Mysql keeps crashing (Kill process 919 (mysqld) score 86 or sacrifice child)

August 29, 2014 2.5k views

I'm using wordpress on ubuntu (standard offer, didn't change any seetings) on minimal configuration (512 MB).
New, small blog, just 1 page and 2 posts. Maximum pageviews per day - 156 (yesterday).

Today in the morning I've found it doesn't work. The reason is that mysql is down.
I've restarted linux. The only visitor was me. But after short time mysql was down again (there were no visitors except me, so not big load). It repeated several times.

Later I've created 1GB swap file. For some time it was ok. So I thought that problem was solved. But later I found that mysql was down again. So 1,5 GB is not enough?

It seems like apache eats a lot of memory at some point. But I'm not sure.

Did anyone experience the same problem? Should I change any apache or mysql settings? I thought standard offer by DigitalOcean should work properly.

Here is the part of mysql error.log during crash:

140829 23:12:04 [Warning] Using unique option prefix myisam-recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
140829 23:12:04 [Note] Plugin 'FEDERATED' is disabled.
140829 23:12:04 InnoDB: The InnoDB memory heap is disabled
140829 23:12:04 InnoDB: Mutexes and rw_locks use GCC atomic builtins
140829 23:12:04 InnoDB: Compressed tables use zlib 1.2.8
140829 23:12:04 InnoDB: Using Linux native AIO
140829 23:12:04 InnoDB: Initializing buffer pool, size = 128.0M
InnoDB: mmap(137363456 bytes) failed; errno 12
140829 23:12:04 InnoDB: Completed initialization of buffer pool
140829 23:12:04 InnoDB: Fatal error: cannot allocate memory for the buffer pool
140829 23:12:04 [ERROR] Plugin 'InnoDB' init function returned error.
140829 23:12:04 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
140829 23:12:04 [ERROR] Unknown/unsupported storage engine: InnoDB
140829 23:12:04 [ERROR] Aborting

140829 23:12:04 [Note] /usr/sbin/mysqld: Shutdown complete

2 Answers
evgeny February 5, 2017
Accepted Answer

The reason was an XML-RPC attack. Here you can find an article about how to protect you WordPress site: https://www.digitalocean.com/community/tutorials/how-to-protect-wordpress-from-xml-rpc-attacks-on-ubuntu-14-04

P.S. Sorry for keeping silence. I just did't use my DigitalOcean account for a long time:)

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.

I always build 512MB SWAP file and is enough to run Apache + MariaDB + WordPress. I run three WordPress blogs into same droplet (512 MB RAM).

I don't know what DO guys installed into the default WordPress image, but i suggest you to install byourself Apache + MariaDB + WordPress. You can find several tutorial and comentation into the DO community.

For this unexpected crashes i use one bash script that runs with cron every 10 min and check that some services are up (if they are down it restar them). Perhaps it helps you in the future, you can find it here

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