How Orion marks a node as down

This article explains how Orion determines that a node is down.

What’s going on behind the scenes when a node goes into warning status, or when it’s actually down?  It starts with a simple ping.  Orion pings its nodes at regular intervals to determine the status of those nodes.  When Orion gets a response, the node is marked as up and its icon is green.
 

What happens when Orion doesn’t get a response?  When that happens, Orion can’t immediately assume the node is down, as there are a number of other reasons why the node may not be responding other than it being down.  Orion will perform additional checks to confirm the node is really down.  How is this done?
 

On the initial missed ping, Orion puts the node into warning status by marking it yellow.  When the node goes into a warning status, Orion initiates a fast polling cycle where it pings the node every 10 seconds to try and determine if it’s really down.  If Orion doesn’t receive any responses during this cycle, it determines the node is officially down and marks it red. By default, this fast polling cycle will last for 2 minutes.
 

There is one other piece to this, which is how Orion calculates a node's availability over time.  What’s the difference between status and availability?  To keep it very simple, a node’s status is an indicator of what the node is doing now; a node’s availability is a measurement of that node’s status over time.  Orion calculates availability in two possible ways: either by historical node status or by packet loss percentage over time.  Orion includes the option of specifying which calculation to use.  This setting is under Settings > All Settings > Polling Settings in the Web Console (screenshot below).