private void fetchBlockByteRange(
LocatedBlock block,
long start,
long end,
byte[] buf,
int offset,
Map<ExtendedBlock, Set<DatanodeInfo>> corruptedBlockMap)
throws IOException {
//
// Connect to best DataNode for desired Block, with potential offset
//
int refetchToken = 1; // only need to get a new access token once
while (true) {
// cached block locations may have been updated by chooseDataNode()
// or fetchBlockAt(). Always get the latest list of locations at the
// start of the loop.
block = getBlockAt(block.getStartOffset(), false);
DNAddrPair retval = chooseDataNode(block);
DatanodeInfo chosenNode = retval.info;
InetSocketAddress targetAddr = retval.addr;
BlockReader reader = null;
try {
Token<BlockTokenIdentifier> blockToken = block.getBlockToken();
int len = (int) (end - start + 1);
reader =
getBlockReader(
targetAddr,
chosenNode,
src,
block.getBlock(),
blockToken,
start,
len,
buffersize,
verifyChecksum,
dfsClient.clientName);
int nread = reader.readAll(buf, offset, len);
if (nread != len) {
throw new IOException(
"truncated return from reader.read(): " + "excpected " + len + ", got " + nread);
}
return;
} catch (ChecksumException e) {
DFSClient.LOG.warn(
"fetchBlockByteRange(). Got a checksum exception for "
+ src
+ " at "
+ block.getBlock()
+ ":"
+ e.getPos()
+ " from "
+ chosenNode);
// we want to remember what we have tried
addIntoCorruptedBlockMap(block.getBlock(), chosenNode, corruptedBlockMap);
} catch (AccessControlException ex) {
DFSClient.LOG.warn("Short circuit access failed ", ex);
dfsClient.disableShortCircuit();
continue;
} catch (IOException e) {
if (e instanceof InvalidBlockTokenException && refetchToken > 0) {
DFSClient.LOG.info(
"Will get a new access token and retry, "
+ "access token was invalid when connecting to "
+ targetAddr
+ " : "
+ e);
refetchToken--;
fetchBlockAt(block.getStartOffset());
continue;
} else {
DFSClient.LOG.warn(
"Failed to connect to "
+ targetAddr
+ " for file "
+ src
+ " for block "
+ block.getBlock()
+ ":"
+ e);
if (DFSClient.LOG.isDebugEnabled()) {
DFSClient.LOG.debug("Connection failure ", e);
}
}
} finally {
if (reader != null) {
closeBlockReader(reader);
}
}
// Put chosen node into dead list, continue
addToDeadNodes(chosenNode);
}
}
/**
* Open a DataInputStream to a DataNode so that it can be read from. We get block ID and the IDs
* of the destinations at startup, from the namenode.
*/
private synchronized DatanodeInfo blockSeekTo(long target) throws IOException {
if (target >= getFileLength()) {
throw new IOException("Attempted to read past end of file");
}
// Will be getting a new BlockReader.
if (blockReader != null) {
closeBlockReader(blockReader);
blockReader = null;
}
//
// Connect to best DataNode for desired Block, with potential offset
//
DatanodeInfo chosenNode = null;
int refetchToken = 1; // only need to get a new access token once
boolean connectFailedOnce = false;
while (true) {
//
// Compute desired block
//
LocatedBlock targetBlock = getBlockAt(target, true);
assert (target == pos) : "Wrong postion " + pos + " expect " + target;
long offsetIntoBlock = target - targetBlock.getStartOffset();
DNAddrPair retval = chooseDataNode(targetBlock);
chosenNode = retval.info;
InetSocketAddress targetAddr = retval.addr;
try {
ExtendedBlock blk = targetBlock.getBlock();
Token<BlockTokenIdentifier> accessToken = targetBlock.getBlockToken();
blockReader =
getBlockReader(
targetAddr,
chosenNode,
src,
blk,
accessToken,
offsetIntoBlock,
blk.getNumBytes() - offsetIntoBlock,
buffersize,
verifyChecksum,
dfsClient.clientName);
if (connectFailedOnce) {
DFSClient.LOG.info(
"Successfully connected to " + targetAddr + " for block " + blk.getBlockId());
}
return chosenNode;
} catch (IOException ex) {
if (ex instanceof InvalidBlockTokenException && refetchToken > 0) {
DFSClient.LOG.info(
"Will fetch a new access token and retry, "
+ "access token was invalid when connecting to "
+ targetAddr
+ " : "
+ ex);
/*
* Get a new access token and retry. Retry is needed in 2 cases. 1)
* When both NN and DN re-started while DFSClient holding a cached
* access token. 2) In the case that NN fails to update its
* access key at pre-set interval (by a wide margin) and
* subsequently restarts. In this case, DN re-registers itself with
* NN and receives a new access key, but DN will delete the old
* access key from its memory since it's considered expired based on
* the estimated expiration date.
*/
refetchToken--;
fetchBlockAt(target);
} else {
connectFailedOnce = true;
DFSClient.LOG.warn(
"Failed to connect to "
+ targetAddr
+ " for block"
+ ", add to deadNodes and continue. "
+ ex,
ex);
// Put chosen node into dead list, continue
addToDeadNodes(chosenNode);
}
}
}
}