Exemple #1
0
func (s *commonSuite) TestAuthFuncForTagKind(c *gc.C) {
	// TODO(dimitern): This list of all supported tags and kinds needs
	// to live in juju/names.
	uuid, err := utils.NewUUID()
	c.Assert(err, jc.ErrorIsNil)

	allTags := []names.Tag{
		nil, // invalid tag
		names.NewActionTag(uuid.String()),
		names.NewCharmTag("cs:precise/missing"),
		names.NewModelTag(uuid.String()),
		names.NewFilesystemTag("20/20"),
		names.NewLocalUserTag("user"),
		names.NewMachineTag("42"),
		names.NewNetworkTag("public"),
		names.NewRelationTag("wordpress:mysql mysql:db"),
		names.NewServiceTag("wordpress"),
		names.NewSpaceTag("apps"),
		names.NewStorageTag("foo/42"),
		names.NewUnitTag("wordpress/5"),
		names.NewUserTag("joe"),
		names.NewVolumeTag("80/20"),
	}
	for i, allowedTag := range allTags {
		c.Logf("test #%d: allowedTag: %v", i, allowedTag)

		var allowedKind string
		if allowedTag != nil {
			allowedKind = allowedTag.Kind()
		}
		getAuthFunc := common.AuthFuncForTagKind(allowedKind)

		authFunc, err := getAuthFunc()
		if allowedKind == "" {
			c.Check(err, gc.ErrorMatches, "tag kind cannot be empty")
			c.Check(authFunc, gc.IsNil)
			continue
		} else if !c.Check(err, jc.ErrorIsNil) {
			continue
		}

		for j, givenTag := range allTags {
			c.Logf("test #%d.%d: givenTag: %v", i, j, givenTag)

			var givenKind string
			if givenTag != nil {
				givenKind = givenTag.Kind()
			}
			if allowedKind == givenKind {
				c.Check(authFunc(givenTag), jc.IsTrue)
			} else {
				c.Check(authFunc(givenTag), jc.IsFalse)
			}
		}
	}
}
Exemple #2
0
func (s *WatcherSuite) TestRelationsChanged(c *gc.C) {
	signalAll(&s.st, &s.leadership)
	assertNotifyEvent(c, s.watcher.RemoteStateChanged(), "waiting for remote state change")

	relationTag := names.NewRelationTag("mysql:peer")
	s.st.relations[relationTag] = &mockRelation{
		id: 123, life: params.Alive,
	}
	s.st.relationUnitsWatchers[relationTag] = &mockRelationUnitsWatcher{
		changes: make(chan multiwatcher.RelationUnitsChange, 1),
	}
	s.st.unit.service.relationsWatcher.changes <- []string{relationTag.Id()}

	// There should not be any signal until the relation units watcher has
	// returned its initial event also.
	assertNoNotifyEvent(c, s.watcher.RemoteStateChanged(), "remote state change")
	s.st.relationUnitsWatchers[relationTag].changes <- multiwatcher.RelationUnitsChange{
		Changed: map[string]multiwatcher.UnitSettings{"mysql/1": {1}, "mysql/2": {2}},
	}
	assertNotifyEvent(c, s.watcher.RemoteStateChanged(), "waiting for remote state change")
	c.Assert(
		s.watcher.Snapshot().Relations,
		jc.DeepEquals,
		map[int]remotestate.RelationSnapshot{
			123: remotestate.RelationSnapshot{
				Life:    params.Alive,
				Members: map[string]int64{"mysql/1": 1, "mysql/2": 2},
			},
		},
	)

	// If a relation is known, then updating it does not require any input
	// from the relation units watcher.
	s.st.relations[relationTag].life = params.Dying
	s.st.unit.service.relationsWatcher.changes <- []string{relationTag.Id()}
	assertNotifyEvent(c, s.watcher.RemoteStateChanged(), "waiting for remote state change")
	c.Assert(s.watcher.Snapshot().Relations[123].Life, gc.Equals, params.Dying)

