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Posted to common-commits@hadoop.apache.org by cu...@apache.org on 2008/10/21 23:42:50 UTC
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
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 @@
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+<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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+<script type="text/javascript">ndeSetTextSize();</script>
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+<!--+
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+<div title="Portable Document Format" class="pdflink">
+<a class="dida" href="libhdfs.pdf"><img alt="PDF -icon" src="skin/images/pdfdoc.gif" 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"> </div>
+</div>
+<div id="footer">
+<!--+
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+<script type="text/javascript"><!--
+document.write("Last Published: " + document.lastModified);
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+ 2008 <a href="http://www.apache.org/licenses/">The Apache Software Foundation.</a>
+</div>
+<!--+
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+</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)
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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"/>