Jonathan Mace created HDFS-5445:
-----------------------------------
Summary: PacketReceiver populates PacketHeader dataPlusChecksumLen
incorrectly
Key: HDFS-5445
URL: https://issues.apache.org/jira/browse/HDFS-5445
Project: Hadoop HDFS
Issue Type: Bug
Components: datanode
Affects Versions: 2.2.0, 2.1.0-beta
Environment: Ubuntu 12.10, Hadoop 2.1.0-beta
Reporter: Jonathan Mace
Priority: Minor
Summary: PacketReceiver reconstructs PacketHeaders with a packetLen 4 bytes
fewer than it should be. It doesn't cause any exceptions because the
reconstructed header is never reserialized, and the packetLen field is not used
in this part of the code.
In the BlockSender class, when a Packet is constructed it must be passed the
field packetLen, which is defined as the data length, checksum data length,
PLUS the length of the packetLen field itself (4 byte integer).
{code:title=BlockSender.java|borderStyle=solid}
484: private int sendPacket(ByteBuffer pkt, int maxChunks, OutputStream out,
485: boolean transferTo, DataTransferThrottler throttler) throws
IOException {
...
491: int packetLen = dataLen + checksumDataLen + 4;
...
504: int headerLen = writePacketHeader(pkt, dataLen, packetLen);
...
586: }
...
792: private int writePacketHeader(ByteBuffer pkt, int dataLen, int packetLen)
{
793: pkt.clear();
794: // both syncBlock and syncPacket are false
795: PacketHeader header = new PacketHeader(packetLen, offset, seqno,
796: (dataLen == 0), dataLen, false);
...
802: }
{code}
In the PacketReceiver class, the PacketHeader is reconstructed using the method
setFieldsFromData. However, the 4 bytes for the packetLen field length are
missing.
{code:title=PacketReceiver.java|borderStyle=solid}
112: private void doRead(ReadableByteChannel ch, InputStream in)
113: throws IOException {
...
136: int payloadLen = curPacketBuf.getInt();
...
144: int dataPlusChecksumLen = payloadLen - Ints.BYTES;
...
181: curHeader.setFieldsFromData(dataPlusChecksumLen, headerBuf);
...
192: }
{code}
I found this because I was making small modifications to the code that exposed
this inconsistency.
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