nginx配置总是404，也找不到哪里有问题

 upstream cluster{
        server 127.0.0.1:3333;
        server 127.0.0.1:4444;
        server 127.0.0.1:5555;
        }
    server {
        listen       1111;
        server_name  localhost;

        #charset koi8-r;

        #access_log  logs/host.access.log  main;

        location / {
            #root   html;
            #index  index.html index.htm;
            proxy_pass http://cluster;
        }

这是nginx.conf中我修改的地方，原先nginx是好的，自从我加了这个upstream后就404了，但是upstream里的转发地址都在浏览器中测试过可以访问，那到底是啥问题啊，访问localhost:1111显示404，访问localhost：3333，localhost：4444，localhost：5555都是可以正常访问的

3333，4444，5555都是什么服务？
我本地没有这些端口的服务，但我如果稍微改一下你的配置，把这三个端口也起在nginx上，是可以访问的。
所以问题可能不在nginx配置，你想想有没有什么可能导致nginx无法连同3333,4444,5555这三个端口的服务？

确认一下nginx正常启动没有，看看服务状态和nginx的日志
贴一个最简单能跑的配置吧，你可以参考一下

user www-data;
worker_processes auto;
pid /run/nginx.pid;
include /etc/nginx/modules-enabled/*.conf;

events {
        worker_connections 768;
        # multi_accept on;
}

http {
    upstream cluster {
        server 127.0.0.1:3333;
        server 127.0.0.1:4444;
    }

    server {
        listen       1111;
        server_name  localhost;

        location / {
            proxy_pass http://cluster;
        }
    }
    
    server {
        listen       3333;
        server_name  localhost;

        return 200 '{"msg":"3333","code":0,"data":""}';
    }

    server {
        listen       4444;
        server_name  localhost;

        return 200 '{"msg":"4444","code":0,"data":""}';
    }
}

listen 直接接听80端口，直接访问localhost试试

http {
    include       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"';

    #access_log  logs/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    #keepalive_timeout  0;
    keepalive_timeout  65;

    #gzip  on;
    upstream cluster{
        server 127.0.0.1:3333;
        server 127.0.0.1:4444;
        server 127.0.0.1:5555;
        }
    server {
        listen       1111;
        server_name  localhost;

        #charset koi8-r;
        #access_log  logs/host.access.log  main;

        location / {
            #root   html;
            #index  index.html index.htm;
            proxy_pass http://cluster;
        }

        #error_page  404              /404.html;

        # redirect server error pages to the static page /50x.html
        #
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }

        # proxy the PHP scripts to Apache listening on 127.0.0.1:80
        #
        #location ~ \.php$ {
        #    proxy_pass   http://127.0.0.1;
        #}

        # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
        #
        #location ~ \.php$ {
        #    root           html;
        #    fastcgi_pass   127.0.0.1:9000;
        #    fastcgi_index  index.php;
        #    fastcgi_param  SCRIPT_FILENAME  /scripts$fastcgi_script_name;
        #    include        fastcgi_params;
        #}

        # deny access to .htaccess files, if Apache's document root
        # concurs with nginx's one
        #
        #location ~ /\.ht {
        #    deny  all;
        #}
    }


    # another virtual host using mix of IP-, name-, and port-based configuration
    #
    #server {
    #    listen       8000;
    #    listen       somename:8080;
    #    server_name  somename  alias  another.alias;

    #    location / {
    #        root   html;
    #        index  index.html index.htm;
    #    }
    #}


    # HTTPS server
    #
    #server {
    #    listen       443 ssl;
    #    server_name  localhost;

    #    ssl_certificate      cert.pem;
    #    ssl_certificate_key  cert.key;

    #    ssl_session_cache    shared:SSL:1m;
    #    ssl_session_timeout  5m;

    #    ssl_ciphers  HIGH:!aNULL:!MD5;
    #    ssl_prefer_server_ciphers  on;

    #    location / {
    #        root   html;
    #        index  index.html index.htm;
    #    }
    #}

}