	// If a relation is not found, then it should be removed from the
	// snapshot and its relation units watcher stopped.
	delete(s.st.relations, relationTag)
	s.st.unit.service.relationsWatcher.changes <- []string{relationTag.Id()}
	assertNotifyEvent(c, s.watcher.RemoteStateChanged(), "waiting for remote state change")
	c.Assert(s.watcher.Snapshot().Relations, gc.HasLen, 0)
	c.Assert(s.st.relationUnitsWatchers[relationTag].stopped, jc.IsTrue)
}
Exemple #3
0
func (s *relationsSuite) TestNewRelationsWithExistingRelations(c *gc.C) {
	unitTag := names.NewUnitTag("wordpress/0")
	abort := make(chan struct{})

	var numCalls int32
	unitEntity := params.Entities{Entities: []params.Entity{params.Entity{Tag: "unit-wordpress-0"}}}
	relationUnits := params.RelationUnits{RelationUnits: []params.RelationUnit{
		{Relation: "relation-wordpress.db#mysql.db", Unit: "unit-wordpress-0"},
	}}
	relationResults := params.RelationResults{
		Results: []params.RelationResult{
			{
				Id:   1,
				Key:  "wordpress:db mysql:db",
				Life: params.Alive,
				Endpoint: multiwatcher.Endpoint{
					ServiceName: "wordpress",
					Relation:    charm.Relation{Name: "mysql", Role: charm.RoleProvider, Interface: "db"},
				}},
		},
	}

	apiCaller := mockAPICaller(c, &numCalls,
		uniterApiCall("Life", unitEntity, params.LifeResults{Results: []params.LifeResult{{Life: params.Alive}}}, nil),
		uniterApiCall("JoinedRelations", unitEntity, params.StringsResults{Results: []params.StringsResult{{Result: []string{"relation-wordpress:db mysql:db"}}}}, nil),
		uniterApiCall("Relation", relationUnits, relationResults, nil),
		uniterApiCall("Relation", relationUnits, relationResults, nil),
		uniterApiCall("Watch", unitEntity, params.NotifyWatchResults{Results: []params.NotifyWatchResult{{NotifyWatcherId: "1"}}}, nil),
		uniterApiCall("EnterScope", relationUnits, params.ErrorResults{Results: []params.ErrorResult{{}}}, nil),
	)
	st := uniter.NewState(apiCaller, unitTag)
	r, err := relation.NewRelations(st, unitTag, s.stateDir, s.relationsDir, abort)
	c.Assert(err, jc.ErrorIsNil)
	assertNumCalls(c, &numCalls, 6)

	info := r.GetInfo()
	c.Assert(info, gc.HasLen, 1)
	oneInfo := info[1]
	c.Assert(oneInfo.RelationUnit.Relation().Tag(), gc.Equals, names.NewRelationTag("wordpress:db mysql:db"))
	c.Assert(oneInfo.RelationUnit.Endpoint(), jc.DeepEquals, uniter.Endpoint{
		Relation: charm.Relation{Name: "mysql", Role: "provider", Interface: "db", Optional: false, Limit: 0, Scope: ""},
	})
	c.Assert(oneInfo.MemberNames, gc.HasLen, 0)
}
Exemple #4
0
// relationsChanged responds to service relation changes.
func (w *RemoteStateWatcher) relationsChanged(keys []string) error {
	w.mu.Lock()
	defer w.mu.Unlock()
	for _, key := range keys {
		relationTag := names.NewRelationTag(key)
		rel, err := w.st.Relation(relationTag)
		if params.IsCodeNotFoundOrCodeUnauthorized(err) {
			// If it's actually gone, this unit cannot have entered
			// scope, and therefore never needs to know about it.
			if ruw, ok := w.relations[relationTag]; ok {
				worker.Stop(ruw)
				delete(w.relations, relationTag)
				delete(w.current.Relations, ruw.relationId)
			}
		} else if err != nil {
			return errors.Trace(err)
		} else {
			if _, ok := w.relations[relationTag]; ok {
				relationSnapshot := w.current.Relations[rel.Id()]
				relationSnapshot.Life = rel.Life()
				w.current.Relations[rel.Id()] = relationSnapshot
				continue
			}
			ruw, err := w.st.WatchRelationUnits(relationTag, w.unit.Tag())
			if err != nil {
				return errors.Trace(err)
			}
			// Because of the delay before handing off responsibility to
			// newRelationUnitsWatcher below, add to our own catacomb to
			// ensure errors get picked up if they happen.
			if err := w.catacomb.Add(ruw); err != nil {
				return errors.Trace(err)
			}
			if err := w.watchRelationUnits(rel, relationTag, ruw); err != nil {
				return errors.Trace(err)
			}
		}
	}
	return nil
}
Exemple #5
0
func (s *WatcherSuite) TestRelationUnitsChanged(c *gc.C) {
	signalAll(&s.st, &s.leadership)
	assertNotifyEvent(c, s.watcher.RemoteStateChanged(), "waiting for remote state change")

	relationTag := names.NewRelationTag("mysql:peer")
	s.st.relations[relationTag] = &mockRelation{
		id: 123, life: params.Alive,
	}
	s.st.relationUnitsWatchers[relationTag] = &mockRelationUnitsWatcher{
		changes: make(chan multiwatcher.RelationUnitsChange, 1),
	}

	s.st.unit.service.relationsWatcher.changes <- []string{relationTag.Id()}
	s.st.relationUnitsWatchers[relationTag].changes <- multiwatcher.RelationUnitsChange{
		Changed: map[string]multiwatcher.UnitSettings{"mysql/1": {1}},
	}
	assertNotifyEvent(c, s.watcher.RemoteStateChanged(), "waiting for remote state change")

	s.st.relationUnitsWatchers[relationTag].changes <- multiwatcher.RelationUnitsChange{
		Changed: map[string]multiwatcher.UnitSettings{"mysql/1": {2}, "mysql/2": {1}},
	}
	assertNotifyEvent(c, s.watcher.RemoteStateChanged(), "waiting for remote state change")
	c.Assert(
		s.watcher.Snapshot().Relations[123].Members,
		jc.DeepEquals,
		map[string]int64{"mysql/1": 2, "mysql/2": 1},
	)

	s.st.relationUnitsWatchers[relationTag].changes <- multiwatcher.RelationUnitsChange{
		Departed: []string{"mysql/1", "mysql/42"},
	}
	assertNotifyEvent(c, s.watcher.RemoteStateChanged(), "waiting for remote state change")
	c.Assert(
		s.watcher.Snapshot().Relations[123].Members,
		jc.DeepEquals,
		map[string]int64{"mysql/2": 1},
	)
}
Exemple #6
0
// relationsChanged responds to service relation changes.
func (w *RemoteStateWatcher) relationsChanged(keys []string) error {
	w.mu.Lock()
	defer w.mu.Unlock()
	for _, key := range keys {
		relationTag := names.NewRelationTag(key)
		rel, err := w.st.Relation(relationTag)
		if params.IsCodeNotFoundOrCodeUnauthorized(err) {
			// If it's actually gone, this unit cannot have entered
			// scope, and therefore never needs to know about it.
			if ruw, ok := w.relations[relationTag]; ok {
				if err := ruw.Stop(); err != nil {
					return errors.Trace(err)
				}
				delete(w.relations, relationTag)
				delete(w.current.Relations, ruw.relationId)
			}
		} else if err != nil {
			return err
		} else {
			if _, ok := w.relations[relationTag]; ok {
				relationSnapshot := w.current.Relations[rel.Id()]
				relationSnapshot.Life = rel.Life()
				w.current.Relations[rel.Id()] = relationSnapshot
				continue
			}
			in, err := w.st.WatchRelationUnits(relationTag, w.unit.Tag())
			if err != nil {
				return errors.Trace(err)
			}
			if err := w.watchRelationUnits(rel, relationTag, in); err != nil {
				watcher.Stop(in, &w.tomb)
				return errors.Trace(err)
			}
		}
	}
	return nil
}
Exemple #7
0
// RelationById returns the existing relation with the given id.
func (st *State) RelationById(id int) (*Relation, error) {
	var results params.RelationResults
	args := params.RelationIds{
		RelationIds: []int{id},
	}
	err := st.facade.FacadeCall("RelationById", args, &results)
	if err != nil {
		return nil, err
	}
	if len(results.Results) != 1 {
		return nil, fmt.Errorf("expected 1 result, got %d", len(results.Results))
	}
	result := results.Results[0]
	if err := result.Error; err != nil {
		return nil, err
	}
	relationTag := names.NewRelationTag(result.Key)
	return &Relation{
		id:   result.Id,
		tag:  relationTag,
		life: result.Life,
		st:   st,
	}, nil
}
Exemple #8
0
// Tag returns a name identifying the relation.
func (r *Relation) Tag() names.Tag {
	return names.NewRelationTag(r.doc.Key)
}
Exemple #9
0
			c.Assert(names.IsValidRelation(key), gc.Equals, isValid)
			c.Assert(names.IsValidRelation(peerKey), gc.Equals, isValid)
		}
	}
}

var parseRelationTagTests = []struct {
	tag      string
	expected names.Tag
	err      error
}{{
	tag: "",
	err: names.InvalidTagError("", ""),
}, {
	tag:      "relation-wordpress:db mysql:db",
	expected: names.NewRelationTag("wordpress:db mysql:db"),
}, {
	tag:      "relation-wordpress:mysql",
	expected: names.NewRelationTag("wordpress:mysql"),
}, {
	tag: "dave",
	err: names.InvalidTagError("dave", ""),
}, {
	tag: "service-dave",
	err: names.InvalidTagError("service-dave", names.RelationTagKind),
}}

func (s *relationSuite) TestParseRelationTag(c *gc.C) {
	for i, t := range parseRelationTagTests {
		c.Logf("test %d: %s", i, t.tag)
		got, err := names.ParseRelationTag(t.tag)
Exemple #10
0
func (f *filter) loop(unitTag string) (err error) {
	// TODO(dfc) named return value is a time bomb
	defer func() {
		if params.IsCodeNotFoundOrCodeUnauthorized(err) {
			err = worker.ErrTerminateAgent
		}
	}()
	tag, err := names.ParseUnitTag(unitTag)
	if err != nil {
		return err
	}
	if f.unit, err = f.st.Unit(tag); err != nil {
		return err
	}
	if err = f.unitChanged(); err != nil {
		return err
	}
	f.service, err = f.unit.Service()
	if err != nil {
		return err
	}
	if err = f.serviceChanged(); err != nil {
		return err
	}
	unitw, err := f.unit.Watch()
	if err != nil {
		return err
	}
	defer f.maybeStopWatcher(unitw)
	servicew, err := f.service.Watch()
	if err != nil {
		return err
	}
	defer f.maybeStopWatcher(servicew)
	// configw and relationsw can get restarted, so we need to use
	// their eventual values in the defer calls.
	var configw apiwatcher.NotifyWatcher
	var configChanges <-chan struct{}
	curl, err := f.unit.CharmURL()
	if err == nil {
		configw, err = f.unit.WatchConfigSettings()
		if err != nil {
			return err
		}
		configChanges = configw.Changes()
		f.upgradeFrom.url = curl
	} else if err != uniter.ErrNoCharmURLSet {
		filterLogger.Errorf("unit charm: %v", err)
		return err
	}
	defer func() {
		if configw != nil {
			watcher.Stop(configw, &f.tomb)
		}
	}()
	actionsw, err := f.unit.WatchActions()
	if err != nil {
		return err
	}
	f.actionsPending = make([]string, 0)
	defer func() {
		if actionsw != nil {
			watcher.Stop(actionsw, &f.tomb)
		}
	}()
	relationsw, err := f.service.WatchRelations()
	if err != nil {
		return err
	}
	defer func() {
		if relationsw != nil {
			watcher.Stop(relationsw, &f.tomb)
		}
	}()
	var addressChanges <-chan struct{}
	addressesw, err := f.unit.WatchAddresses()
	if err != nil {
		return err
	}
	defer watcher.Stop(addressesw, &f.tomb)

	// Config events cannot be meaningfully discarded until one is available;
	// once we receive the initial change, we unblock discard requests by
	// setting this channel to its namesake on f.
	var discardConfig chan struct{}
	for {
		var ok bool
		select {
		case <-f.tomb.Dying():
			return tomb.ErrDying

		// Handle watcher changes.
		case _, ok = <-unitw.Changes():
			filterLogger.Debugf("got unit change")
			if !ok {
				return watcher.MustErr(unitw)
			}
			if err = f.unitChanged(); err != nil {
				return err
			}
		case _, ok = <-servicew.Changes():
			filterLogger.Debugf("got service change")
			if !ok {
				return watcher.MustErr(servicew)
			}
			if err = f.serviceChanged(); err != nil {
				return err
			}
		case _, ok = <-configChanges:
			filterLogger.Debugf("got config change")
			if !ok {
				return watcher.MustErr(configw)
			}
			if addressChanges == nil {
				// We start reacting to address changes after the
				// first config-changed is processed, ignoring the
				// initial address changed event.
				addressChanges = addressesw.Changes()
				if _, ok := <-addressChanges; !ok {
					return watcher.MustErr(addressesw)
				}
			}
			filterLogger.Debugf("preparing new config event")
			f.outConfig = f.outConfigOn
			discardConfig = f.discardConfig
		case _, ok = <-addressChanges:
			filterLogger.Debugf("got address change")
			if !ok {
				return watcher.MustErr(addressesw)
			}
			// address change causes config-changed event
			filterLogger.Debugf("preparing new config event")
			f.outConfig = f.outConfigOn
		case ids, ok := <-actionsw.Changes():
			filterLogger.Debugf("got %d actions", len(ids))
			if !ok {
				return watcher.MustErr(actionsw)
			}
			f.actionsPending = append(f.actionsPending, ids...)
			f.nextAction = f.getNextAction()
		case keys, ok := <-relationsw.Changes():
			filterLogger.Debugf("got relations change")
			if !ok {
				return watcher.MustErr(relationsw)
			}
			var ids []int
			for _, key := range keys {
				relationTag := names.NewRelationTag(key).String()
				rel, err := f.st.Relation(relationTag)
				if params.IsCodeNotFoundOrCodeUnauthorized(err) {
					// If it's actually gone, this unit cannot have entered
					// scope, and therefore never needs to know about it.
				} else if err != nil {
					return err
				} else {
					ids = append(ids, rel.Id())
				}
			}
			f.relationsChanged(ids)

		// Send events on active out chans.
		case f.outUpgrade <- f.upgrade:
			filterLogger.Debugf("sent upgrade event")
			f.outUpgrade = nil
		case f.outResolved <- f.resolved:
			filterLogger.Debugf("sent resolved event")
			f.outResolved = nil
		case f.outConfig <- nothing:
			filterLogger.Debugf("sent config event")
			f.outConfig = nil
		case f.outAction <- f.nextAction:
			f.nextAction = f.getNextAction()
			filterLogger.Debugf("sent action event")
		case f.outRelations <- f.relations:
			filterLogger.Debugf("sent relations event")
			f.outRelations = nil
			f.relations = nil

		// Handle explicit requests.
		case curl := <-f.setCharm:
			filterLogger.Debugf("changing charm to %q", curl)
			// We need to restart the config watcher after setting the
			// charm, because service config settings are distinct for
			// different service charms.
			if configw != nil {
				if err := configw.Stop(); err != nil {
					return err
				}
			}
			if err := f.unit.SetCharmURL(curl); err != nil {
				filterLogger.Debugf("failed setting charm url %q: %v", curl, err)
				return err
			}
			select {
			case <-f.tomb.Dying():
				return tomb.ErrDying
			case f.didSetCharm <- nothing:
			}
			configw, err = f.unit.WatchConfigSettings()
			if err != nil {
				return err
			}
			configChanges = configw.Changes()

			// Restart the relations watcher.
			if err := relationsw.Stop(); err != nil {
				return err
			}
			relationsw, err = f.service.WatchRelations()
			if err != nil {
				return err
			}

			f.upgradeFrom.url = curl
			if err = f.upgradeChanged(); err != nil {
				return err
			}
		case force := <-f.wantForcedUpgrade:
			filterLogger.Debugf("want forced upgrade %v", force)
			f.upgradeFrom.force = force
			if err = f.upgradeChanged(); err != nil {
				return err
			}
		case <-f.wantResolved:
			filterLogger.Debugf("want resolved event")
			if f.resolved != params.ResolvedNone {
				f.outResolved = f.outResolvedOn
			}
		case <-f.clearResolved:
			filterLogger.Debugf("resolved event handled")
			f.outResolved = nil
			if err := f.unit.ClearResolved(); err != nil {
				return err
			}
			if err := f.unitChanged(); err != nil {
				return err
			}
			select {
			case <-f.tomb.Dying():
				return tomb.ErrDying
			case f.didClearResolved <- nothing:
			}
		case <-discardConfig:
			filterLogger.Debugf("discarded config event")
			f.outConfig = nil
		}
	}
}
Exemple #11
0
// Tag returns a name identifying the relation that is safe to use
// as a file name.
func (r *Relation) Tag() string {
	return names.NewRelationTag(r.doc.Key).String()
}
Exemple #12
0
	resultId:   "wordpress" + names.ActionMarker + "333",
}, {
	tag:        "action-wordpress/0" + names.ActionMarker + "333",
	expectKind: names.ActionTagKind,
	expectType: names.ActionTag{},
	resultId:   "wordpress/0" + names.ActionMarker + "333",
}, {
	tag:       "foo",
	resultErr: `"foo" is not a valid tag`,
}}

var makeTag = map[string]func(string) names.Tag{
	names.MachineTagKind:  func(tag string) names.Tag { return names.NewMachineTag(tag) },
	names.UnitTagKind:     func(tag string) names.Tag { return names.NewUnitTag(tag) },
	names.ServiceTagKind:  func(tag string) names.Tag { return names.NewServiceTag(tag) },
	names.RelationTagKind: func(tag string) names.Tag { return names.NewRelationTag(tag) },
	names.EnvironTagKind:  func(tag string) names.Tag { return names.NewEnvironTag(tag) },
	names.UserTagKind:     func(tag string) names.Tag { return names.NewUserTag(tag) },
	names.NetworkTagKind:  func(tag string) names.Tag { return names.NewNetworkTag(tag) },
	names.ActionTagKind:   func(tag string) names.Tag { return names.NewActionTag(tag) },
}

func (*tagSuite) TestParseTag(c *gc.C) {
	for i, test := range parseTagTests {
		c.Logf("test %d: %q expectKind %q", i, test.tag, test.expectKind)
		tag, err := names.ParseTag(test.tag)
		if test.resultErr != "" {
			c.Assert(err, gc.ErrorMatches, test.resultErr)
			c.Assert(tag, gc.IsNil)

			// If the tag has a valid kind which matches the
Exemple #13
0
func (f *filter) loop(unitTag names.UnitTag) (err error) {
	// TODO(dfc) named return value is a time bomb
	defer func() {
		if params.IsCodeNotFoundOrCodeUnauthorized(err) {
			err = worker.ErrTerminateAgent
		}
	}()
	if f.unit, err = f.st.Unit(unitTag); err != nil {
		return err
	}
	if err = f.unitChanged(); err != nil {
		return err
	}
	if err = f.meterStatusChanged(); err != nil {
		return err
	}
	f.service, err = f.unit.Service()
	if err != nil {
		return err
	}
	if err = f.serviceChanged(); err != nil {
		return err
	}
	unitw, err := f.unit.Watch()
	if err != nil {
		return err
	}
	defer f.maybeStopWatcher(unitw)
	servicew, err := f.service.Watch()
	if err != nil {
		return err
	}
	defer f.maybeStopWatcher(servicew)
	// configw and relationsw can get restarted, so we need to use
	// their eventual values in the defer calls.
	var configw apiwatcher.NotifyWatcher
	var configChanges <-chan struct{}
	curl, err := f.unit.CharmURL()
	if err == nil {
		configw, err = f.unit.WatchConfigSettings()
		if err != nil {
			return err
		}
		configChanges = configw.Changes()
		f.upgradeFrom.url = curl
	} else if err != uniter.ErrNoCharmURLSet {
		filterLogger.Errorf("unit charm: %v", err)
		return err
	}
	defer f.maybeStopWatcher(configw)
	actionsw, err := f.unit.WatchActionNotifications()
	if err != nil {
		return err
	}
	f.actionsPending = make([]string, 0)
	defer f.maybeStopWatcher(actionsw)
	relationsw, err := f.service.WatchRelations()
	if err != nil {
		return err
	}
	defer f.maybeStopWatcher(relationsw)
	meterStatusw, err := f.unit.WatchMeterStatus()
	if err != nil {
		return err
	}
	defer f.maybeStopWatcher(meterStatusw)
	addressesw, err := f.unit.WatchAddresses()
	if err != nil {
		return err
	}
	defer watcher.Stop(addressesw, &f.tomb)
	storagew, err := f.unit.WatchStorage()
	if err != nil {
		return err
	}
	defer watcher.Stop(storagew, &f.tomb)
	leaderSettingsw, err := f.st.LeadershipSettings.WatchLeadershipSettings(f.service.Tag().Id())
	if err != nil {
		return err
	}
	defer watcher.Stop(leaderSettingsw, &f.tomb)

