##### 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 Changelog

## Release 0.20.1 - 2009-09-01

### INCOMPATIBLE CHANGES:

JIRA | Summary | Priority | Component | Reporter | Contributor
--- | --- | --- | --- | --- | ---
HADOOP-5726 | Remove pre-emption from the capacity scheduler code base | Major | . | Hemanth Yamijala | rahul k singh
HADOOP-5881 | Simplify configuration related to task-memory-monitoring and memory-based scheduling | Major | . | Vinod Kumar Vavilapalli | Vinod Kumar Vavilapalli

### NEW FEATURES:

JIRA | Summary | Priority | Component | Reporter | Contributor
--- | --- | --- | --- | --- | ---
HADOOP-5714 | Metric to show number of fs.exists (or number of getFileInfo) calls | Minor | metrics | Koji Noguchi | Jakob Homan
HADOOP-3315 | New binary file format | Major | io | Owen O’Malley | Hong Tang
HADOOP-6080 | Handling of Trash with quota | Major | fs | Koji Noguchi | Jakob Homan

### IMPROVEMENTS:

JIRA | Summary | Priority | Component | Reporter | Contributor
--- | --- | --- | --- | --- | ---
MAPREDUCE-465 | Deprecate org.apache.hadoop.mapred.lib.MultithreadedMapRunner | Minor | . | Amareshwari Sriramadasu | Amareshwari Sriramadasu
HDFS-527 | Refactor DFSClient constructors | Major | hdfs-client | Tsz Wo Nicholas Sze | Tsz Wo Nicholas Sze
MAPREDUCE-767 | to remove mapreduce dependency on commons-cli2 | Major | contrib/streaming | Giridharan Kesavan | Amar Kamat
HDFS-635 | HDFS Project page does not show 0.20.1 documentation/release information. | Major | documentation | Andy Sautins |

