cron job to auto restart mysql or httpd or even droplet when errors

Question

Hi all,

Sometimes my droplet has a problem Error establishing database connection. Im fixing it now. The temp way is to restart mysql then things would be ok for few hours or days.

Im also thinking a temporary way until i can truly solve the above problem. Step A. Auto restart mysql whenever error happens => I created a cron job to do this. Step B. But sometimes even the mysql or http were hanging out and cant be restarted. In this time I had to poweroff my droplet then turn it on again.

So how to define the way for this cron job? I knew how to do A but not B. Mine: Wordpress, Centos 6.5 64, Virtualmin

Thank you, Minh PS: Im not a tech guy so pls dont use complex jargons :-)

Ryan Quinn · Answer

The most common reason for MySQL to crash like this is that the process is running out of memory. Rather than treat the symptom by restarting the process (this will eventually lead to data corruption due to the crashes) we can treat the cause. There are a couple things you can do. 1.) Set up a swap file on your droplet . This file will be used when your physical memory is exhausted, swapping data out here rather than allowing services to crash. 2.) Optimize the processes running on your droplet. A number of tutorials on optimizing various apps can be found here . 3.) Finally, you can choose to upgrade to a droplet plan which provides more RAM. A useful command while doing this is free -m This will display a summary of your used and available memory and help you to track how your changes and optimizations are affecting resource use.

Ritchie · Answer

if you have a cron job to restart apache and mysql sometimes the service can’t be correctly stopped, this is some kind of issue with users, so you need to kill the process, you can try to read pid file for process id and kill -9 that id, then restart. Again as suggested, fix MySQL problem or this will solve nothing, only cause you a db corruption. here some samples for restarts, you can try to add a counter of tries, if you restart X service more than 3 times in a row then #reboot: #!/bin/bash #Memcachedif service memcached status | grep -q “running”; thenecho “MemCached is up”elseservice memcached restartcat /root/alert.txt | mail -s “MemCached Service Down” myemail@gmail .comfi #This if is just a sample of reboot, you need to use correct syntax here #---------------------------------------------------------------------if cat /root/count.txt = 111; thenrebootfi#Sample end #Nginx + counterif service nginx status | grep -q “running”; thenecho “Nginx is up”echo 0 > /root/count.txtelseservice nginx restartcat /root/alert.txt | mail -s “Nginx Service Down” myemail@gmail .comecho 1 >> /root/count.txtfi #--------------------------------------------------------------------- #PHP-FPMif service php-fpm status | grep -q “running”; thenecho “PHP-FPM is up”elseservice php-fpm restartcat /root/alert.txt | mail -s “PHP-FPM Service Down” myemail@gmail .comfi #PHP-FPM Max Children Statusif curl -s http://site.com/status | grep -q “max children reached: 0”; thenecho PHP running normal;elseservice php-fpm reloadcat /root/alert.txt | mail -s “PHP-FPM Max Children reached!” myemail@gmail .comfi

minhbkx · Answer

thanks EpicCDN for your detailed answer :-)

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cron job to auto restart mysql or httpd or even droplet when errors

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cron job to auto restart mysql or httpd or even droplet when errors