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// Copyright 2013 Canonical Ltd.
// Licensed under the AGPLv3, see LICENCE file for details.
package agent
import (
"fmt"
"io/ioutil"
"os"
"path"
"strings"
"launchpad.net/juju-core/utils"
)
// The format file in the agent config directory is used to identify the
// method of serialization. This is used by individual format readers and
// writers to be able to translate from the file format to the in-memory
// structure.
//
// Juju only supports upgrading from single steps, so Juju only needs to know
// about the current format and the format of the previous stable release.
// For convenience, the format name includes the version number of the stable
// release that it will be released with. Once this release has happened, the
// format should be considered FIXED, and should no longer be modified. If
// changes are necessary to the format, a new format should be created.
//
// We don't need to create new formats for each release, the version number is
// just a convenience for us to know which stable release introduced that
// format.
const (
formatFilename = "format"
currentFormat = format_1_16
previousFormat = format_1_12
)
var (
currentFormatter = &formatter_1_16{}
previousFormatter = &formatter_1_12{}
)
// The formatter defines the two methods needed by the formatters for
// translating to and from the internal, format agnostic, structure.
type formatter interface {
read(dirName string) (*configInternal, error)
write(config *configInternal) error
writeCommands(config *configInternal) ([]string, error)
// Migrate is called when upgrading from the previous format to the current format.
migrate(config *configInternal)
}
func formatFile(dirName string) string {
return path.Join(dirName, formatFilename)
}
func readFormat(dirName string) (string, error) {
contents, err := ioutil.ReadFile(formatFile(dirName))
// Once the previousFormat is defined to have a format file (1.16 or
// above), not finding a format file should be a real error.
if err != nil {
return previousFormat, nil
}
return strings.TrimSpace(string(contents)), nil
}
func newFormatter(format string) (formatter, error) {
switch format {
case currentFormat:
return currentFormatter, nil
case previousFormat:
return previousFormatter, nil
}
return nil, fmt.Errorf("unknown agent config format")
}
func writeFormatFile(dirName string, format string) error {
if err := os.MkdirAll(dirName, 0755); err != nil {
return err
}
newFile := path.Join(dirName, formatFilename+"-new")
if err := ioutil.WriteFile(newFile, []byte(format+"\n"), 0644); err != nil {
return err
}
return os.Rename(newFile, formatFile(dirName))
}
func writeFileCommands(filename, contents string, permission int) []string {
quotedFilename := utils.ShQuote(filename)
return []string{
fmt.Sprintf("install -m %o /dev/null %s", permission, quotedFilename),
fmt.Sprintf(`printf '%%s\n' %s > %s`, utils.ShQuote(contents), quotedFilename),
}
}
func writeCommandsForFormat(dirName, format string) []string {
commands := []string{"mkdir -p " + utils.ShQuote(dirName)}
commands = append(commands, writeFileCommands(formatFile(dirName), format, 0644)...)
return commands
}
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