### BUG FIXES:

JIRA | Summary | Priority | Component | Reporter | Contributor
--- | --- | --- | --- | --- | ---
HADOOP-5210 | Reduce Task Progress shows > 100% when the total size of map outputs (for a single reducer) is high | Minor | . | Jothi Padmanabhan | Ravi Gummadi
HADOOP-5654 | TestReplicationPolicy.<init> fails on java.net.BindException | Major | test | Hairong Kuang | Hairong Kuang
HADOOP-5655 | TestMRServerPorts fails on java.net.BindException | Major | . | Hairong Kuang | Devaraj Das
HADOOP-5533 | Recovery duration shown on the jobtracker webpage is inaccurate | Major | . | Amar Kamat | Amar Kamat
HADOOP-5646 | TestQueueCapacities is failing Hudson tests for the last few builds | Major | . | Jothi Padmanabhan | Vinod Kumar Vavilapalli
HADOOP-5691 | org.apache.hadoop.mapreduce.Reducer should not be abstract. | Major | . | Amareshwari Sriramadasu | Amareshwari Sriramadasu
HADOOP-5688 | HftpFileSystem.getChecksum(..) does not work for the paths with scheme and authority | Major | . | Tsz Wo Nicholas Sze | Tsz Wo Nicholas Sze
HADOOP-4674 | hadoop fs -help should list detailed help info for the following commands: test, text, tail, stat & touchz | Trivial | fs | David NeSmith | Ravi Phulari
HADOOP-5711 | Change Namenode file close log to info | Minor | . | Tsz Wo Nicholas Sze | Tsz Wo Nicholas Sze
HADOOP-5213 | BZip2CompressionOutputStream NullPointerException | Blocker | io | Zheng Shao | Zheng Shao
HADOOP-5736 | Update CapacityScheduler documentation to reflect latest changes | Major | . | Sreekanth Ramakrishnan | Sreekanth Ramakrishnan
HADOOP-5718 | Capacity Scheduler should not check for presence of default queue while starting up. | Major | . | Sreekanth Ramakrishnan | Sreekanth Ramakrishnan
HADOOP-5719 | Jobs failed during job initalization are never removed from Capacity Schedulers waiting list | Major | . | Sreekanth Ramakrishnan | Sreekanth Ramakrishnan
HADOOP-5349 | When the size required for a path is -1, LocalDirAllocator.getLocalPathForWrite fails with a DiskCheckerException when the disk it selects is bad. | Major | . | Vinod Kumar Vavilapalli | Vinod Kumar Vavilapalli
HADOOP-5636 | Job is left in Running state after a killJob | Critical | . | Amareshwari Sriramadasu | Amar Kamat
HADOOP-5641 | Possible NPE in CapacityScheduler’s MemoryMatcher | Major | . | Vinod Kumar Vavilapalli | Hemanth Yamijala
HADOOP-5828 | Use absolute path for JobTracker’s mapred.local.dir in MiniMRCluster | Major | test | Hemanth Yamijala | Hemanth Yamijala
HADOOP-5850 | map/reduce doesn’t run jobs with 0 maps | Critical | . | Owen O’Malley | Vinod Kumar Vavilapalli
HADOOP-4626 | API link in forrest doc should point to the same version of hadoop. | Minor | documentation | Tsz Wo Nicholas Sze | Tsz Wo Nicholas Sze
HADOOP-5883 | TaskMemoryMonitorThread might shoot down tasks even if their processes momentarily exceed the requested memory | Major | . | Hemanth Yamijala | Hemanth Yamijala
HADOOP-5539 | o.a.h.mapred.Merger not maintaining map out compression on intermediate files | Blocker | . | Billy Pearson | Jothi Padmanabhan
HADOOP-5932 | MemoryMatcher logs 0 as freeMemOnTT even though there are free slots available on TaskTraker | Major | . | Karam Singh | Vinod Kumar Vavilapalli
HADOOP-5951 | StorageInfo needs Apache license header. | Major | . | Suresh Srinivas | Suresh Srinivas
HADOOP-5648 | Not able to generate gridmix.jar on already compiled version of hadoop | Major | benchmarks | Suman Sehgal | Giridharan Kesavan
HADOOP-5908 | ArithmeticException in heartbeats with zero map jobs | Major | . | Vinod Kumar Vavilapalli | Amar Kamat
HADOOP-5924 | JT fails to recover the jobs after restart after HADOOP:4372 | Major | . | Ramya Sunil | Amar Kamat
HADOOP-5882 | Progress is not updated when the New Reducer is running reduce phase | Blocker | . | Jothi Padmanabhan | Amareshwari Sriramadasu
HADOOP-5746 | Errors encountered in MROutputThread after the last map/reduce call can go undetected | Major | . | Devaraj Das | Amar Kamat
HADOOP-5884 | Capacity scheduler should account high memory jobs as using more capacity of the queue | Major | . | Hemanth Yamijala | Vinod Kumar Vavilapalli
HADOOP-5937 | Correct info message “Use hadoop dfs -safemode option” to " Use hdfs dfsadmin -safemode option" . | Minor | . | Ravi Phulari | Ravi Phulari
HADOOP-5921 | JobTracker does not come up because of NotReplicatedYetException | Major | . | Amareshwari Sriramadasu | Amar Kamat
