nginx connection refused - tcp connection error - docker

Question

I have following nginx config:
# https://github.com/KyleAMathews/docker-nginx/blob/master/nginx.conf
# https://linode.com/docs/web-servers/nginx/configure-nginx-for-optimized-performance/
# https://docs.gunicorn.org/en/stable/deploy.html
worker_processes 1;
events {
worker_connections 2000; # increase if you have lots of clients
accept_mutex off; # set to 'on' if nginx worker_processes > 1
use epoll; # Enable epoll for Linux 2.6+
# 'use kqueue;' to enable for FreeBSD, OSX
}
http {
include mime.types;
# fallback in case we can't determine a type
default_type application/octet-stream;
sendfile on;
upstream app_server {
# ip_hash; # For load-balancing
#
# fail_timeout=0 means we always retry an upstream even if it failed
# to return a good HTTP response
server unix:/nginx/gunicorn.socket fail_timeout=0;
# for a TCP configuration
# server web:8080 fail_timeout=0;
keepalive 32;
}
server {
access_log off;
listen 8080 deferred;
charset utf-8;
keepalive_timeout 75s;
# https://thoughts.t37.net/nginx-optimization-understanding-sendfile-tcp-nodelay-and-tcp-nopush-c55cdd276765
# tcp_nopush on;
# tcp_nodelay on;
gzip on;
gzip_min_length 1000;
gzip_comp_level 2;
# text/html is always included by default
gzip_types text/plain text/css application/json application/javascript application/x-javascript text/javascript text/xml application/xml application/rss+xml application/atom+xml application/rdf+xml;
gzip_disable "MSIE [1-6]\.";
location /static {
alias /nginx/staticfiles;
expires 365d;
}
location / {
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header Host $host;
# we don't want nginx trying to do something clever with
# redirects, we set the Host: header above already.
proxy_redirect off;
proxy_pass http://app_server/;
proxy_set_header X-Forwarded-Host $server_name;
proxy_set_header X-Real-IP $remote_addr;
add_header Front-End-Https on;
}
}
}
but when i try to hit http://localhost:8000/cgw/v1/chains/43214913/about/master-copies
I get this error:
{
"code": 1337,
"message": "reqwest::Error { kind: Request, url: Url { scheme: \"http\", host: Some(Ipv4(127.0.0.1)), port: Some(8080), path: \"/api/v1/about/master-copies/\", query: None, fragment: None }, source: hyper::Error(Connect, ConnectError(\"tcp connect error\", Os { code: 111, kind: ConnectionRefused, message: \"Connection refused\" })) }"
}
any idea what i'm doing wrong in nginx config ( totally newbie with nginx sorry about that )