Multi-Command Plans

Autopilot relies on a Plan for defining the Commands that should be executed, the Signal Nodes that each should be run on, and the status of each Command.

A Plan:

  • Defines one or many Commands that specify what actions should be performed.
  • Specifies how Signal Nodes should be discovered per-Command.
  • Saves the status of the Plan execution by resolved Signal Nodes

A Command:

  • An instructional step inside of a Plan that is applied against a Signal Node

A Signal Node:

  • Any node (controller or worker) that can receive updates with Autopilot.

Execution

The execution of a Plan is the result of processing Commands through a number of Processing States.

When a Plan is executed, each of the Commands are executed in the order of their appearance in the Plan.

  • A Plan transitions to the next Command only when the current Command posts a state of Completed.
  • Any Command that posts one of the recognized Error States will result in the current Command and Plan to abort processing.
    • The status of the Command and Plan will reflect this.
  • A Plan is considered finished only when all of its defined Commands post a Completed state.

Status

The progress and state of each Command is recorded in the Plan status.

  • Every Command in the Plan has an associated status entry with the same index as the Command
    • ie. The second Command in a Plan has an index of 1, and so does its status.
  • The status of all Commands is taken into consideration when determining if the Plan is finished.

Example

The following is an example of a Plan that has been applied as is currently being processed by autopilot.

(line numbers added for commentary below)

  1.  1: apiVersion: autopilot.k0sproject.io/v1beta2
  2.  2:  kind: Plan
  3.  3:  metadata:
  4.  4:    annotations:
  5.  5:      <omitted>
  6.  6:  spec:
  7.  7:    commands:
  8.  8:    - airgapupdate:
  9.  9:        version: v1.26.8+k0s.0
  10. 10:        platforms:
  11. 11:          linux-amd64:
  12. 12:            url: https://github.com/k0sproject/k0s/releases/download/v1.26.8+k0s.0/k0s-airgap-bundle-v1.26.8+k0s.0-amd64
  13. 13:        workers:
  14. 14:          discovery:
  15. 15:            static:
  16. 16:              nodes:
  17. 17:              - worker0
  18. 18:    - k0supdate:
  19. 19:        version: v1.26.8+k0s.0
  20. 20:        platforms:
  21. 21:          linux-amd64:
  22. 22:            url: https://github.com/k0sproject/k0s/releases/download/v1.26.8+k0s.0/k0s-v1.26.8+k0s.0-amd64
  23. 23:        targets:
  24. 24:          controllers:
  25. 25:            discovery:
  26. 26:              static:
  27. 27:                nodes:
  28. 28:                - controller0
  29. 29:          workers:
  30. 30:            discovery:
  31. 31:              static:
  32. 32:                nodes:
  33. 33:                - worker0
  34. 34:    id: id123
  35. 35:    timestamp: now
  36. 36:  status:
  37. 37:    commands:
  38. 38:    - airgapupdate:
  39. 39:        workers:
  40. 40:        - lastUpdatedTimestamp: "2022-05-11T19:13:02Z"
  41. 41:          name: worker0
  42. 42:          state: SignalSent
  43. 43:      id: 0
  44. 44:      state: SchedulableWait
  45. 45:    - id: 1
  46. 46:      k0supdate:
  47. 47:        controllers:
  48. 48:        - lastUpdatedTimestamp: "2022-05-11T19:13:02Z"
  49. 49:          name: controller0
  50. 50:          state: SignalPending
  51. 51:        workers:
  52. 52:        - lastUpdatedTimestamp: "2022-05-11T19:13:02Z"
  53. 53:          name: worker0
  54. 54:          state: SignalPending
  55. 55:      state: SchedulableWait
  56. 56:    state: SchedulableWait
  • Lines 7-33 are the two Commands that make up this plan — an airgapupdate and k0supdate.
  • Lines 38-55 are the associated status entries for the two Commands.

The state of this Plan exerpt is that autopilot has successfully processed the Plan, and has begun processing the airgapupdate Command. Its status indicates SignalSent which means that the Signal Node has been sent signaling information to perform an airgap update.

Processing States

The following are the various states that both Plans and Commands adhere to.

  1. stateDiagram-v2
  2.     [*]-->NewPlan
  3.     NewPlan-->SchedulableWait
  4.     NewPlan-->Errors***
  6.     SchedulableWait-->Schedulable
  7.     SchedulableWait-->Completed
  8.     Schedulable-->SchedulableWait
  10.     Errors***-->[*]
  11.     Completed-->[*]

Note that the Errors state is elaborated in detail below in Error States*.

NewPlan

When a Plan is created with the name autopilot, the NewPlan state processing takes effect.

It is the responsibility of NewPlan to ensure that the status of all the Commands are represented in the Plan status. This Plan status is needed at later points in Plan processing to determine if the entire Plan is completed.