HADOOP-6017 | NameNode and SecondaryNameNode fail to restart because of abnormal filenames. | Blocker | . | Raghu Angadi | Tsz Wo Nicholas Sze
HADOOP-5920 | TestJobHistory fails some times. | Major | . | Amareshwari Sriramadasu | Amar Kamat
HDFS-26 | HADOOP-5862 for version .20 (Namespace quota exceeded message unclear) | Major | . | Boris Shkolnik | Boris Shkolnik
HDFS-438 | Improve help message for quotas | Minor | . | Raghu Angadi | Raghu Angadi
MAPREDUCE-2 | ArrayOutOfIndex error in KeyFieldBasedPartitioner on empty key | Major | . | Amar Kamat | Amar Kamat
MAPREDUCE-130 | Delete the jobconf copy from the log directory of the JobTracker when the job is retired | Major | . | Devaraj Das | Amar Kamat
MAPREDUCE-657 | CompletedJobStatusStore hardcodes filesystem to hdfs | Major | jobtracker | Amar Kamat | Amar Kamat
MAPREDUCE-179 | setProgress not called for new RecordReaders | Blocker | . | Chris Douglas | Chris Douglas
MAPREDUCE-124 | When abortTask of OutputCommitter fails with an Exception for a map-only job, the task is marked as success | Major | . | Jothi Padmanabhan | Amareshwari Sriramadasu
HADOOP-6139 | Incomplete help message is displayed for rm and rmr options. | Minor | . | Suman Sehgal | Jakob Homan
HADOOP-6141 | hadoop 0.20 branch “test-patch” is broken | Major | build | Hong Tang | Hong Tang
HADOOP-6145 | No error message for deleting non-existant file or directory. | Major | fs | Suman Sehgal | Jakob Homan
MAPREDUCE-565 | Partitioner does not work with new API | Blocker | task | Jothi Padmanabhan | Owen O’Malley
MAPREDUCE-18 | Under load the shuffle sometimes gets incorrect data | Blocker | . | Owen O’Malley | Ravi Gummadi
MAPREDUCE-735 | ArrayIndexOutOfBoundsException is thrown by KeyFieldBasedPartitioner | Major | . | Suman Sehgal | Amar Kamat
MAPREDUCE-383 | pipes combiner does not reset properly after a spill | Major | . | Christian Kunz | Christian Kunz
MAPREDUCE-40 | Memory management variables need a backwards compatibility option after HADOOP-5881 | Blocker | . | Hemanth Yamijala | rahul k singh
MAPREDUCE-796 | Encountered “ClassCastException” on tasktracker while running wordcount with MultithreadedMapRunner | Major | examples | Suman Sehgal | Amar Kamat
MAPREDUCE-838 | Task succeeds even when committer.commitTask fails with IOException | Blocker | task | Koji Noguchi | Amareshwari Sriramadasu
MAPREDUCE-805 | Deadlock in Jobtracker | Major | . | Michael Tamm | Amar Kamat
HDFS-167 | DFSClient continues to retry indefinitely | Minor | hdfs-client | Derek Wollenstein | Bill Zeller
MAPREDUCE-832 | Too many WARN messages about deprecated memorty config variables in JobTacker log | Major | . | Karam Singh | rahul k singh
MAPREDUCE-745 | TestRecoveryManager fails sometimes | Major | jobtracker | Amareshwari Sriramadasu | Amar Kamat
MAPREDUCE-834 | When TaskTracker config use old memory management values its memory monitoring is diabled. | Major | . | Karam Singh | Sreekanth Ramakrishnan
MAPREDUCE-818 | org.apache.hadoop.mapreduce.Counters.getGroup returns null if the group name doesnt exist. | Minor | . | Amareshwari Sriramadasu | Amareshwari Sriramadasu
MAPREDUCE-807 | Stray user files in mapred.system.dir with permissions other than 777 can prevent the jobtracker from starting up. | Blocker | jobtracker | Amar Kamat | Amar Kamat
MAPREDUCE-430 | Task stuck in cleanup with OutOfMemoryErrors | Major | . | Amareshwari Sriramadasu | Amar Kamat
HADOOP-6215 | fix GenericOptionParser to deal with -D with ‘=’ in the value | Major | . | Owen O’Malley | Amar Kamat
MAPREDUCE-421 | mapred pipes might return exit code 0 even when failing | Major | pipes | Christian Kunz | Christian Kunz
HDFS-525 | ListPathsServlet.java uses static SimpleDateFormat that has threading issues | Major | namenode | Suresh Srinivas | Suresh Srinivas
MAPREDUCE-911 | TestTaskFail fail sometimes | Major | test | Amareshwari Sriramadasu | Amareshwari Sriramadasu
MAPREDUCE-687 | TestMiniMRMapRedDebugScript fails sometimes | Major | test | Amar Kamat | Amareshwari Sriramadasu
MAPREDUCE-924 | TestPipes must not directly invoke ‘main’ of pipes as an exit from main could cause the testcase to crash. | Major | pipes | Amareshwari Sriramadasu | Amareshwari Sriramadasu
HDFS-1022 | Merge under-10-min tests specs into one file | Major | test | Erik Steffl | Erik Steffl

### SUB-TASKS:

JIRA | Summary | Priority | Component | Reporter | Contributor
--- | --- | --- | --- | --- | ---
HADOOP-6213 | Remove commons dependency on commons-cli2 | Blocker | util | Amar Kamat | Amar Kamat