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new 105a5a2c76e HADOOP-19166. [DOC] Drop Migrating from Apache Hadoop 1.x
to Apache Hadoop 2.x (#7981)
105a5a2c76e is described below
commit 105a5a2c76e2b15a15fafd7d6ccafb6422d2401c
Author: 石川 敦也 Ishikawa Atsuya <120706596+lshik...@users.noreply.github.com>
AuthorDate: Fri Sep 19 13:55:18 2025 +0900
HADOOP-19166. [DOC] Drop Migrating from Apache Hadoop 1.x to Apache Hadoop
2.x (#7981)
---
.../src/site/markdown/Compatibility.md | 4 +-
.../MapReduce_Compatibility_Hadoop1_Hadoop2.md | 71 ----------------------
hadoop-project/src/site/site.xml | 1 -
3 files changed, 1 insertion(+), 75 deletions(-)
diff --git
a/hadoop-common-project/hadoop-common/src/site/markdown/Compatibility.md
b/hadoop-common-project/hadoop-common/src/site/markdown/Compatibility.md
index 0ccb6a8b5c3..e4bbb75f4a8 100644
--- a/hadoop-common-project/hadoop-common/src/site/markdown/Compatibility.md
+++ b/hadoop-common-project/hadoop-common/src/site/markdown/Compatibility.md
@@ -201,8 +201,7 @@ release as the original build target.
For MapReduce applications in particular, i.e. applications using the
org.apache.hadoop.mapred and/or org.apache.hadoop.mapreduce APIs, the developer
community SHALL support binary compatibility across major releases. The
-MapReduce APIs SHALL be supported compatibly across major releases. See
-[Compatibility for MapReduce applications between hadoop-1.x and
hadoop-2.x](../../hadoop-mapreduce-client/hadoop-mapreduce-client-core/MapReduce_Compatibility_Hadoop1_Hadoop2.html)
for more details.
+MapReduce APIs SHALL be supported compatibly across major releases.
Some applications may be affected by changes to disk layouts or other internal
changes. See the sections that follow for policies on how incompatible
@@ -765,7 +764,6 @@ References
Here are some relevant JIRAs and pages related to the topic:
* The evolution of this document -
[HADOOP-9517](https://issues.apache.org/jira/browse/HADOOP-9517)
-* Binary compatibility for MapReduce end-user applications between hadoop-1.x
and hadoop-2.x - [MapReduce Compatibility between hadoop-1.x and
hadoop-2.x](../../hadoop-mapreduce-client/hadoop-mapreduce-client-core/MapReduce_Compatibility_Hadoop1_Hadoop2.html)
* Annotations for interfaces as per interface classification schedule -
[HADOOP-7391](https://issues.apache.org/jira/browse/HADOOP-7391) [Hadoop
Interface Classification](./InterfaceClassification.html)
* Compatibility for Hadoop 1.x releases -
[HADOOP-5071](https://issues.apache.org/jira/browse/HADOOP-5071)
* The [Hadoop Roadmap](http://wiki.apache.org/hadoop/Roadmap) page that
captures other release policies
diff --git
a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/site/markdown/MapReduce_Compatibility_Hadoop1_Hadoop2.md
b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/site/markdown/MapReduce_Compatibility_Hadoop1_Hadoop2.md
deleted file mode 100644
index 2b8454479b1..00000000000
---
a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/site/markdown/MapReduce_Compatibility_Hadoop1_Hadoop2.md
+++ /dev/null
@@ -1,71 +0,0 @@
-<!---
- Licensed under the Apache License, Version 2.0 (the "License");
- you may not use this file except in compliance with the License.
- You may obtain a copy of the License at
-
- http://www.apache.org/licenses/LICENSE-2.0
-
- Unless required by applicable law or agreed to in writing, software
- distributed under the License is distributed on an "AS IS" BASIS,
- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- See the License for the specific language governing permissions and
- limitations under the License. See accompanying LICENSE file.
--->
-
-Apache Hadoop MapReduce - Migrating from Apache Hadoop 1.x to Apache Hadoop 2.x
-===============================================================================
-
-<!-- MACRO{toc|fromDepth=0|toDepth=3} -->
-
-Introduction
-------------
-
-This document provides information for users to migrate their Apache Hadoop
MapReduce applications from Apache Hadoop 1.x to Apache Hadoop 2.x.
-
-In Apache Hadoop 2.x we have spun off resource management capabilities into
Apache Hadoop YARN, a general purpose, distributed application management
framework while Apache Hadoop MapReduce (aka MRv2) remains as a pure
distributed computation framework.
-
-In general, the previous MapReduce runtime (aka MRv1) has been reused and no
major surgery has been conducted on it. Therefore, MRv2 is able to ensure
satisfactory compatibility with MRv1 applications. However, due to some
improvements and code refactorings, a few APIs have been rendered
backward-incompatible.
-
-The remainder of this page will discuss the scope and the level of backward
compatibility that we support in Apache Hadoop MapReduce 2.x (MRv2).
