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Subject yetus git commit: YETUS-80 update missing docs from Hadoop
Date Thu, 15 Sep 2016 20:13:24 GMT
Repository: yetus
Updated Branches:
  refs/heads/master 4779af3da -> d9abd010b

YETUS-80 update missing docs from Hadoop

Signed-off-by: Allen Wittenauer <>


Branch: refs/heads/master
Commit: d9abd010b1d2eaa8f6d21e278051eec9ee47db61
Parents: 4779af3
Author: Ajay Yadava <>
Authored: Tue Aug 2 18:41:09 2016 +0530
Committer: Allen Wittenauer <>
Committed: Thu Sep 15 13:13:26 2016 -0700

 .../source/documentation/    |   3 +-
 .../in-progress/     | 211 +++++++++++++++++++
 .../in-progress/           |   2 +-
 .../in-progress/         |   2 +-
 4 files changed, 214 insertions(+), 4 deletions(-)
diff --git a/asf-site-src/source/documentation/ b/asf-site-src/source/documentation/
index 15f44d8..a558efb 100644
--- a/asf-site-src/source/documentation/
+++ b/asf-site-src/source/documentation/
@@ -58,5 +58,4 @@ You can mark a file to be ignored by shelldocs by adding "SHELLDOC-IGNORE"
as a
 # Yetus Audience Annotations
 Audience Annotations allows you to use Java Annotations to denote which parts of your Java
library is publicly consumable and which parts are reserved for a more restricted use. It
also provides doclets and examples for generating javadocs limited by audience.
-See [the javadocs](audience-annotations-apidocs/) for details.
+You can refer the user documentation [here](interface-classification) and the javadocs [here](audience-annotations-apidocs/).
diff --git a/asf-site-src/source/documentation/in-progress/ b/asf-site-src/source/documentation/in-progress/
new file mode 100644
index 0000000..197e52d
--- /dev/null
+++ b/asf-site-src/source/documentation/in-progress/
@@ -0,0 +1,211 @@
+  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
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  See the License for the specific language governing permissions and
+  limitations under the License. See accompanying LICENSE file.
+Apache Yetus Interface Taxonomy: Audience and Stability Classification
+The interface taxonomy classification provided by Apache Yetus annotations is for guidance
+developers and users of interfaces. The classification guides a developer to
+declare the targeted audience or users of an interface and also its stability.
+* Benefits to the user of an interface: Knows which interfaces to use or not use and their
+* Benefits to the developer: to prevent accidental changes of interfaces and
+  hence accidental impact on users or other components or system. This is
+  particularly useful in large systems with many developers who may not all have
+  a shared state/history of the project.
+Interface Classification
+Yetus provides the following interface classification, derived from the
+[OpenSolaris taxonomy](
+and, to some extent, from taxonomy used inside Yahoo.
+Interfaces have two main attributes: Audience and Stability
+### Audience
+Audience denotes the potential consumers of the interface. While many interfaces
+are internal/private to the implementation, others are public/external interfaces
+and are meant for wider consumption by applications and/or clients. For example,
+POSIX definitions in libc are external, while large parts of the kernel are internal or private
+Also, some interfaces are targeted towards other specific subsystems.
+Identifying the audience of an interface helps define the impact of breaking
+it. For instance, it might be okay to break the compatibility of an interface
+whose audience is a small number of specific subsystems. On the other hand, it
+is probably not okay to break a protocol interfaces that millions of Internet
+users depend on.
+Yetus uses the following kinds of audience in order of increasing/wider visibility:
+#### Private
+The interface is for internal use within a project(such as Apache Hadoop)
+and should not be used by applications or by other projects. It is subject to
+change at anytime without notice. Most interfaces of a project are Private (also
+referred to as project-private).
+#### Limited-Private
+The interface is used by a specified set of projects or systems (typically
+closely related projects). Other projects or systems should not use the
+interface. Changes to the interface will be communicated/ negotiated with the
+specified projects. For example, in the Apache Hadoop project, some interfaces are
+LimitedPrivate{HDFS, MapReduce} in that they are private to the HDFS and
+MapReduce subprojects.
+#### Public
+The interface is for general use by any application.
+### Stability
+Stability denotes how stable an interface is, as in when incompatible changes to
+the interface are allowed. Yetus provides the following levels of stability.
