github.com/axw/juju@v0.0.0-20161005053422-4bd6544d08d4/apiserver/client/status.go

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

package client

import (
	"fmt"
	"sort"
	"strings"

	"github.com/juju/errors"
	"github.com/juju/utils/set"
	"gopkg.in/juju/charm.v6-unstable"
	"gopkg.in/juju/names.v2"

	"github.com/juju/juju/apiserver/common"
	"github.com/juju/juju/apiserver/params"
	"github.com/juju/juju/network"
	"github.com/juju/juju/state"
	"github.com/juju/juju/state/multiwatcher"
	"github.com/juju/juju/status"
)

func agentStatusFromStatusInfo(s []status.StatusInfo, kind status.HistoryKind) []params.DetailedStatus {
	result := []params.DetailedStatus{}
	for _, v := range s {
		result = append(result, params.DetailedStatus{
			Status: string(v.Status),
			Info:   v.Message,
			Data:   v.Data,
			Since:  v.Since,
			Kind:   string(kind),
		})
	}
	return result

}

type byTime []params.DetailedStatus

func (s byTime) Len() int {
	return len(s)
}
func (s byTime) Swap(i, j int) {
	s[i], s[j] = s[j], s[i]
}
func (s byTime) Less(i, j int) bool {
	return s[i].Since.Before(*s[j].Since)
}

// unitStatusHistory returns a list of status history entries for unit agents or workloads.
func (c *Client) unitStatusHistory(unitTag names.UnitTag, filter status.StatusHistoryFilter, kind status.HistoryKind) ([]params.DetailedStatus, error) {
	unit, err := c.api.stateAccessor.Unit(unitTag.Id())
	if err != nil {
		return nil, errors.Trace(err)
	}
	statuses := []params.DetailedStatus{}
	if kind == status.KindUnit || kind == status.KindWorkload {
		unitStatuses, err := unit.StatusHistory(filter)
		if err != nil {
			return nil, errors.Trace(err)
		}
		statuses = agentStatusFromStatusInfo(unitStatuses, status.KindWorkload)

	}
	if kind == status.KindUnit || kind == status.KindUnitAgent {
		agentStatuses, err := unit.AgentHistory().StatusHistory(filter)
		if err != nil {
			return nil, errors.Trace(err)
		}
		statuses = append(statuses, agentStatusFromStatusInfo(agentStatuses, status.KindUnitAgent)...)
	}

	sort.Sort(byTime(statuses))
	if kind == status.KindUnit && filter.Size > 0 {
		if len(statuses) > filter.Size {
			statuses = statuses[len(statuses)-filter.Size:]
		}
	}

	return statuses, nil
}

// machineStatusHistory returns status history for the given machine.
func (c *Client) machineStatusHistory(machineTag names.MachineTag, filter status.StatusHistoryFilter, kind status.HistoryKind) ([]params.DetailedStatus, error) {
	machine, err := c.api.stateAccessor.Machine(machineTag.Id())
	if err != nil {
		return nil, errors.Trace(err)
	}
	var sInfo []status.StatusInfo
	if kind == status.KindMachineInstance || kind == status.KindContainerInstance {
		sInfo, err = machine.InstanceStatusHistory(filter)
	} else {
		sInfo, err = machine.StatusHistory(filter)
	}
	if err != nil {
		return nil, errors.Trace(err)
	}
	return agentStatusFromStatusInfo(sInfo, kind), nil
}

// StatusHistory returns a slice of past statuses for several entities.
func (c *Client) StatusHistory(request params.StatusHistoryRequests) params.StatusHistoryResults {

	results := params.StatusHistoryResults{}
	// TODO(perrito666) the contents of the loop could be split into
	// a oneHistory method for clarity.
	for _, request := range request.Requests {
		filter := status.StatusHistoryFilter{
			Size:  request.Filter.Size,
			Date:  request.Filter.Date,
			Delta: request.Filter.Delta,
		}
		if err := c.checkCanRead(); err != nil {
			history := params.StatusHistoryResult{
				Error: common.ServerError(err),
			}
			results.Results = append(results.Results, history)
			continue

