DOC: Key Design Points

Element state and element operations are fully separated.

• The command interface and the “state store” are completely independent, being normally run on different hosts.
• The system has architectural provisions for extending the operation set for different kinds of objects (e.g., “VM migrate”, “VM suspend”, “AI fail”).
• A new instance of the CLI can be “attached” to a running experiment at any moment, for the execution of operations on an element (e.g., start an experiment at the office, attach a CLI instance later from home to check the progress).

Element state information stored as key-value pairs.

• Use of in-memory key-value store (Redis) allows high-throughput (10K’s of inserts/sec) on low-power servers.
• Key-value servers have (typically) a scalable (scale-out) architecture.

The execution of an operation is delegated to the element that is closer to the actual locus of the action.

• The load management (i.e., how high is the load, and for how is it going to be executed?) is performed by the “driver VM” on each AI.
• Performance collection for all VMs on an AI is also performed by the “driver VM”.