Request đến nginx bị 502

Hello mọi người, mình có config nginx cho server puma của rails app. Hiện đang có 1 vấn đề là request gửi đến bị 502 mặc dù mình check thì thấy nginx đã nhận request. Hi vọng mọi người giúp mình case này.

Log lỗi Nginx:

2022/05/01 14:16:37 [error] 918#918: *17 connect() to unix:/home/ubuntu/cupcake/shared/tmp/sockets/puma.sock failed (111: Connection refused) while connecting to upstream, client: 27.72.32.40, server: 13.229.114.123, request: "GET /api/v1/hello HTTP/1.1", upstream: "http://unix:/home/ubuntu/cupcake/shared/tmp/sockets/puma.sock:/api/v1/hello", host: "13.250.11.121" 2022/05/01 14:16:37 [error] 918#918: *17 connect() to unix:/home/ubuntu/cupcake/shared/tmp/sockets/puma.sock failed (111: Connection refused) while connecting to upstream, client: 27.72.32.40, server: 13.229.114.123, request: "GET /favicon.ico HTTP/1.1", upstream: "http://unix:/home/ubuntu/cupcake/shared/tmp/sockets/puma.sock:/favicon.ico", host: "13.250.11.121", referrer: "http://13.250.11.121/api/v1/hello"

Nginx config:

upstream app {
    server unix:/home/ubuntu/cupcake/shared/tmp/sockets/puma.sock fail_timeout=0;
}
server {
        listen 80 default_server;
        listen [::]:80 default_server;
        
        server_name 13.229.114.123;
        
        location ^~ /assets/ {
                gzip_static on;
                expires max;
                add_header Cache-Control public;
        }

        try_files $uri $uri/ @app;

        location @app {
                proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
                proxy_set_header Host $http_host;
                proxy_redirect off;
                proxy_pass http://app;                
        }

        #error_page 500 502 503 504 /500.html;
        client_max_body_size 10M;
        keepalive_timeout 20;
}