Service State #

Formal Definition: A service state St is a set of service variables that can happen in at least one of St's lifetimes.

Active or Inactive Service State #

An active service state St means that it is the current service state and therefore it's currently happening, otherwise, it is an inactive service state.

Service State Lifetime #

A service state St's lifetime is the duration that starts from when it was transitioned to by a previous active service state St - 1 and ends right before it transitions to the next active service state St + 1. St can become active at any time depending on the availability of its service's ServiceTransitionFunctions and the future ServiceInputs encountered, therefore St can have multiple lifetimes.

Concrete Example #

An UploadInProgress state of a naive cloud storage service can activate and deactivate (or Inactive) and this is equivalent to one lifetime. However, it can get re-activated when a a file is uploaded by a different user thus it can have multiple lifetimes.

Child of a Service #

A service S's child is a service state St that can happen sometime in S's lifetime.

Parent of a Service State #

A service S is called a parent of a service state St if and only if St is a child of S.

In practice, a service state can be monitored by monitoring a subset of service variable values. Using the naive cloud storage service example, the values of service variables totalUploadedBytes, uploadTimeElapsed, and uploadAverageThroughput can be used to monitor a UploadThrouputLow service state that indicates the service's current upload throughput is lower than its average upload throughput.

The following is an illustration of the example in the previous paragraph.

Kind: ServiceMonitor
metadata:
  name: "Monitor Low Upload Throughput"
spec:
    - TargetServiceState: UploadThrougputLow
    - ServiceVariables:
        - name: totalUploadedBytes
          description: Real-time count of uploaded file data in bytes
        - name: uploadTimeElapsed
          description: Total time elapsed since the file data upload started
        - name: uploadAverageThroughput
          description: Current average file data upload throughput.