##### 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 3.2.1 Release Notes

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

- YARN-8986 | Minor | publish all exposed ports to random ports when using bridge network

support -p and -P for bridge type network;

- YARN-9071 | Critical | NM and service AM don’t have updated status for reinitialized containers

In progress upgrade status may show READY state sooner than actual upgrade operations. External caller to upgrade API is recommended to wait minimum 30 seconds before querying yarn app -status.

- YARN-9084 | Major | Service Upgrade: With default readiness check, the status of upgrade is reported to be successful prematurely

Improve transient container status accuracy for upgrade.

- HADOOP-15922 | Major | DelegationTokenAuthenticationFilter get wrong doAsUser since it does not decode URL

- Fix DelegationTokenAuthentication filter for incorrectly double encode doAs user parameter.

- YARN-8761 | Major | Service AM support for decommissioning component instances

- Component instance number is not linear increment when decommission feature is used. Application with assumption of linear increment component instance number maybe impacted by introduction of this feature.

- HDFS-14305 | Major | Serial number in BlockTokenSecretManager could overlap between different namenodes

NameNodes rely on independent block token key ranges to communicate block token identities to DataNodes and clients in a way that does not create conflicts between the tokens issued by multiple NameNodes. HDFS-6440 introduced the potential for overlaps in key ranges; this fixes the issue by creating 64 possible key ranges that NameNodes assign themselves to, allowing for up to 64 NameNodes to run safely. This limitation only applies within a single Namespace; there may be more than 64 NameNodes total spread among multiple federated Namespaces.

- HDFS-14396 | Blocker | Failed to load image from FSImageFile when downgrade from 3.x to 2.x

During a rolling upgrade from Hadoop 2.x to 3.x, NameNode cannot persist erasure coding information, and therefore a user cannot start using erasure coding feature until finalize is done.

- YARN-7055 | Major | YARN Timeline Service v.2: beta 1 / GA

Application Timeline Server v2 is ready for production. It is GA from 3.2.1 release on wards.