After the OS (Ubuntu 16.04) was upgraded to Ubuntu 18.04, Icingaweb2's user interface was suddenly full with errors:
The MySQL related PHP error could also be seen in the Apache error logs:
[Tue Jul 27 11:33:08.176860 2021] [:error] [pid 1479098] [client 10.162.210.49:64794] PHP Fatal error: Uncaught Error: Undefined class constant 'MYSQL_ATTR_INIT_COMMAND' in /usr/share/php/Icinga/Data/Db/DbConnection.php:203\nStack trace:\n#0 /usr/share/php/Icinga/Data/Db/DbConnection.php(78): Icinga\\Data\\Db\\DbConnection->connect()\n#1 /usr/share/php/Icinga/Data/ResourceFactory.php(103): Icinga\\Data\\Db\\DbConnection->__construct(Object(Icinga\\Data\\ConfigObject))\n#2 /usr/share/icingaweb2/modules/monitoring/library/Monitoring/Backend/MonitoringBackend.php(229): Icinga\\Data\\ResourceFactory::createResource(Object(Icinga\\Data\\ConfigObject))\n#3 /usr/share/icingaweb2/modules/monitoring/library/Monitoring/Backend/MonitoringBackend.php(304): Icinga\\Module\\Monitoring\\Backend\\MonitoringBackend->getResource()\n#4 /usr/share/icingaweb2/modules/monitoring/library/Monitoring/DataView/DataView.php(53): Icinga\\Module\\Monitoring\\Backend\\MonitoringBackend->query('ServiceStatus', Array)\n#5 /usr/share/icingaweb2/modules/monitoring/library/Monitoring/Backend/MonitoringBackend.php(259): Icinga\\Module\\Monitoring\\DataView\\DataView->__constr in /usr/share/php/Icinga/Data/Db/DbConnection.php on line 203, referer: http://10.166.15.51/icingaweb2/dashboard
A closer look to the installed PHP packages shows that both PHP 7.0 and 7.2 packages exist on this upgraded Ubuntu machine. Interesting however is that the php7.0-mysql package was removed:
root@icingaweb:~# dpkg -l|grep php | awk '{print $1" "$2"\t\t"$3}'
ii icinga-php-common 1.0.0-1.bionic
ii icinga-php-library 0.6.0-1.bionic
ii icinga-php-thirdparty 0.10.0-2.bionic
ii libapache2-mod-php7.0 7.0.33-0ubuntu0.16.04.16
ii libapache2-mod-php7.2 7.2.24-0ubuntu0.18.04.8
ii php 1:7.2+60ubuntu1
ii php-common 1:60ubuntu1
ii php-curl 1:7.0+35ubuntu6.1
rc php-htmlpurifier 4.7.0-1build1
ii php-icinga 2.9.0-1.bionic
ii php-imagick 3.4.3~rc2-2ubuntu4.1
ii php-intl 1:7.2+60ubuntu1
ii php-ldap 1:7.2+60ubuntu1
ii php-mysql 1:7.2+60ubuntu1
ii php-soap 1:7.2+60ubuntu1
ii php-xml 1:7.2+60ubuntu1
ii php7.0 7.0.33-0ubuntu0.16.04.16
ii php7.0-cli 7.0.33-0ubuntu0.16.04.16
ii php7.0-common 7.0.33-0ubuntu0.16.04.16
ii php7.0-curl 7.0.33-0ubuntu0.16.04.16
ii php7.0-fpm 7.0.33-0ubuntu0.16.04.16
ii php7.0-gd 7.0.33-0ubuntu0.16.04.16
ii php7.0-gmp 7.0.33-0ubuntu0.16.04.16
ii php7.0-intl 7.0.33-0ubuntu0.16.04.16
ii php7.0-json 7.0.33-0ubuntu0.16.04.16
ii php7.0-ldap 7.0.33-0ubuntu0.16.04.16
rc php7.0-mysql 7.0.33-0ubuntu0.16.04.16
ii php7.0-opcache 7.0.33-0ubuntu0.16.04.16
ii php7.0-readline 7.0.33-0ubuntu0.16.04.16
ii php7.0-xml 7.0.33-0ubuntu0.16.04.16
ii php7.2 7.2.24-0ubuntu0.18.04.8
ii php7.2-cli 7.2.24-0ubuntu0.18.04.8
ii php7.2-common 7.2.24-0ubuntu0.18.04.8
ii php7.2-intl 7.2.24-0ubuntu0.18.04.8
ii php7.2-json 7.2.24-0ubuntu0.18.04.8
ii php7.2-ldap 7.2.24-0ubuntu0.18.04.8
ii php7.2-mysql 7.2.24-0ubuntu0.18.04.8
ii php7.2-opcache 7.2.24-0ubuntu0.18.04.8
ii php7.2-readline 7.2.24-0ubuntu0.18.04.8
ii php7.2-soap 7.2.24-0ubuntu0.18.04.8
ii php7.2-xml 7.2.24-0ubuntu0.18.04.8
Which PHP version is actually in use by Apache?
