/// <summary>
/// Get
/// <see cref="BlockReaderLocalLegacy"/>
/// for short circuited local reads.
/// This block reader implements the path-based style of local reads
/// first introduced in HDFS-2246.
/// </summary>
/// <exception cref="System.IO.IOException"/>
private BlockReader GetLegacyBlockReaderLocal()
{
if (Log.IsTraceEnabled())
{
Log.Trace(this + ": trying to construct BlockReaderLocalLegacy");
}
if (!DFSClient.IsLocalAddress(inetSocketAddress))
{
if (Log.IsTraceEnabled())
{
Log.Trace(this + ": can't construct BlockReaderLocalLegacy because " + "the address "
+ inetSocketAddress + " is not local");
}
return(null);
}
if (clientContext.GetDisableLegacyBlockReaderLocal())
{
PerformanceAdvisory.Log.Debug(this + ": can't construct " + "BlockReaderLocalLegacy because "
+ "disableLegacyBlockReaderLocal is set.");
return(null);
}
IOException ioe = null;
try
{
return(BlockReaderLocalLegacy.NewBlockReader(conf, userGroupInformation, configuration
, fileName, block, token, datanode, startOffset, length, storageType));
}
catch (RemoteException remoteException)
{
ioe = remoteException.UnwrapRemoteException(typeof(SecretManager.InvalidToken), typeof(
AccessControlException));
}
catch (IOException e)
{
ioe = e;
}
if ((!(ioe is AccessControlException)) && IsSecurityException(ioe))
{
// Handle security exceptions.
// We do not handle AccessControlException here, since
// BlockReaderLocalLegacy#newBlockReader uses that exception to indicate
// that the user is not in dfs.block.local-path-access.user, a condition
// which requires us to disable legacy SCR.
throw ioe;
}
Log.Warn(this + ": error creating legacy BlockReaderLocal. " + "Disabling legacy local reads."
, ioe);
clientContext.SetDisableLegacyBlockReaderLocal();
return(null);
}
// Multiple datanodes could be running on the local machine. Store proxies in
// a map keyed by the ipc port of the datanode.
// reader for the data file
// reader for the checksum file
/// <summary>The only way this object can be instantiated.</summary>
/// <exception cref="System.IO.IOException"/>
internal static BlockReaderLocalLegacy NewBlockReader(DFSClient.Conf conf, UserGroupInformation
userGroupInformation, Configuration configuration, string file, ExtendedBlock blk
, Org.Apache.Hadoop.Security.Token.Token <BlockTokenIdentifier> token, DatanodeInfo
node, long startOffset, long length, StorageType storageType)
{
BlockReaderLocalLegacy.LocalDatanodeInfo localDatanodeInfo = GetLocalDatanodeInfo
(node.GetIpcPort());
// check the cache first
BlockLocalPathInfo pathinfo = localDatanodeInfo.GetBlockLocalPathInfo(blk);
if (pathinfo == null)
{
if (userGroupInformation == null)
{
userGroupInformation = UserGroupInformation.GetCurrentUser();
}
pathinfo = GetBlockPathInfo(userGroupInformation, blk, node, configuration, conf.
socketTimeout, token, conf.connectToDnViaHostname, storageType);
}
// check to see if the file exists. It may so happen that the
// HDFS file has been deleted and this block-lookup is occurring
// on behalf of a new HDFS file. This time, the block file could
// be residing in a different portion of the fs.data.dir directory.
// In this case, we remove this entry from the cache. The next
// call to this method will re-populate the cache.
FileInputStream dataIn = null;
FileInputStream checksumIn = null;
BlockReaderLocalLegacy localBlockReader = null;
bool skipChecksumCheck = conf.skipShortCircuitChecksums || storageType.IsTransient
();
try
{
// get a local file system
FilePath blkfile = new FilePath(pathinfo.GetBlockPath());
dataIn = new FileInputStream(blkfile);
if (Log.IsDebugEnabled())
{
Log.Debug("New BlockReaderLocalLegacy for file " + blkfile + " of size " + blkfile
.Length() + " startOffset " + startOffset + " length " + length + " short circuit checksum "
+ !skipChecksumCheck);
}
if (!skipChecksumCheck)
{
// get the metadata file
FilePath metafile = new FilePath(pathinfo.GetMetaPath());
checksumIn = new FileInputStream(metafile);
DataChecksum checksum = BlockMetadataHeader.ReadDataChecksum(new DataInputStream(
checksumIn), blk);
long firstChunkOffset = startOffset - (startOffset % checksum.GetBytesPerChecksum
());
localBlockReader = new BlockReaderLocalLegacy(conf, file, blk, token, startOffset
, length, pathinfo, checksum, true, dataIn, firstChunkOffset, checksumIn);
}
else
{
localBlockReader = new BlockReaderLocalLegacy(conf, file, blk, token, startOffset
, length, pathinfo, dataIn);
}
}
catch (IOException e)
{
// remove from cache
localDatanodeInfo.RemoveBlockLocalPathInfo(blk);
DFSClient.Log.Warn("BlockReaderLocalLegacy: Removing " + blk + " from cache because local file "
+ pathinfo.GetBlockPath() + " could not be opened.");
throw;
}
finally
{
if (localBlockReader == null)
{
if (dataIn != null)
{
dataIn.Close();
}
if (checksumIn != null)
{
checksumIn.Close();
}
}
}
return(localBlockReader);
}
