func (f *FileWriter) startNewBlock() error {
// TODO: we don't need to wait for previous blocks to ack before continuing
if f.blockWriter != nil {
err := f.blockWriter.Close()
if err != nil {
return err
}
}
var previous *hdfs.ExtendedBlockProto
if f.block != nil {
previous = f.block.GetB()
}
addBlockReq := &hdfs.AddBlockRequestProto{
Src: proto.String(f.name),
ClientName: proto.String(f.client.namenode.ClientName()),
Previous: previous,
}
addBlockResp := &hdfs.AddBlockResponseProto{}
err := f.client.namenode.Execute("addBlock", addBlockReq, addBlockResp)
if err != nil {
if nnErr, ok := err.(*rpc.NamenodeError); ok {
err = interpretException(nnErr.Exception, err)
}
return &os.PathError{"create", f.name, err}
}
f.block = addBlockResp.GetBlock()
f.blockWriter = rpc.NewBlockWriter(f.block, f.client.namenode, f.blockSize)
return nil
}
// Append opens an existing file in HDFS and returns an io.WriteCloser for
// writing to it. Because of the way that HDFS writes are buffered and
// acknowledged asynchronously, it is very important that Close is called after
// all data has been written.
func (c *Client) Append(name string) (*FileWriter, error) {
info, err := c.getFileInfo(name)
if err != nil {
return nil, &os.PathError{"append", name, err}
}
appendReq := &hdfs.AppendRequestProto{
Src: proto.String(name),
ClientName: proto.String(c.namenode.ClientName()),
}
appendResp := &hdfs.AppendResponseProto{}
err = c.namenode.Execute("append", appendReq, appendResp)
if err != nil {
if nnErr, ok := err.(*rpc.NamenodeError); ok {
err = interpretException(nnErr.Exception, err)
}
return nil, &os.PathError{"append", name, err}
}
req := &hdfs.GetBlockLocationsRequestProto{
Src: proto.String(name),
Offset: proto.Uint64(0),
Length: proto.Uint64(uint64(info.Size())),
}
resp := &hdfs.GetBlockLocationsResponseProto{}
err = c.namenode.Execute("getBlockLocations", req, resp)
if err != nil {
return nil, err
}
blocks := resp.GetLocations().GetBlocks()
f := &FileWriter{
client: c,
name: name,
replication: int(appendResp.Stat.GetBlockReplication()),
blockSize: int64(appendResp.Stat.GetBlocksize()),
}
if len(blocks) == 0 {
return f, nil
}
f.block = blocks[len(blocks)-1]
f.blockWriter = rpc.NewBlockWriter(f.block, c.namenode, f.blockSize)
return f, nil
}