The main difference between NewPlan and all the other states is that NewPlan will iterate over all commands; the other states deal with the active command.

SchedulableWait

Used to evaluate a Command to determine if it can be scheduled for processing. If the Command is determined that it can be processed, the state is set to Schedulable.

Schedulable

The Schedulable state is set by SchedulableWait to indicate that this command should execute. The execution of a Command in this state will be whichever logic is defined by the Command.

The ending of this state should either transition to SchedulableWait for further processing + completion detection, or transition to an error.

Completed

The Completed state indicates that the command has finished processing. Once a plan/command are in the Completed state, no further processing will occur on this plan/command.

Error States

When a plan or command processing goes into one of the designated error states, this is considered fatal and the plan/command processing will terminate.

Error states are generally defined by the Command implementation. The core autopilot functionality is only interested when in the 4 core states (NewPlan, SchedulableWait, Schedulable, Completed), and treats all other states as an error.

  1. flowchart TD
  2.     Errors --> InconsistentTargets
  3.     Errors --> IncompleteTargets
  4.     Errors --> Restricted
  5.     Errors --> MissingPlatform
  6.     Errors --> MissingSignalNode
Error StateCommandStatesDescription
InconsistentTargetsk0supdateSchedulableIndicates that a Signal Node probe has failed for any node that was previously discovered during NewPlan.
IncompleteTargetsairgapupdate, k0supdateNewPlan, SchedulableIndicates that a Signal Node that existed during the discover phase in NewPlan no longer exists (ie. no ControlNode or Node object)
Restrictedairgapupdate, k0supdateNewPlanIndicates that a Plan has requested an update of a Signal Node type that contradicts the startup exclusions (the —exclude-from-plans argument)
MissingSignalNodeairgapupdate, k0supdateSchedulableIndicates that a Signal Node that existed during the discover phase in NewPlan no longer exists (ie. no matching ControlNode or Node object)

Sequence: Example

Using the example above as a reference, this outlines the basic sequence of events of state transitions to the operations performed on each object.

  1. sequenceDiagram
  2.   PlanStateHandler->>+AirgapUpdateCommand: State: NewPlan
  3.   AirgapUpdateCommand->>-AirgapUpdateCommand: cmd.NewPlan() -- >SchedulableWait
  4.   PlanStateHandler->>+K0sUpdateCommand: State: NewPlan
  5.   K0sUpdateCommand->>-K0sUpdateCommand: cmd.NewPlan() --> SchedulableWait
  6.   Note over PlanStateHandler,SignalNode(worker0): NewPlan Finished / All Commands
  8.   PlanStateHandler->>+AirgapUpdateCommand: State: SchedulableWait
  9.   AirgapUpdateCommand->>-AirgapUpdateCommand: cmd.SchedulableWait() --> Schedulable
  10.   PlanStateHandler->>+AirgapUpdateCommand: State: Schedulable
  11.   AirgapUpdateCommand->>-SignalNode(worker0): signal_v2(airgap-data) --> SchedulableWait
  12.   PlanStateHandler->>+AirgapUpdateCommand: State: SchedulableWait
  13.   AirgapUpdateCommand->>-AirgapUpdateCommand: cmd.SchedulableWait() --> Completed
  14.   Note over PlanStateHandler,SignalNode(worker0): AirgapUpdate Finished / worker0
  16.   PlanStateHandler->>+K0sUpdateCommand: State: SchedulableWait
  17.   K0sUpdateCommand->>-K0sUpdateCommand: cmd.SchedulableWait() --> Schedulable
  18.   PlanStateHandler->>+K0sUpdateCommand: State: Schedulable
  19.   K0sUpdateCommand->>-SignalNode(controller0): signal_v2(k0s-data) --> SchedulableWait
  20.   PlanStateHandler->>+K0sUpdateCommand: State: SchedulableWait
  21.   K0sUpdateCommand->>-K0sUpdateCommand: cmd.SchedulableWait() --> Completed
  22.   Note over PlanStateHandler,SignalNode(controller0): K0sUpdate Finished / controller0
  24.   PlanStateHandler->>+K0sUpdateCommand: State: SchedulableWait
  25.   K0sUpdateCommand->>-K0sUpdateCommand: cmd.SchedulableWait() --> Schedulable
  26.   PlanStateHandler->>+K0sUpdateCommand: State: Schedulable
  27.   K0sUpdateCommand->>-SignalNode(worker0): signal_v2(k0s-data) --> SchedulableWait
  28.   PlanStateHandler->>+K0sUpdateCommand: State: SchedulableWait
  29.   K0sUpdateCommand->>-K0sUpdateCommand: cmd.SchedulableWait() --> Completed
  30.   Note over PlanStateHandler,SignalNode(worker0): K0sUpdate Finished / worker0
  32.   PlanStateHandler->>PlanStateHandler: Completed