func assertToolsList(c *gc.C, list coretools.List, expected []version.Binary) {
	urls := list.URLs()
	c.Check(urls, gc.HasLen, len(expected))
	for _, vers := range expected {
		c.Assert(urls[vers], gc.Not(gc.Equals), "")
	}
}

// findCompatibleTools finds tools in the list that have the same major, minor
// and patch level as version.Current.
//
// Build number is not important to match; uploaded tools will have
// incremented build number, and we want to match them.
func findCompatibleTools(possibleTools coretools.List, version version.Number) (version.Number, coretools.List) {
	var compatibleTools coretools.List
	for _, tools := range possibleTools {
		if isCompatibleVersion(tools.Version.Number, version) {
			compatibleTools = append(compatibleTools, tools)
		}
	}
	return compatibleTools.Newest()
}

// checkToolsSeries verifies that all the given possible tools are for the
// given OS series.
func checkToolsSeries(toolsList coretools.List, series string) error {
	toolsSeries := toolsList.AllSeries()
	if len(toolsSeries) != 1 {
		return fmt.Errorf("expected single series, got %v", toolsSeries)
	}
	if toolsSeries[0] != series {
		return fmt.Errorf("tools mismatch: expected series %v, got %v", series, toolsSeries[0])
	}
	return nil
}

// matchHostArchTools filters the given list of tools to the host architecture.
func matchHostArchTools(allTools tools.List) (tools.List, error) {
	arch := arch.HostArch()
	archTools, err := allTools.Match(tools.Filter{Arch: arch})
	if err == tools.ErrNoMatches {
		return nil, errors.Errorf(
			"need tools for arch %s, only found %s",
			arch, allTools.Arches(),
		)
	} else if err != nil {
		return nil, errors.Trace(err)
	}
	return archTools, nil
}

// SetBootstrapTools returns the newest tools from the given tools list,
// and updates the agent-version configuration attribute.
func SetBootstrapTools(environ environs.Environ, possibleTools coretools.List) (coretools.List, error) {
	if len(possibleTools) == 0 {
		return nil, fmt.Errorf("no bootstrap tools available")
	}
	var newVersion version.Number
	newVersion, toolsList := possibleTools.Newest()
	logger.Infof("newest version: %s", newVersion)
	cfg := environ.Config()
	if agentVersion, _ := cfg.AgentVersion(); agentVersion != newVersion {
		cfg, err := cfg.Apply(map[string]interface{}{
			"agent-version": newVersion.String(),
		})
		if err == nil {
			err = environ.SetConfig(cfg)
		}
		if err != nil {
			return nil, fmt.Errorf("failed to update environment configuration: %v", err)
		}
	}
	bootstrapVersion := newVersion
	// We should only ever bootstrap the exact same version as the client,
	// or we risk bootstrap incompatibility. We still set agent-version to
	// the newest version, so the agent will immediately upgrade itself.
	if !isCompatibleVersion(newVersion, version.Current.Number) {
		compatibleVersion, compatibleTools := findCompatibleTools(possibleTools, version.Current.Number)
		if len(compatibleTools) == 0 {
			logger.Warningf(
				"failed to find %s tools, will attempt to use %s",
				version.Current.Number, newVersion,
			)
		} else {
			bootstrapVersion, toolsList = compatibleVersion, compatibleTools
		}
	}
	logger.Infof("picked bootstrap tools version: %s", bootstrapVersion)
	return toolsList, nil
}

// getBootstrapToolsVersion returns the newest tools from the given tools list.
func getBootstrapToolsVersion(possibleTools coretools.List) (coretools.List, error) {
	if len(possibleTools) == 0 {
		return nil, errors.New("no bootstrap tools available")
	}
	var newVersion version.Number
	newVersion, toolsList := possibleTools.Newest()
	logger.Infof("newest version: %s", newVersion)
	bootstrapVersion := newVersion
	// We should only ever bootstrap the exact same version as the client,
	// or we risk bootstrap incompatibility.
	if !isCompatibleVersion(newVersion, jujuversion.Current) {
		compatibleVersion, compatibleTools := findCompatibleTools(possibleTools, jujuversion.Current)
		if len(compatibleTools) == 0 {
			logger.Infof(
				"failed to find %s tools, will attempt to use %s",
				jujuversion.Current, newVersion,
			)
		} else {
			bootstrapVersion, toolsList = compatibleVersion, compatibleTools
		}
	}
	logger.Infof("picked bootstrap tools version: %s", bootstrapVersion)
	return toolsList, nil
}

func (s *ListSuite) TestURLs(c *gc.C) {
	empty := tools.List{}
	c.Check(empty.URLs(), gc.DeepEquals, map[version.Binary]string{})

	full := tools.List{t100precise, t190quantal, t2001precise}
	c.Check(full.URLs(), gc.DeepEquals, map[version.Binary]string{
		t100precise.Version:  t100precise.URL,
		t190quantal.Version:  t190quantal.URL,
		t2001precise.Version: t2001precise.URL,
	})
}

func (s *ListSuite) TestURLs(c *gc.C) {
	empty := tools.List{}
	c.Check(empty.URLs(), gc.DeepEquals, map[version.Binary][]string{})

	alt := *t100quantal
	alt.URL = strings.Replace(alt.URL, "testing.invalid", "testing.invalid2", 1)
	full := tools.List{
		t100precise,
		t190quantal,
		t100quantal,
		&alt,
		t2001precise,
	}
	c.Check(full.URLs(), gc.DeepEquals, map[version.Binary][]string{
		t100precise.Version:  []string{t100precise.URL},
		t100quantal.Version:  []string{t100quantal.URL, alt.URL},
		t190quantal.Version:  []string{t190quantal.URL},
		t2001precise.Version: []string{t2001precise.URL},
	})
}

