Documentation
¶
Overview ¶
Package transfer implements wire transfer with the datanodes.
Index ¶
Constants ¶
This section is empty.
Variables ¶
var ErrEndOfBlock = errors.New("end of block")
var ErrInvalidSeqno = errors.New("invalid ack sequence number")
Functions ¶
This section is empty.
Types ¶
type BlockReader ¶
type BlockReader struct {
// ClientName is the unique ID used by the NamenodeConnection to locate the
// block.
ClientName string
// Block is the block location provided by the namenode.
Block *hdfs.LocatedBlockProto
// Offset is the current read offset in the block.
Offset int64
// UseDatanodeHostname specifies whether the datanodes should be connected to
// via their hostnames (if true) or IP addresses (if false).
UseDatanodeHostname bool
// DialFunc is used to connect to the datanodes. If nil, then
// (&net.Dialer{}).DialContext is used.
DialFunc func(ctx context.Context, network, addr string) (net.Conn, error)
// contains filtered or unexported fields
}
BlockReader implements io.ReadCloser, for reading a block. It abstracts over reading from multiple datanodes, in order to be robust to connection failures, timeouts, and other shenanigans.
func (*BlockReader) Read ¶
func (br *BlockReader) Read(b []byte) (int, error)
Read implements io.Reader.
In the case that a failure (such as a disconnect) occurs while reading, the BlockReader will failover to another datanode and continue reading transparently. In the case that all the datanodes fail, the error from the most recent attempt will be returned.
Any datanode failures are recorded in a global cache, so subsequent reads, even reads for different blocks, will prioritize them lower.
func (*BlockReader) SetDeadline ¶
func (br *BlockReader) SetDeadline(t time.Time) error
SetDeadline sets the deadline for future Read calls. A zero value for t means Read will not time out.
type BlockWriter ¶
type BlockWriter struct {
// ClientName is the unique ID used by the NamenodeConnection to initialize
// the block.
ClientName string
// Block is the block location provided by the namenode.
Block *hdfs.LocatedBlockProto
// BlockSize is the target size of the new block (or the existing one, if
// appending). The represents the configured value, not the actual number
// of bytes currently in the block.
BlockSize int64
// Offset is the current write offset in the block.
Offset int64
// Append indicates whether this is an append operation on an existing block.
Append bool
// UseDatanodeHostname indicates whether the datanodes will be connected to
// via hostname (if true) or IP address (if false).
UseDatanodeHostname bool
// DialFunc is used to connect to the datanodes. If nil, then
// (&net.Dialer{}).DialContext is used.
DialFunc func(ctx context.Context, network, addr string) (net.Conn, error)
// contains filtered or unexported fields
}
BlockWriter implements io.WriteCloser for writing a block to a datanode. Given a block location, it handles pipeline construction and failures, including communicating with the namenode if need be.
func (*BlockWriter) Close ¶
func (bw *BlockWriter) Close() error
Close implements io.Closer. It flushes any unwritten packets out to the datanode, and sends a final packet indicating the end of the block. The block must still be finalized with the namenode.
func (*BlockWriter) Flush ¶
func (bw *BlockWriter) Flush() error
Flush flushes any unwritten packets out to the datanode.
func (*BlockWriter) SetDeadline ¶
func (bw *BlockWriter) SetDeadline(t time.Time) error
SetDeadline sets the deadline for future Write, Flush, and Close calls. A zero value for t means those calls will not time out.
func (*BlockWriter) Write ¶
func (bw *BlockWriter) Write(b []byte) (int, error)
Write implements io.Writer.
Unlike BlockReader, BlockWriter currently has no ability to recover from write failures (timeouts, datanode failure, etc). Once it returns an error from Write or Close, it may be in an invalid state.
This will hopefully be fixed in a future release.
type ChecksumReader ¶
type ChecksumReader struct {
// Block is the block location provided by the namenode.
Block *hdfs.LocatedBlockProto
// UseDatanodeHostname specifies whether the datanodes should be connected to
// via their hostnames (if true) or IP addresses (if false).
UseDatanodeHostname bool
// DialFunc is used to connect to the datanodes. If nil, then (&net.Dialer{}).DialContext is used
DialFunc func(ctx context.Context, network, addr string) (net.Conn, error)
// contains filtered or unexported fields
}
ChecksumReader provides an interface for reading the "MD5CRC32" checksums of individual blocks. It abstracts over reading from multiple datanodes, in order to be robust to failures.
func (*ChecksumReader) ReadChecksum ¶
func (cr *ChecksumReader) ReadChecksum() ([]byte, error)
ReadChecksum returns the checksum of the block.
func (*ChecksumReader) SetDeadline ¶
func (cr *ChecksumReader) SetDeadline(t time.Time) error
SetDeadline sets the deadline for future ReadChecksum calls. A zero value for t means Read will not time out.
type SaslDialer ¶
type SaslDialer struct {
DialFunc func(ctx context.Context, network, addr string) (net.Conn, error)
Key *hdfs.DataEncryptionKeyProto
Token *hadoop.TokenProto
EnforceQop string
}
SaslDialer dials using the underlying DialFunc, then negotiates authentication with the datanode. The resulting Conn implements whatever data protection level is specified by the server, whether it be wire encryption or integrity checks.
Source Files