// Restore takes the snapshot from the reader and attempts to apply it to the
// given Raft instance.
func Restore(logger *log.Logger, in io.Reader, r *raft.Raft) error {
// Wrap the reader in a gzip decompressor.
decomp, err := gzip.NewReader(in)
if err != nil {
return fmt.Errorf("failed to decompress snapshot: %v", err)
}
defer func() {
if err := decomp.Close(); err != nil {
logger.Printf("[ERR] snapshot: Failed to close snapshot decompressor: %v", err)
}
}()
// Make a scratch file to receive the contents of the snapshot data so
// we can avoid buffering in memory.
snap, err := ioutil.TempFile("", "snapshot")
if err != nil {
return fmt.Errorf("failed to create temp snapshot file: %v", err)
}
defer func() {
if err := snap.Close(); err != nil {
logger.Printf("[ERR] snapshot: Failed to close temp snapshot: %v", err)
}
if err := os.Remove(snap.Name()); err != nil {
logger.Printf("[ERR] snapshot: Failed to clean up temp snapshot: %v", err)
}
}()
// Read the archive.
var metadata raft.SnapshotMeta
if err := read(decomp, &metadata, snap); err != nil {
return fmt.Errorf("failed to read snapshot file: %v", err)
}
// Sync and rewind the file so it's ready to be read again.
if err := snap.Sync(); err != nil {
return fmt.Errorf("failed to sync temp snapshot: %v", err)
}
if _, err := snap.Seek(0, 0); err != nil {
return fmt.Errorf("failed to rewind temp snapshot: %v", err)
}
// Feed the snapshot into Raft.
if err := r.Restore(&metadata, snap, 60*time.Second); err != nil {
return fmt.Errorf("Raft error when restoring snapshot: %v", err)
}
return nil
}