+#### Stable
+Can evolve while retaining compatibility for minor release boundaries; in other
+words, incompatible changes to APIs marked Stable are generally  only allowed
+at major releases (i.e. at m.0).
+#### Evolving
+Evolving, but incompatible changes are allowed at minor release (i.e. m .x)
+#### Unstable
+Incompatible changes to Unstable APIs are allowed any time. This usually makes
+sense for only private interfaces.
+However one may call this out for a supposedly public interface to highlight
+that it should not be used as an interface; for public interfaces, labeling it
+as Not-an-interface is probably more appropriate than "Unstable".
+Examples of publicly visible interfaces that are unstable
+(i.e. not-an-interface): GUI, CLIs whose output format will change
+#### Deprecated
+APIs that could potentially be removed in the future and should not be used.
+How are the Classifications Recorded
+[//]: # (This section needs improvement. Refer YETUS-458)
+How should the classification be recorded for the annotated APIs?
+* Each interface or class will have the audience and stability recorded using
+  annotations in org.apache.yetus.classification package.
+* The javadoc generated by the maven target javadoc:javadoc lists only the public API.
+* One can derive the audience of java classes and java interfaces by the
+  audience of the package in which they are contained. Hence it is useful to
+  declare the audience of each java package as public or private (along with the
+  private audience variations).
+* Why aren't the java scopes (private, package private and public) good enough?
+    * Java's scoping is not very complete. One is often forced to make a class
+      public in order for other internal components to use it. It does not have
+      friends or sub-package-private like C++.
+* But I can easily access a private implementation interface if it is Java public.
+  Where is the protection and control?
+    * The purpose of this is not providing absolute access control. Its purpose
+      is to communicate to users and developers. One can access private
+      implementation functions in libc; however if they change the internal
+      implementation details, your application will break and you will have
+      little sympathy from the folks who are supplying libc. If you use a
+      non-public interface you understand the risks.
+* Why bother declaring the stability of a private interface?
+  Aren't private interfaces always unstable?
+    * Private interfaces are not always unstable. In the cases where they are
+      stable they capture internal properties of the system and can communicate
+      these properties to its internal users and to developers of the interface.
+        * e.g. In HDFS, NN-DN protocol is private but stable and can help
+          implement rolling upgrades. It communicates that this interface should
+          not be changed in incompatible ways even though it is private.
+        * e.g. In HDFS, FSImage stability can help provide more flexible roll backs.
+* What is the harm in applications using a private interface that is stable? How
+  is it different than a public stable interface?
+    * While a private interface marked as stable is targeted to change only at
+      major releases, it may break at other times if the providers of that
+      interface are willing to changes the internal users of that
+      interface. Further, a public stable interface is less likely to break even
+      at major releases (even though it is allowed to break compatibility)
+      because the impact of the change is larger. If you use a private interface
+      (regardless of its stability) you run the risk of incompatibility.
+* Why bother with Limited-private? Isn't it giving special treatment to some projects?
+  That is not fair.
+    * First, most interfaces should be public or private; actually let us state
+      it even stronger: make it private unless you really want to expose it to
+      public for general use.
+    * Limited-private is for interfaces that are not intended for general
+      use. They are exposed to related projects that need special hooks. Such a
+      classification has a cost to both the supplier and consumer of the limited
+      interface. Both will have to work together if ever there is a need to
+      break the interface in the future; for example the supplier and the
+      consumers will have to work together to get coordinated releases of their
+      respective projects. This should not be taken lightly - if you can get
+      away with private then do so; if the interface is really for general use
+      for all applications then you should consider making it public. But remember
