Vagrant – a swiss Army knife for every developer

Whenever we move to a new project, or we want to explore a new stack of technologies; we face the problem of environments. Being a developer we generally have a tendency to install everything on our local environment; which many times proves to be a disaster.

Today, modern web applications involve a lot of moving parts, numerous underlying technologies and a lot of complexity.Read More »

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Use ENUM and map to remove conditional logic in your code.

Using ENUM and a map could be a neat way to remove conditional logic, like switch cases in our code.
Another approach could be to use State design pattern, but if you don’t want to create many classes and your use case is pretty simple and using ENUM will not involve repetition of logic. Then using this approach might not be a bad option.

Let see an example :
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Implement single click deployment using Jenkins and DeployIt

Problem statement : Implement single click deployment using Jenkins and DeployIt
Tools used: Jenkins CI Server, DeplyIt Plugin for Jenkins, Github plugin for jenkins, Maven for building artifact.

Detailed use case :
Lets suppose we have our code in github in a public repository and we want that every fix which goes to “deployment” branch should get propagated to a dev environment automatically.

In order to get this set up working we would need to do:
1.) Configure Jenkins with gitHub and deployIt Plugin.
2.) Configure application placeholder and environment (including infrastructure) in which deployment would take place in DeployIt.
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chef-solo with vagrant

To learn the concepts of chef, we can start by using chef-solo with Vagrant.
See my previous post on Vagrant to install vagrant and know more about it.

Next, lets install chef-solo on our machine.
We will install chef-solo using ruby gem,(for both Linux and Mac) make sure you have ruby installed.

root@intro:~# cd ~
root@intro:~# sudo gem install chef
Thank you for installing Chef!

So, now we have installed chef-solo and vagrant on our machine.
In this exercise, we will try and install apache2 on an ubuntu virtual machine (virtual box)
using chef-solo and vagrant.
To begin we would first need to understand few concepts; which would be required to run chef-solo in Vagrant.
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What are Reentrant Locks?

In Java 5.0 a new addition was made to enhance the intrinsic locking capabilities, called as Reentrant Lock.
Prior to this, ‘synchronized’ and ‘volatile’ were the means for achieving concurrency.

public synchronized void doAtomicTransfer(){
     //enter synchronized block , acquire lock over this object.
    operation1()
    operation2();    
} // exiting synchronized block, release lock over this object.

Synchronized uses intrinsic locks or monitors. Every object in Java has an intrinsic lock associated with it. Whenever a thread tries to access a synchronized block or method it acquires the intrinsic lock or the monitor on that object. In case of static methods, the thread acquires the lock over the class object.
Intrinsic locking mechanism is a clean approach in terms of writing code and is pretty good for most of the use-cases. So why do we need additional feature of Explicit Locks? Lets discuss.

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Create an Ubuntu VM Using Vagrant and Virtual Box

I have been using Vagrant for some time with virtual box to play around with vms on my ubuntu machine.
Vagrant is a tool to help create and provision VirtualBox machines.Few of the reasons for using it would be:

1.) The development environment can be isolated from all the other junk that accumulates on my primary computer.
2.) The development environment can be tuned to match a production server environment as closely as possible.
3.) Provisioning scripts define the machine configuration in code. This means the configuration is repeatable and versionable.
So, lets play with it.
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