	// Ignore external requests for leader settings behaviour until we see the first change.
	var discardLeaderSettings <-chan struct{}
	var wantLeaderSettings <-chan bool
	// By default we send all leaderSettings onwards.
	sendLeaderSettings := true

	// Config events cannot be meaningfully discarded until one is available;
	// once we receive the initial config and address changes, we unblock
	// discard requests by setting this channel to its namesake on f.
	var discardConfig chan struct{}
	var seenConfigChange bool
	var seenAddressChange bool
	maybePrepareConfigEvent := func() {
		if !seenAddressChange {
			filterLogger.Debugf("no address change seen yet, skipping config event")
			return
		}
		if !seenConfigChange {
			filterLogger.Debugf("no config change seen yet, skipping config event")
			return
		}
		filterLogger.Debugf("preparing new config event")
		f.outConfig = f.outConfigOn
		discardConfig = f.discardConfig
	}

	for {
		var ok bool
		select {
		case <-f.tomb.Dying():
			return tomb.ErrDying

		// Handle watcher changes.
		case _, ok = <-unitw.Changes():
			filterLogger.Debugf("got unit change")
			if !ok {
				return watcher.EnsureErr(unitw)
			}
			if err = f.unitChanged(); err != nil {
				return err
			}
		case _, ok = <-servicew.Changes():
			filterLogger.Debugf("got service change")
			if !ok {
				return watcher.EnsureErr(servicew)
			}
			if err = f.serviceChanged(); err != nil {
				return err
			}
		case _, ok = <-configChanges:
			filterLogger.Debugf("got config change")
			if !ok {
				return watcher.EnsureErr(configw)
			}
			seenConfigChange = true
			maybePrepareConfigEvent()
		case _, ok = <-addressesw.Changes():
			filterLogger.Debugf("got address change")
			if !ok {
				return watcher.EnsureErr(addressesw)
			}
			seenAddressChange = true
			maybePrepareConfigEvent()
		case _, ok = <-meterStatusw.Changes():
			filterLogger.Debugf("got meter status change")
			if !ok {
				return watcher.EnsureErr(meterStatusw)
			}
			if err = f.meterStatusChanged(); err != nil {
				return errors.Trace(err)
			}
		case ids, ok := <-actionsw.Changes():
			filterLogger.Debugf("got %d actions", len(ids))
			if !ok {
				return watcher.EnsureErr(actionsw)
			}
			f.actionsPending = append(f.actionsPending, ids...)
			f.nextAction = f.getNextAction()
		case keys, ok := <-relationsw.Changes():
			filterLogger.Debugf("got relations change")
			if !ok {
				return watcher.EnsureErr(relationsw)
			}
			var ids []int
			for _, key := range keys {
				relationTag := names.NewRelationTag(key)
				rel, err := f.st.Relation(relationTag)
				if params.IsCodeNotFoundOrCodeUnauthorized(err) {
					// If it's actually gone, this unit cannot have entered
					// scope, and therefore never needs to know about it.
				} else if err != nil {
					return err
				} else {
					ids = append(ids, rel.Id())
				}
			}
			f.relationsChanged(ids)
		case ids, ok := <-storagew.Changes():
			filterLogger.Debugf("got storage change")
			if !ok {
				return watcher.EnsureErr(storagew)
			}
			tags := make([]names.StorageTag, len(ids))
			for i, id := range ids {
				tag := names.NewStorageTag(id)
				tags[i] = tag
			}
			f.storageChanged(tags)
		case _, ok = <-leaderSettingsw.Changes():
			filterLogger.Debugf("got leader settings change: ok=%t", ok)
			if !ok {
				return watcher.EnsureErr(leaderSettingsw)
			}
			if sendLeaderSettings {
				// only send the leader settings changed event
				// if it hasn't been explicitly disabled
				f.outLeaderSettings = f.outLeaderSettingsOn
			} else {
				filterLogger.Debugf("not sending leader settings change (want=false)")
			}
			discardLeaderSettings = f.discardLeaderSettings
			wantLeaderSettings = f.wantLeaderSettings

		// Send events on active out chans.
		case f.outUpgrade <- f.upgrade:
			filterLogger.Debugf("sent upgrade event")
			f.outUpgrade = nil
		case f.outResolved <- f.resolved:
			filterLogger.Debugf("sent resolved event")
			f.outResolved = nil
		case f.outConfig <- nothing:
			filterLogger.Debugf("sent config event")
			f.outConfig = nil
		case f.outLeaderSettings <- nothing:
			filterLogger.Debugf("sent leader settings event")
			f.outLeaderSettings = nil
		case f.outAction <- f.nextAction:
			f.nextAction = f.getNextAction()
			filterLogger.Debugf("sent action event")
		case f.outRelations <- f.relations:
			filterLogger.Debugf("sent relations event")
			f.outRelations = nil
			f.relations = nil
		case f.outMeterStatus <- nothing:
			filterLogger.Debugf("sent meter status change event")
			f.outMeterStatus = nil
		case f.outStorage <- f.storage:
			filterLogger.Debugf("sent storage event")
			f.outStorage = nil
			f.storage = nil

		// Handle explicit requests.
		case curl := <-f.setCharm:
			filterLogger.Debugf("changing charm to %q", curl)
			// We need to restart the config watcher after setting the
			// charm, because service config settings are distinct for
			// different service charms.
			if configw != nil {
				if err := configw.Stop(); err != nil {
					return err
				}
			}
			if err := f.unit.SetCharmURL(curl); err != nil {
				filterLogger.Debugf("failed setting charm url %q: %v", curl, err)
				return err
			}
			select {
			case <-f.tomb.Dying():
				return tomb.ErrDying
			case f.didSetCharm <- nothing:
			}
			configw, err = f.unit.WatchConfigSettings()
			if err != nil {
				return err
			}
			configChanges = configw.Changes()

			// Restart the relations watcher.
			if err := relationsw.Stop(); err != nil {
				return err
			}
			relationsw, err = f.service.WatchRelations()
			if err != nil {
				return err
			}

			f.upgradeFrom.url = curl
			if err = f.upgradeChanged(); err != nil {
				return err
			}
		case force := <-f.wantForcedUpgrade:
			filterLogger.Debugf("want forced upgrade %v", force)
			f.upgradeFrom.force = force
			if err = f.upgradeChanged(); err != nil {
				return err
			}
		case <-f.wantResolved:
			filterLogger.Debugf("want resolved event")
			if f.resolved != params.ResolvedNone {
				f.outResolved = f.outResolvedOn
			}
		case sendEvents := <-wantLeaderSettings:
			filterLogger.Debugf("want leader settings event: %t", sendEvents)
			sendLeaderSettings = sendEvents
			if sendEvents {
				// go ahead and send an event right now,
				// they're waiting for us
				f.outLeaderSettings = f.outLeaderSettingsOn
			} else {
				// Make sure we don't have a pending event
				f.outLeaderSettings = nil
			}
		case <-f.clearResolved:
			filterLogger.Debugf("resolved event handled")
			f.outResolved = nil
			if err := f.unit.ClearResolved(); err != nil {
				return err
			}
			if err := f.unitChanged(); err != nil {
				return err
			}
			select {
			case <-f.tomb.Dying():
				return tomb.ErrDying
			case f.didClearResolved <- nothing:
			}
		case <-discardConfig:
			filterLogger.Debugf("discarded config event")
			f.outConfig = nil
		case <-discardLeaderSettings:
			filterLogger.Debugf("discarded leader settings event")
			f.outLeaderSettings = nil
		}
	}
}