packer-cn/packer/provisioner.go

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package packer
import (
"fmt"
"sync"
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"time"
)
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// A provisioner is responsible for installing and configuring software
// on a machine prior to building the actual image.
type Provisioner interface {
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// Prepare is called with a set of configurations to setup the
// internal state of the provisioner. The multiple configurations
// should be merged in some sane way.
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Prepare(...interface{}) error
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// Provision is called to actually provision the machine. A UI is
// given to communicate with the user, and a communicator is given that
// is guaranteed to be connected to some machine so that provisioning
// can be done.
Provision(Ui, Communicator) error
// Cancel is called to cancel the provisioning. This is usually called
// while Provision is still being called. The Provisioner should act
// to stop its execution as quickly as possible in a race-free way.
Cancel()
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}
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// A Hook implementation that runs the given provisioners.
type ProvisionHook struct {
// The provisioners to run as part of the hook. These should already
// be prepared (by calling Prepare) at some earlier stage.
Provisioners []Provisioner
lock sync.Mutex
runningProvisioner Provisioner
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}
// Runs the provisioners in order.
func (h *ProvisionHook) Run(name string, ui Ui, comm Communicator, data interface{}) error {
defer func() {
h.lock.Lock()
defer h.lock.Unlock()
h.runningProvisioner = nil
}()
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for _, p := range h.Provisioners {
h.lock.Lock()
h.runningProvisioner = p
h.lock.Unlock()
if err := p.Provision(ui, comm); err != nil {
return err
}
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}
return nil
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}
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// Cancels the privisioners that are still running.
func (h *ProvisionHook) Cancel() {
h.lock.Lock()
defer h.lock.Unlock()
if h.runningProvisioner != nil {
h.runningProvisioner.Cancel()
}
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}
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// PausedProvisioner is a Provisioner implementation that pauses before
// the provisioner is actually run.
type PausedProvisioner struct {
PauseBefore time.Duration
Provisioner Provisioner
cancelCh chan struct{}
doneCh chan struct{}
lock sync.Mutex
}
func (p *PausedProvisioner) Prepare(raws ...interface{}) error {
return p.Provisioner.Prepare(raws...)
}
func (p *PausedProvisioner) Provision(ui Ui, comm Communicator) error {
p.lock.Lock()
cancelCh := make(chan struct{})
p.cancelCh = cancelCh
// Setup the done channel, which is trigger when we're done
doneCh := make(chan struct{})
defer close(doneCh)
p.doneCh = doneCh
p.lock.Unlock()
defer func() {
p.lock.Lock()
defer p.lock.Unlock()
if p.cancelCh == cancelCh {
p.cancelCh = nil
}
if p.doneCh == doneCh {
p.doneCh = nil
}
}()
// Use a select to determine if we get cancelled during the wait
ui.Say(fmt.Sprintf("Pausing %s before the next provisioner...", p.PauseBefore))
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select {
case <-time.After(p.PauseBefore):
case <-cancelCh:
return nil
}
provDoneCh := make(chan error, 1)
go p.provision(provDoneCh, ui, comm)
select {
case err := <-provDoneCh:
return err
case <-cancelCh:
p.Provisioner.Cancel()
return <-provDoneCh
}
}
func (p *PausedProvisioner) Cancel() {
var doneCh chan struct{}
p.lock.Lock()
if p.cancelCh != nil {
close(p.cancelCh)
p.cancelCh = nil
}
if p.doneCh != nil {
doneCh = p.doneCh
}
p.lock.Unlock()
<-doneCh
}
func (p *PausedProvisioner) provision(result chan<- error, ui Ui, comm Communicator) {
result <- p.Provisioner.Provision(ui, comm)
}