Question

How to know the reason MySQL keep crashing?

Posted September 10, 2014 48.5k views

Hi, currently I have a simple droplet (5 USD) with debian, a basic webserver with a wordpress with 100 visits per day, for some reason Mysql crash randomly, at the beginning I started the service manually, this was very annoying because my site was offline for several days until I realized wordpress was down, right now I have monit who monitors mysql and restart the service if it crash, I solved partially the problem but I still dont know why mysql keep crashing.

Note: there is no mysql.log in /var/log/mysql/

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I had the same issue, with a 2GB droplet size. Tried everything and eventually discovered it was an XML-RPC attack (Wordpress related).

Check this article for help:
How To Protect WordPress from XML-RPC Attacks on Ubuntu 14.04

by Jon Schwenn
WordPress is a popular and powerful CMS (content management system) platform. Its popularity can bring unwanted attention in the form of malicious traffic specially targeted at a WordPress site. There are many instances where a server that has not been protected or optimized could experience issues or errors after receiving a small amount of malicious traffic. This guide will show you how to protect WordPress from XML-RPC attacks on an Ubuntu 14.04 system.

This is definitely caused by the oom kernel killer beacause of mysql using up all your RAM (and swap if any). I solved this by looking at my mysql error log at /var/log/mysql/error.log and reverting changes made to my systems/sites by the time of error.

Turns out a wordpress plugin caused my problem and once it was out. I was back up with lots of free memory. (I deleted the plugin manually since there was no way to access the site without crashing mysql - see Managing Plugins - WordPress)

You could use the free -m command when logged in via ssh to check which specific site is causing mysql to use up so much memory and debug appropriately. Hope this helps

Most likely this due to running out of memory. Take a look through /var/log/syslog for any messages from the kernel’s Out Of Memory (OOM) killer.

MySql logs are sometimes also found in /var/log/mysql.log and /var/log/mysql.err instead of the /var/log/mysql/ directory. They might provide some hints.

If you haven’t done so already, you should add a swap file to give yourself some leeway when your memory consumption grows.

by Justin Ellingwood
Swap space can be used as an "overflow" area for your system when you run out of RAM. The operating system can store data that would normally be kept in RAM on the hard drive in a specially formatted file. In this guide, we'll demonstrate how to create and use one of these files in Ubuntu 14.04.

Perhaps try specifying a log file in /etc/mysql/my.cnf as follows:

general_log_file      = /var/log/mysql/mysql.log
general_log             = 1

I’m also guessing memory issues.

Currently having this problem as well. Just added swap, but now my 512MB droplet has become seriously slow and my site wont even open.

Will try the other stuff adityars suggested.

Hi,

We are having the same issue here. I find lots of forum posts about the same issue, but no ‘official’ recommendation… just 'try this’, 'could be that’, 'perhaps its..’.

PLEASE is there any procedure to follow in order to know 1) what´s causing the issue and 2) take proper action?

thks for your time.

I had mysql crashing every 30 minutes exactly. Turns out mysql installs on Windows still default the flushtime to 1800 seconds (on nix boxes this value defaults to 0). Normally this is not a problem, but because I was using federated tables it was a problem. I guess mysql doesn’t know how to flush federated tables, therefore crash. So I set flushtime = 0 in my.ini and the problem went away.

This bug has been reported here: https://bugs.mysql.com/bug.php?id=47525&thanks=3&notify=87

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