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From cutt...@apache.org
Subject svn commit: r706781 - in /hadoop/core/trunk: CHANGES.txt docs/libhdfs.html docs/libhdfs.pdf src/docs/src/documentation/content/xdocs/libhdfs.xml src/docs/src/documentation/content/xdocs/site.xml
Date Tue, 21 Oct 2008 21:42:50 GMT
Author: cutting
Date: Tue Oct 21 14:42:50 2008
New Revision: 706781

URL: http://svn.apache.org/viewvc?rev=706781&view=rev
Log:
HADOOP-4105.  Add Forrest documentation for libhdfs.

Added:
    hadoop/core/trunk/docs/libhdfs.html
    hadoop/core/trunk/docs/libhdfs.pdf
    hadoop/core/trunk/src/docs/src/documentation/content/xdocs/libhdfs.xml
Modified:
    hadoop/core/trunk/CHANGES.txt
    hadoop/core/trunk/src/docs/src/documentation/content/xdocs/site.xml

Modified: hadoop/core/trunk/CHANGES.txt
URL: http://svn.apache.org/viewvc/hadoop/core/trunk/CHANGES.txt?rev=706781&r1=706780&r2=706781&view=diff
==============================================================================
--- hadoop/core/trunk/CHANGES.txt (original)
+++ hadoop/core/trunk/CHANGES.txt Tue Oct 21 14:42:50 2008
@@ -523,6 +523,9 @@
     HADOOP-4438. Update forrest documentation to include missing FsShell
     commands. (Suresh Srinivas via cdouglas)
 
+    HADOOP-4105.  Add forrest documentation for libhdfs.
+    (Pete Wyckoff via cutting)
+
   OPTIMIZATIONS
 
