Question

Error establishing a database connection whit kernel BSD

Posted April 23, 2016 3.6k views
MySQLServer OptimizationFreeBSD

I get: Error Establishing a database connection. Relaunch the console system. But after a series of swap errors prompt tells me: assocond-cconafi kernel: pid 830 (httpd), vid80 was killed. What does it mean? What can I do to fix it? This server behavior occurs now every day after a few hours of successful operation. Untenable situation.

1 comment
  • Here is the list of errors that appear at the prompt:
    assocond-cconafi kernel: pid 1096 (mysqld), uid 88, was killed: out of swap space
    assocond-cconafi kernel: pid 956 (httpd), uid 956, was killed: out of swap space
    assocond-cconafi kernel: pid 864 (httpd), uid 80, was killed: out of swap space
    swappager: out of swap space
    swap
    pager_getswapspace(14): failed
    assocond-cconafi kernel: pid 1104 (mysqld), uid 88, was killed: out of swap space

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6 answers

You are running out of memory and swap space and the kernel OOM killer is killing the Mysqld process.
Possible steps:

  • Use virt instance with more RAM.
  • Add more swap.
  • Reduce Mysql memory utilization in the config.
  • Remove additional services that might be running on the same host.

When you look at your apache logs (/var/log/httpd-access.log), do you see a bunch of requests hitting xmlrpc.php?
I’ve seen this happen a ton of times when servers are under an XMLRPC pingback attack.

  • I installed JetPack to protect against attacks, but it does not always work and sometimes the blog down. I do not know what to do.

    Grazie.

    • I have multiple webservers that had the same issue. I’d get tons of pingback attacks, mysqld memory would balloon and my webserver locked up.

      The only way I was able to totally stop them was to setup an .htaccess file to block all access to that file.

      <Files “xmlrpc.php”>
      Order Allow,Deny
      deny from all
      </Files>

      I’m not sure if that’s an option for you, but hopefully this helps.

Hello, all

I will recommend you to check our article on How To Debug the WordPress Error Establishing Database Connection:

https://www.digitalocean.com/community/tutorials/how-to-debug-the-wordpress-error-establishing-database-connection

This crash is most likely due to your system running out of memory. I’d suggest that you add a swap file to give yourself a bit more of a buffer. Check out this tutorial:

How To Add Swap on Ubuntu

You will most definitely need to upgrade your droplet as you’re running out of memory and your application/website needs more resources in order to continue to operate.

What you can also do is to use the MySQLTuner script.

The MySQLTuner is a script written in Perl and allows you to quickly test your MySQL configuration and it gives you suggestions for adjustments to increase performance and stability.

According to the official GitHub page, it supports 300 indicators for MySQL/MariaDB/Percona Server in this last version.

To run the script you could do the following:

  • SSH to your Droplet
  • Download the script:
wget http://mysqltuner.pl/ -O mysqltuner.pl
  • Then execute it:
perl mysqltuner.pl

The script would run multiple checks against your MySQL instance, all checks done by MySQLTuner are documented here.

Also as stated in the official documentation, it is still extremely important for you to fully understand each change you make to a MySQL database server. If you don’t understand portions of the script’s output, or if you don’t understand the recommendations, you should consult a knowledgeable DBA or system administrator that you trust.

As a good practice make sure to always test your changes on staging environments before implementing them on your production database.

On the same note, if you want to have a worry-free MySQL hosting and focus on your application, I would recommend trying out the DigitalOcean Managed Databases:

https://www.digitalocean.com/products/managed-databases-mysql/

This was mini tutorial was posted from bobbyiliev in this question in our community: https://www.digitalocean.com/community/questions/how-to-tweak-mysql-mariadb-configuration-for-increased-performance-and-stability

You can also create a simple bash script to check if MySQL is running and if not to restart it.

#!/bin/bash

# Check if MySQL is running
sudo service mysql status > /dev/null 2>&1

# Restart the MySQL service if it's not running.
if [ $? != 0 ]; then
    sudo service mysql restart
fi

Run this script every 5 minutes using a cron job like this one:

 */5 * * * * /home/user/scripts/monitor.sh > /dev/null 2>&1

Hope that this helps!
Regards,
Alex

by Brian Boucheron
WordPress is one of the most popular open source content management systems in the world. Although it started out focused on blogging, over the years it has developed into a more flexible platform for websites in general. After almost fifteen years of development it is quite polished and robust, yet issues can still come up. If you've recently attempted to load your WordPress-powered website and instead saw a message stating "Error Establishing Database Connection", the cause is most often...