Nova datasource Driver queries all Nova instances, or gets a message bus
notification about a new Nova instance
Nova datasource Driver sends corresponding events to the Entity Queue
The Entity Processor polls the Entity Queue and gets the new Nova Instance
event
The Entity Processor passes the event to the Nova Instance Transformer,
which returns a Vertex with the instance data, with an edge to the host
Vertex in the graph
The Entity Processor adds the new vertex and edge to the Graph
(steps 1-4) Nagios datasource driver pushes a nagios alarm on a switch to
the Entity Queue, which is converted by Nagios Transformer to a vertex and
inserted to the Graph
The Evaluator is notified about a new Vertex (Nagios switch alarm) that was
added to the graph
The Evaluator performs its calculations and deduces that alarms should be
triggered on every instance on every host attached to this switch
The Evaluator pushes alarms to the Entity Queue
The graph is updated with these new alarms
The graph writes to the message bus that new alarms were created
Aodh Notifier creates new alarm definitions in Aodh, and sets their states
to “alarm”
The Evaluator evaluates the templates and the Graph, and decides that there
is a root cause relation between Alarm-X and Alarm-Y. It adds a “causes”
edge to the Graph
Note that in future versions the graph with RCA information may become more
complex, for example: