Apache Hadoop 2.6.0 Release Notes

These release notes cover new developer and user-facing incompatibilities, important issues, features, and major improvements.

Fix of inappropriate test of delete functionality.

bin/hadoop key with no args would throw an NPE.

SASL now can be used to secure the DataTransferProtocol, which transfers file block content between HDFS clients and DataNodes. In this configuration, it is no longer required for secured clusters to start the DataNode as root and bind to privileged ports.

The MetricsSystem abstract class has added a new abstract method, unregisterSource, for unregistering a previously registered metrics source. Custom subclasses of MetricsSystem must be updated to provide an implementation of this method.

This change enables the TCP_NODELAY flag for all Hadoop IPC connections, hence bypassing TCP Nagling. Nagling interacts poorly with TCP delayed ACKs especially for request-response protocols.

The directory structure for finalized replicas on DNs has been changed. Now, the directory that a finalized replica goes in is determined uniquely by its ID. Specifically, we use a two-level directory structure, with the 24th through 17th bits identifying the correct directory at the first level and the 16th through 8th bits identifying the correct directory at the second level.

The “hadoop classpath” command has been enhanced to support options for automatic expansion of wildcards in classpath elements and writing the classpath to a jar file manifest. These options make it easier to construct a correct classpath for libhdfs applications.

The libhdfs C API is now supported on Windows.

Implements -h option for fs -count to show file sizes in human readable format. Additionally, ContentSummary.getHeader() now returns a different string that is incompatible with previous releases.

Allow distcp to copy data between HA clusters. Users can use a new configuration property “dfs.internal.nameservices” to explicitly specify the name services belonging to the local cluster, while continue using the configuration property “dfs.nameservices” to specify all the name services in the local and remote clusters.

WARNING: No release note provided for this change.

WARNING: No release note provided for this change.

Remove unnecessary synchronized blocks from Snappy/Zlib codecs.

WARNING: No release note provided for this change.

HDFS now supports the option to configure AES encryption for block data transfer. AES offers improved cryptographic strength and performance over the prior options of 3DES and RC4.

The following configuration properties are added.