error 503 after I added varnish to magento

I’m having a an issue after I added varnish to magento 2.

website is not working now it give me this error

Error 503 Backend fetch failed Backend fetch failed

Guru Meditation: XID: 261

Varnish cache server

this is my confs files

file : /etc/default/varnish

# Configuration file for varnish
#
# /etc/init.d/varnish expects the variables $DAEMON_OPTS, $NFILES and $MEMLOCK
# to be set from this shell script fragment.
#
# Note: If systemd is installed, this file is obsolete and ignored.  Please see 
# /usr/share/doc/varnish/examples/varnish.systemd-drop-in.conf

# Should we start varnishd at boot?  Set to "no" to disable.
START=yes

# Maximum number of open files (for ulimit -n)
NFILES=131072

# Maximum locked memory size (for ulimit -l)
# Used for locking the shared memory log in memory.  If you increase log size,
# you need to increase this number as well
MEMLOCK=82000

# Default varnish instance name is the local nodename.  Can be overridden with
# the -n switch, to have more instances on a single server.
# You may need to uncomment this variable for alternatives 1 and 3 below.
# INSTANCE=$(uname -n)

# This file contains 4 alternatives, please use only one.

## Alternative 1, Minimal configuration, no VCL
#
# Listen on port 6081, administration on localhost:6082, and forward to
# content server on localhost:8080.  Use a 1GB fixed-size cache file.
#
# This example uses the INSTANCE variable above, which you need to uncomment.
#
# DAEMON_OPTS="-a :6081 
#              -T localhost:6082 
#        -b localhost:8080 
#        -u varnish -g varnish 
#            -S /etc/varnish/secret 
#        -s file,/var/lib/varnish/$INSTANCE/varnish_storage.bin,1G"


## Alternative 2, Configuration with VCL
#
# Listen on port 6081, administration on localhost:6082, and forward to
# one content server selected by the vcl file, based on the request.
#
DAEMON_OPTS="-a :6081 
             -T localhost:6082 
             -f /etc/varnish/default.vcl 
             -S /etc/varnish/secret 
             -s malloc,256m"
             -p http_resp_hdr_len=70000 
             -p http_resp_size=100000 


## Alternative 3, Advanced configuration
#
# This example uses the INSTANCE variable above, which you need to uncomment.
#
# See varnishd(1) for more information.
#
# # Main configuration file. You probably want to change it :)
# VARNISH_VCL_CONF=/etc/varnish/default.vcl
#
# # Default address and port to bind to
# # Blank address means all IPv4 and IPv6 interfaces, otherwise specify
# # a host name, an IPv4 dotted quad, or an IPv6 address in brackets.
# VARNISH_LISTEN_ADDRESS=
#
# # Telnet admin interface listen address and port
# VARNISH_ADMIN_LISTEN_ADDRESS=127.0.0.1
# VARNISH_ADMIN_LISTEN_PORT=6082
#
# # Cache file location
# VARNISH_STORAGE_FILE=/var/lib/varnish/$INSTANCE/varnish_storage.bin
#
# # Cache file size: in bytes, optionally using k / M / G / T suffix,
# # or in percentage of available disk space using the % suffix.
# VARNISH_STORAGE_SIZE=1G
#
# # File containing administration secret
# VARNISH_SECRET_FILE=/etc/varnish/secret
# 
# # Backend storage specification
# VARNISH_STORAGE="file,${VARNISH_STORAGE_FILE},${VARNISH_STORAGE_SIZE}"
#
# # Default TTL used when the backend does not specify one
# VARNISH_TTL=120
#
# # DAEMON_OPTS is used by the init script.  If you add or remove options, make
# # sure you update this section, too.
# DAEMON_OPTS="-a ${VARNISH_LISTEN_ADDRESS}:${VARNISH_LISTEN_PORT} 
#              -f ${VARNISH_VCL_CONF} 
#              -T ${VARNISH_ADMIN_LISTEN_ADDRESS}:${VARNISH_ADMIN_LISTEN_PORT} 
#              -t ${VARNISH_TTL} 
#          -S ${VARNISH_SECRET_FILE} 
#              -s ${VARNISH_STORAGE}"
#