     HADOOP-3556. Removed lock contention in MD5Hash by changing the 

Added: hadoop/core/trunk/docs/libhdfs.html
URL: http://svn.apache.org/viewvc/hadoop/core/trunk/docs/libhdfs.html?rev=706781&view=auto
==============================================================================
--- hadoop/core/trunk/docs/libhdfs.html (added)
+++ hadoop/core/trunk/docs/libhdfs.html Tue Oct 21 14:42:50 2008
@@ -0,0 +1,329 @@
+<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
+<html>
+<head>
+<META http-equiv="Content-Type" content="text/html; charset=UTF-8">
+<meta content="Apache Forrest" name="Generator">
+<meta name="Forrest-version" content="0.8">
+<meta name="Forrest-skin-name" content="pelt">
+<meta name="http-equiv" content="Content-Type">
+<meta name="content" content="text/html;">
+<meta name="charset" content="utf-8">
+<title>C API to HDFS: libhdfs</title>
+<link type="text/css" href="skin/basic.css" rel="stylesheet">
+<link media="screen" type="text/css" href="skin/screen.css" rel="stylesheet">
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+<link type="text/css" href="skin/profile.css" rel="stylesheet">
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src="skin/getMenu.js" language="javascript" type="text/javascript"></script><script
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class="skin"><br>
+        PDF</a>
+</div>
+<h1>C API to HDFS: libhdfs</h1>
+<div id="minitoc-area">
+<ul class="minitoc">
+<li>
+<a href="#C+API+to+HDFS%3A+libhdfs">C API to HDFS: libhdfs</a>
+</li>
+<li>
+<a href="#The+APIs">The APIs</a>
+</li>
+<li>
+<a href="#A+sample+program">A sample program</a>
+</li>
+<li>
+<a href="#How+to+link+with+the+library">How to link with the library</a>
+</li>
+<li>
+<a href="#Common+problems">Common problems</a>
+</li>
+<li>
+<a href="#libhdfs+is+thread+safe">libhdfs is thread safe</a>
+</li>
+</ul>
+</div>
+
+<a name="N10019"></a><a name="C+API+to+HDFS%3A+libhdfs"></a>
+<h2 class="h3">C API to HDFS: libhdfs</h2>
+<div class="section">
+<p>
+libhdfs is a JNI based C api for Hadoop's DFS. It provides C apis to a subset of the HDFS
APIs to manipulate DFS files and the filesystem. libhdfs is part of the hadoop distribution
and comes pre-compiled in ${HADOOP_HOME}/libhdfs/libhdfs.so .
+</p>
+</div>
+
+<a name="N10023"></a><a name="The+APIs"></a>
+<h2 class="h3">The APIs</h2>
+<div class="section">
+<p>
+The libhdfs APIs are a subset of: <a href="api/org/apache/hadoop/fs/FileSystem.html">hadoop
fs APIs</a>.  
+</p>
+<p>
+The header file for libhdfs describes each API in detail and is available in ${HADOOP_HOME}/src/c++/libhdfs/hdfs.h
+</p>
+</div>
+
+<a name="N10034"></a><a name="A+sample+program"></a>
+<h2 class="h3">A sample program</h2>
+<div class="section">
+<pre class="code">
+#include "hdfs.h" 
+
+int main(int argc, char **argv) {
+
+    hdfsFS fs = hdfsConnect("default", 0);
+    const char* writePath = "/tmp/testfile.txt";
+    hdfsFile writeFile = hdfsOpenFile(fs, writePath, O_WRONLY|O_CREAT, 0, 0, 0);
+    if(!writeFile) {
+          fprintf(stderr, "Failed to open %s for writing!\n", writePath);
+          exit(-1);
+    }
+    char* buffer = "Hello, World!";
+    tSize num_written_bytes = hdfsWrite(fs, writeFile, (void*)buffer, strlen(buffer)+1);
+    if (hdfsFlush(fs, writeFile)) {
+           fprintf(stderr, "Failed to 'flush' %s\n", writePath); 
+          exit(-1);
+    }
+   hdfsCloseFile(fs, writeFile);
+}
+
+</pre>
+</div>
+
+
+<a name="N1003F"></a><a name="How+to+link+with+the+library"></a>
+<h2 class="h3">How to link with the library</h2>
+<div class="section">
+<p>
+See the Makefile for hdfs_test.c in the libhdfs source directory (${HADOOP_HOME}/src/c++/libhdfs/Makefile)
or something like:
+gcc above_sample.c -I${HADOOP_HOME}/src/c++/libhdfs -L${HADOOP_HOME}/libhdfs -lhdfs -o above_sample
+</p>
+</div>
+
+<a name="N10049"></a><a name="Common+problems"></a>
+<h2 class="h3">Common problems</h2>
+<div class="section">
+<p>
+The most common problem is the CLASSPATH is not set properly when calling a program that
uses libhdfs. Make sure you set it to all the hadoop jars needed to run Hadoop itself. Currently,
there is no way to programmatically generate the classpath, but a good bet is to include all
the jar files in ${HADOOP_HOME} and ${HADOOP_HOME}/lib as well as the right configuration
directory containing hadoop-site.xml
+</p>
+</div>
+
+<a name="N10053"></a><a name="libhdfs+is+thread+safe"></a>
+<h2 class="h3">libhdfs is thread safe</h2>
+<div class="section">
+<p>Concurrency and Hadoop FS "handles" - the hadoop FS implementation includes a FS
handle cache which caches based on the URI of the namenode along with the user connecting.
So, all calls to hdfsConnect will return the same handle but calls to hdfsConnectAsUser with
different users will return different handles.  But, since HDFS client handles are completely
thread safe, this has no bearing on concurrency. 
+</p>
+<p>Concurrency and libhdfs/JNI - the libhdfs calls to JNI should always be creating
thread local storage, so (in theory), libhdfs should be as thread safe as the underlying calls
to the Hadoop FS.
+</p>
+</div>
+
+</div>
+<!--+
+    |end content
+    +-->
+<div class="clearboth">&nbsp;</div>
+</div>
+<div id="footer">
+<!--+
+    |start bottomstrip
+    +-->
+<div class="lastmodified">
+<script type="text/javascript"><!--
+document.write("Last Published: " + document.lastModified);
+//  --></script>
+</div>
+<div class="copyright">
+        Copyright &copy;
+         2008 <a href="http://www.apache.org/licenses/">The Apache Software Foundation.</a>
+</div>
+<!--+
+    |end bottomstrip
+    +-->
+</div>
+</body>
+</html>

