On default Digital Ocean WordPress installation, sometimes you may find following error while opening website:
Error establishing a database connection
Looking in the /var/log/syslog, we have:
May 3 08:08:13 myDigitalOceanDroplet kernel: [391622.639370] Out of memory: Killed process 98542 (mysqld) total-vm:165880kB, anon-rss:59772kB, file-rss:2396kB,
shmem-rss:0kB, UID:112 pgtables:276kB oom_score_adj:0
It happens usually when the Wordpress is installed on the lowest droplet size, and not tuned properly. A large number of requests through Apache web server causes the memory to be exhaused and system automatically kills processes, to stay alive. As a fast workaround, you can monitor the MySQL process every minute and restart it if/when needed.
So, how you will do this ?
Save this script to
#!/bin/sh TEST=$(/usr/bin/pgrep -a mysqld | grep -v $0) if [ -z "$TEST" ]; then DATE=$(date) echo "$DATE Restarting mysql service..." /usr/sbin/service mysql start fi
Run this script from cron, every minute:
* * * * * /root/monitor-mysqld-process.sh >> /tmp/cron.monitor-mysqld-process.txt 2>&1
And finally, monitor temporary log:
tail -F /tmp/cron.monitor-mysqld-process.txt Tue May 3 08:17:02 UTC 2022 Restarting mysql service...