// downloadCharm downloads the given charm name from the provider storage and
// saves the corresponding zip archive to the given charmArchivePath.
func (h *charmsHandler) downloadCharm(name, charmArchivePath string) error {
// Get the provider storage.
storage, err := environs.GetStorage(h.state)
if err != nil {
return errors.Annotate(err, "cannot access provider storage")
}
// Use the storage to retrieve and save the charm archive.
reader, err := storage.Get(name)
if err != nil {
return errors.Annotate(err, "charm not found in the provider storage")
}
defer reader.Close()
data, err := ioutil.ReadAll(reader)
if err != nil {
return errors.Annotate(err, "cannot read charm data")
}
// In order to avoid races, the archive is saved in a temporary file which
// is then atomically renamed. The temporary file is created in the
// charm cache directory so that we can safely assume the rename source and
// target live in the same file system.
cacheDir := filepath.Dir(charmArchivePath)
if err = os.MkdirAll(cacheDir, 0755); err != nil {
return errors.Annotate(err, "cannot create the charms cache")
}
tempCharmArchive, err := ioutil.TempFile(cacheDir, "charm")
if err != nil {
return errors.Annotate(err, "cannot create charm archive temp file")
}
defer tempCharmArchive.Close()
if err = ioutil.WriteFile(tempCharmArchive.Name(), data, 0644); err != nil {
return errors.Annotate(err, "error processing charm archive download")
}
if err = os.Rename(tempCharmArchive.Name(), charmArchivePath); err != nil {
defer os.Remove(tempCharmArchive.Name())
return errors.Annotate(err, "error renaming the charm archive")
}
return nil
}
// repackageAndUploadCharm expands the given charm archive to a
// temporary directoy, repackages it with the given curl's revision,
// then uploads it to providr storage, and finally updates the state.
func (h *charmsHandler) repackageAndUploadCharm(archive *charm.Bundle, curl *charm.URL) error {
// Create a temp dir to contain the extracted charm
// dir and the repackaged archive.
tempDir, err := ioutil.TempDir("", "charm-download")
if err != nil {
return errors.Annotate(err, "cannot create temp directory")
}
defer os.RemoveAll(tempDir)
extractPath := filepath.Join(tempDir, "extracted")
repackagedPath := filepath.Join(tempDir, "repackaged.zip")
repackagedArchive, err := os.Create(repackagedPath)
if err != nil {
return errors.Annotate(err, "cannot repackage uploaded charm")
}
defer repackagedArchive.Close()
// Expand and repack it with the revision specified by curl.
archive.SetRevision(curl.Revision)
if err := archive.ExpandTo(extractPath); err != nil {
return errors.Annotate(err, "cannot extract uploaded charm")
}
charmDir, err := charm.ReadDir(extractPath)
if err != nil {
return errors.Annotate(err, "cannot read extracted charm")
}
// Bundle the charm and calculate its sha256 hash at the
// same time.
hash := sha256.New()
err = charmDir.BundleTo(io.MultiWriter(hash, repackagedArchive))
if err != nil {
return errors.Annotate(err, "cannot repackage uploaded charm")
}
bundleSHA256 := hex.EncodeToString(hash.Sum(nil))
size, err := repackagedArchive.Seek(0, 2)
if err != nil {
return errors.Annotate(err, "cannot get charm file size")
}
// Now upload to provider storage.
if _, err := repackagedArchive.Seek(0, 0); err != nil {
return errors.Annotate(err, "cannot rewind the charm file reader")
}
storage, err := environs.GetStorage(h.state)
if err != nil {
return errors.Annotate(err, "cannot access provider storage")
}
name := charm.Quote(curl.String())
if err := storage.Put(name, repackagedArchive, size); err != nil {
return errors.Annotate(err, "cannot upload charm to provider storage")
}
storageURL, err := storage.URL(name)
if err != nil {
return errors.Annotate(err, "cannot get storage URL for charm")
}
bundleURL, err := url.Parse(storageURL)
if err != nil {
return errors.Annotate(err, "cannot parse storage URL")
}
// And finally, update state.
_, err = h.state.UpdateUploadedCharm(archive, curl, bundleURL, bundleSHA256)
if err != nil {
return errors.Annotate(err, "cannot update uploaded charm in state")
}
return nil
}