DNS lookup failure in mysqli_real_connect()

[nyaka111]

Description

We're getting an intermittent error when calling mysqli_real_connect function. This is the error:

PHP Warning: mysqli_real_connect(): php_network_getaddresses: getaddrinfo for MYSQL_SEVER_HOSTNAME failed: Name or service not known in ...

It happens every time the DNS record TTL expires. We're using AWS Aurora and the DNS record TTL's every 5 seconds. Running mysqli_real_connect in a cycle would fail every 5 seconds. To rule out the other possibilities we created a DNS name with a TTL of 60 seconds and it failed every 60 seconds.

This is the code we were able to consistently replicate the issue with:

for ($i = 0; $i < 100; $i++) {
	
	test_mysqli_connect($i);
	
	usleep(250000);
}

function test_mysqli_connect() {
	global $CONF;
	
	$dbh = mysqli_init();
	mysqli_real_connect($dbh, $CONF["DB"]["db_host"], $CONF["DB"]["db_user"], $CONF["DB"]["db_pass"], $CONF["DB"]["db_name"], 3306, NULL, MYSQLI_CLIENT_SSL|MYSQLI_CLIENT_SSL_DONT_VERIFY_SERVER_CERT);
}

We also tried running gethostbyname and dns_get_record in the same cycle, and they never seem to fail.

Setup:

PHP Version => 8.2.7
System => Linux XX.XX.XX.XX 6.1.0-13-cloud-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.55-1 (2023-09-29) x86_64
PHP API => 20220829
PHP Extension => 20220829
Zend Extension => 420220829
Zend Extension Build => API420220829,NTS
PHP Extension Build => API20220829,NTS

MySQL server:

5.7.40-log MySQL Community Server (GPL)

Debian packages:

default-libmysqlclient-dev/stable,now 1.1.0 amd64 [installed]
default-mysql-client/stable,now 1.1.0 all [installed]
mysql-common/stable,now 5.8+1.1.0 all [installed]
libapache2-mod-php8.2/stable,stable-security,now 8.2.7-1deb12u1 amd64 [installed,automatic]
php-bz2/stable,now 2:8.2+93 all [installed]
php-cli/stable,now 2:8.2+93 all [installed]
php-common/stable,now 2:93 all [installed]
php-curl/stable,now 2:8.2+93 all [installed]
php-dev/stable,now 2:8.2+93 all [installed]
php-gd/stable,now 2:8.2+93 all [installed]
php-imap/stable,now 2:8.2+93 all [installed]
php-json/stable,now 2:8.2+93 all [installed]
php-mcrypt/stable,now 3:1.0.5-4 amd64 [installed]
php-memcache/stable,now 8.0+4.0.5.2+3.0.920170802.e702b5f9+-8 amd64 [installed]
php-mysql/stable,now 2:8.2+93 all [installed]
php-pear/stable,now 1:1.10.13+submodules+notgz+2022032202-2 all [installed]
php-readline/stable,now 2:8.2+93 all [installed]
php-snmp/stable,now 2:8.2+93 all [installed]
php-xml/stable,now 2:8.2+93 all [installed]
php-xmlrpc/stable,now 3:1.0.0rc3-6 amd64 [installed]
php8.2-bz2/stable,stable-security,now 8.2.7-1deb12u1 amd64 [installed,automatic]
php8.2-cli/stable,stable-security,now 8.2.7-1deb12u1 amd64 [installed,automatic]
php8.2-common/stable,stable-security,now 8.2.7-1deb12u1 amd64 [installed,automatic]
php8.2-curl/stable,stable-security,now 8.2.7-1deb12u1 amd64 [installed,automatic]
php8.2-dev/stable,stable-security,now 8.2.7-1deb12u1 amd64 [installed]
php8.2-gd/stable,stable-security,now 8.2.7-1deb12u1 amd64 [installed,automatic]
php8.2-imap/stable,stable-security,now 8.2.7-1deb12u1 amd64 [installed,automatic]
php8.2-mcrypt/stable,now 3:1.0.5-4 amd64 [installed,automatic]
php8.2-memcache/stable,now 8.0+4.0.5.2+3.0.920170802.e702b5f9+-8 amd64 [installed,automatic]
php8.2-mysql/stable,stable-security,now 8.2.7-1deb12u1 amd64 [installed,automatic]
php8.2-opcache/stable,stable-security,now 8.2.7-1deb12u1 amd64 [installed,automatic]
php8.2-readline/stable,stable-security,now 8.2.7-1deb12u1 amd64 [installed,automatic]
php8.2-snmp/stable,stable-security,now 8.2.7-1deb12u1 amd64 [installed,automatic]
php8.2-xml/stable,stable-security,now 8.2.7-1deb12u1 amd64 [installed,automatic]
php8.2-xmlrpc/stable,now 3:1.0.0rc3-6 amd64 [installed,automatic]
php8.2/stable,stable-security,now 8.2.7-1deb12u1 all [installed,automatic]
php/stable,now 2:8.2+93 all [installed]
pkg-php-tools/stable,now 1.44 all [installed,automatic]

Also, we ran the same script on our “old” system (PHP 7.0.33-0+deb9u12, Debian 4.9.189-3+deb9u2 (2019-11-11) x86_64) which connects to the same MySQL server, and it worked without failing.

PHP Version

PHP 8.2.7

Operating System

Debian 6.1.55-1 (2023-09-29) x86_64

[nyaka111]

There are also MariaDB libraries installed in the system:

libmariadb-dev-compat/stable,now 1:10.11.4-1deb12u1 amd64 [installed,automatic]
libmariadb-dev/stable,now 1:10.11.4-1deb12u1 amd64 [installed,automatic]
libmariadb3/stable,now 1:10.11.4-1deb12u1 amd64 [installed,automatic]
mariadb-client-core/stable,now 1:10.11.4-1deb12u1 amd64 [installed,automatic]
mariadb-client/stable,now 1:10.11.4-1deb12u1 amd64 [installed,automatic]
mariadb-common/stable,now 1:10.11.4-1deb12u1 all [installed,automatic]

[kamil-tekiela]

php_network_getaddresses is not a mysqli or mysqlnd error. It comes from sockets. I mean, it's always possible that mysqlnd code uses sockets incorrectly, but I doubt that's the case.

You can put a breakpoint in network.c on the line that throws this warning and then check what code path in mysqlnd leads to this error.

[nielsdos]

Given that this error likely comes from the operating system itself instead of PHP, and there has been no further feedback, I'm suspending this issue.
If there is more information, feel free to post it and I'll reopen.