##### 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 1.1.0 Release Notes

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

- HADOOP-5464 | Major | DFSClient does not treat write timeout of 0 properly

Zero values for dfs.socket.timeout and dfs.datanode.socket.write.timeout are now respected. Previously zero values for these parameters resulted in a 5 second timeout.

- MAPREDUCE-1906 | Major | Lower default minimum heartbeat interval for tasktracker > Jobtracker

The default minimum heartbeat interval has been dropped from 3 seconds to 300ms to increase scheduling throughput on small clusters. Users may tune mapreduce.jobtracker.heartbeats.in.second to adjust this value.

- HADOOP-6995 | Minor | Allow wildcards to be used in ProxyUsers configurations

When configuring proxy users and hosts, the special wildcard value “*” may be specified to match any host or any user.

- MAPREDUCE-2517 | Major | Porting Gridmix v3 system tests into trunk branch.

Adds system tests to Gridmix. These system tests cover various features like job types (load and sleep), user resolvers (round-robin, submitter-user, echo) and submission modes (stress, replay and serial).

- MAPREDUCE-3008 | Major | [Gridmix] Improve cumulative CPU usage emulation for short running tasks

Improves cumulative CPU emulation for short running tasks.

- MAPREDUCE-3118 | Major | Backport Gridmix and Rumen features from trunk to Hadoop 0.20 security branch

Backports latest features from trunk to 0.20.206 branch.

- HDFS-2465 | Major | Add HDFS support for fadvise readahead and drop-behind

HDFS now has the ability to use posix_fadvise and sync_data_range syscalls to manage the OS buffer cache. This support is currently considered experimental, and may be enabled by configuring the following keys: dfs.datanode.drop.cache.behind.writes - set to true to drop data out of the buffer cache after writing dfs.datanode.drop.cache.behind.reads - set to true to drop data out of the buffer cache when performing sequential reads dfs.datanode.sync.behind.writes - set to true to trigger dirty page writeback immediately after writing data dfs.datanode.readahead.bytes - set to a non-zero value to trigger readahead for sequential reads

- MAPREDUCE-3597 | Major | Provide a way to access other info of history file from Rumentool

Rumen now provides {{Parsed*}} objects. These objects provide extra information that are not provided by {{Logged*}} objects.

- HDFS-2741 | Minor | dfs.datanode.max.xcievers missing in 0.20.205.0

Document and raise the maximum allowed transfer threads on a DataNode to 4096. This helps Apache HBase in particular.

- HDFS-3044 | Major | fsck move should be non-destructive by default

The fsck “move” option is no longer destructive. It copies the accessible blocks of corrupt files to lost and found as before, but no longer deletes the corrupt files after copying the blocks. The original, destructive behavior can be enabled by specifying both the “move” and “delete” options.

- HADOOP-8154 | Major | DNS#getIPs shouldn’t silently return the local host IP for bogus interface names

WARNING: No release note provided for this change.

- MAPREDUCE-4087 | Major | [Gridmix] GenerateDistCacheData job of Gridmix can become slow in some cases

Fixes the issue of GenerateDistCacheData job slowness.

- HDFS-3055 | Minor | Implement recovery mode for branch-1

This is a new feature. It is documented in hdfs_user_guide.xml.

- HDFS-3094 | Major | add -nonInteractive and -force option to namenode -format command

The ‘namenode -format’ command now supports the flags ‘-nonInteractive’ and ‘-force’ to improve usefulness without user input.

- HADOOP-8314 | Major | HttpServer#hasAdminAccess should return false if authorization is enabled but user is not authenticated

WARNING: No release note provided for this change.

- HADOOP-8230 | Major | Enable sync by default and disable append

Append is not supported in Hadoop 1.x. Please upgrade to 2.x if you need append. If you enabled dfs.support.append for HBase, you’re OK, as durable sync (why HBase required dfs.support.append) is now enabled by default. If you really need the previous functionality, to turn on the append functionality set the flag “dfs.support.broken.append” to true.

- HDFS-3522 | Major | If NN is in safemode, it should throw SafeModeException when getBlockLocations has zero locations

getBlockLocations(), and hence open() for read, will now throw SafeModeException if the NameNode is still in safe mode and there are no replicas reported yet for one of the blocks in the file.

- HDFS-3518 | Major | Provide API to check HDFS operational state

Add a utility method HdfsUtils.isHealthy(uri) for checking if the given HDFS is healthy.

- HADOOP-8365 | Blocker | Add flag to disable durable sync

This patch enables durable sync by default. Installation where HBase was not used, that used to run without setting “dfs.support.append” or setting it to false explicitly in the configuration, must add a new flag “dfs.durable.sync” and set it to false to preserve the previous semantics.

- HADOOP-8552 | Major | Conflict: Same security.log.file for multiple users.

WARNING: No release note provided for this change.

- HDFS-2617 | Major | Replaced Kerberized SSL for image transfer and fsck with SPNEGO-based solution

Due to the requirement that KSSL use weak encryption types for Kerberos tickets, HTTP authentication to the NameNode will now use SPNEGO by default. This will require users of previous branch-1 releases with security enabled to modify their configurations and create new Kerberos principals in order to use SPNEGO. The old behavior of using KSSL can optionally be enabled by setting the configuration option “hadoop.security.use-weak-http-crypto” to “true”.

- HDFS-3814 | Major | Make the replication monitor multipliers configurable in 1.x

This change adds two new configuration parameters.

# {{dfs.namenode.invalidate.work.pct.per.iteration}} for controlling deletion rate of blocks.

# {{dfs.namenode.replication.work.multiplier.per.iteration}} for controlling replication rate. This in turn allows controlling the time it takes for decommissioning.

Please see hdfs-default.xml for detailed description.

- HDFS-3703 | Major | Decrease the datanode failure detection time

This jira adds a new DataNode state called “stale” at the NameNode. DataNodes are marked as stale if it does not send heartbeat message to NameNode within the timeout configured using the configuration parameter “dfs.namenode.stale.datanode.interval” in seconds (default value is 30 seconds). NameNode picks a stale datanode as the last target to read from when returning block locations for reads.

This feature is by default turned * off *. To turn on the feature, set the HDFS configuration “dfs.namenode.check.stale.datanode” to true.

- MAPREDUCE-4673 | Major | make TestRawHistoryFile and TestJobHistoryServer more robust

Fixed TestRawHistoryFile and TestJobHistoryServer to not write to /tmp.

- MAPREDUCE-4675 | Major | TestKillSubProcesses fails as the process is still alive after the job is done

Fixed a race condition caused in TestKillSubProcesses caused due to a recent commit.

- MAPREDUCE-4698 | Minor | TestJobHistoryConfig throws Exception in testJobHistoryLogging

Optionally call initialize/initializeFileSystem in JobTracker::startTracker() to allow for proper initialization when offerService is not being called.