## Alternative 4, Do It Yourself
#
# DAEMON_OPTS=""

file : /etc/nginx/sites-enabled/mydomian.conf

upstream mydomian_backend {
 server   unix:/var/run/php/php8.1-fpm-mydomian.sock;
}

server {
    server_name mydomian.com www.mydomian.com;
    listen 127.0.0.1:8080;
    set $MAGE_ROOT /var/www/mydomian-upgrade;
    set $MAGE_MODE production;
    include /etc/nginx/magento/mydomian.conf;
   
    location / {
    try_files $uri $uri/ /index.php$is_args$args;
    }

}
server {
   listen 80;
   server_name mydomian www.mydomian;

   return 301 https://mydomian.com$request_uri;
}
server {
   listen 443 ssl http2;
   server_name mydomian www.mydomian;

    ssl on;

    # ssl_certificate /etc/nginx/pems/public_cert.pem;
    # ssl_certificate_key /etc/nginx/pems/privat_key.pem;
    ssl_certificate /etc/letsencrypt/live/mydomian/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/mydomian/privkey.pem; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
   

   access_log /var/log/nginx/mydomian-access.log;
   error_log /var/log/nginx/mydomian-error.log;



location / {
        proxy_pass http://127.0.0.1:6081;
        proxy_set_header Host $http_host;
        proxy_set_header X-Forwarded-Host $http_host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Ssl-Offloaded "1";
        proxy_set_header X-Forwarded-Proto https;
        proxy_set_header X-Forwarded-Port 443;
        proxy_http_version 1.1;
    proxy_set_header Accept-Encoding "";
    proxy_set_header GEOIP_COUNTRY_CODE $geoip_country_code;
    proxy_set_header Connection "";

    proxy_buffer_size          128k;
    proxy_buffers              4 256k;
    proxy_busy_buffers_size    256k;


    proxy_read_timeout 300s;
    proxy_connect_timeout 75s;

}
}

file : /etc/varnish/default.vcl

# VCL version 5.0 is not supported so it should be 4.0 even though actually used Varnish version is 6
vcl 4.0;

import std;
# The minimal Varnish version is 6.0
# For SSL offloading, pass the following header in your proxy server or load balancer: 'X-Forwarded-Proto: https'

backend default {
    .host = "127.0.0.1";
    .port = "8080";
    .first_byte_timeout = 600s;
    .probe = {
        .url = "/pub/health_check.php";
        .timeout = 2s;
        .interval = 5s;
        .window = 10;
        .threshold = 5;
   }
}
acl purge {
    "127.0.0.1";
}

sub vcl_recv {
    if (req.restarts > 0) {
        set req.hash_always_miss = true;
    }

    if (req.method == "PURGE") {
        if (client.ip !~ purge) {
            return (synth(405, "Method not allowed"));
        }
        # To use the X-Pool header for purging varnish during automated deployments, make sure the X-Pool header
        # has been added to the response in your backend server config. This is used, for example, by the
        # capistrano-magento2 gem for purging old content from varnish during it's deploy routine.
        if (!req.http.X-Magento-Tags-Pattern && !req.http.X-Pool) {
            return (synth(400, "X-Magento-Tags-Pattern or X-Pool header required"));
        }
        if (req.http.X-Magento-Tags-Pattern) {
          ban("obj.http.X-Magento-Tags ~ " + req.http.X-Magento-Tags-Pattern);
        }
        if (req.http.X-Pool) {
          ban("obj.http.X-Pool ~ " + req.http.X-Pool);
        }
        return (synth(200, "Purged"));
    }

    if (req.method != "GET" &&
        req.method != "HEAD" &&
        req.method != "PUT" &&
        req.method != "POST" &&
        req.method != "TRACE" &&
        req.method != "OPTIONS" &&
        req.method != "DELETE") {
          /* Non-RFC2616 or CONNECT which is weird. */
          return (pipe);
    }

