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Unify symlink handling in http cache #1071

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Merged
merged 3 commits into from
Apr 19, 2022
Merged

Unify symlink handling in http cache #1071

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6d814d1
Unify symlink handling in http cache
Apr 18, 2022
e79202e
Merge branch 'main' into gsoltis/http_symlink
Apr 18, 2022
d5b1463
Merge branch 'main' into gsoltis/http_symlink
Apr 19, 2022
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81 changes: 52 additions & 29 deletions cli/internal/cache/cache_http.go
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Original file line number Diff line number Diff line change
Expand Up @@ -89,21 +89,24 @@ func (cache *httpCache) write(w io.WriteCloser, hash string, files []string) {
}
}

func (cache *httpCache) storeFile(tw *tar.Writer, name string) error {
info, err := os.Lstat(name)
func (cache *httpCache) storeFile(tw *tar.Writer, repoRelativePath string) error {
info, err := os.Lstat(repoRelativePath)
if err != nil {
return err
}
target := ""
if info.Mode()&os.ModeSymlink != 0 {
target, _ = os.Readlink(name)
target, err = os.Readlink(repoRelativePath)
if err != nil {
return err
}
}
hdr, err := tar.FileInfoHeader(info, filepath.ToSlash(target))
if err != nil {
return err
}
// Ensure posix path for filename written in header.
hdr.Name = filepath.ToSlash(name)
hdr.Name = filepath.ToSlash(repoRelativePath)
// Zero out all timestamps.
hdr.ModTime = mtime
hdr.AccessTime = mtime
Expand All @@ -118,7 +121,7 @@ func (cache *httpCache) storeFile(tw *tar.Writer, name string) error {
} else if info.IsDir() || target != "" {
return nil // nothing to write
}
f, err := os.Open(name)
f, err := os.Open(repoRelativePath)
if err != nil {
return err
}
Expand Down Expand Up @@ -202,7 +205,7 @@ func (cache *httpCache) retrieve(hash string) (bool, []string, int, error) {
}
gzr, err := gzip.NewReader(artifactReader)
if err != nil {
return false, files, duration, err
return false, nil, 0, err
}
defer gzr.Close()
tr := tar.NewReader(gzr)
Expand All @@ -211,58 +214,78 @@ func (cache *httpCache) retrieve(hash string) (bool, []string, int, error) {
if err != nil {
if err == io.EOF {
for _, link := range missingLinks {
if err := os.Symlink(link.Linkname, link.Name); err != nil {
return false, files, duration, err
err := restoreSymlink(link, true)
if err != nil {
return false, nil, 0, err
}
}

return true, files, duration, nil
}
return false, files, duration, err
return false, nil, 0, err
}
files = append(files, hdr.Name)
switch hdr.Typeflag {
case tar.TypeDir:
if err := os.MkdirAll(hdr.Name, fs.DirPermissions); err != nil {
return false, files, duration, err
return false, nil, 0, err
}
case tar.TypeReg:
if dir := path.Dir(hdr.Name); dir != "." {
if err := os.MkdirAll(dir, fs.DirPermissions); err != nil {
return false, files, duration, err
return false, nil, 0, err
}
}
if f, err := os.OpenFile(hdr.Name, os.O_WRONLY|os.O_TRUNC|os.O_CREATE, os.FileMode(hdr.Mode)); err != nil {
return false, files, duration, err
return false, nil, 0, err
} else if _, err := io.Copy(f, tr); err != nil {
return false, files, duration, err
return false, nil, 0, err
} else if err := f.Close(); err != nil {
return false, files, duration, err
return false, nil, 0, err
}
case tar.TypeSymlink:
if dir := path.Dir(hdr.Name); dir != "." {
if err := os.MkdirAll(dir, fs.DirPermissions); err != nil {
return false, files, duration, err
}
}
if _, err := os.Lstat(hdr.Name); err == nil {
if err := os.Remove(hdr.Name); err != nil {
return false, files, duration, err
}
} else if os.IsNotExist(err) {
if err := restoreSymlink(hdr, false); errors.Is(err, errNonexistentLinkTarget) {
missingLinks = append(missingLinks, hdr)
continue
}

if err := os.Symlink(hdr.Linkname, hdr.Name); err != nil {
return false, files, duration, err
} else if err != nil {
return false, nil, 0, err
}
default:
log.Printf("Unhandled file type %d for %s", hdr.Typeflag, hdr.Name)
}
}
}

var errNonexistentLinkTarget = errors.New("the link target does not exist")

func restoreSymlink(hdr *tar.Header, allowNonexistentTargets bool) error {
// Note that hdr.Linkname is really the link target
linkTarget := filepath.FromSlash(hdr.Linkname)
repoRelativeLinkFilename := filepath.FromSlash(hdr.Name)
err := fs.EnsureDir(repoRelativeLinkFilename)
if err != nil {
return err
}
repoRelativeLinkTarget := filepath.Join(filepath.Dir(repoRelativeLinkFilename), linkTarget)
if _, err := os.Lstat(repoRelativeLinkTarget); err != nil {
if os.IsNotExist(err) {
if !allowNonexistentTargets {
return errNonexistentLinkTarget
}
// if we're allowing nonexistent link targets, proceed to creating the link
} else {
return err
}
}
// Ensure that the link we're about to create doesn't already exist
if err := os.Remove(repoRelativeLinkFilename); err != nil && !errors.Is(err, os.ErrNotExist) {
return err
}
if err := os.Symlink(linkTarget, repoRelativeLinkFilename); err != nil {
return err
}
return nil
}

func (cache *httpCache) Clean(target string) {
// Not possible; this implementation can only clean for a hash.
}
Expand Down