		}

		if err := filter.Validate(); err != nil {
			history := params.StatusHistoryResult{
				Error: common.ServerError(errors.Annotate(err, "cannot validate status history filter")),
			}
			results.Results = append(results.Results, history)
			continue
		}

		var (
			err  error
			hist []params.DetailedStatus
		)
		kind := status.HistoryKind(request.Kind)
		err = errors.NotValidf("%q requires a unit, got %T", kind, request.Tag)
		switch kind {
		case status.KindUnit, status.KindWorkload, status.KindUnitAgent:
			var u names.UnitTag
			if u, err = names.ParseUnitTag(request.Tag); err == nil {
				hist, err = c.unitStatusHistory(u, filter, kind)
			}
		default:
			var m names.MachineTag
			if m, err = names.ParseMachineTag(request.Tag); err == nil {
				hist, err = c.machineStatusHistory(m, filter, kind)
			}
		}

		if err == nil {
			sort.Sort(byTime(hist))
		}

		results.Results = append(results.Results,
			params.StatusHistoryResult{
				History: params.History{Statuses: hist},
				Error:   common.ServerError(errors.Annotatef(err, "fetching status history for %q", request.Tag)),
			})
	}
	return results
}

// FullStatus gives the information needed for juju status over the api
func (c *Client) FullStatus(args params.StatusParams) (params.FullStatus, error) {
	if err := c.checkCanRead(); err != nil {
		return params.FullStatus{}, err
	}

	var noStatus params.FullStatus
	var context statusContext
	var err error
	if context.services, context.units, context.latestCharms, err =
		fetchAllApplicationsAndUnits(c.api.stateAccessor, len(args.Patterns) <= 0); err != nil {
		return noStatus, errors.Annotate(err, "could not fetch services and units")
	}
	if context.machines, err = fetchMachines(c.api.stateAccessor, nil); err != nil {
		return noStatus, errors.Annotate(err, "could not fetch machines")
	}
	if context.relations, err = fetchRelations(c.api.stateAccessor); err != nil {
		return noStatus, errors.Annotate(err, "could not fetch relations")
	}
	if len(context.services) > 0 {
		if context.leaders, err = c.api.stateAccessor.ApplicationLeaders(); err != nil {
			return noStatus, errors.Annotate(err, " could not fetch leaders")
		}
	}

	logger.Debugf("Applications: %v", context.services)

	if len(args.Patterns) > 0 {
		predicate := BuildPredicateFor(args.Patterns)

		// First, attempt to match machines. Any units on those
		// machines are implicitly matched.
		matchedMachines := make(set.Strings)
		for _, machineList := range context.machines {
			for _, m := range machineList {
				matches, err := predicate(m)
				if err != nil {
					return noStatus, errors.Annotate(
						err, "could not filter machines",
					)
				}
				if matches {
					matchedMachines.Add(m.Id())
				}
			}
		}

		// Filter units
		matchedSvcs := make(set.Strings)
		unitChainPredicate := UnitChainPredicateFn(predicate, context.unitByName)
		for _, unitMap := range context.units {
			for name, unit := range unitMap {
				machineId, err := unit.AssignedMachineId()
				if err != nil {
					machineId = ""
				} else if matchedMachines.Contains(machineId) {
					// Unit is on a matching machine.
					matchedSvcs.Add(unit.ApplicationName())
					continue
				}

				// Always start examining at the top-level. This
				// prevents a situation where we filter a subordinate
				// before we discover its parent is a match.
				if !unit.IsPrincipal() {
					continue
				} else if matches, err := unitChainPredicate(unit); err != nil {
					return noStatus, errors.Annotate(err, "could not filter units")
				} else if !matches {
					delete(unitMap, name)
					continue
				}
				matchedSvcs.Add(unit.ApplicationName())
				if machineId != "" {
					matchedMachines.Add(machineId)
				}
			}
		}

		// Filter services
		for svcName, svc := range context.services {
			if matchedSvcs.Contains(svcName) {
				// There are matched units for this service.
				continue
			} else if matches, err := predicate(svc); err != nil {
				return noStatus, errors.Annotate(err, "could not filter applications")
			} else if !matches {
				delete(context.services, svcName)
			}
		}

		// Filter machines
		for status, machineList := range context.machines {
			matched := make([]*state.Machine, 0, len(machineList))
			for _, m := range machineList {
				machineContainers, err := m.Containers()
				if err != nil {
					return noStatus, err
				}
				machineContainersSet := set.NewStrings(machineContainers...)

				if matchedMachines.Contains(m.Id()) || !matchedMachines.Intersection(machineContainersSet).IsEmpty() {
					// The machine is matched directly, or contains a unit
					// or container that matches.
					logger.Tracef("machine %s is hosting something.", m.Id())
					matched = append(matched, m)
					continue
				}
			}
			context.machines[status] = matched
		}
	}

	modelStatus, err := c.modelStatus()
	if err != nil {
		return noStatus, errors.Annotate(err, "cannot determine model status")
	}
	return params.FullStatus{
		Model:        modelStatus,
		Machines:     processMachines(context.machines),
		Applications: context.processApplications(),
		Relations:    context.processRelations(),
	}, nil
}

// newToolsVersionAvailable will return a string representing a tools
// version only if the latest check is newer than current tools.
func (c *Client) modelStatus() (params.ModelStatusInfo, error) {
	var info params.ModelStatusInfo

	m, err := c.api.stateAccessor.Model()
	if err != nil {
		return info, errors.Annotate(err, "cannot get model")
	}
	info.Name = m.Name()
	info.CloudTag = names.NewCloudTag(m.Cloud()).String()
	info.CloudRegion = m.CloudRegion()

	cfg, err := m.Config()
	if err != nil {
		return info, errors.Annotate(err, "cannot obtain current model config")
	}

	latestVersion := m.LatestToolsVersion()
	current, ok := cfg.AgentVersion()
	if ok {
		info.Version = current.String()
		if current.Compare(latestVersion) < 0 {
			info.AvailableVersion = latestVersion.String()
		}
	}

	migStatus, err := c.getMigrationStatus()
	if err != nil {
		// It's not worth killing the entire status out if migration
		// status can't be retrieved.
		logger.Errorf("error retrieving migration status: %v", err)
		info.Migration = "error retrieving migration status"
	} else {
		info.Migration = migStatus
	}

	return info, nil
}

func (c *Client) getMigrationStatus() (string, error) {
	mig, err := c.api.stateAccessor.LatestMigration()
	if err != nil {
		if errors.IsNotFound(err) {
			return "", nil
		}
		return "", errors.Trace(err)
	}

	phase, err := mig.Phase()
	if err != nil {
		return "", errors.Trace(err)
	}
	if phase.IsTerminal() {
		// There has been a migration attempt but it's no longer
		// active - don't include this in status.
		return "", nil
	}

	return mig.StatusMessage(), nil
}

type statusContext struct {
	// machines: top-level machine id -> list of machines nested in
	// this machine.
	machines map[string][]*state.Machine
	// services: service name -> service
	services     map[string]*state.Application
	relations    map[string][]*state.Relation
	units        map[string]map[string]*state.Unit
	latestCharms map[charm.URL]*state.Charm
	leaders      map[string]string
}

// fetchMachines returns a map from top level machine id to machines, where machines[0] is the host
// machine and machines[1..n] are any containers (including nested ones).
//
// If machineIds is non-nil, only machines whose IDs are in the set are returned.
func fetchMachines(st Backend, machineIds set.Strings) (map[string][]*state.Machine, error) {
	v := make(map[string][]*state.Machine)
	machines, err := st.AllMachines()
	if err != nil {
		return nil, err
	}
	// AllMachines gives us machines sorted by id.
	for _, m := range machines {
		if machineIds != nil && !machineIds.Contains(m.Id()) {
			continue
		}
		parentId, ok := m.ParentId()
		if !ok {
			// Only top level host machines go directly into the machine map.
			v[m.Id()] = []*state.Machine{m}
		} else {
			topParentId := state.TopParentId(m.Id())
			machines, ok := v[topParentId]
			if !ok {
				panic(fmt.Errorf("unexpected machine id %q", parentId))
			}
			machines = append(machines, m)
			v[topParentId] = machines
		}
	}
	return v, nil
}

// fetchAllApplicationsAndUnits returns a map from service name to service,
// a map from service name to unit name to unit, and a map from base charm URL to latest URL.
func fetchAllApplicationsAndUnits(
	st Backend,
	matchAny bool,
) (map[string]*state.Application, map[string]map[string]*state.Unit, map[charm.URL]*state.Charm, error) {

	svcMap := make(map[string]*state.Application)
	unitMap := make(map[string]map[string]*state.Unit)
	latestCharms := make(map[charm.URL]*state.Charm)
	services, err := st.AllApplications()
	if err != nil {
		return nil, nil, nil, err
	}
	for _, s := range services {
		units, err := s.AllUnits()
		if err != nil {
			return nil, nil, nil, err
		}
		svcUnitMap := make(map[string]*state.Unit)
		for _, u := range units {
			svcUnitMap[u.Name()] = u
		}
		if matchAny || len(svcUnitMap) > 0 {
			unitMap[s.Name()] = svcUnitMap
			svcMap[s.Name()] = s
			// Record the base URL for the application's charm so that
			// the latest store revision can be looked up.
			charmURL, _ := s.CharmURL()
			if charmURL.Schema == "cs" {
				latestCharms[*charmURL.WithRevision(-1)] = nil
			}
		}
	}
	for baseURL := range latestCharms {
		ch, err := st.LatestPlaceholderCharm(&baseURL)
		if errors.IsNotFound(err) {
			continue
		}
		if err != nil {
			return nil, nil, nil, err
		}
		latestCharms[baseURL] = ch
	}

	return svcMap, unitMap, latestCharms, nil
}

// fetchRelations returns a map of all relations keyed by service name.
//
// This structure is useful for processServiceRelations() which needs
// to have the relations for each service. Reading them once here
// avoids the repeated DB hits to retrieve the relations for each
// service that used to happen in processServiceRelations().
func fetchRelations(st Backend) (map[string][]*state.Relation, error) {
	relations, err := st.AllRelations()
	if err != nil {
		return nil, err
	}
	out := make(map[string][]*state.Relation)
	for _, relation := range relations {
		for _, ep := range relation.Endpoints() {
			out[ep.ApplicationName] = append(out[ep.ApplicationName], relation)
		}
	}
	return out, nil
}

type machineAndContainers map[string][]*state.Machine

func (m machineAndContainers) HostForMachineId(id string) *state.Machine {
	// Element 0 is assumed to be the top-level machine.
	return m[id][0]
}

func (m machineAndContainers) Containers(id string) []*state.Machine {
	return m[id][1:]
}

func processMachines(idToMachines map[string][]*state.Machine) map[string]params.MachineStatus {
	machinesMap := make(map[string]params.MachineStatus)
	cache := make(map[string]params.MachineStatus)
	for id, machines := range idToMachines {

		if len(machines) <= 0 {
			continue
		}

		// Element 0 is assumed to be the top-level machine.
		tlMachine := machines[0]
		hostStatus := makeMachineStatus(tlMachine)
		machinesMap[id] = hostStatus
		cache[id] = hostStatus

		for _, machine := range machines[1:] {
			parent, ok := cache[state.ParentId(machine.Id())]
			if !ok {
				panic("We've broken an assumpution.")
			}

			status := makeMachineStatus(machine)
			parent.Containers[machine.Id()] = status
			cache[machine.Id()] = status
		}
	}
	return machinesMap
}

func makeMachineStatus(machine *state.Machine) (status params.MachineStatus) {
	var err error
	status.Id = machine.Id()
	agentStatus := processMachine(machine)
	status.AgentStatus = agentStatus

	status.Series = machine.Series()
	status.Jobs = paramsJobsFromJobs(machine.Jobs())
	status.WantsVote = machine.WantsVote()
	status.HasVote = machine.HasVote()
	sInfo, err := machine.InstanceStatus()
	populateStatusFromStatusInfoAndErr(&status.InstanceStatus, sInfo, err)
	instid, err := machine.InstanceId()
	if err == nil {
		status.InstanceId = instid
		addr, err := machine.PublicAddress()
		if err != nil {
			// Usually this indicates that no addresses have been set on the
			// machine yet.
			addr = network.Address{}
			logger.Debugf("error fetching public address: %q", err)
		}
		status.DNSName = addr.Value
	} else {
		if errors.IsNotProvisioned(err) {
			status.InstanceId = "pending"
		} else {
			status.InstanceId = "error"
		}
	}
	hc, err := machine.HardwareCharacteristics()
	if err != nil {
		if !errors.IsNotFound(err) {
			status.Hardware = "error"
		}
	} else {
		status.Hardware = hc.String()
	}
	status.Containers = make(map[string]params.MachineStatus)
	return
}

func (context *statusContext) processRelations() []params.RelationStatus {
	var out []params.RelationStatus
	relations := context.getAllRelations()
	for _, relation := range relations {
		var eps []params.EndpointStatus
		var scope charm.RelationScope
		var relationInterface string
		for _, ep := range relation.Endpoints() {
			eps = append(eps, params.EndpointStatus{
				ApplicationName: ep.ApplicationName,
				Name:            ep.Name,
				Role:            string(ep.Role),
				Subordinate:     context.isSubordinate(&ep),
			})
			// these should match on both sides so use the last
			relationInterface = ep.Interface
			scope = ep.Scope
		}
		relStatus := params.RelationStatus{
			Id:        relation.Id(),
			Key:       relation.String(),
			Interface: relationInterface,
			Scope:     string(scope),
			Endpoints: eps,
		}
		out = append(out, relStatus)
	}
	return out
}

// This method exists only to dedup the loaded relations as they will
// appear multiple times in context.relations.
func (context *statusContext) getAllRelations() []*state.Relation {
	var out []*state.Relation
	seenRelations := make(map[int]bool)
	for _, relations := range context.relations {
		for _, relation := range relations {
			if _, found := seenRelations[relation.Id()]; !found {
				out = append(out, relation)
				seenRelations[relation.Id()] = true
			}
		}
	}
	return out
}

func (context *statusContext) isSubordinate(ep *state.Endpoint) bool {
	service := context.services[ep.ApplicationName]
	if service == nil {
		return false
	}
	return isSubordinate(ep, service)
}

func isSubordinate(ep *state.Endpoint, service *state.Application) bool {
	return ep.Scope == charm.ScopeContainer && !service.IsPrincipal()
}

// paramsJobsFromJobs converts state jobs to params jobs.
func paramsJobsFromJobs(jobs []state.MachineJob) []multiwatcher.MachineJob {
	paramsJobs := make([]multiwatcher.MachineJob, len(jobs))
	for i, machineJob := range jobs {
		paramsJobs[i] = machineJob.ToParams()
	}
	return paramsJobs
}

func (context *statusContext) processApplications() map[string]params.ApplicationStatus {
	servicesMap := make(map[string]params.ApplicationStatus)
	for _, s := range context.services {
		servicesMap[s.Name()] = context.processApplication(s)
	}
	return servicesMap
}

func (context *statusContext) processApplication(service *state.Application) params.ApplicationStatus {
	serviceCharm, _, err := service.Charm()
	if err != nil {
		return params.ApplicationStatus{Err: common.ServerError(err)}
	}

	var processedStatus = params.ApplicationStatus{
		Charm:   serviceCharm.URL().String(),
		Series:  service.Series(),
		Exposed: service.IsExposed(),
		Life:    processLife(service),
	}

	if latestCharm, ok := context.latestCharms[*serviceCharm.URL().WithRevision(-1)]; ok && latestCharm != nil {
		if latestCharm.Revision() > serviceCharm.URL().Revision {
			processedStatus.CanUpgradeTo = latestCharm.String()
		}
	}

	processedStatus.Relations, processedStatus.SubordinateTo, err = context.processServiceRelations(service)
	if err != nil {
		processedStatus.Err = common.ServerError(err)
		return processedStatus
	}
	units := context.units[service.Name()]
	if service.IsPrincipal() {
		processedStatus.Units = context.processUnits(units, serviceCharm.URL().String())
	}
	applicationStatus, err := service.Status()
	if err != nil {
		processedStatus.Err = common.ServerError(err)
		return processedStatus
	}
	processedStatus.Status.Status = applicationStatus.Status.String()
	processedStatus.Status.Info = applicationStatus.Message
	processedStatus.Status.Data = applicationStatus.Data
	processedStatus.Status.Since = applicationStatus.Since

	metrics := serviceCharm.Metrics()
	planRequired := metrics != nil && metrics.Plan != nil && metrics.Plan.Required
	if planRequired || len(service.MetricCredentials()) > 0 {
		processedStatus.MeterStatuses = context.processUnitMeterStatuses(units)
	}

	versions := make([]status.StatusInfo, 0, len(units))
	for _, unit := range units {
		statuses, err := unit.WorkloadVersionHistory().StatusHistory(
			status.StatusHistoryFilter{Size: 1},
		)
		if err != nil {
			processedStatus.Err = common.ServerError(err)
			return processedStatus
		}
		// Even though we fully expect there to be historical values there,
		// even the first should be the empty string, the status history
		// collection is not added to in a transactional manner, so it may be
		// not there even though we'd really like it to be. Such is mongo.
		if len(statuses) > 0 {
			versions = append(versions, statuses[0])
		}
	}
	if len(versions) > 0 {
		sort.Sort(bySinceDescending(versions))
		processedStatus.WorkloadVersion = versions[0].Message
	}

	return processedStatus
}

func isColorStatus(code state.MeterStatusCode) bool {
	return code == state.MeterGreen || code == state.MeterAmber || code == state.MeterRed
}

func (context *statusContext) processUnitMeterStatuses(units map[string]*state.Unit) map[string]params.MeterStatus {
	unitsMap := make(map[string]params.MeterStatus)
	for _, unit := range units {
		meterStatus, err := unit.GetMeterStatus()
		if err != nil {
			continue
		}
		if isColorStatus(meterStatus.Code) {
			unitsMap[unit.Name()] = params.MeterStatus{Color: strings.ToLower(meterStatus.Code.String()), Message: meterStatus.Info}
		}
	}
	if len(unitsMap) > 0 {
		return unitsMap
	}
	return nil
}

func (context *statusContext) processUnits(units map[string]*state.Unit, serviceCharm string) map[string]params.UnitStatus {
	unitsMap := make(map[string]params.UnitStatus)
	for _, unit := range units {
		unitsMap[unit.Name()] = context.processUnit(unit, serviceCharm)
	}
	return unitsMap
}

func (context *statusContext) processUnit(unit *state.Unit, serviceCharm string) params.UnitStatus {
	var result params.UnitStatus
	addr, err := unit.PublicAddress()
	if err != nil {
		// Usually this indicates that no addresses have been set on the
		// machine yet.
		addr = network.Address{}
		logger.Debugf("error fetching public address: %v", err)
	}
	result.PublicAddress = addr.Value
	unitPorts, _ := unit.OpenedPorts()
	for _, port := range unitPorts {
		result.OpenedPorts = append(result.OpenedPorts, port.String())
	}
	if unit.IsPrincipal() {
		result.Machine, _ = unit.AssignedMachineId()
	}
	curl, _ := unit.CharmURL()
	if serviceCharm != "" && curl != nil && curl.String() != serviceCharm {
		result.Charm = curl.String()
	}
	workloadVersion, err := unit.WorkloadVersion()
	if err == nil {
		result.WorkloadVersion = workloadVersion
	} else {
		logger.Debugf("error fetching workload version: %v", err)
	}

	processUnitAndAgentStatus(unit, &result)

	if subUnits := unit.SubordinateNames(); len(subUnits) > 0 {
		result.Subordinates = make(map[string]params.UnitStatus)
		for _, name := range subUnits {
			subUnit := context.unitByName(name)
			// subUnit may be nil if subordinate was filtered out.
			if subUnit != nil {
				result.Subordinates[name] = context.processUnit(subUnit, serviceCharm)
			}
		}
	}
	if leader := context.leaders[unit.ApplicationName()]; leader == unit.Name() {
		result.Leader = true
	}
	return result
}

