Hi, all!

I've stumbled upon a problem I can't find a solution for many hours in a row. I use nginx as a reverse proxy to python/spawning web-server. I've done it for 1000 times already and all worked fine before this day.

Nginx on a server I'm talking about serves 3 separate projects (hostnames) as a reverse proxy. I've added fourth. Three existing projects continued to work perfectly. But the new one sometimes works and sometimes returns 502.

The observation is: once it began to return 502 it would return it on every browser refresh. However if I'll throttle F5 fast, after 5-10 refreshes it starts to work properly. And vice versa: once it works like it should, slow refreshes keep it working, but if I'd throttle F5 again or if I'd wait for a minute or so nginx declines back to 502-state.

There is nothing recorded in neither log (access/error nginx/backend) if it is in 502-state. The deal is not in a backend. I've tried to set proxy_pass to the same value as in a sibling well-working project conf and the same story repeats. Problem exists for static resources as well. Is this conf cursed?

++++
user www-data;
worker_processes 1;

error_log /var/log/nginx/error.log debug;
pid /var/run/nginx.pid;

events {
worker_connections 1024;
# multi_accept on;
}

http {
include /etc/nginx/mime.types;

access_log /var/log/nginx/access.log;

sendfile on;
#tcp_nopush on;

#keepalive_timeout 0;
keepalive_timeout 65;
tcp_nodelay on;

gzip on;
gzip_disable "MSIE [1-6]\.(?!.*SV1)";

include /etc/nginx/conf.d/*.conf;
include /etc/nginx/sites-enabled/*;
}

#### /etc/nginx/sites-enabled/my-cursed-conf ####

server {
listen 80;
server_name hostname.iam.listening.to;

# Main location
location / {
proxy_pass http://127.0.0.1:8084;
proxy_redirect off;

proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}

location /static/ { alias /srv/some/path/static/; }
}


++++

I feel I've tried all combinations of buffer-tweaking and none of them helped. The system has > 700 Mb or RAM free and mostly idle CPU. Could someone guess what the hell is going on?