I created an endpoint on my flask which generates a spreadsheet from a database query (remote db) and then sends it as a download in the browser. Flask doesn't throw any errors. Uwsgi doesn't complain.
But when I check nginx's error.log I see a lot of
2014/12/10 05:06:24 [error] 14084#0: *239436 upstream prematurely closed connection while reading response header from upstream, client: 34.34.34.34, server: me.com, request: "GET /download/export.csv HTTP/1.1", upstream: "uwsgi://0.0.0.0:5002", host: "me.com", referrer: "https://me.com/download/export.csv"
I deploy the uwsgi like
uwsgi --socket 0.0.0.0:5002 --buffer-size=32768 --module server --callab app
my nginx config:
server {
listen 80;
merge_slashes off;
server_name me.com www.me.cpm;
location / { try_files $uri @app; }
location @app {
include uwsgi_params;
uwsgi_pass 0.0.0.0:5002;
uwsgi_buffer_size 32k;
uwsgi_buffers 8 32k;
uwsgi_busy_buffers_size 32k;
}
}
server {
listen 443;
merge_slashes off;
server_name me.com www.me.com;
location / { try_files $uri @app; }
location @app {
include uwsgi_params;
uwsgi_pass 0.0.0.0:5002;
uwsgi_buffer_size 32k;
uwsgi_buffers 8 32k;
uwsgi_busy_buffers_size 32k;
}
}
Is this an nginx or uwsgi issue, or both?
As mentioned by @mahdix, the error can be caused by Nginx sending a request with the uwsgi protocol while uwsgi is listening on that port for http packets.
When in the Nginx config you have something like:
upstream org_app {
server 10.0.9.79:9597;
}
location / {
include uwsgi_params;
uwsgi_pass org_app;
}
Nginx will use the uwsgi protocol. But if in uwsgi.ini
you have something like (or its equivalent in the command line):
http-socket=:9597
uwsgi will speak http, and the error mentioned in the question appears. See native HTTP support.
A possible fix is to have instead:
socket=:9597
In which case Nginx and uwsgi will communicate with each other using the uwsgi protocol over a TCP connection.
Side note: if Nginx and uwsgi are in the same node, a Unix socket will be faster than TCP. See using Unix sockets instead of ports.