-
-Binary Compatibility
---------------------
-
-First, we ensure binary compatibility to the applications that use old
**mapred** APIs. This means that applications which were built against MRv1
**mapred** APIs can run directly on YARN without recompilation, merely by
pointing them to an Apache Hadoop 2.x cluster via configuration.
-
-Source Compatibility
---------------------
-
-We cannot ensure complete binary compatibility with the applications that use
**mapreduce** APIs, as these APIs have evolved a lot since MRv1. However, we
ensure source compatibility for **mapreduce** APIs that break binary
compatibility. In other words, users should recompile their applications that
use **mapreduce** APIs against MRv2 jars. One notable binary incompatibility
break is Counter and CounterGroup.
-
-Not Supported
--------------
-
-MRAdmin has been removed in MRv2 because `mradmin` commands no longer exist.
They have been replaced by the commands in `rmadmin`. We neither support binary
compatibility nor source compatibility for the applications that use this class
directly.
-
-Tradeoffs between MRv1 Users and Early MRv2 Adopters
-----------------------------------------------------
-
-Unfortunately, maintaining binary compatibility for MRv1 applications may lead
to binary incompatibility issues for early MRv2 adopters, in particular Hadoop
0.23 users. For **mapred** APIs, we have chosen to be compatible with MRv1
applications, which have a larger user base. For **mapreduce** APIs, if they
don't significantly break Hadoop 0.23 applications, we still change them to be
compatible with MRv1 applications. Below is the list of MapReduce APIs which
are incompatible with Hado [...]
-
-| **Problematic Function** | **Incompatibility Issue** |
-|:---- |:---- |
-| `org.apache.hadoop.util.ProgramDriver#drive` | Return type changes from
`void` to `int` |
-| `org.apache.hadoop.mapred.jobcontrol.Job#getMapredJobID` | Return type
changes from `String` to `JobID` |
-| `org.apache.hadoop.mapred.TaskReport#getTaskId` | Return type changes from
`String` to `TaskID` |
-| `org.apache.hadoop.mapred.ClusterStatus#UNINITIALIZED_MEMORY_VALUE` | Data
type changes from `long` to `int` |
-|
`org.apache.hadoop.mapreduce.filecache.DistributedCache#getArchiveTimestamps` |
Return type changes from `long[]` to `String[]` |
-| `org.apache.hadoop.mapreduce.filecache.DistributedCache#getFileTimestamps` |
Return type changes from `long[]` to `String[]` |
-| `org.apache.hadoop.mapreduce.Job#failTask` | Return type changes from `void`
to `boolean` |
-| `org.apache.hadoop.mapreduce.Job#killTask` | Return type changes from `void`
to `boolean` |
-| `org.apache.hadoop.mapreduce.Job#getTaskCompletionEvents` | Return type
changes from `o.a.h.mapred.TaskCompletionEvent[]` to
`o.a.h.mapreduce.TaskCompletionEvent[]` |
-
-Malicious
----------
-
-For the users who are going to try `hadoop-examples-1.x.x.jar` on YARN, please
note that `hadoop -jar hadoop-examples-1.x.x.jar` will still use
`hadoop-mapreduce-examples-2.x.x.jar`, which is installed together with other
MRv2 jars. By default Hadoop framework jars appear before the users' jars in
the classpath, such that the classes from the 2.x.x jar will still be picked.
Users should remove `hadoop-mapreduce-examples-2.x.x.jar` from the classpath of
all the nodes in a cluster. Otherwi [...]
-
- <property>
- <name>mapreduce.job.user.classpath.first</name>
- <value>true</value>
- </property>
diff --git a/hadoop-project/src/site/site.xml b/hadoop-project/src/site/site.xml
index 6c1f9b0e38f..6cc69a08267 100644
--- a/hadoop-project/src/site/site.xml
+++ b/hadoop-project/src/site/site.xml
@@ -112,7 +112,6 @@
<menu name="MapReduce" inherit="top">
<item name="Tutorial"
href="hadoop-mapreduce-client/hadoop-mapreduce-client-core/MapReduceTutorial.html"/>
<item name="Commands Reference"
href="hadoop-mapreduce-client/hadoop-mapreduce-client-core/MapredCommands.html"/>
- <item name="Compatibility with 1.x"
href="hadoop-mapreduce-client/hadoop-mapreduce-client-core/MapReduce_Compatibility_Hadoop1_Hadoop2.html"/>
<item name="Encrypted Shuffle"
href="hadoop-mapreduce-client/hadoop-mapreduce-client-core/EncryptedShuffle.html"/>
<item name="Pluggable Shuffle/Sort"
href="hadoop-mapreduce-client/hadoop-mapreduce-client-core/PluggableShuffleAndPluggableSort.html"/>
<item name="Distributed Cache Deploy"
href="hadoop-mapreduce-client/hadoop-mapreduce-client-core/DistributedCacheDeploy.html"/>
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