Site can't be reached- server DNS address could not be found

Question

My company's website went offline briefly somehow- a colleague just mentioned that they were getting an error page whenever trying to view any of the pages on the site.

I looked at the site, and was getting the same error when trying to view any pages on it for about 5 minutes.

The error said:

Site cannot be reached. The server DNS address could not be found

However, the site is now back up and running, and everything appears to be working as normal again. I am responsible for the development of the site, and have been making some changes to it (adding new features, fixing existing bugs, etc), & pushing those changes to the server using Git as and when a bug fix or new feature is complete.

However, I had not made any changes to the live version prior to it going offline- the last change I pushed to the server was yesterday, and the site had been fully functioning after that right up until it seemingly randomly went offline.

What are the possible causes for this, and is there any way I can prevent/ minimise the risk of it happening again? My thought was that it could have possibly been something to do with where the site is hosted? Maybe the host restarted their servers or something?

Answer 1

Error means that nameservers for the domain of your site could not be reached or found, and that your site hostname was not resolved to IP.

It could have been due to nameservers being restarted, or some issues with DNS zones on the server, or network issues with reaching them.

This was not caused by any changes to the site code, it was a DNS issue.

If your site and DNS servers are on the same machine, and you have admin access to it, you can check its uptime to see if it was rebooted.

Also, if your site and DNS are on the same server, you should consider using multiple nameservers to reduce possibilities of DNS failure.

You can use nameservers of your domain registrar, or sign up for a free CloudFlare or some similar service, and use their nameservers for your domain, to avoid site not being available if DNS service on your server goes down.