"ERR_EMPTY_RESPONSE" on nginx server with nginx reverse proxy.

[alone8sniper]

Hello, I built a Nginx server that hosts WordPress. (Nginx version:1.23.2 PHP:7.4.33 MySQL:10.3.28 MariaDB)

WordPress hosts about 110 users (not at once) and cannot access to the web.

site worked perfectly until I update the Centos and after that i got Error **ERR_EMPTY_RESPONSE**

I know what might be the Problem just don't know where to look.

This is the issue that I found so far:

• When Nginx Cache Plugin purge the Cache (only When I made change to the [site) I Get "ERR_EMPTY_RESPONSE" Because the Cache folder stays empty after purge (this is the problem i found after I didn't do any changes in server config)

  However when I restart Nginx. files will be written to the Cache folder and site works again until next purge.

I put my configs down blow.

nginx.conf

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

# Load dynamic modules. See /usr/share/doc/nginx/README.dynamic.
include /usr/share/nginx/modules/*.conf;

events {
    worker_connections 1024;
}

http {
    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  /var/log/nginx/access.log  main;

    sendfile            on;
    tcp_nopush          on;
    tcp_nodelay         on;
    keepalive_timeout   65;
    types_hash_max_size 4096;
    client_max_body_size 128M;

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

    # Load modular configuration files from the /etc/nginx/conf.d directory.
    # See http://nginx.org/en/docs/ngx_core_module.html#include
    # for more information.
    include /etc/nginx/conf.d/*.conf;

    # enables GZIP compression
    gzip on; 

    # compression level (1-9)
    # 6 is a good compromise between CPU usage and file size
    gzip_comp_level 5;

    # minimum file size limit in bytes to avoid negative compression outcomes
    gzip_min_length 256;

    # compress data for clients connecting via proxies
    gzip_proxied any;

    # directs proxies to cache both the regular and GZIP versions of an asset
    gzip_vary on;

    # disables GZIP compression for ancient browsers that don't support it
    gzip_disable "msie6";

    # compress outputs labeled with the following file extensions or MIME-types
    # text/html MIME-type is enabled by default and need not be included
    gzip_types
    application/atom+xml
    application/geo+json
    application/javascript
    application/x-javascript
    application/json
    application/ld+json
    application/manifest+json
    application/rdf+xml
    application/rss+xml
    application/vnd.ms-fontobject
    application/wasm
    application/x-web-app-manifest+json
    application/xhtml+xml
    application/xml
    font/eot
    font/otf
    font/ttf
    image/bmp
    image/svg+xml
    text/cache-manifest
    text/calendar
    text/css
    text/javascript
    text/markdown
    text/plain
    text/xml
    text/vcard
    text/vnd.rim.location.xloc
    text/vtt
    text/x-component
    text/x-cross-domain-policy;

    server {
        listen       80;
        listen       [::]:80;
    server_tokens off;
    root         /usr/share/nginx/html;

        # Load configuration files for the default server block.
        include /etc/nginx/default.d/*.conf;

        error_page 404 /404.html;
        location = /404.html {
        }
        error_page 500 502 503 504 /50x.html;
        location = /50x.html {
        }

 }
}

site config file

`fastcgi_cache_path /var/cache/nginx levels=1:2 keys_zone=CACHZONE:100m inactive=60m max_size=5g;
fastcgi_cache_key "$scheme$request_method$host$request_uri";

server {
    listen 80; 
    server_name intranet.saipalogistics.ir;

    root /sites/interanet.saipalogistics.ir/public_html/;

    index index.html index.php;

    access_log /sites/interanet.saipalogistics.ir/logs/access.log;
    error_log /sites/interanet.saipalogistics.ir/logs/error.log;

   # BEGIN WebP Converter

    set $ext_avif ".avif";
    if ($http_accept !~* "image/avif") {
        set $ext_avif "";
    }

    set $ext_webp ".webp";
    if ($http_accept !~* "image/webp") {
        set $ext_webp "";
    }

    location ~ /wp-content/(?<path>.+)\.(?<ext>jpe?g|png|gif|webp)$ {
        add_header Vary Accept;
        add_header Cache-Control "private" always;
        expires 365d;
        try_files
        /wp-content/uploads-webpc/$path.$ext$ext_avif
        /wp-content/uploads-webpc/$path.$ext$ext_webp
        $uri =404;
    }
   # END WebP Converter

   # Don't allow pages to be rendered in an iframe on external domains.
    add_header X-Frame-Options "SAMEORIGIN";

   # MIME sniffing prevention
    add_header X-Content-Type-Options "nosniff";

   # Enable cross-site scripting filter in supported browsers.
    add_header X-Xss-Protection "1; mode=block";

   # Prevent access to hidden files
    location ~* /\.(?!well-known\/) {
        deny all;
    }

   # Prevent access to certain file extensions
    location ~\.(ini|log|conf)$ {
        deny all;
    }

   # Enable WordPress Permananent Links
    location / {
        try_files $uri $uri/ /index.php?$args;
    }

    set $skip_cache 0;

   # POST requests and urls with a query string should always go to PHP
    if ($request_method = POST) {
     set $skip_cache 1;
    }
    if ($query_string != "") {
        set $skip_cache 1;
    }

    # Don't cache uris containing the following segments
    if ($request_uri ~* "/wp-admin/|/xmlrpc.php|wp-.*.php|^/feed/*|/tag/.*/feed/*|index.php|/.*sitemap.*\.(xml|xsl)") {
        set $skip_cache 1;
    }

    # Don't use the cache for logged in users or recent commenters
    if ($http_cookie ~* "comment_author|wordpress_[a-f0-9]+|wp-postpass|wordpress_no_cache|wordpress_logged_in") {
      set $skip_cache 1;
    }

    #for plugin that perevents direct access to files

    #Put our rewrite rules here, i.e.
    rewrite wp-content/uploads(/_pda/.*\.\w+)$ "/index.php?pda_v3_pf=$1" last;
    rewrite private/([a-zA-Z0-9-_]+)$ "/index.php?pda_v3_pf=$1&pdav3_rexypo=ymerexy" last;

    location ~ \.php$ {
        fastcgi_cache_bypass $skip_cache;
        fastcgi_no_cache $skip_cache;

         include /etc/nginx/fastcgi_params;

        fastcgi_pass 127.0.0.1:9000;
        fastcgi_index index.php;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;

        fastcgi_cache_min_uses 3;
        fastcgi_cache_revalidate on;

        fastcgi_cache_background_update on;
        fastcgi_cache_lock on;

        fastcgi_cache CACHZONE;
        fastcgi_cache_valid 60m;

    add_header X-Cache $upstream_cache_status;
    }
}
`

[alone8sniper]

I solved the problem by disabling fastcgi cache and i turned the site cache on. its not that fast but it gets the job done. nginx new update has compability problem with fastcgi cache