    # We only deal with GET and HEAD by default
    if (req.method != "GET" && req.method != "HEAD") {
        return (pass);
    }

    # Bypass customer, shopping cart, checkout
    if (req.url ~ "/customer" || req.url ~ "/checkout") {
        return (pass);
    }

    # Bypass health check requests
    if (req.url ~ "/pub/health_check.php") {
        return (pass);
    }

    # Set initial grace period usage status
    set req.http.grace = "none";

    # normalize url in case of leading HTTP scheme and domain
    set req.url = regsub(req.url, "^http[s]?://", "");

    # collect all cookies
    std.collect(req.http.Cookie);

    # Compression filter. See https://www.varnish-cache.org/trac/wiki/FAQ/Compression
    if (req.http.Accept-Encoding) {
        if (req.url ~ ".(jpg|jpeg|png|gif|gz|tgz|bz2|tbz|mp3|ogg|swf|flv)$") {
            # No point in compressing these
            unset req.http.Accept-Encoding;
        } elsif (req.http.Accept-Encoding ~ "gzip") {
            set req.http.Accept-Encoding = "gzip";
        } elsif (req.http.Accept-Encoding ~ "deflate" && req.http.user-agent !~ "MSIE") {
            set req.http.Accept-Encoding = "deflate";
        } else {
            # unknown algorithm
            unset req.http.Accept-Encoding;
        }
    }

    # Remove all marketing get parameters to minimize the cache objects
    if (req.url ~ "(?|&)(gclid|cx|ie|cof|siteurl|zanpid|origin|fbclid|mc_[a-z]+|utm_[a-z]+|_bta_[a-z]+)=") {
        set req.url = regsuball(req.url, "(gclid|cx|ie|cof|siteurl|zanpid|origin|fbclid|mc_[a-z]+|utm_[a-z]+|_bta_[a-z]+)=[-_A-z0-9+()%.]+&?", "");
        set req.url = regsub(req.url, "[?|&]+$", "");
    }

    # Static files caching
    if (req.url ~ "^/(pub/)?(media|static)/") {
        # Static files should not be cached by default
        return (pass);

        # But if you use a few locales and don't use CDN you can enable caching static files by commenting previous line (#return (pass);) and uncommenting next 3 lines
        #unset req.http.Https;
        #unset req.http.X-Forwarded-Proto;
        #unset req.http.Cookie;
    }

    # Bypass authenticated GraphQL requests without a X-Magento-Cache-Id
    if (req.url ~ "/graphql" && !req.http.X-Magento-Cache-Id && req.http.Authorization ~ "^Bearer") {
        return (pass);
    }

    return (hash);
}

sub vcl_hash {
    if ((req.url !~ "/graphql" || !req.http.X-Magento-Cache-Id) && req.http.cookie ~ "X-Magento-Vary=") {
        hash_data(regsub(req.http.cookie, "^.*?X-Magento-Vary=([^;]+);*.*$", "1"));
    }

    # To make sure http users don't see ssl warning
    if (req.http.X-Forwarded-Proto) {
        hash_data(req.http.X-Forwarded-Proto);
    }
    

    if (req.url ~ "/graphql") {
        call process_graphql_headers;
    }
}

sub process_graphql_headers {
    if (req.http.X-Magento-Cache-Id) {
        hash_data(req.http.X-Magento-Cache-Id);

        # When the frontend stops sending the auth token, make sure users stop getting results cached for logged-in users
        if (req.http.Authorization ~ "^Bearer") {
            hash_data("Authorized");
        }
    }

    if (req.http.Store) {
        hash_data(req.http.Store);
    }

    if (req.http.Content-Currency) {
        hash_data(req.http.Content-Currency);
    }
}

sub vcl_backend_response {

    set beresp.grace = 3d;

    if (beresp.http.content-type ~ "text") {
        set beresp.do_esi = true;
    }

    if (bereq.url ~ ".js$" || beresp.http.content-type ~ "text") {
        set beresp.do_gzip = true;
    }

    if (beresp.http.X-Magento-Debug) {
        set beresp.http.X-Magento-Cache-Control = beresp.http.Cache-Control;
    }

