Question

Error establishing a database connection without heavy load

Posted February 3, 2015 3.4k views

Hello all,

Usually my droplet is using 25-30% of the memory, CPU. But sometimes it was increase nearly 100%. Im using a 4gb droplet
then it kill the database and led to Error establishing a database connection.
No increase in the site’s traffic.
Then I restarted the mysql server and it was good for a while, then the error repeated again.

What would be the problem? And how can i check the server log
im using wordpress, centos and im just a non-tech newbie.

Thanks for all your help.
Minh

4 comments
  • Two things to check:

    sometimes a plugin or theme can cause this. You can check by disabling plugins one by one…wait…wait..and see if the problem continues. If not, then re-enable that plugin and try the next one.
    It is surprising how plugins can sometimes do this.

    Also, Wordpress will often have brute-force attacks. This traffic will not show as regular traffic. You can use the plugin “Login Lockdown” to help. Also, you can change the login page in Wordpress from wp-login.php to something else.
    I do this on all Wordpress sites I manage, and it makes a lot of difference.

    Google to find how to do this..It is not very difficult

  • I would recommend you check your domain access log (requests.log) and grep for wp-login. You can also grep the log for the word “POST.”

    Finally you should check to see if there is a single ip address that is repeatedly hitting your site more frequently than others. It could be that your site is being hit by bot traffic. You might want to use a robots.txt file to block the more aggressive bots.

  • Try this:

    #change logfile to the location of your log file.
    logfile='/var/log/apache2/sundayhelp.com-access.log'
    for i in `cat $logfile|awk '{print $1}'|sort -u`;do count=`grep -c $i $logfile`;echo "$i;$count";done > ip_count.csv
    

    The ipcount.csv_ file will have IP, NUMBEROF_TIMESSEEN

    the other alternative is installing goaccess

  • thanks you all. your guides look very helpful.
    i will check it out.

These answers are provided by our Community. If you find them useful, show some love by clicking the heart. If you run into issues leave a comment, or add your own answer to help others.

×
Submit an Answer
2 answers

This question was answered by @sierracircle:

Two things to check:

sometimes a plugin or theme can cause this. You can check by disabling plugins one by one…wait…wait..and see if the problem continues. If not, then re-enable that plugin and try the next one.
It is surprising how plugins can sometimes do this.

Also, Wordpress will often have brute-force attacks. This traffic will not show as regular traffic. You can use the plugin “Login Lockdown” to help. Also, you can change the login page in Wordpress from wp-login.php to something else.
I do this on all Wordpress sites I manage, and it makes a lot of difference.

Google to find how to do this..It is not very difficult

View the original comment

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