Tuesday, 17 July 2018

Introduction to SonarQube - Continuous code quality

In this post, we will see the uses and benefits of SonarQube.

Background
One of the important process in CI/CD is code scan wherein it scans the code for code smells, vulnerabilities, non-standard code etc.

Introduction
To maintain good code quality, it requires continuous scanning of code after each code-checkin. One of the important tool for code scanning is SonarQube which doesn't only scans the code but provide details about its standard and list out where all the issue with its quality. SonarQube job is to provide you with Blockers (i.e. code that is poorly written that can potentially cause issues with the application running in production), critical, major and minor. It also presents you with a value of how much standard your code is. SonarQube currently supports 21 language. Even you can scan your code directly without writing any linting configuration. 

Features
SonarQube scans the code by using methodology called as Quality Gates. This means each scan that we do on our code is by comparing our code with the quality gates. SonarQube has a default quality gate called “SonarQube way”. Whenever we scan the code, it is scanned against default quality gate “SonarQube way” and results are displayed. SonarQube also gives us the ability to configure our own Quality Gate.

SonarQube Quality gates are the best way to ensure that standards are met and regulated across all the projects and every developer oblige it in the organization.  Quality gates are defined with set of threshold measures set on your project like code coverage, technical debt measure (which can increase software entropy), number of blockers/critical issues, security rating, unit test pass rate etc.
 
In order to pass a Quality gate, the project should pass through each of the thresholds defined and it is just a set of conditions the project must meet before it can qualify for production release. When SonarQube runs it will identify if the code meets all the quality thresholds we have defined – else it will fail the quality gate and will not allow you to check in code to the Source code system. 

It also acts as a gatekeeper for bad code when it is integrated with repository tool like GitHub. GitHub provides a way to not allow merging of code (i.e. Pull request) if SonarQube scan fails. Using Quality Gates, we can also scan for new issues that may arise with our new code which is being written.

We can define a quality gate in SonarQube by using an option "create a Quality gate". This is the place where we configure the thresholds for the project / code to meet. After configuring quality gate, it need to be assigned to the project. After assigning, the subsequent scan on the project will be scanned against the quality gates.


That's all the brief introduction to SonarQube. If you have a question / comment, please mention in comment section. Thanks!

Saturday, 14 July 2018

[solved] local variable defined in an enclosing scope must be final or effectively final

In this article we will see how to resolve local variable defined in an enclosing scope must be final or effectively final error for lambda expression.


Background


Java 8 introduces lambda expression which makes an easy way to implement interface which has only one abstract method (also known as functional interfaces). It is a requirement for lambda expression that if it is using local variable, it must be effective final. 


Meaning of Effectively final:


Effectively final are those variable which value doesn't change after it has been set. The sudden question that came in our mind that if this is the meaning of effectively final, why doesn't we declare the variable with final keyword. The difference between effectively final (its a terminology and not a java keyword) and keyword final is that effectively final behaves like final variable even it has not been declared final. 
If you declare a variable as final, its value cannot be changed (will throw compilation error) while those variable which value has been set once and never changed (without declaring as final) is called effectively final. This has to be taken care by developer if he is considering any variable as effectively final because compiler will not throw exception in this case, if the coder changes the value (not in context of lambda expression).


Code Example and Solution:


Consider the below code example which will give the following compilation error:
local variable defined in an enclosing scope must be final or effectively final


Code with Compilation error:



@FunctionalInterface

interface  SingleMethodInterface{

    void value();

}



public class Test {  

    public static void main(String[] args) {

        int i = 10; // This should be effectively final because it is being used by lambda expression.

        // If the value of i changes, it will throw the exception.

        // lambda expression implementing the value method. This is just implementation of interface

        // Here intentionally changing the value of i (increasing by one)

        SingleMethodInterface singleMethodInterface = ()-> System.out.println("Value of i is " + ++i); 

        // Calling the implemented interface method. Since the value is changed, so it will give compilation error

        singleMethodInterface.value();

    }

}


Code with no error


@FunctionalInterface

interface  SingleMethodInterface{

    void value();

}



public class Test {  

    public static void main(String[] args) {

        int i = 10; // This should be effectively final because it is being used by lambda expression.

        // If the value of i changes, it will throw the exception.

        // lambda expression implementing the value method. This is just implementation of interface

        // Here no changing the value of i

        SingleMethodInterface singleMethodInterface = ()-> System.out.println("Value of i is " + i); 

        // Calling the implemented interface method. Since the value is not changed so no error here

        singleMethodInterface.value();

    }

}


That's all for resolution of error for lambda expression with respect to local variable. If you have any further query, feel free to write out in comment section.

Friday, 13 July 2018

How to encrypt string using ansible vault with example

In this article we will see how to encrypt string in Ansible using vault.

Introduction

Encrypting password, keys and variable is required to make system roboust. Using Ansible vault we can store the sensitive data and use the vault when running playbooks on remote machines. Using vault, the sensitive data remains safe.

