GIT getting started

A very good tutorial on git : http://www.sbf5.com/~cduan/technical/git/

GIT commands:

• Git Pull

  From what I understand, git pull will pull down from a remote whatever you ask (so, whatever trunk you’re asking for) and instantly merge it into the branch you’re in when you make the request. Pull is a high-level request that runs ‘fetch’ then a ‘merge’ by default, or a rebase with ‘–rebase’. You could do without it, it’s just a convenience.

• Git fetch

  Fetch is similar to pull, except it won’t do any merging.

• Git clone

  Git clone will clone a repo int a newly created directory. It’s useful for when you’re setting up your local doodah
• 
  

If you get stuck, run ‘git branch -a’ and it will show you exactly what’s going on with your branches. You can see which are remotes and which are local. 

http://betterexplained.com/articles/aha-moments-when-learning-git/
http://jonas.nitro.dk/git/quick-reference.html

Reading: http://blog.mikepearce.net/2010/05/18/the-difference-between-git-pull-git-fetch-and-git-clone-and-git-rebase/

Finding your gateway IP address in Linux, windows and MAC

Original Source: http://wiki.amahi.org/index.php/Find_Your_Gateway_IP

• Windows:
  
  
  • Click Start > All Programs > Accessories > Command Prompt.
    
  • When Command Prompt is open, type the following command: ipconfig | findstr /i "Gateway" (You can copy & paste it in the command prompt; just right-click anywhere in the command prompt window and select Paste.)
    
  • You should see something like this:
    C:\Documents and Settings\administrator>ipconfig | findstr /i "Gateway"
Default Gateway . . . . . . . . . : 192.168.1.1
    
  • In this example, your default gateway (router) IP address is 192.168.1.1.

• Linux:
  
  
  • You'll need to open a Terminal. Depending on your Linux distribution, it can be located in the menu items at the top, or at the bottom of your screen. In this example, we will use Fedora. Click Applications > System Tools > Terminal.
    
  • When terminal is open, type the following command: ip route | grep default
    
  • The output of this should look something like the following:
    joe$ ip route | grep default
default via 192.168.1.1 dev eth0 proto static
    
  • In this example, again, 192.168.1.1 is your default gateway (router) IP address.

• Mac OS X:
  
  
  • Open the Terminal application. Do do this, click Finder > Applications > Utilities > Terminal.app.
    
  • When Terminal.app is open, type the following command: netstat -nr | grep default
    
  • This will output the following:
    joe$ netstat -nr | grep default
default 192.168.1.1 UGSc 50 46 en1
    
  • In this example, again, 192.168.1.1 is your default gateway (router) IP address.

Java Applications Monitoring and Instrumentation using JMX

Finally was successfully able to integrate the HTTP web interface for JMX caled JMiniX ( http://code.google.com/p/jminix/wiki/Documentation ).

To download the dependency jars:

• Download the pom.xml of the project JMiniX
• Run maven command "mvn compile pom.xml", this downloads the dependency jars to the .m2 maven folder in your user profile folder.
• Copy these jars to your project's lib.

Important Note: In the web.xml you must specify the url pattern as "<url-pattern>/jmx/*</url-pattern>" otherwise JMiniX doesn't seem to work.

Reading: http://www.ibm.com/developerworks/java/library/j-jtp09196/index.html

http://www.mularien.com/blog/2007/11/09/5-minute-guide-to-spring-and-jmx/
http://today.java.net/pub/a/today/2005/12/20/introduction-to-jmxremote.html

Using Spring with vanilla Servlets without MVC

http://blogs.sourceallies.com/2012/02/injecting-spring-beans-into-java-servlets/

http://www.codeproject.com/Tips/251636/How-to-inject-Spring-beans-into-Servlets

http://andykayley.blogspot.in/2008/06/how-to-inject-spring-beans-into.html

http://static.springsource.org/spring/docs/3.0.0.M3/reference/html/ch04s11.html

Debugging hadoop mapreduce jobs using eclipse in local setup

Add the following line to 'conf/hadoop-env.sh':

export HADOOP_OPTS="-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=5009"

Then setup eclipse to connect to the above port (5009) using remote debugging configuration.

Detailed steps: http://code.google.com/p/hadoop-clusternet/wiki/DebuggingJobsUsingEclipse

I tried running this is in the Stand alone configuration of Hadoop.
Have to try this in the pseudo-distributed mode as well, does it work ?

Here is an article that claims to debug the daemon processes:
http://srinathsview.blogspot.in/2012/05/debugging-hadoop-task-tracker-job.html

Routing protocols

A good link to read about routing, various routing protocols IGP, OSPF and BGP is Module 7 at the link: http://nptel.iitm.ac.in/courses/Webcourse-contents/IIT%20Kharagpur/Computer%20networks/New_index1.html

http://nptel.iitm.ac.in/courses/IIT-MADRAS/Computer_Networks/index.php

Learning Hadoop

Read the first 4 chapters of "Hadoop in Action" by Chuck Lam. These chapters introduce the basics of the MapReduce and Hadoop framework in easy language.

Run the word count example which comes with the hadoop installation.

http://hadoop.apache.org/docs/r0.20.1/quickstart.html
http://hadoop.apache.org/docs/r0.20.1/mapred_tutorial.html
https://confluence.guavus.com/display/GTR/Install+and+Setup+Hadoop+on+Mac


Exercise: Implement the median function in an efficient manner using Hadoop.