Amazon EC2 MySQL Failed to Start

I also had faced the same challenge this is what I explored, the reason for restarting can be one of the below:

1. There have been updates applied at your EC2 instance, causing the MySql service to stop and not able to restart again.
2. There may be other processes running along which cause a crunch in memory, thus not allowing the MySql to restart.

To Tackle this you can either use one of the below:

1. If your MySql service is going down because of memory issue -- Upgrade your instance.

2. If your mysqld restart command fails, try to restart the httpd service first and then your mysql service. Here are the commands:

   • sudo service httpd restart
   • sudo service mysqld restart

3. If none of the above work restart your EC2 Instance. Not a permanent fix, but help if you want your services to be up and running, and later want to do an RCA of the issue

If you want you can create a script shown below, and execute it after via a cron-job every 5-10 mins depending on your requirement :

#!/bin/bash
dateFormat=`date "+%Y-%m-%d %T"`
log_file_path="/home/ec2-user/mysql_restart_log.dat"

sudo service mysqld status | grep "is running"
if [ $? -ne 0 ]; then
   echo "HTTPD restart attempted ${dateFormat}" >> ${log_file_path}

   sudo service httpd restart
   if [ $? -ne 0 ]; then
     echo "HTTPD restart failed... ${dateFormat}" >> ${log_file_path}
   else
     echo "HTTPD restart success... ${dateFormat}" >> ${log_file_path}
   fi

   echo "MYSQL restart attempted ${dateFormat}" >> ${log_file_path}
   sudo service mysqld restart
   if [ $? -ne 0 ]; then
     echo "MYSQL restart failed... ${dateFormat}" >> ${log_file_path}
   else
     echo "MYSQL restart success... ${dateFormat}" >> ${log_file_path}
   fi
fi

Also found this link helpful: mysql on amazon linux - MySQL Daemon failed to start

I fixed this by restarting my EC2 instance.

In My case i solved it by clearing some space in server.

I was taking backup of database on daily basis which results in consumption of lots of space. I deleted all those backup and started mysql.

Restarting the instance helps, but it doesn't resolve it permanently.

This is what I used to resolve it: http://www.prowebdev.us/2012/05/amazon-ec2-linux-micro-swap-space.html

Amazon EC2 Micro Instance Swap Space - Linux

I have a Amazon EC2 Linux Micro instance. Since Micro instances have only 613MB of memory, MySQL crashed every now and then. After a long search about MySQL, Micro Instance and Memory Managment I found out there is no default SWAP space for Micro instance. So if you want to avoid the crash you may need to setup a swap space for your micro instance. Actually performance wise is better to enable swap.

Steps below show how to make a swap space for your Micro instance. I assume you have AWS Account with a Micro instance running.

1.) Run dd if=/dev/zero of=/swapfile bs=1M count=1024
2.) Run mkswap /swapfile
3.) Run swapon /swapfile
4.) Add this line /swapfile swap swap defaults 0 0 to /etc/fstab  

Step 4 is needed if you would like to automatically enable swap file after each reboot.

Some useful command related to SWAP space:

$ swapon -s $ free -k

$ swapoff -a $ swapon -a

References:

http://www.thegeekstuff.com/2010/08/how-to-add-swap-space/

http://cloudstory.in/2012/02/getting-the-best-out-of-amazon-ec2-micro-instances/

http://cloudstory.in/2012/02/adding-swap-space-to-amazon-ec2-linux-micro-instance-to-increase-the-performance/

http://aws.amazon.com/ec2/instance-types/