How to encrypt string using vault

It is required to pass sensitive information if we are using Ansible as a configuration management system or a orchestration engine. For eg. we might need to pass password or ssh key while running playbook. By using vault, we can write sensitive data to a file which Ansible can read and utilize the data from within.

For these ansible provides a way to protect your data at rest. This feature is called vault, which allows user to encrypt text files, strings etc so that they are stored "at rest" in encrypted format. Without the key or a significant amount of computing power, the data is indecipherable.ansible-vault command is provided by Ansible in securing stuff.

Code Example


[root@server1 vault]# ansible-vault encrypt_string --vault-id a_password_file 'pass123' --name 'user1'


Result:

user1: !vault |

      $ANSIBLE_VAULT;1.1;AES256

      64576845869345693586856858858685086748057683457845788957865897856045876085707851

      20364856840580208230475024378508247502483650489658498568436856486584685684658445

      34085620345824852034850824598622865984065893460598263846598406895248658094856249

      23452345
 

If you want to use vault-id label then:

[root@server1 vault]# ansible-vault encrypt_string --vault-id myuser@password 'pass123' --name 'user1'
  

Result:

user1: !vault |

      $ANSIBLE_VAULT;1.1;AES256;myuser

      64576845869345693586856858858685086748057683457845788957865897856045876085707851

      20364856840580208230475024378508247502483650489658498568436856486584685684658445

      34085620345824852034850824598622865984065893460598263846598406895248658094856249

      23452345
 

This is how we can encrypt string in Ansible using vault. If you have any query related to Ansible vault, feel free to ask in comment section. Thanks.

Tuesday, 3 July 2018

Jenkins how to clear cache

In this article we will see how to clear cache for Jenkins

Introduction:

While deploying new installation or driver, there is a need to clear cache for Jenkins. Even though Jenkins is removed, the previous installation details (as cache) can cause issue to the new installation. The solution lies in clearing the cache.

Background & Solution:

To understand this, first find out which all paths / locations where jenkins will be installed.

[root@server1 install]# rpm -ql jenkins
/etc/init.d/jenkins
/etc/logrotate.d/jenkins
/etc/sysconfig/jenkins
/usr/lib/jenkins
/usr/lib/jenkins/jenkins.war
/usr/sbin/rcjenkins /var/cache/jenkins
/var/lib/jenkins
/var/log/jenkins

So, as you can see these are the above paths / locations where jenkins will be installed. Any jenkins cache files, which remains in these paths might cause trouble to the new installation. So as a solution to this problem, we need to remove all files from these paths:
/var/cache/jenkins
/var/lib/jenkins
/var/log/jenkins

Here are the steps / commands to clear cache:

[root@server1 install]# rm -rf /var/cache/jenkins/*
[root@server1 install]# rm -rf  /var/lib/jenkins/*
[root@server1 install]# rm -rf /var/log/jenkins/*

After these paths / locations are cleared, we can go ahead with a new installation with no previous cache.

That's all about steps to clear cache for Jenkins. If you have queries, please write in comment section. Thanks.

Monday, 2 July 2018

Design Chess game

Chess Game Design


Here give an example about an object oriented design of a chess game.

The design can be modularized into four parts: board, piece sets, game and player.





Board

A Board class has an attribute of Squares Array (8x8) and PieceSets (black and white).

A Board class also has an attribute of "pieceSetOnTop". The attribute helps to figure the piece moves that are direction-restricted.


PieceSets

A PieceSet class has an attribute of a List<Piece>. The size of the List<Piece> is initially set to 16.

A Piece class has two attributes: color and placeAt (i.e. located at which square).

A Piece class is an abstract class. The extended classes (Pawn, King, Queen, Rook, Knight, Bishop) implements the abstracted operations:

  • validMoves() - The valid movement for a Piece
  • attackSquares() - The squares that a Piece can attack
  • captureFreeMove - The squares that a Piece can move to without being captured. 
  • toBeCaptured() - The boolean indicates whether a Piece is going to be captured.

The validMoves() operation implements the movement rules. For example, the validMoves of a Pawn class ensures that the Pawn can only move in the direction towards the opponent side. A Pawn class has additional attributes of promoted and promotedTo, which describes the movement/conversion rule of a Pawn at reaching the end of an opponent side and at the conversion about the piece that a Pawn converted to.

Game

A Game class controls the flow of a game. The class has attributes:

  • playedMoves - Keep a record of moves
  • turn - Indicate either it is a Black's turn or a White's turn
  • players - Represent the two players, this can be Human/Human, Computer/Computer or Human/Computer
  • result - Indicate the result of a game
  • checkStatus - Indicate which side is being checked or checkmated

Player

A Player class represents a Player. A Player has two attributes:

  • pieceColor - The color that used by a Player
  • engine - The engine that makes the moves. This can be a human or a computer