worker/undertaker/undertaker.go

// Copyright 2015-2016 Canonical Ltd.
// Licensed under the AGPLv3, see LICENCE file for details.

package undertaker

import (
	"fmt"

	"github.com/juju/errors"
	"gopkg.in/juju/worker.v1/catacomb"

	"github.com/juju/juju/apiserver/params"
	"github.com/juju/juju/environs"
	"github.com/juju/juju/environs/context"
	"github.com/juju/juju/status"
	"github.com/juju/juju/watcher"
	"github.com/juju/juju/worker/common"
)

// Facade covers the parts of the api/undertaker.UndertakerClient that we
// need for the worker. It's more than a little raw, but we'll survive.
type Facade interface {
	ModelInfo() (params.UndertakerModelInfoResult, error)
	WatchModelResources() (watcher.NotifyWatcher, error)
	ProcessDyingModel() error
	RemoveModel() error
	SetStatus(status status.Status, message string, data map[string]interface{}) error
}

// Config holds the resources and configuration necessary to run an
// undertaker worker.
type Config struct {
	Facade        Facade
	Destroyer     environs.CloudDestroyer
	CredentialAPI common.CredentialAPI
}

// Validate returns an error if the config cannot be expected to drive
// a functional undertaker worker.
func (config Config) Validate() error {
	if config.Facade == nil {
		return errors.NotValidf("nil Facade")
	}
	if config.CredentialAPI == nil {
		return errors.NotValidf("nil CredentialAPI")
	}
	if config.Destroyer == nil {
		return errors.NotValidf("nil Destroyer")
	}
	return nil
}

// NewUndertaker returns a worker which processes a dying model.
func NewUndertaker(config Config) (*Undertaker, error) {
	if err := config.Validate(); err != nil {
		return nil, errors.Trace(err)
	}

	u := &Undertaker{
		config:  config,
		callCtx: common.NewCloudCallContext(config.CredentialAPI),
	}
	err := catacomb.Invoke(catacomb.Plan{
		Site: &u.catacomb,
		Work: u.run,
	})
	if err != nil {
		return nil, errors.Trace(err)
	}
	return u, nil
}

type Undertaker struct {
	catacomb catacomb.Catacomb
	config   Config

	callCtx context.ProviderCallContext
}

// Kill is part of the worker.Worker interface.
func (u *Undertaker) Kill() {
	u.catacomb.Kill(nil)
}

// Wait is part of the worker.Worker interface.
func (u *Undertaker) Wait() error {
	return u.catacomb.Wait()
}

func (u *Undertaker) run() error {
	result, err := u.config.Facade.ModelInfo()
	if err != nil {
		return errors.Trace(err)
	}
	if result.Error != nil {
		return errors.Trace(result.Error)
	}
	modelInfo := result.Result

	if modelInfo.Life == params.Alive {
		return errors.Errorf("model still alive")
	}

	if modelInfo.Life == params.Dying {
		// TODO(axw) 2016-04-14 #1570285
		// We should update status with information
		// about the remaining resources here, and
		// also make the worker responsible for
		// checking the emptiness criteria before
		// attempting to remove the model.
		if err := u.setStatus(
			status.Destroying,
			"cleaning up cloud resources",
		); err != nil {
			return errors.Trace(err)
		}
		// Process the dying model. This blocks until the model
		// is dead or the worker is stopped.
		if err := u.processDyingModel(); err != nil {
			return errors.Trace(err)
		}
	}

	// If we get this far, the model must be dead (or *have been*
	// dead, but actually removed by something else since the call).
	if modelInfo.IsSystem {
		// Nothing to do. We don't destroy environ resources or
		// delete model docs for a controller model, because we're
		// running inside that controller and can't safely clean up
		// our own infrastructure. (That'll be the client's job in
		// the end, once we've reported that we've tidied up what we
		// can, by returning nil here, indicating that we've set it
		// to Dead -- implied by processDyingModel succeeding.)
		return nil
	}

	// Now the model is known to be hosted and dead, we can tidy up any
	// provider resources it might have used.
	if err := u.setStatus(
		status.Destroying, "tearing down cloud environment",
	); err != nil {
		return errors.Trace(err)
	}
	if err := u.config.Destroyer.Destroy(u.callCtx); err != nil {
		return errors.Trace(err)
	}

	// Finally, remove the model.
	if err := u.config.Facade.RemoveModel(); err != nil {
		return errors.Annotate(err, "cannot remove model")
	}
	return nil
}

func (u *Undertaker) setStatus(modelStatus status.Status, message string) error {
	return u.config.Facade.SetStatus(modelStatus, message, nil)
}

func (u *Undertaker) processDyingModel() error {
	watcher, err := u.config.Facade.WatchModelResources()
	if err != nil {
		return errors.Trace(err)
	}
	if err := u.catacomb.Add(watcher); err != nil {
		return errors.Trace(err)
	}
	defer watcher.Kill()

	attempt := 1
	for {
		select {
		case <-u.catacomb.Dying():
			return u.catacomb.ErrDying()
		case <-watcher.Changes():
			err := u.config.Facade.ProcessDyingModel()
			if err == nil {
				// ProcessDyingModel succeeded. We're free to
				// destroy any remaining environ resources.
				return nil
			}
			if !params.IsCodeModelNotEmpty(err) && !params.IsCodeHasHostedModels(err) {
				return errors.Trace(err)
			}
			// Retry once there are changes to the model's resources.
			u.setStatus(
				status.Destroying,
				fmt.Sprintf("attempt %d to destroy model failed (will retry):  %v", attempt, err),
			)
		}
		attempt++
	}
}