root@icingaweb:~# ls -la /etc/apache2/mods-enabled/php*
lrwxrwxrwx 1 root root 29 Dec 7 2017 /etc/apache2/mods-enabled/php7.0.conf -> ../mods-available/php7.0.conf
lrwxrwxrwx 1 root root 29 Dec 7 2017 /etc/apache2/mods-enabled/php7.0.load -> ../mods-available/php7.0.load
lrwxrwxrwx 1 root root 29 Jul 26 11:24 /etc/apache2/mods-enabled/php7.2.conf -> ../mods-available/php7.2.conf
lrwxrwxrwx 1 root root 29 Jul 26 11:24 /etc/apache2/mods-enabled/php7.2.load -> ../mods-available/php7.2.load
Both mod_php versions are enabled since the OS upgrade - which of course does not work and throws a warning:
root@icingaweb:~# apache2ctl configtest
[Tue Jul 27 11:35:50.755188 2021] [so:warn] [pid 1508896] AH01574: module php7_module is already loaded, skipping
Syntax OK
By disabling the PHP 7.0 Apache module, the remaining PHP 7.2 module should be picked up and loaded by Apache:
root@icingaweb:~# a2dismod php7.0
Module php7.0 disabled.
To activate the new configuration, you need to run:
systemctl restart apache2
root@icingaweb:~# systemctl restart apache2
And as expected, the errors are gone:
When upgrading PHP with a OS/distribution release upgrade, always make sure to enable only one mod_php Apache module - as Apache runs into a conflict otherwise. Now some people might say that the PHP package upgrade (namely libapache2-mod-php7.2) should properly remove the old PHP version from Apache. But I see it as a "safe" upgrade procedure which allows a quick switch between PHP 7.0 or PHP 7.2 in this particular case (Xenial to Bionic). A systems admin should know the managed system well enough to know how and when to do the switch. But what is confusing me is why the php7.0-mysql package was removed.
The reason can actually be found in the apt history logs and this package (as the sole php package) was removed due to apt autoremove:
Start-Date: 2021-07-26 11:59:34
Commandline: apt autoremove
Remove: libisccfg140:amd64 (1:9.10.3.dfsg.P4-8ubuntu1.19), libmpfr4:amd64 (3.1.4-1), sgml-base:amd64 (1.29), libevent-core-2.0-5:amd64 (2.0.21-stable-2ubuntu0.16.04.1), rename:amd64 (0.20-7), libfile-slurp-tiny-perl:amd64 (0.003-1), libtxc-dxtn-s2tc0:amd64 (0~git20131104-1.1), libpython3.5:amd64 (3.5.2-2ubuntu0~16.04.13), libisc160:amd64 (1:9.10.3.dfsg.P4-8ubuntu1.19), zlib1g-dev:amd64 (1:1.2.11.dfsg-0ubuntu2), python3.5-dev:amd64 (3.5.2-2ubuntu0~16.04.13), libvpx3:amd64 (1.5.0-2ubuntu1.1), python3-pycurl:amd64 (7.43.0.1-0.2), xml-core:amd64 (0.18), libstdc++-5-dev:amd64 (5.5.0-12ubuntu1), libllvm6.0:amd64 (1:6.0-1ubuntu2), libapparmor-perl:amd64 (2.12-4ubuntu5.1), g++-5:amd64 (5.5.0-12ubuntu1), libgdbm3:amd64 (1.8.3-13.1), liblwres141:amd64 (1:9.10.3.dfsg.P4-8ubuntu1.19), liblua5.1-0:amd64 (5.1.5-8.1build2), libpython3.5-dev:amd64 (3.5.2-2ubuntu0~16.04.13), libdbus-glib-1-2:amd64 (0.110-2), libdns162:amd64 (1:9.10.3.dfsg.P4-8ubuntu1.19), rsync:amd64 (3.1.2-2.1ubuntu1.1), libunistring0:amd64 (0.9.3-5.2ubuntu1), imagemagick-common:amd64 (8:6.9.7.4+dfsg-16ubuntu6.11), libisccc140:amd64 (1:9.10.3.dfsg.P4-8ubuntu1.19), libbind9-140:amd64 (1:9.10.3.dfsg.P4-8ubuntu1.19), libboost-iostreams1.58.0:amd64 (1.58.0+dfsg-5ubuntu3.1), libxapian22v5:amd64 (1.2.22-2), php7.0-mysql:amd64 (7.0.33-0ubuntu0.16.04.16)
End-Date: 2021-07-26 11:59:36
This of course does not apply when using PHP-FPM as a separate process daemon for PHP.
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