How does Site24x7 calculate downtime of a website?
When a website availability check from its primary monitoring location fails, Site24x7 waits up to 15 seconds to get a response from the website (15 seconds is the default connectiontimeout period).
If there is no response within 15 seconds, rechecks will be done from the secondary monitoring locations (selected by the user) asynchronously based on the downtime rule selected in the threshold profiles (3 secondary locations, by default). If the website does not respond to any of these down rechecks, Site24x7 declares the website as unavailable and sends out alerts. However, it will also trigger an aggressive polling, until the next poll. In between the aggressive poll, if a status change is identified, an alert will be immediately triggered, though. Also, during the asynchronous check, if at least any one poll returns an UP status, the monitor will be deemed UP and no alert will be triggered until the next recheck is performed and the same validated.
Let's take an example to explain this case. Assume your website is being monitored every 5 minutes (check frequency) with a connection timeout of 30 seconds; you've selected the downtime rules in threshold configuration as "alert if down from 3 monitoring location"; Now,
At10:30:00 AM - Site24x7 polls your website from primary location (e.g.- California). Now assume your site does not respond within 30 seconds.
At10:30:30 AM - Site24x7 does a down recheck from secondary location #1, #2, and #3 asynchronously. If none of these locations receive an UP status, an alert will be triggered immediately followed by aggressive polling until the next poll at 10:35:30 AM.
At 10:32:00 AM - Aggressive poll detects the status change to UP and instantly triggers an alert. Hence, the total outage duration is detected as 2 minutes. However, if the aggressive poll fails until the next poll at 10:35:30 AM, the outage duration is calculated as 5 minutes 30 seconds.
On the contrary, if any one location recheck returns an UP status, it will fail the downtime rule and no alert will be triggered.