github.com/cloud-green/juju@v0.0.0-20151002100041-a00291338d3d/worker/upgrader/upgrader.go

// Copyright 2012, 2013 Canonical Ltd.
// Licensed under the AGPLv3, see LICENCE file for details.

package upgrader

import (
	"fmt"
	"net/http"
	"time"

	"github.com/juju/errors"
	"github.com/juju/loggo"
	"github.com/juju/names"
	"github.com/juju/utils"
	"launchpad.net/tomb"

	"github.com/juju/juju/agent"
	agenttools "github.com/juju/juju/agent/tools"
	"github.com/juju/juju/api/upgrader"
	"github.com/juju/juju/state/watcher"
	coretools "github.com/juju/juju/tools"
	"github.com/juju/juju/version"
)

// retryAfter returns a channel that receives a value
// when a failed download should be retried.
var retryAfter = func() <-chan time.Time {
	return time.After(5 * time.Second)
}

var logger = loggo.GetLogger("juju.worker.upgrader")

// Upgrader represents a worker that watches the state for upgrade
// requests.
type Upgrader struct {
	tomb                   tomb.Tomb
	st                     *upgrader.State
	dataDir                string
	tag                    names.Tag
	origAgentVersion       version.Number
	areUpgradeStepsRunning func() bool
	agentUpgradeComplete   chan struct{}
}

// NewAgentUpgrader returns a new upgrader worker. It watches changes to the
// current version of the current agent (with the given tag) and tries to
// download the tools for any new version into the given data directory.  If
// an upgrade is needed, the worker will exit with an UpgradeReadyError
// holding details of the requested upgrade. The tools will have been
// downloaded and unpacked.
func NewAgentUpgrader(
	st *upgrader.State,
	agentConfig agent.Config,
	origAgentVersion version.Number,
	areUpgradeStepsRunning func() bool,
	agentUpgradeComplete chan struct{},
) *Upgrader {
	u := &Upgrader{
		st:                     st,
		dataDir:                agentConfig.DataDir(),
		tag:                    agentConfig.Tag(),
		origAgentVersion:       origAgentVersion,
		areUpgradeStepsRunning: areUpgradeStepsRunning,
		agentUpgradeComplete:   agentUpgradeComplete,
	}
	go func() {
		defer u.tomb.Done()
		u.tomb.Kill(u.loop())
	}()
	return u
}

// Kill implements worker.Worker.Kill.
func (u *Upgrader) Kill() {
	u.tomb.Kill(nil)
}

// Wait implements worker.Worker.Wait.
func (u *Upgrader) Wait() error {
	return u.tomb.Wait()
}

// Stop stops the upgrader and returns any
// error it encountered when running.
func (u *Upgrader) Stop() error {
	u.Kill()
	return u.Wait()
}

// allowedTargetVersion checks if targetVersion is too different from
// curVersion to allow a downgrade.
func allowedTargetVersion(
	origAgentVersion version.Number,
	curVersion version.Number,
	upgradeRunning bool,
	targetVersion version.Number,
) bool {
	if upgradeRunning && targetVersion == origAgentVersion {
		return true
	}
	if targetVersion.Major < curVersion.Major {
		return false
	}
	if targetVersion.Major == curVersion.Major && targetVersion.Minor < curVersion.Minor {
		return false
	}
	return true
}

// closeChannel can be called multiple times to
// close the channel without panicing.
func closeChannel(ch chan struct{}) {
	select {
	case <-ch:
		return
	default:
		close(ch)
	}
}

func (u *Upgrader) loop() error {
	// Start by reporting current tools (which includes arch/series, and is
	// used by the state server in communicating the desired version below).
	if err := u.st.SetVersion(u.tag.String(), version.Current); err != nil {
		return errors.Annotate(err, "cannot set agent version")
	}
	versionWatcher, err := u.st.WatchAPIVersion(u.tag.String())
	if err != nil {
		return err
	}
	changes := versionWatcher.Changes()
	defer watcher.Stop(versionWatcher, &u.tomb)
	var retry <-chan time.Time

	// We don't read on the dying channel until we have received the
	// initial event from the API version watcher, thus ensuring
	// that we attempt an upgrade even if other workers are dying
	// all around us.
	var (
		dying       <-chan struct{}
		wantTools   *coretools.Tools
		wantVersion version.Number
	)
	for {
		select {
		case _, ok := <-changes:
			if !ok {
				return watcher.EnsureErr(versionWatcher)
			}
			wantVersion, err = u.st.DesiredVersion(u.tag.String())
			if err != nil {
				return err
			}
			logger.Infof("desired tool version: %v", wantVersion)
			dying = u.tomb.Dying()
		case <-retry:
		case <-dying:
			return nil
		}
		if wantVersion == version.Current.Number {
			closeChannel(u.agentUpgradeComplete)
			continue
		} else if !allowedTargetVersion(u.origAgentVersion, version.Current.Number,
			u.areUpgradeStepsRunning(), wantVersion) {
			// See also bug #1299802 where when upgrading from
			// 1.16 to 1.18 there is a race condition that can
			// cause the unit agent to upgrade, and then want to
			// downgrade when its associate machine agent has not
			// finished upgrading.
			logger.Infof("desired tool version: %s is older than current %s, refusing to downgrade",
				wantVersion, version.Current)
			closeChannel(u.agentUpgradeComplete)
			continue
		}
		logger.Infof("upgrade requested from %v to %v", version.Current, wantVersion)

		// Check if tools have already been downloaded.
		wantVersionBinary := toBinaryVersion(wantVersion)
		if u.toolsAlreadyDownloaded(wantVersionBinary) {
			return u.newUpgradeReadyError(wantVersionBinary)
		}

		// Check if tools are available for download.
		wantTools, err = u.st.Tools(u.tag.String())
		if err != nil {
			// Not being able to lookup Tools is considered fatal
			return err
		}
		// The worker cannot be stopped while we're downloading
		// the tools - this means that even if the API is going down
		// repeatedly (causing the agent to be stopped), as long
		// as we have got as far as this, we will still be able to
		// upgrade the agent.
		err := u.ensureTools(wantTools)
		if err == nil {
			return u.newUpgradeReadyError(wantTools.Version)
		}
		logger.Errorf("failed to fetch tools from %q: %v", wantTools.URL, err)
		retry = retryAfter()
	}
}

func toBinaryVersion(vers version.Number) version.Binary {
	outVers := version.Current
	outVers.Number = vers
	return outVers
}

func (u *Upgrader) toolsAlreadyDownloaded(wantVersion version.Binary) bool {
	_, err := agenttools.ReadTools(u.dataDir, wantVersion)
	return err == nil
}

func (u *Upgrader) newUpgradeReadyError(newVersion version.Binary) *UpgradeReadyError {
	return &UpgradeReadyError{
		OldTools:  version.Current,
		NewTools:  newVersion,
		AgentName: u.tag.String(),
		DataDir:   u.dataDir,
	}
}

func (u *Upgrader) ensureTools(agentTools *coretools.Tools) error {
	logger.Infof("fetching tools from %q", agentTools.URL)
	// The reader MUST verify the tools' hash, so there is no
	// need to validate the peer. We cannot anyway: see http://pad.lv/1261780.
	resp, err := utils.GetNonValidatingHTTPClient().Get(agentTools.URL)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("bad HTTP response: %v", resp.Status)
	}
	err = agenttools.UnpackTools(u.dataDir, agentTools, resp.Body)
	if err != nil {
		return fmt.Errorf("cannot unpack tools: %v", err)
	}
	logger.Infof("unpacked tools %s to %s", agentTools.Version, u.dataDir)
	return nil
}