The collector receives messages from the server which contain the details of the device it should connect to, including its credentials. As a first step, the collector interrogates the device, to determine what it is. The result of this interrogation process is a set of tags describing the device. Once the interrogation phase is done, the collector will continue to run all "monitoring" commands repeatedly, collecting data from the device and parsing it into metrics.
Interrogation
In the platform's data model, each device has tags. These tags can include "device-id", which is a unique identifier for a device, as well as others. The tags describe the device and give us extra information about it. The process of generating these tags occurs only during interrogation. If a device is changed later, for example by updating the software running on it, the collector will throw away everything it knows about the device and will restart interrogation.
...
If we lose connectivity to a device, we will restart the interrogation once we re-establish connectivity. We will essentially delete all the tags we have for the device and start over.
Monitoring
Once a device has been interrogated, the collector will load all the monitoring commands (those of type "monitoring") whose requirements are met for the device (based on the "requires" directive of the monitoring script). See sample scripts here.
...