember how to solve the problem Looking at the Nginx error logs, which weren’t that much more helpful:

2021/02/14 17:41:26 [error] 45774#101333: *53 upstream prematurely closed connection while reading response header from upstream, client: 192.168.1.1, server: dotdotvote.com, request: "GET / HTTP/1.1", upstream: "http://10.0.1.6:8000/", host: "dotdotvote.com"
2021/02/14 17:41:26 [error] 45774#101333: *53 upstream prematurely closed connection while reading response header from upstream, client: 192.168.1.1, server: dotdotvote.com, request: "GET /favicon.ico HTTP/1.1", upstream: "http://10.0.1.6:8000/favicon.ico", host: "dotdotvote.com", referrer: "https://dotdotvote.com/"

Eventually I stumbled into this closed GitHub issue which had the critical missing configuration snippet I was missing: proxy_http_version 1.1; It seems that the async-h1 crate cannot parse HTTP 1.0, or 2.0, or some version of HTTP other than 1.1. I’m honestly not really sure what format was being sent along to the Tide application.

My full location block below for reference:

  location / {
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host            $host;
    proxy_set_header X-Real-IP       $remote_addr;
    # https://github.com/http-rs/tide/issues/458#issuecomment-619243201
    proxy_http_version 1.1;

    proxy_pass http://dotdotvote;
  }

With that one weird trick, Nginx is happily reverse-proxying my little Tide application!