user nginx;
worker_processes auto;
error_log /var/log/nginx/error.log warn;
pid /var/run/nginx.pid;

events {
    worker_connections 4096;
    use epoll;
    multi_accept on;
}

http {
    include /etc/nginx/mime.types;
    default_type application/octet-stream;

    log_format main '$remote_addr - $remote_user [$time_local] "$request" '
                    '$status $body_bytes_sent "$http_referer" '
                    '"$http_user_agent" "$http_x_forwarded_for" '
                    'rt=$request_time uct="$upstream_connect_time" '
                    'uht="$upstream_header_time" urt="$upstream_response_time" '
                    'correlation_id=$http_x_correlation_id';

    access_log /var/log/nginx/access.log main;
    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    keepalive_timeout 65;
    keepalive_requests 1000;
    types_hash_max_size 2048;

    gzip on;
    gzip_vary on;
    gzip_min_length 1024;
    gzip_proxied expired no-cache no-store private auth;
    gzip_types text/plain text/css text/xml text/javascript application/javascript application/xml+rss application/json;

    limit_req_zone $binary_remote_addr zone=api_limit:10m rate=100r/s;
    limit_req_zone $binary_remote_addr zone=health_limit:10m rate=10r/s;
    limit_conn_zone $binary_remote_addr zone=addr_limit:10m;

    upstream api_backend {
        least_conn;
        server api:8000 max_fails=3 fail_timeout=30s;
        keepalive 32;
    }

    ssl_protocols TLSv1.2 TLSv1.3;
    ssl_ciphers ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384;
    ssl_prefer_server_ciphers off;
    ssl_session_cache shared:SSL:10m;
    ssl_session_timeout 10m;

    server {
        listen 80;
        server_name _;

        location /health {
            limit_req zone=health_limit burst=20 nodelay;
            proxy_pass http://api_backend;
            proxy_http_version 1.1;
            proxy_set_header Connection "";
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            proxy_connect_timeout 5s;
            proxy_send_timeout 60s;
            proxy_read_timeout 60s;
        }

        location /metrics {
            allow 10.0.0.0/8;
            allow 172.16.0.0/12;
            allow 192.168.0.0/16;
            deny all;
            proxy_pass http://api_backend;
            proxy_http_version 1.1;
            proxy_set_header Host $host;
        }

        location / {
            limit_req zone=api_limit burst=200 nodelay;
            limit_conn addr_limit 50;
            proxy_pass http://api_backend;
            proxy_http_version 1.1;
            proxy_set_header Connection "";
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            proxy_set_header X-Correlation-ID $http_x_correlation_id;
            proxy_connect_timeout 10s;
            proxy_send_timeout 300s;
            proxy_read_timeout 300s;
            proxy_buffering off;
            proxy_cache off;
            proxy_redirect off;
            proxy_intercept_errors on;
            error_page 502 503 504 /maintenance.html;
        }

        location /maintenance.html {
            root /usr/share/nginx/html;
            internal;
        }

        location /ws {
            proxy_pass http://api_backend;
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection "upgrade";
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_read_timeout 86400;
        }
    }
}