4d7e42220b
* Implement Stringer inteface for multistep.StepAction * scaleway: add pre validate step (check image and snapshot names) Before, it was possible to create multiple images with the same name, leading to a confusing and wasteful situation (same for snapshots). Now, we perform the same kind of checks done by the AWS EC2 builder, and refuse to proceed if there is an existing image with the same name (same for snapshots). As usual, invoking `packer build -force` will bypass the checks. Closes #9839.
64 lines
1.9 KiB
Go
64 lines
1.9 KiB
Go
// multistep is a library for building up complex actions using individual,
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// discrete steps.
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package multistep
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import (
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"context"
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"strconv"
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)
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// A StepAction determines the next step to take regarding multi-step actions.
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type StepAction uint
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const (
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ActionContinue StepAction = iota
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ActionHalt
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)
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// Implement the stringer interface; useful for testing.
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func (a StepAction) String() string {
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switch a {
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case ActionContinue:
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return "ActionContinue"
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case ActionHalt:
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return "ActionHalt"
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default:
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return "Unexpected value: " + strconv.Itoa(int(a))
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}
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}
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// This is the key set in the state bag when using the basic runner to
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// signal that the step sequence was cancelled.
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const StateCancelled = "cancelled"
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// This is the key set in the state bag when a step halted the sequence.
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const StateHalted = "halted"
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// Step is a single step that is part of a potentially large sequence
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// of other steps, responsible for performing some specific action.
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type Step interface {
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// Run is called to perform the action. The passed through context will be
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// cancelled when the runner is cancelled. The second parameter is a "state
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// bag" of untyped things. Please be very careful about type-checking the
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// items in this bag.
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//
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// The return value determines whether multi-step sequences continue
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// or should halt.
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Run(context.Context, StateBag) StepAction
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// Cleanup is called in reverse order of the steps that have run
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// and allow steps to clean up after themselves. Do not assume if this
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// ran that the entire multi-step sequence completed successfully. This
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// method can be ran in the face of errors and cancellations as well.
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//
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// The parameter is the same "state bag" as Run, and represents the
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// state at the latest possible time prior to calling Cleanup.
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Cleanup(StateBag)
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}
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// Runner is a thing that runs one or more steps.
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type Runner interface {
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// Run runs the steps with the given initial state.
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Run(context.Context, StateBag)
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}
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