+      that making an interface public has huge responsibility. Sometimes
+      Limited-private is just right.
+    * A good example of a limited-private interface is BlockLocations in the Apache
+      Hadoop Project, This is fairly low-level interface that they are willing to
+      expose to MR and perhaps HBase. They are likely to change it down the road
+      and at that time they will have to get a coordinated effort with the MR
+      team to release matching releases. While MR and HDFS are always released
+      in sync today, they may change down the road.
+    * If you have a limited-private interface with many projects listed then you
+      are fooling yourself. It is practically public.
+    * It might be worth declaring a special audience classification called
+      {YourProjectName}-Private for your closely related projects.
+* Can't a private interface be treated as project-private also? For example what is
+  the harm in projects in the Apache Hadoop extended ecosystem, having access to
+  private classes?
+    * Do we want MR accessing class files that are implementation details inside
+      HDFS? There used to be many such layer violations in the Apache Hadoop
+      project that they have been cleaning up over the last few years. It is highly
+      undesirable for such layer violations to creep back in by no separation
+      between the major components like HDFS and MR.
+* Aren't all public interfaces stable?
+    * One may mark a public interface as evolving in its early days. Here one is
+      promising to make an effort to make compatible changes but may need to
+      break it at minor releases.
+    * One example of a public interface that is unstable is where one is
+      providing an implementation of a standards-body based interface that is
+      still under development. For example, many companies, in an attempt to be
+      first to market, have provided implementations of a new NFS protocol even
+      when the protocol was not fully completed by IETF. The implementor cannot
+      evolve the interface in a fashion that causes least disruption because
+      the stability is controlled by the standards body. Hence it is appropriate
+      to label the interface as unstable.
diff --git a/asf-site-src/source/documentation/in-progress/ b/asf-site-src/source/documentation/in-progress/
index d9fdc28..7bdb8db 100644
--- a/asf-site-src/source/documentation/in-progress/
+++ b/asf-site-src/source/documentation/in-progress/
@@ -103,7 +103,7 @@ Similarly, there are other functions that may be defined during the test-patch
 Plug-ins are imported from several key directories:
-* core.d is an internal-to-Yetus directory that first loads the basic Yetus library, followed
by the common routines used by all of the precommit shell code.  This order is dictated by
prefixing the plug-in files with a number.  Other files in this directory are loaded in shell
collated order.
+* core.d is an internal-to-Yetus directory that first loads the basic Apache Yetus library,
followed by the common routines used by all of the precommit shell code.  This order is dictated
by prefixing the plug-in files with a number.  Other files in this directory are loaded in
shell collated order.
 * personality contains bundled personalities for various projects.  These will be imported
individually based upon either a project name or if specifically identified with the `--personality`
diff --git a/asf-site-src/source/documentation/in-progress/ b/asf-site-src/source/documentation/in-progress/
index d09323b..734c827 100644
--- a/asf-site-src/source/documentation/in-progress/
+++ b/asf-site-src/source/documentation/in-progress/
@@ -162,4 +162,4 @@ By default, test-patch will pass -Ptest-patch to Maven. This will allow
you to c
 Maven will test eclipse and site if maven is being used as the build tool and appropriate
files trigger them.
-Maven will trigger add a maven install test when the `maven_add_install` function has been
used and the related tests are requierd. Plug-ins that need to run maven before MUST call
it as part of their respective initialize functions, otherwise maven may fail unexpectedly.
 All Yetus provided plug-ins that require maven will trigger the maven install functionality.
+Maven will trigger add a maven install test when the `maven_add_install` function has been
used and the related tests are requierd. Plug-ins that need to run maven before MUST call
it as part of their respective initialize functions, otherwise maven may fail unexpectedly.
 All Apache Yetus provided plug-ins that require maven will trigger the maven install functionality.

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