// bootstrapImageMetadata returns the image metadata to use for bootstrapping
// the given environment. If the environment provider does not make use of
// simplestreams, no metadata will be returned.
//
// If a bootstrap image ID is specified, image metadat will be synthesised
// using that image ID, and the architecture and series specified by the
// initiator. In addition, the custom image metadat that is saved into the
// state database will have the synthesised image metadata added to it.
func bootstrapImageMetadata(
	environ environs.Environ,
	availableTools coretools.List,
	bootstrapImageId string,
	customImageMetadata *[]*imagemetadata.ImageMetadata,
) ([]*imagemetadata.ImageMetadata, error) {

	hasRegion, ok := environ.(simplestreams.HasRegion)
	if !ok {
		if bootstrapImageId != "" {
			// We only support specifying image IDs for providers
			// that use simplestreams for now.
			return nil, errors.NotSupportedf(
				"specifying bootstrap image for %q provider",
				environ.Config().Type(),
			)
		}
		// No region, no metadata.
		return nil, nil
	}
	region, err := hasRegion.Region()
	if err != nil {
		return nil, errors.Trace(err)
	}

	if bootstrapImageId != "" {
		arches := availableTools.Arches()
		if len(arches) != 1 {
			return nil, errors.NotValidf("multiple architectures with bootstrap image")
		}
		allSeries := availableTools.AllSeries()
		if len(allSeries) != 1 {
			return nil, errors.NotValidf("multiple series with bootstrap image")
		}
		seriesVersion, err := series.SeriesVersion(allSeries[0])
		if err != nil {
			return nil, errors.Trace(err)
		}
		// The returned metadata does not have information about the
		// storage or virtualisation type. Any provider that wants to
		// filter on those properties should allow for empty values.
		meta := &imagemetadata.ImageMetadata{
			Id:         bootstrapImageId,
			Arch:       arches[0],
			Version:    seriesVersion,
			RegionName: region.Region,
			Endpoint:   region.Endpoint,
			Stream:     environ.Config().ImageStream(),
		}
		*customImageMetadata = append(*customImageMetadata, meta)
		return []*imagemetadata.ImageMetadata{meta}, nil
	}

	// For providers that support making use of simplestreams
	// image metadata, search public image metadata. We need
	// to pass this onto Bootstrap for selecting images.
	sources, err := environs.ImageMetadataSources(environ)
	if err != nil {
		return nil, errors.Trace(err)
	}
	imageConstraint := imagemetadata.NewImageConstraint(simplestreams.LookupParams{
		CloudSpec: region,
		Series:    availableTools.AllSeries(),
		Arches:    availableTools.Arches(),
		Stream:    environ.Config().ImageStream(),
	})
	publicImageMetadata, _, err := imagemetadata.Fetch(sources, imageConstraint)
	if err != nil {
		return nil, errors.Annotate(err, "searching image metadata")
	}
	return publicImageMetadata, nil
}

//.........这里部分代码省略.........
		return err
	}
	constraintsValidator.UpdateVocabulary(constraints.Arch, architectures.SortedValues())

	bootstrapConstraints, err := constraintsValidator.Merge(
		args.ModelConstraints, args.BootstrapConstraints,
	)
	if err != nil {
		return errors.Trace(err)
	}

	// The arch we use to find tools isn't the boostrapConstraints arch.
	// We copy the constraints arch to a separate variable and
	// update it from the host arch if not specified.
	// (axw) This is still not quite right:
	// For e.g. if there is a MAAS with only ARM64 machines,
	// on an AMD64 client, we're going to look for only AMD64 tools,
	// limiting what the provider can bootstrap anyway.
	var bootstrapArch string
	if bootstrapConstraints.Arch != nil {
		bootstrapArch = *bootstrapConstraints.Arch
	} else {
		// If no arch is specified as a constraint, we'll bootstrap
		// on the same arch as the client used to bootstrap.
		bootstrapArch = arch.HostArch()
		// We no longer support controllers on i386.
		// If we are bootstrapping from an i386 client,
		// we'll look for amd64 tools.
		if bootstrapArch == arch.I386 {
			bootstrapArch = arch.AMD64
		}
	}

	var availableTools coretools.List
	if !args.BuildAgent {
		ctx.Infof("Looking for packaged Juju agent version %s for %s", args.AgentVersion, bootstrapArch)
		availableTools, err = findPackagedTools(environ, args.AgentVersion, &bootstrapArch, bootstrapSeries)
		if err != nil && !errors.IsNotFound(err) {
			return err
		}
	}
	// If there are no prepackaged tools and a specific version has not been
	// requested, look for or build a local binary.
	var builtTools *sync.BuiltAgent
	if len(availableTools) == 0 && (args.AgentVersion == nil || isCompatibleVersion(*args.AgentVersion, jujuversion.Current)) {
		if args.BuildAgentTarball == nil {
			return errors.New("cannot build agent binary to upload")
		}
		if err := validateUploadAllowed(environ, &bootstrapArch, bootstrapSeries, constraintsValidator); err != nil {
			return err
		}
		if args.BuildAgent {
			ctx.Infof("Building local Juju agent binary version %s for %s", args.AgentVersion, bootstrapArch)
		} else {
			ctx.Infof("No packaged binary found, preparing local Juju agent binary")
		}
		var forceVersion version.Number
		availableTools, forceVersion = locallyBuildableTools(bootstrapSeries)
		builtTools, err = args.BuildAgentTarball(args.BuildAgent, &forceVersion, cfg.AgentStream())
		if err != nil {
			return errors.Annotate(err, "cannot package bootstrap agent binary")
		}
		defer os.RemoveAll(builtTools.Dir)
		for i, tool := range availableTools {
			if tool.URL != "" {
				continue