##### General

- Overview
- Single Node Setup
- Cluster Setup
- Commands Reference
- FileSystem Shell
- Compatibility Specification
- Downstream Developer's Guide
- Admin Compatibility Guide
- Interface Classification
- FileSystem Specification

##### Common

- CLI Mini Cluster
- Native Libraries
- Proxy User
- Rack Awareness
- Secure Mode
- Service Level Authorization
- HTTP Authentication
- Credential Provider API
- Hadoop KMS
- Tracing
- Unix Shell Guide

##### HDFS

- Architecture
- User Guide
- Commands Reference
- NameNode HA With QJM
- NameNode HA With NFS
- Observer NameNode
- Federation
- ViewFs
- ViewFsOverloadScheme
- Snapshots
- Edits Viewer
- Image Viewer
- Permissions and HDFS
- Quotas and HDFS
- libhdfs (C API)
- WebHDFS (REST API)
- HttpFS
- Short Circuit Local Reads
- Centralized Cache Management
- NFS Gateway
- Rolling Upgrade
- Extended Attributes
- Transparent Encryption
- Multihoming
- Storage Policies
- Memory Storage Support
- Synthetic Load Generator
- Erasure Coding
- Disk Balancer
- Upgrade Domain
- DataNode Admin
- Router Federation
- Provided Storage

##### MapReduce

- Tutorial
- Commands Reference
- Compatibility with 1.x
- Encrypted Shuffle
- Pluggable Shuffle/Sort
- Distributed Cache Deploy
- Support for YARN Shared Cache

##### MapReduce REST APIs

- MR Application Master
- MR History Server

##### YARN

- Architecture
- Commands Reference
- Capacity Scheduler
- Fair Scheduler
- ResourceManager Restart
- ResourceManager HA
- Resource Model
- Node Labels
- Node Attributes
- Web Application Proxy
- Timeline Server
- Timeline Service V.2
- Writing YARN Applications
- YARN Application Security
- NodeManager
- Running Applications in Docker Containers
- Using CGroups
- Secure Containers
- Registry
- Reservation System
- Graceful Decommission
- Opportunistic Containers
- YARN Federation
- Shared Cache
- Using GPU
- Using FPGA
- Placement Constraints
- YARN UI2

##### YARN REST APIs

- Introduction
- Resource Manager
- Node Manager
- Timeline Server
- Timeline Service V.2

##### YARN Service

- Overview
- QuickStart
- Concepts
- Yarn Service API
- Service Discovery
- System Services

##### Submarine

- Index
- QuickStart
- Examples

##### Hadoop Compatible File Systems

- Aliyun OSS
- Amazon S3
- Azure Blob Storage
- Azure Data Lake Storage
- OpenStack Swift

##### Auth

- Overview
- Examples
- Configuration
- Building

##### Tools

- Hadoop Streaming
- Hadoop Archives
- Hadoop Archive Logs
- DistCp
- GridMix
- Rumen
- Resource Estimator Service
- Scheduler Load Simulator
- Hadoop Benchmarking

##### Reference

- Changelog and Release Notes
- Java API docs
- Unix Shell API
- Metrics

##### Configuration

- core-default.xml
- hdfs-default.xml
- hdfs-rbf-default.xml
- mapred-default.xml
- yarn-default.xml
- kms-default.xml
- httpfs-default.xml
- Deprecated Properties

# Apache Hadoop 0.20.204.0 Release Notes

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

- HDFS-1445 | Major | Batch the calls in DataStorage to FileUtil.createHardLink(), so we call it once per directory instead of once per file

Batch hardlinking during “upgrade” snapshots, cutting time from aprx 8 minutes per volume to aprx 8 seconds. Validated in both Linux and Windows. Depends on prior integration with patch for HADOOP-7133.

- MAPREDUCE-2479 | Major | Backport MAPREDUCE-1568 to hadoop security branch

Added mapreduce.tasktracker.distributedcache.checkperiod to the task tracker that defined the period to wait while cleaning up the distributed cache. The default is 1 min.

- HADOOP-6255 | Major | Create an rpm integration project

Added RPM/DEB packages to build system.

- MAPREDUCE-2524 | Minor | Backport trunk heuristics for failing maps when we get fetch failures retrieving map output during shuffle

Added a new configuration option: mapreduce.reduce.shuffle.maxfetchfailures, and removed a no longer used option: mapred.reduce.copy.backoff.

- MAPREDUCE-2529 | Major | Recognize Jetty bug 1342 and handle it

Added 2 new config parameters:

mapreduce.reduce.shuffle.catch.exception.stack.regex mapreduce.reduce.shuffle.catch.exception.message.regex

- HDFS-2218 | Blocker | Disable TestHdfsProxy.testHdfsProxyInterface in 0.20-security and branch-1 until HDFS-2217 is fixed

Test case TestHdfsProxy.testHdfsProxyInterface has been temporarily disabled for this release, due to failure in the Hudson automated test environment.

- MAPREDUCE-2846 | Blocker | a small % of all tasks fail with DefaultTaskController

Fixed a race condition in writing the log index file that caused tasks to ‘fail’.

- MAPREDUCE-2804 | Blocker | “Creation of symlink to attempt log dir failed.” message is not useful

Removed duplicate chmods of job log dir that were vulnerable to race conditions between tasks. Also improved the messages when the symlinks failed to be created.