I have an Apache2 server with PHP-FPM (working on Ubuntu 20) and often I getting empty $_POST data from the clients, but Content-Length in header is > 0. I have not a small traffic (~20 req/sec (max) on PHP-FPM) and from some clients I receive an empty POST request (it can be 1 in hour or sometimes > 10). Here is the example header that I receiving:
[Content-Length] => 454 [Content-Type] => application/x-www-form-urlencoded [User-Agent] => BestHTTP/2 v2.3.1 [Te] => identity [Keep-Alive] => timeout=21 [Connection] => Keep-Alive, TE [Accept-Encoding] => gzip, identity [Host] => example.com
And some info from $_SERVER:
[USER] => www-data [HOME] => /var/www [SCRIPT_NAME] => some/path/set_score.php [REQUEST_URI] => some/path/set_score.php [REQUEST_METHOD] => POST [SERVER_PROTOCOL] => HTTP/1.1 [GATEWAY_INTERFACE] => CGI/1.1 [REMOTE_PORT] => 43852 [SCRIPT_FILENAME] => //var/www/example.com/public_html/some/path/set_score.php [SERVER_ADMIN] => webmaster@localhost [CONTEXT_DOCUMENT_ROOT] => /var/www/example.com/public_html/ [REQUEST_SCHEME] => https [DOCUMENT_ROOT] => /var/www/example.com/public_html/ [REMOTE_ADDR] => **.**.***.** [SERVER_PORT] => 443 [SERVER_ADDR] => ***.***.***.*** [SERVER_NAME] => example.com [SERVER_SOFTWARE] => Apache [SERVER_SIGNATURE] => <address>Apache Server at example.com Port 443</address> [PATH] => /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin [CONTENT_LENGTH] => 454 [CONTENT in /var/www/example.com/public_html/some/path/set_score.php on line 3
As you can see Content-Length is > 0, but $_POST data array is empty. At the same time, this empty POST request often following with proxy_fcgi error:
[Sun May 02 04:17:59.777441 2021] [proxy_fcgi:error] [pid 105827:tid 140667812566784] (70007)The timeout specified has expired: [client ***.***.***.***:40171] AH01075: Error dispatching request to : (reading input brigade)
Also when this error occurs, in the access.log I see 408 code. And I don’t know the problem is the Apache configuration or PHP-FPM, because POST data that I sending from clients is small and it’s only text data. Strange that on the previous server (cloudways) I didn’t have those problems. But now when I did my own server, this magic error happens. Maybe they just ignore these types of errors or the timeout value was to big. My scripts execute time is < 0.1 seconds and I don’t need big timeout values (I guess).
Here is some important settings in my configurations:
apache2.conf
Timeout 60 KeepAlive On MaxKeepAliveRequests 164 KeepAliveTimeout 5 HostnameLookups Off <Directory /> Options FollowSymLinks AllowOverride None Require all denied </Directory> <Directory /usr/share> AllowOverride None Require all granted </Directory> <Directory /var/www/> Options FollowSymLinks AllowOverride None Require all granted </Directory>
/apache2/sites-available/example.com.conf
<VirtualHost *:443> ServerAdmin webmaster@localhost ServerName example.com ServerAlias www.example.com DocumentRoot /var/www/example.com/public_html/ SSLEngine on SSLProtocol -all +TLSv1.2 +TLSv1.3 SSLCertificateFile /etc/ssl/certs/example.com.crt SSLCertificateKeyFile /etc/ssl/private/example.com.key SSLCertificateChainFile /etc/ssl/certs/ca-example.com.crt # tried to fix that "Error dispatching request to" <IfModule reqtimeout_module> RequestReadTimeout header=20-40,minrate=150 RequestReadTimeout body=20,minrate=150 </IfModule> <FilesMatch ".+.ph(ar|p|tml)$"> SetHandler "proxy:unix:/run/php/php7.4-fpm-example.com.sock|fcgi://localhost/" </FilesMatch> </VirtualHost> <VirtualHost *:80> ServerName example.com ServerAlias www.example.com Redirect 301 / https://example.com/ </VirtualHost>
/php/7.4/fpm/pool.d/example.com.conf
[example.com] user = www-data group = www-data listen = /run/php/php7.4-fpm-example.com.sock listen.owner = www-data listen.group = www-data pm = dynamic pm.max_children = 64 pm.start_servers = 16 pm.min_spare_servers = 8 pm.max_spare_servers = 16 php_admin_value[error_log] = /var/www/example.com/logs/error-fpm-php.log php_admin_flag[log_errors] = on
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Answer
Fixed the appearance of timeout errors by switching from HTTP/1.1 protocol to HTTP/2. Empty POST requests now come rarely, but they do.