    # cache only successfully responses and 404s that are not marked as private
    if (beresp.status != 200 &&
            beresp.status != 404 &&
            beresp.http.Cache-Control ~ "private") {
        set beresp.uncacheable = true;
        set beresp.ttl = 86400s;
        return (deliver);
    }

    # validate if we need to cache it and prevent from setting cookie
    if (beresp.ttl > 0s && (bereq.method == "GET" || bereq.method == "HEAD")) {
        unset beresp.http.set-cookie;
    }

   # If page is not cacheable then bypass varnish for 2 minutes as Hit-For-Pass
   if (beresp.ttl <= 0s ||
       beresp.http.Surrogate-control ~ "no-store" ||
       (!beresp.http.Surrogate-Control &&
       beresp.http.Cache-Control ~ "no-cache|no-store") ||
       beresp.http.Vary == "*") {
        # Mark as Hit-For-Pass for the next 2 minutes
        set beresp.ttl = 120s;
        set beresp.uncacheable = true;
   }

   # If the cache key in the Magento response doesn't match the one that was sent in the request, don't cache under the request's key
   if (bereq.url ~ "/graphql" && bereq.http.X-Magento-Cache-Id && bereq.http.X-Magento-Cache-Id != beresp.http.X-Magento-Cache-Id) {
      set beresp.ttl = 0s;
      set beresp.uncacheable = true;
   }

    return (deliver);
}

sub vcl_deliver {
    if (resp.http.x-varnish ~ " ") {
        set resp.http.X-Magento-Cache-Debug = "HIT";
        set resp.http.Grace = req.http.grace;
    } else {
        set resp.http.X-Magento-Cache-Debug = "MISS";
    }

    # Not letting browser to cache non-static files.
    if (resp.http.Cache-Control !~ "private" && req.url !~ "^/(pub/)?(media|static)/") {
        set resp.http.Pragma = "no-cache";
        set resp.http.Expires = "-1";
        set resp.http.Cache-Control = "no-store, no-cache, must-revalidate, max-age=0";
    }

    if (!resp.http.X-Magento-Debug) {
        unset resp.http.Age;
    }
    unset resp.http.X-Magento-Debug;
    unset resp.http.X-Magento-Tags;
    unset resp.http.X-Powered-By;
    unset resp.http.Server;
    unset resp.http.X-Varnish;
    unset resp.http.Via;
    unset resp.http.Link;
}

sub vcl_hit {
    if (obj.ttl >= 0s) {
        # Hit within TTL period
        return (deliver);
    }
    if (std.healthy(req.backend_hint)) {
        if (obj.ttl + 300s > 0s) {
            # Hit after TTL expiration, but within grace period
            set req.http.grace = "normal (healthy server)";
            return (deliver);
        } else {
            # Hit after TTL and grace expiration
            return (restart);
        }
    } else {
        # server is not healthy, retrieve from cache
        set req.http.grace = "unlimited (unhealthy server)";
        return (deliver);
    }
}

file : /etc/systemd/system/varnish.service

[Unit]
Description=Varnish HTTP accelerator
Documentation=https://www.varnish-cache.org/docs/6.1/ man:varnishd

[Service]
Type=simple
LimitNOFILE=131072
LimitMEMLOCK=82000
ExecStart=/usr/sbin/varnishd -j unix,user=vcache -F -a :6081 -T localhost:6082 -f /etc/varnish/default.vcl -S /etc/varnish/secret -s malloc,256m
ExecReload=/usr/share/varnish/varnishreload
ProtectSystem=full
ProtectHome=true
PrivateTmp=true
PrivateDevices=true

[Install]
WantedBy=multi-user.target

I am looking how to fix this for 2 days now and most people just copy past the same thing from each other they all talking about the default.vcl file and try to remove “/pub” from this line “url = “/pub/health_check.php”;” I tried that but still not working.

can someone please look into my config files and tell me what is wrong with it.