Question

Error establishing a database connection - recurring (Ubuntu)

  • Posted November 24, 2013

After a reboot of the droplet, all works fine for a while. I’m in the 512 MB memory plan. I have 2 WP sites installed. A backup plugin is installed but running weekly.

In addition, when I get the error, and check on the status of mysql I get this: mysql stop/waiting

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Are you running Apache? If so, use this set-up, instead: <a href=“https://www.digitalocean.com/community/articles/how-to-install-wordpress-nginx-php-and-varnish-on-ubuntu-12-04”>How To Install Wordpress, Nginx, PHP, and Varnish on Ubuntu 12.04</a>. If you want to know why, check out: <a href=“http://kbeezie.com/caching-wordpress/”>The Importance of Caching WordPress</a> and/or <a href=“http://www.wpexplorer.com/wordpress-caching/”>What is WordPress Caching and Why is it Important?</a>. <br> <br>Swap & memcache will also help. <i>See</i> <a href=“https://www.digitalocean.com/community/articles/how-to-add-swap-on-ubuntu-12-04”>How To Add Swap on Ubuntu 12.04</a> and <a href=“https://www.digitalocean.com/community/articles/how-to-install-and-use-memcache-on-ubuntu-12-04”>How To Install and Use Memcache on Ubuntu 12.04</a>.

Looks like your MySQL server is failing out, chances are you’re running out of RAM. Check the logs for reasons as to why MySQL would be stopping.

Hello, all

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

Thank you @Pablo. The pages you provided about WP caching were incredibly illuminating. I really had no clue how much a beast Wordpress is on a system. I did a swap a while back based on @Kamal Nasser’s post, but didn’t install a caching system. <br> <br>Also, if anybody needs to do quick testing, LoadImpact.com helped. Here’s my recent test results for a client http://bit.ly/1hOkym9.

sudo tail /var/log/mysql.err returns empty, swap is never used, there is no problem with apache and wordpress because mysql is the same as for ngix so no need for ngix and no need for more ram. <br>did anyone resolved this??? a lot of bad suggestions i have read all over this community and no one doesn’t even know the source of the problem…

OK, i SSH to my droplet and ran the command: service mysql restart <br>

I too have the same problem, now my wordpress site is down and I don’t know how to access it again, just so I could backup my posts…I really need them all, including a complete mySQL backup…but both “/var/log/mysql.err” and “/var/log/mysql.log” are empty. how to I regain access to my site?

Check MySQL’s error log: <br><pre>sudo tail /var/log/mysql.err</pre>

The logs are empty. I have minimal plugins. I upgraded my droplet to the 1GB and I’m STILL having these issues. <br> <br>So I stand by the fact that this isn’t memory related. Again, I do a memory check and I’m NOT at capacity.

There is a specific mysql log file that you may want to look at if you haven’t already. It should be under /var/log/mysql/mysqld.log for CentOS, but it can vary depending on distribution and setup. There may be some additional information there. Besides the memory allocation and the mysql logs, you may wish to have the wordpress installs be as clean as possible. I try to keep only a few plugins running and installed. I’ve seen folks have 20+ plugins and that can lead to problems.