Performance monitoring

Every site that gets added to Oh Dear will automatically have its performance monitored.

Our performance collection is heavily tied to our uptime monitoring. Every time we check the uptime, we collect and store detailed performance metrics for that website.

This means the uptime monitoring check needs to be enabled before the performance monitoring check will work. Without data collection through the uptime monitoring, we can not show you any details nor alert you of any changes.

Note: you can disable all uptime alerts, so you won't be notified when you don't want to.

Performance thresholds

You can configure 2 kinds of alerts for performance monitoring.

  • Hard threshold: if the site is continuously slower than this value, we will alert you
  • Performance changes: if a site is suddenly this % faster or slower, we will alert you

They both serve their own purpose and will keep you informed on the overall health of your site.

How do we determine a sudden change in performance

We look at the difference between the average response time in the past two hours vs average response time in past 15 minutes. Any change faster or slower than the Site performance change notification percentage defined in your site performance settings (e.g. 50%) will trigger an alert.

Your Site performance threshold is your maximum allowable site speed (in milliseconds) before your site is considered slow and alert is sent.

Performance metrics breakdown

We will be able to show you the following detailed metrics.

  • DNS lookup: The time it takes to resolve the domain name to an IP address via DNS.
  • TCP Connection Time: The time it takes to connect to the remote host (TCP three-way handshake).
  • TLS Connection Time: The total time it took for the TLS handshake to complete (cipher negotiation & encryption).
  • Remote Server Processing: The time it took the server to process the request and start sending the first byte of the page.
  • Content Download: The time, in seconds, it took for the page to be downloaded.

The Time To First Byte (or TTFB) is the same as our Remote Server Processing time.

Reason why your site may be slow

Why is my site slow?

The transferring of data is almost always the fastest piece, unless it's about MB's of data - in which case, bandwidth becomes an issue, so most time in a request is spent setting up TCP, SSL & waiting for the server.

The results you see could indicate issues in a number of different areas of your application such as server health, slow database queries or missed caches.

Your hosting provider could have also changed firewall/WAF or routing which would up increase TLS times, if packets are dropped & have to be resent.

There could also be large-scale outages from hosting companies affecting different regions.

Oh Dear can be configured to perform uptime checks from a location of your choice and will always perform downtime verification from a secondary location.

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