// ShardReader returns a reader for streaming shard data.
// Returned ReadCloser must be closed by the caller.
func (c *Client) ShardReader(id uint64) (io.ReadCloser, error) {
// Connect to remote server.
conn, err := tcp.Dial("tcp", c.host, MuxHeader)
if err != nil {
return nil, err
}
// Send request to server.
if err := c.writeRequest(conn, &internal.Request{ShardID: proto.Uint64(id)}); err != nil {
return nil, fmt.Errorf("write request: %s", err)
}
// Read response from the server.
resp, err := c.readResponse(conn)
if err != nil {
return nil, fmt.Errorf("read response: %s", err)
}
// If there was an error then return it and close connection.
if resp.GetError() != "" {
conn.Close()
return nil, errors.New(resp.GetError())
}
// Returning remaining stream for caller to consume.
return conn, nil
}
// download downloads a snapshot of either the metastore or a shard from a host to a given path.
func (cmd *Command) download(req *snapshotter.Request, path string) error {
// Create local file to write to.
f, err := os.Create(path)
if err != nil {
return fmt.Errorf("open temp file: %s", err)
}
defer f.Close()
// Connect to snapshotter service.
conn, err := tcp.Dial("tcp", cmd.host, snapshotter.MuxHeader)
if err != nil {
return err
}
defer conn.Close()
// Write the request
if err := json.NewEncoder(conn).Encode(req); err != nil {
return fmt.Errorf("encode snapshot request: %s", err)
}
// Read snapshot from the connection
if _, err := io.Copy(f, conn); err != nil {
return fmt.Errorf("copy backup to file: %s", err)
}
return nil
}
// requestInfo will request the database or retention policy information from the host
func (cmd *Command) requestInfo(request *snapshotter.Request) (*snapshotter.Response, error) {
// Connect to snapshotter service.
conn, err := tcp.Dial("tcp", cmd.host, snapshotter.MuxHeader)
if err != nil {
return nil, err
}
defer conn.Close()
// Write the request
if err := json.NewEncoder(conn).Encode(request); err != nil {
return nil, fmt.Errorf("encode snapshot request: %s", err)
}
// Read the response
var r snapshotter.Response
if err := json.NewDecoder(conn).Decode(&r); err != nil {
return nil, err
}
return &r, nil
}