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HADOOP-10821. Prepare the release notes for Hadoop 2.5.0. (Andrew Wang and Karthik Kambatla via kasha) 

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1614232 13f79535-47bb-0310-9956-ffa450edef68
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Karthik Kambatla 2014-07-29 00:47:57 +00:00
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Apache Hadoop ${project.version} Apache Hadoop ${project.version}
Apache Hadoop ${project.version} consists of significant Apache Hadoop ${project.version} is a minor release in the 2.x.y release
improvements over the previous stable release (hadoop-1.x). line, building upon the previous stable release 2.4.1.
Here is a short overview of the improvments to both HDFS and MapReduce. Here is a short overview of the major features and improvements.
* {HDFS Federation} * {Common}
In order to scale the name service horizontally, federation uses multiple * Authentication improvements when using an HTTP proxy server. This is
independent Namenodes/Namespaces. The Namenodes are federated, that is, the useful when accessing WebHDFS via a proxy server.
Namenodes are independent and don't require coordination with each other.
The datanodes are used as common storage for blocks by all the Namenodes.
Each datanode registers with all the Namenodes in the cluster. Datanodes
send periodic heartbeats and block reports and handles commands from the
Namenodes.
More details are available in the * A new Hadoop metrics sink that allows writing directly to Graphite.
{{{./hadoop-project-dist/hadoop-hdfs/Federation.html}HDFS Federation}}
document.
* {MapReduce NextGen aka YARN aka MRv2} * {{{./hadoop-project-dist/hadoop-common/filesystem/index.html}Specification work}}
related to the Hadoop Compatible Filesystem (HCFS) effort.
The new architecture introduced in hadoop-0.23, divides the two major * {HDFS}
functions of the JobTracker: resource management and job life-cycle management
into separate components.
The new ResourceManager manages the global assignment of compute resources to * Support for POSIX-style filesystem extended attributes. See the
applications and the per-application ApplicationMaster manages the {{{./hadoop-project-dist/hadoop-hdfs/ExtendedAttributes.html}user documentation}}
application‚ scheduling and coordination. for more details.
An application is either a single job in the sense of classic MapReduce jobs * Using the OfflineImageViewer, clients can now browse an fsimage via
or a DAG of such jobs. the WebHDFS API.
The ResourceManager and per-machine NodeManager daemon, which manages the * The NFS gateway received a number of supportability improvements and
user processes on that machine, form the computation fabric. bug fixes. The Hadoop portmapper is no longer required to run the gateway,
and the gateway is now able to reject connections from unprivileged ports.
The per-application ApplicationMaster is, in effect, a framework specific * The SecondaryNameNode, JournalNode, and DataNode web UIs have been
library and is tasked with negotiating resources from the ResourceManager and modernized with HTML5 and Javascript.
working with the NodeManager(s) to execute and monitor the tasks.
More details are available in the * {YARN}
{{{./hadoop-yarn/hadoop-yarn-site/YARN.html}YARN}}
document. * YARN's REST APIs now support write/modify operations. Users can submit and
kill applications through REST APIs.
* The timeline store in YARN, used for storing generic and
application-specific information for applications, supports authentication
through Kerberos.
* The Fair Scheduler supports dynamic hierarchical user queues, user queues
are created dynamically at runtime under any specified parent-queue.
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