Should I use or rely on 3rd party website monitoring tools and services?

Question

I use a website monitoring service, and it has reported that my website was down recently. Should I rely on these external monitoring tools?

Answer

There are many possibilities why a website went offline, and it's important to keep in mind that some monitoring methods can produce false positives, and downtime reported by a monitoring service may not always correlate with server logs. Here are some common causes.

• Web server or network failure. The server hosting your site or the network it relies on has stopped responding.
• Server component failure. A service such as MySQL, Apache, or DNS (named/bind) has stopped running.
• Traffic overload or DoS/DDoS attacks. Sudden high traffic can slow or crash a server.
• Script or application error. A broken CGI/PHP script caused by a code change, PHP version update, or incorrect file permissions can take the site offline.
• Firewall misconfiguration. Changes to firewall rules, or a firewall that has stopped running, can block all incoming traffic by default.
• Security compromise. A hacked or defaced site may be taken offline automatically or by your hosting provider.

Websites are not 100% protected from going down. That's why most site owners use a third-party monitoring service to alert you the moment something goes wrong. Determining the right choice for your provider depends on what you want.

• How often does it check my site?
• How many locations worldwide does it check from?
• How will it notify me? email, text, both?

Not all monitoring methods are the same. Some services will use a basic ping test, which simply checks if your site responds, but ping (ICMP) can be disabled on the network device and cause a false positive notification even when your site is online and accessible. More reliable services will use a full HTTP/S check to verify that the site loads.

Note: Monitoring services are a great resource, but they will not tell you why the service stopped responding. You will still need to work with your system administrator to review the server logs to determine why the notifications were sent.