That would be correct - Icinga really doesn’t have a definition of “Master”,
“Satellite” or “Agent” - they’re just convenient terms for humans to use in
understanding the hierarchy.
In fact, it’s not especially mentioned in the documentation, but you can have
as many levels of satellites as you want - anything from zero upwards.
I for example monitor both physical and virtual servers hosted in more than
one location (and belonging to more than one customer), and my hierarchy is:
Master = Internet-based system which can be seen from anywhere, and where I
manage the entire top-down configuration
Satellites, level 1 = Icinga running on a firewall / router at a hosting centre
(receives configuration details only for its “local” machines, not ones on
someone else’s network. Note also that a “hosting centre” might well be a
customer’s office with a server room, and personnel with browsers on the same
network, not necessarily a data centre which nobody normally has access to.)
Agents, level 1 = Standalone (physical) servers at a hosting centre
Satellites, level 2 = Physical server on the customer’s network, running a
virtualisation environment
Agents, level 2 = Virtual servers inside a virtualisation server
So, for the VMs, the hierarchy is:
Master → Satellite 1 → Satellite 2 → Agent
I do it this way for several reasons:
-
it makes sense for the machines I’m managing, the way they’re both
physically and logically grouped, and the fact that different hosting centres
generally belong to different customers
-
in case of a connectivity failure between the Master and a hosting centre,
the service checks still run on the machines at that location and report to
the local Satellite
-
personnel at a hosting centre can access the local icingaweb interface
(which shows only their machines and hides any other customers’ systems)
-
Agents running on virtual machines inside one of the level 2 Satellites can
be auto-configured to talk to “the local machine”, reducing network traffic and
making the configuration simpler.
As a proof-of-concept I’ve even set up a 5-layer system with a Master, an
Agent, and three sets of Satellites in between, just to check that it works
(it does). I haven’t (yet?) come up with a real-world reason for using such
an arrangement, though.
Personally I think it’s a pity that this multi-level system isn’t more clearly
documented as a possibility, because I think it’s a useful arrangement in
certain situations, and it’s good for people to be aware that it works.
Antony.