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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: apiVersion: autopilot.k0sproject.io/v1beta2
 2:  kind: Plan
 3:  metadata:
 4:    annotations:
 5:      <omitted>
 6:  spec:
 7:    commands:
 8:    - airgapupdate:
 9:        version: v1.27.4+k0s.0
10:        platforms:
11:          linux-amd64:
12:            url: https://github.com/k0sproject/k0s/releases/download/v1.27.4+k0s.0/k0s-airgap-bundle-v1.27.4+k0s.0-amd64
13:        workers:
14:          discovery:
15:            static:
16:              nodes:
17:              - worker0
18:    - k0supdate:
19:        version: v1.27.4+k0s.0
20:        platforms:
21:          linux-amd64:
22:            url: https://github.com/k0sproject/k0s/releases/download/v1.27.4+k0s.0/k0s-v1.27.4+k0s.0-amd64
23:        targets:
24:          controllers:
25:            discovery:
26:              static:
27:                nodes:
28:                - controller0
29:          workers:
30:            discovery:
31:              static:
32:                nodes:
33:                - worker0
34:    id: id123
35:    timestamp: now
36:  status:
37:    commands:
38:    - airgapupdate:
39:        workers:
40:        - lastUpdatedTimestamp: "2022-05-11T19:13:02Z"
41:          name: worker0
42:          state: SignalSent
43:      id: 0
44:      state: SchedulableWait
45:    - id: 1
46:      k0supdate:
47:        controllers:
48:        - lastUpdatedTimestamp: "2022-05-11T19:13:02Z"
49:          name: controller0
50:          state: SignalPending
51:        workers:
52:        - lastUpdatedTimestamp: "2022-05-11T19:13:02Z"
53:          name: worker0
54:          state: SignalPending
55:      state: SchedulableWait
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.

stateDiagram-v2
    [*]-->NewPlan
    NewPlan-->SchedulableWait
    NewPlan-->Errors***

    SchedulableWait-->Schedulable
    SchedulableWait-->Completed
    Schedulable-->SchedulableWait

    Errors***-->[*]
    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.

flowchart TD
    Errors --> InconsistentTargets
    Errors --> IncompleteTargets
    Errors --> Restricted
    Errors --> MissingPlatform
    Errors --> MissingSignalNode
Error State Command States Description
InconsistentTargets k0supdate Schedulable Indicates that a Signal Node probe has failed for any node that was previously discovered during NewPlan.
IncompleteTargets airgapupdate, k0supdate NewPlan, Schedulable Indicates that a Signal Node that existed during the discover phase in NewPlan no longer exists (ie. no ControlNode or Node object)
Restricted airgapupdate, k0supdate NewPlan Indicates that a Plan has requested an update of a Signal Node type that contradicts the startup exclusions (the --exclude-from-plans argument)
MissingSignalNode airgapupdate, k0supdate Schedulable Indicates 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.

sequenceDiagram
  PlanStateHandler->>+AirgapUpdateCommand: State: NewPlan
  AirgapUpdateCommand->>-AirgapUpdateCommand: cmd.NewPlan() -- >SchedulableWait
  PlanStateHandler->>+K0sUpdateCommand: State: NewPlan
  K0sUpdateCommand->>-K0sUpdateCommand: cmd.NewPlan() --> SchedulableWait
  Note over PlanStateHandler,SignalNode(worker0): NewPlan Finished / All Commands

  PlanStateHandler->>+AirgapUpdateCommand: State: SchedulableWait
  AirgapUpdateCommand->>-AirgapUpdateCommand: cmd.SchedulableWait() --> Schedulable
  PlanStateHandler->>+AirgapUpdateCommand: State: Schedulable
  AirgapUpdateCommand->>-SignalNode(worker0): signal_v2(airgap-data) --> SchedulableWait
  PlanStateHandler->>+AirgapUpdateCommand: State: SchedulableWait
  AirgapUpdateCommand->>-AirgapUpdateCommand: cmd.SchedulableWait() --> Completed
  Note over PlanStateHandler,SignalNode(worker0): AirgapUpdate Finished / worker0

  PlanStateHandler->>+K0sUpdateCommand: State: SchedulableWait
  K0sUpdateCommand->>-K0sUpdateCommand: cmd.SchedulableWait() --> Schedulable
  PlanStateHandler->>+K0sUpdateCommand: State: Schedulable
  K0sUpdateCommand->>-SignalNode(controller0): signal_v2(k0s-data) --> SchedulableWait
  PlanStateHandler->>+K0sUpdateCommand: State: SchedulableWait
  K0sUpdateCommand->>-K0sUpdateCommand: cmd.SchedulableWait() --> Completed
  Note over PlanStateHandler,SignalNode(controller0): K0sUpdate Finished / controller0

  PlanStateHandler->>+K0sUpdateCommand: State: SchedulableWait
  K0sUpdateCommand->>-K0sUpdateCommand: cmd.SchedulableWait() --> Schedulable
  PlanStateHandler->>+K0sUpdateCommand: State: Schedulable
  K0sUpdateCommand->>-SignalNode(worker0): signal_v2(k0s-data) --> SchedulableWait
  PlanStateHandler->>+K0sUpdateCommand: State: SchedulableWait
  K0sUpdateCommand->>-K0sUpdateCommand: cmd.SchedulableWait() --> Completed
  Note over PlanStateHandler,SignalNode(worker0): K0sUpdate Finished / worker0

  PlanStateHandler->>PlanStateHandler: Completed