Problem:Docker container could not access the MariaDB - ERROR 2002 (HY000): Can't connect to MySQL server

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#1

Problem

The Docker container cannot access the MariaDB on the host, so in our case it was not possible to access the Bluespice Media wiki page.

Backtrace:

#0 /var/www/bluespice/includes/libs/rdbms/loadbalancer/LoadBalancer.php(1140): Wikimedia\Rdbms\Database->reportConnectionError('Connection refu...')
#1 /var/www/bluespice/includes/libs/rdbms/loadbalancer/LoadBalancer.php(750): Wikimedia\Rdbms\LoadBalancer->reportConnectionError()
#2 /var/www/bluespice/includes/GlobalFunctions.php(2813): Wikimedia\Rdbms\LoadBalancer->getConnection(0, Array, false)
#3 /var/www/bluespice/includes/user/User.php(534): wfGetDB(-1)
#4 /var/www/bluespice/includes/libs/objectcache/WANObjectCache.php(1095): User->{closure}(false, 3600, Array, NULL)
#5 /var/www/bluespice/includes/libs/objectcache/WANObjectCache.php(1243): WANObjectCache->{closure}(false, 3600, Array, NULL)
#6 /var/www/bluespice/includes/libs/objectcache/WANObjectCache.php(1078): WANObjectCache->doGetWithSetCallback('global:user:id:...', 3600, Object(Closure), Array, NULL)
#7 /var/www/bluespice/includes/user/User.php(561): WANObjectCache->getWithSetCallback('global:user:id:...', 3600, Object(Closure), Array)
#8 /var/www/bluespice/includes/user/User.php(482): User->loadFromCache()
#9 /var/www/bluespice/includes/user/User.php(420): User->loadFromId(0)
#10 /var/www/bluespice/includes/session/UserInfo.php(88): User->load()
#11 /var/www/bluespice/includes/session/CookieSessionProvider.php(126): MediaWiki\Session\UserInfo::newFromId('1')
#12 /var/www/bluespice/includes/session/SessionManager.php(488): MediaWiki\Session\CookieSessionProvider->provideSessionInfo(Object(WebRequest))
#13 /var/www/bluespice/includes/session/SessionManager.php(191): MediaWiki\Session\SessionManager->getSessionInfoForRequest(Object(WebRequest))
#14 /var/www/bluespice/includes/WebRequest.php(736): MediaWiki\Session\SessionManager->getSessionForRequest(Object(WebRequest))
#15 /var/www/bluespice/includes/session/SessionManager.php(130): WebRequest->getSession()
#16 /var/www/bluespice/includes/Setup.php(847): MediaWiki\Session\SessionManager::getGlobalSession()
#17 /var/www/bluespice/includes/WebStart.php(88): require_once('/var/www/bluesp...')
#18 /var/www/bluespice/index.php(39): require('/var/www/bluesp...')
#19 {main}

Solution

By setting the port to MariaDB, the container was able to reconnect to the database. This made the Bluespice Media wiki site accessible again.

  1. ucr set security/packetfilter/tcp/3306/all=ACCEPT
  2. service univention-firewall restart
  3. systemctl restart docker.service
  4. univention-app restart bluespice

Investigation

The first idea was to check the status of the database itself, to see if it was up and running.

root@srv-wiki:/var/log# systemctl status mariadb
● mariadb.service - MariaDB 10.3.39 database server
   Loaded: loaded (/lib/systemd/system/mariadb.service; enabled; vendor preset: enabled)
  Drop-In: /lib/systemd/system/mariadb.service.d
           └─univention.conf
   Active: active (running) since Wed 2024-09-18 14:58:17 CEST; 27min ago
     Docs: man:mysqld(8)
           https://mariadb.com/kb/en/library/systemd/
  Process: 25980 ExecStartPre=/usr/bin/install -m 755 -o mysql -g root -d /var/run/mysqld (code=exited, status=0/SUCCESS)
  Process: 25981 ExecStartPre=/bin/sh -c systemctl unset-environment _WSREP_START_POSITION (code=exited, status=0/SUCCESS)
  Process: 25983 ExecStartPre=/bin/sh -c [ ! -e /usr/bin/galera_recovery ] && VAR= ||   VAR=`cd /usr/bin/..; /usr/bin/galera_recovery`; [ $? -eq 0 ]   && systemctl set-enviro
  Process: 26088 ExecStartPost=/bin/sh -c systemctl unset-environment _WSREP_START_POSITION (code=exited, status=0/SUCCESS)
  Process: 26090 ExecStartPost=/etc/mysql/debian-start (code=exited, status=0/SUCCESS)
 Main PID: 26057 (mysqld)
   Status: "Taking your SQL requests now..."
    Tasks: 34 (limit: 4915)
   Memory: 360.6M
   CGroup: /system.slice/mariadb.service
           └─26057 /usr/sbin/mysqld

Sep 18 14:58:16 srv-wiki systemd[1]: Starting MariaDB 10.3.39 database server...
Sep 18 14:58:17 srv-wiki systemd[1]: Started MariaDB 10.3.39 database server.

DB information is copied from the environment variables so that the MariaDB can be queried directly.

root@srv-wiki:/var/log# docker inspect 2de

root@srv-wiki:/var/log# mariadb -u bluespice -p bluespice
Enter password:
ERROR 1045 (28000): Access denied for user 'bluespice'@'localhost' (using password: YES)

I can’t access the DB server from the container?

root@srv-wiki:/var/log#docker exec -it 2de /bin/bash
root@blues-13288299:/# mariadb -h 172.17.42.1 -u bluespice -p bluespice
Enter password:
ERROR 2002 (HY000): Can't connect to MySQL server on '172.17.42.1' (115)
root@blues-13288299:/#

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