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![Igor Fedorenko](/assets/img/avatar_default.png)
Much simpler implementation that guarantees each required pack is downloaded only once (and hence does not need to manage pack cache). Also improves large file restore performance. Signed-off-by: Igor Fedorenko <igor@ifedorenko.com>
93 lines
1.8 KiB
Go
93 lines
1.8 KiB
Go
package restorer
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import (
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"os"
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"sync"
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"github.com/cespare/xxhash"
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)
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// writes blobs to target files.
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// multiple files can be written to concurrently.
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// multiple blobs can be concurrently written to the same file.
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// TODO I am not 100% convinced this is necessary, i.e. it may be okay
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// to use multiple os.File to write to the same target file
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type filesWriter struct {
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buckets []filesWriterBucket
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}
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type filesWriterBucket struct {
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lock sync.Mutex
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files map[string]*os.File
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users map[string]int
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}
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func newFilesWriter(count int) *filesWriter {
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buckets := make([]filesWriterBucket, count)
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for b := 0; b < count; b++ {
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buckets[b].files = make(map[string]*os.File)
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buckets[b].users = make(map[string]int)
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}
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return &filesWriter{
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buckets: buckets,
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}
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}
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func (w *filesWriter) writeToFile(path string, blob []byte, offset int64, create bool) error {
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bucket := &w.buckets[uint(xxhash.Sum64String(path))%uint(len(w.buckets))]
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acquireWriter := func() (*os.File, error) {
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bucket.lock.Lock()
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defer bucket.lock.Unlock()
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if wr, ok := bucket.files[path]; ok {
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bucket.users[path]++
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return wr, nil
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}
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var flags int
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if create {
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flags = os.O_CREATE | os.O_TRUNC | os.O_WRONLY
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} else {
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flags = os.O_WRONLY
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}
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wr, err := os.OpenFile(path, flags, 0600)
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if err != nil {
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return nil, err
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}
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bucket.files[path] = wr
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bucket.users[path] = 1
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return wr, nil
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}
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releaseWriter := func(wr *os.File) error {
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bucket.lock.Lock()
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defer bucket.lock.Unlock()
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if bucket.users[path] == 1 {
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delete(bucket.files, path)
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delete(bucket.users, path)
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return wr.Close()
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}
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bucket.users[path]--
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return nil
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}
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wr, err := acquireWriter()
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if err != nil {
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return err
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}
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_, err = wr.WriteAt(blob, offset)
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if err != nil {
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releaseWriter(wr)
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return err
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}
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return releaseWriter(wr)
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}
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