Nginx On HDFS

1. What It Is?

Nginx Oh HDFS is a Nginx extension module, for nginx support HDFS reading.
After install it into Nginx, when resource requested is in HDFS, Nginx can
automatically get resource from HDFS and send it to you.

2. How To Install It?

2.1 download Nginx, hadoop and JDK

Goto the official web site to download nginx-1.8.0, hadoop-2.6.0 and newest
JDK. Because the nginx-hdfs module is written and tested in nginx-1.8.0
and hadoop-2.6.0, so you'd better download the same version as we mentioned
before. nginx-hdfs needs hdfs of hadoop, and hadoop needs JDK.

2.2 Install Hadoop, JDK and set environment variables.

2.2.1 JDK

Install JDK to you system. After it, set environment variables about java
in /etc/profile, we have to set JAVA_HOME and JRE_HOME. for example, we can
add two environment variables following to /etc/profile:

    export JAVA_HOME=/usr/local/jdk1.8.0_40
    export JRE_HOME=$JAVA_HOME/jre

The value of JAVA_HOME and JRE_HOME is determined by JDK install path. The
environment variables should be globally visible, so we set them in
/etc/profile, rather than ~/.bashrc.

2.2.2 Hadoop

Decompress hadoop-2.6.0 to a directory. Add following environment variables to
/etc/profile:

    export HADOOP_HOME=/home/dell/usr/hadoop-2.6.0
    export HADOOP_PREFIX=/home/dell/usr/hadoop-2.6.0
    export LD_LIBRARY_PATH=$HADOOP_HOME/lib/native:$JRE_HOME/lib/i386/server
    export CLASSPATH=$CLASSPATH:`$HADOOP_HOME/bin/hadoop classpath --glob`

The value of environment variables is determined by installing path of
software and the version. The environment variables should be globally
visible, so we set them in /etc/profile.

2.3 Compile Nginx and Configure

Decompress Nginx-1.8.0 to a directory. Before compile nginx and install it,
we have a lot work to do.

2.3.1 compile and install Nginx with nginx-hdfs module.

Goto to directory of Nginx-1.8.0 and run configure like this:

    ./configure --add-module=path/to/your/new/module/directory

This command would add nginx-hdfs module into Nginx. for example, if I put
nginx module's files in /home/dell/nginx-hdfs, I would typed:

    ./configure --add-module=/home/dell/nginx-hdfs

Then you can compile nginx and install it by typing "make" and
"make install". If you OS is 32-bit, you probably got an error, like:

/usr/bin/ld: skipping incompatible
/home/dell/usr/hadoop-2.6.0/lib/native/libhdfs.so when searching for -lhdfs
/usr/bin/ld: skipping incompatible
/home/dell/usr/hadoop-2.6.0/lib/native/libhdfs.a when searching for -lhdfs
/usr/bin/ld: cannot find -lhdfs
collect2: error: ld returned 1 exit status
make[1]: *** [objs/nginx] Error 1
make[1]: Leaving directory `/home/dell/mnt/nginx-1.8.0'
make: *** [build] Error 2

Override $HADOOP_HOME/lib/native/ with native/ contained in our module
source code directory, just type:

    tar -zxf hadoop-native-32bit.tar.gz
    cp -r nginx-hdfs/native/ $HADOOP_HOME/lib/

and compile again, the error would gone.

2.4.1 configure nginx 

Open nginx configuration file (generally, it stores in /usr/local/nginx/ 
conf/nginx.conf). Adding two lines following into nginx.conf:

    env CLASSPATH;
    env JAVA_HOME;

2.5 directive about nginx-hdfs module 

2.5.1 syntax

syntax:    hdfs namenode=<NAMENODE> [username=<USER>] [port=<PORT>]
default:   NONE
context:   location

This directive enabling nginx-hdfs module at a given location. The only
required parameter is "namenode", for specifying the HDFS you want to use.
"username" specifying the user name when connecting with HDFS. "port"
specifies the port when connecting with HDFS. The more details you can
reference hdfs.h in ${HADOOP_HOME}/include/hdfs.h, function
hdfsBuilderSetNameNode(), hdfsBuilderSetUserName() and
hdfsBuilderSetNameNodePort(). 

2.5.2 sample configuration

    location /hdfs {
        hdfs namenode=default;
    }

or 
    location /hdfs {
        hdfs namenode=default username=dell port=0;
    }

"namenode=default" means the Nginx would use the HDFS runs in localhost,
and use the configuration defined in hdfs configuration file. Generally, 
"port" is set to zero.

3. how to use it.

Start Nginx. If you want to GET /index.html in HDFS (if there is no
/index.html in HDFS, you would got an 404 response), you should type
http://localhost/hdfs/index.html in the address bar of web browser. 

4.  Known Issues / TODO / Things You Should Hack On

Currently, we only support GET, HEAD request of http.  We still have a
lot of work to do.

5. Reference 

http://www.evanmiller.org/nginx-modules-guide.html
https://www.packtpub.com/networking-and-servers/nginx-module-extension

6. Contact Author

wuzhouhui250@gmail.com