Added: hadoop/core/trunk/docs/libhdfs.pdf
URL: http://svn.apache.org/viewvc/hadoop/core/trunk/docs/libhdfs.pdf?rev=706781&view=auto
==============================================================================
--- hadoop/core/trunk/docs/libhdfs.pdf (added)
+++ hadoop/core/trunk/docs/libhdfs.pdf Tue Oct 21 14:42:50 2008
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Added: hadoop/core/trunk/src/docs/src/documentation/content/xdocs/libhdfs.xml
URL: http://svn.apache.org/viewvc/hadoop/core/trunk/src/docs/src/documentation/content/xdocs/libhdfs.xml?rev=706781&view=auto
==============================================================================
--- hadoop/core/trunk/src/docs/src/documentation/content/xdocs/libhdfs.xml (added)
+++ hadoop/core/trunk/src/docs/src/documentation/content/xdocs/libhdfs.xml Tue Oct 21 14:42:50
2008
@@ -0,0 +1,96 @@
+<?xml version="1.0"?>
+<!--
+  Copyright 2002-2004 The Apache Software Foundation
+
+  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.
+-->
+
+<!DOCTYPE document PUBLIC "-//APACHE//DTD Documentation V2.0//EN"
+          "http://forrest.apache.org/dtd/document-v20.dtd">
+
+
+<document>
+<header>
+<title>C API to HDFS: libhdfs</title>
+<meta name="http-equiv">Content-Type</meta>
+<meta name="content">text/html;</meta>
+<meta name="charset">utf-8</meta>
+</header>
+<body>
+<section>
+<title>C API to HDFS: libhdfs</title>
+
+<p>
+libhdfs is a JNI based C api for Hadoop's DFS. It provides C apis to a subset of the HDFS
APIs to manipulate DFS files and the filesystem. libhdfs is part of the hadoop distribution
and comes pre-compiled in ${HADOOP_HOME}/libhdfs/libhdfs.so .
+</p>
+
+</section>
+<section>
+<title>The APIs</title>
+
+<p>
+The libhdfs APIs are a subset of: <a href="api/org/apache/hadoop/fs/FileSystem.html" >hadoop
fs APIs</a>.  
+</p>
+<p>
+The header file for libhdfs describes each API in detail and is available in ${HADOOP_HOME}/src/c++/libhdfs/hdfs.h
+</p>
+</section>
+<section>
+<title>A sample program</title>
+
+<source>
+#include "hdfs.h" 
+
+int main(int argc, char **argv) {
+
+    hdfsFS fs = hdfsConnect("default", 0);
+    const char* writePath = "/tmp/testfile.txt";
+    hdfsFile writeFile = hdfsOpenFile(fs, writePath, O_WRONLY|O_CREAT, 0, 0, 0);
+    if(!writeFile) {
+          fprintf(stderr, "Failed to open %s for writing!\n", writePath);
+          exit(-1);
+    }
+    char* buffer = "Hello, World!";
+    tSize num_written_bytes = hdfsWrite(fs, writeFile, (void*)buffer, strlen(buffer)+1);
+    if (hdfsFlush(fs, writeFile)) {
+           fprintf(stderr, "Failed to 'flush' %s\n", writePath); 
+          exit(-1);
+    }
+   hdfsCloseFile(fs, writeFile);
+}
+
+</source>
+</section>
+
+<section>
+<title>How to link with the library</title>
+<p>
+See the Makefile for hdfs_test.c in the libhdfs source directory (${HADOOP_HOME}/src/c++/libhdfs/Makefile)
or something like:
+gcc above_sample.c -I${HADOOP_HOME}/src/c++/libhdfs -L${HADOOP_HOME}/libhdfs -lhdfs -o above_sample
+</p>
+</section>
+<section>
+<title>Common problems</title>
+<p>
+The most common problem is the CLASSPATH is not set properly when calling a program that
uses libhdfs. Make sure you set it to all the hadoop jars needed to run Hadoop itself. Currently,
there is no way to programmatically generate the classpath, but a good bet is to include all
the jar files in ${HADOOP_HOME} and ${HADOOP_HOME}/lib as well as the right configuration
directory containing hadoop-site.xml
+</p>
+</section>
+<section>
+<title>libhdfs is thread safe</title>
+<p>Concurrency and Hadoop FS "handles" - the hadoop FS implementation includes a FS
handle cache which caches based on the URI of the namenode along with the user connecting.
So, all calls to hdfsConnect will return the same handle but calls to hdfsConnectAsUser with
different users will return different handles.  But, since HDFS client handles are completely
thread safe, this has no bearing on concurrency. 
+</p>
+<p>Concurrency and libhdfs/JNI - the libhdfs calls to JNI should always be creating
thread local storage, so (in theory), libhdfs should be as thread safe as the underlying calls
to the Hadoop FS.
+</p>
+</section>
+</body>
+</document>

Modified: hadoop/core/trunk/src/docs/src/documentation/content/xdocs/site.xml
URL: http://svn.apache.org/viewvc/hadoop/core/trunk/src/docs/src/documentation/content/xdocs/site.xml?rev=706781&r1=706780&r2=706781&view=diff
==============================================================================
--- hadoop/core/trunk/src/docs/src/documentation/content/xdocs/site.xml (original)
+++ hadoop/core/trunk/src/docs/src/documentation/content/xdocs/site.xml Tue Oct 21 14:42:50
2008
@@ -47,6 +47,7 @@
     <hdfs      label="HDFS Admin Guide: Permissions"    href="hdfs_permissions_guide.html"
/>
     <hdfs      label="HDFS Admin Guide: Quotas" href="hdfs_quota_admin_guide.html" />
     <fs        label="HDFS Utilities"  href="SLG_user_guide.html" />
+    <libhdfs   label="HDFS C API"         href="libhdfs.html" />
     <hod-user-guide label="HOD User Guide" href="hod_user_guide.html"/>
     <hod-admin-guide label="HOD Admin Guide" href="hod_admin_guide.html"/>
     <hod-config-guide label="HOD Config Guide" href="hod_config_guide.html"/>



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