func (context *statusContext) unitByName(name string) *state.Unit {
	serviceName := strings.Split(name, "/")[0]
	return context.units[serviceName][name]
}

func (context *statusContext) processServiceRelations(service *state.Application) (related map[string][]string, subord []string, err error) {
	subordSet := make(set.Strings)
	related = make(map[string][]string)
	relations := context.relations[service.Name()]
	for _, relation := range relations {
		ep, err := relation.Endpoint(service.Name())
		if err != nil {
			return nil, nil, err
		}
		relationName := ep.Relation.Name
		eps, err := relation.RelatedEndpoints(service.Name())
		if err != nil {
			return nil, nil, err
		}
		for _, ep := range eps {
			if isSubordinate(&ep, service) {
				subordSet.Add(ep.ApplicationName)
			}
			related[relationName] = append(related[relationName], ep.ApplicationName)
		}
	}
	for relationName, serviceNames := range related {
		sn := set.NewStrings(serviceNames...)
		related[relationName] = sn.SortedValues()
	}
	return related, subordSet.SortedValues(), nil
}

type lifer interface {
	Life() state.Life
}

// processUnitAndAgentStatus retrieves status information for both unit and unitAgents.
func processUnitAndAgentStatus(unit *state.Unit, unitStatus *params.UnitStatus) {
	unitStatus.AgentStatus, unitStatus.WorkloadStatus = processUnit(unit)
}

// populateStatusFromStatusInfoAndErr creates AgentStatus from the typical output
// of a status getter.
func populateStatusFromStatusInfoAndErr(agent *params.DetailedStatus, statusInfo status.StatusInfo, err error) {
	agent.Err = err
	agent.Status = statusInfo.Status.String()
	agent.Info = statusInfo.Message
	agent.Data = filterStatusData(statusInfo.Data)
	agent.Since = statusInfo.Since
}

// processMachine retrieves version and status information for the given machine.
// It also returns deprecated legacy status information.
func processMachine(machine *state.Machine) (out params.DetailedStatus) {
	statusInfo, err := common.MachineStatus(machine)
	populateStatusFromStatusInfoAndErr(&out, statusInfo, err)

	out.Life = processLife(machine)

	if t, err := machine.AgentTools(); err == nil {
		out.Version = t.Version.Number.String()
	}
	return
}

// processUnit retrieves version and status information for the given unit.
func processUnit(unit *state.Unit) (agentStatus, workloadStatus params.DetailedStatus) {
	agent, workload := common.UnitStatus(unit)
	populateStatusFromStatusInfoAndErr(&agentStatus, agent.Status, agent.Err)
	populateStatusFromStatusInfoAndErr(&workloadStatus, workload.Status, workload.Err)

	agentStatus.Life = processLife(unit)

	if t, err := unit.AgentTools(); err == nil {
		agentStatus.Version = t.Version.Number.String()
	}
	return
}

// filterStatusData limits what agent StatusData data is passed over
// the API. This prevents unintended leakage of internal-only data.
func filterStatusData(status map[string]interface{}) map[string]interface{} {
	out := make(map[string]interface{})
	for name, value := range status {
		// use a set here if we end up with a larger whitelist
		if name == "relation-id" {
			out[name] = value
		}
	}
	return out
}

func processLife(entity lifer) string {
	if life := entity.Life(); life != state.Alive {
		// alive is the usual state so omit it by default.
		return life.String()
	}
	return ""
}

type bySinceDescending []status.StatusInfo

// Len implements sort.Interface.
func (s bySinceDescending) Len() int { return len(s) }

// Swap implements sort.Interface.
func (s bySinceDescending) Swap(a, b int) { s[a], s[b] = s[b], s[a] }

// Less implements sort.Interface.
func (s bySinceDescending) Less(a, b int) bool { return s[a].Since.After(*s[b].Since) }