Nginx as reverse proxy (111: Connection refused)

[max]

Hi,

I noticed strange error in my Nginx logs:

2018/10/29 09:36:57 [error] 1163#1163: *1057266 connect() failed (111:
Connection refused) while connecting to upstream, client: 127.0.0.1,
server: , request: "GET /database1/Object_VKGSJ-kxWEakirO1VDlA9w HTTP/1.1",
upstream: "http://[::1]:5984/database1/Object_VKGSJ-kxWEakirO1VDlA9w";,
host: "127.0.0.1:80"

I'm using nginx as reverse-proxy with this simple configuration (documented
at https://cwiki.apache.org/confluence/display/COUCHDB/Nginx+as+a+proxy):

#max body size (attachment upload) : disable check
client_max_body_size 0;

server {
    #simple proxy setup
    location / {
        proxy_pass http://localhost:5984;
        proxy_redirect off;
        proxy_set_header Host $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
    #continuous replication
    location ~ ^/(.*)/_changes {
        proxy_pass http://localhost:5984;
        proxy_redirect off;
        proxy_buffering off;
        proxy_set_header Host $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
}

I removed all other Nginx conf files in order to test it but this issue
keeps popping in my log. Please find enclosed my nginx.conf if needed
(which seems to be the default nginx conf).

Anyone know where it could comes from?

Thanks.