Web Technology Experts Notes

Thursday, 26 December 2019

Hadoop - Understanding Hadoop Architecture

Hadoop is an open source framework written in java that allows distributed processing of large datasets across clusters of computers.
Hadoop is designed to scale up from single server to thousands of machines and each have local-computation and storage.

Hadoop Architecture have 4 modules.

Hadoop Common: These are Java libraries which provides filesystem and OS level abstractions which are required to start Hadoop.
Hadoop YARN: This is used for job scheduling and cluster resource management.
Hadoop Distributed File System: It provides high throughput access to application data and is suitable for applications that have large data sets.
Hadoop MapReduce: This is YARN-based system for parallel processing of large data sets.

Question: What is MapReduce?
MapReduce is a software framework for easily writing applications which process big amounts of data in-parallel on large clusters. It consits of master JobTracker and slave TaskTracker per cluster. The JobTracker is responsible for resource management and schedule the task. TaskTracker is responsibel for execute the task.

Question: How Does HadoopwWork at very basic level?

Job Submission by client to Hadoop.
Input and output files are in "distributed file system" and with use of "Hadoop Common files" Initialization the hadoop.
Execute of map and reduce functions.
Scheduling the task by TaskTracker.
Execution the task by JobTracker.

Saturday, 21 December 2019

What are special characters? and how to remove special characters?

Question: What are special characters?
Special characters are selected punctuation characters present on standard US keyboard.

Question: Provide list of special characters?

Character	Name
	Space
!	Exclamation
"	Double quote
#	Number sign (hash)
$	Dollar sign
%	Percent
&	Ampersand
'	Single quote
(	Left parenthesis
)	Right parenthesis
*	Asterisk
+	Plus
,	Comma
-	Minus
.	Full stop
/	Slash
:	Colon
;	Semicolon
<	Less than
=	Equal sign
>	Greater than
?	Question mark
@	At sign
[	Left bracket
\	Backslash
]	Right bracket
^	Caret
_	Underscore
`	Grave accent (backtick)
{	Left brace
\|	Vertical bar
}	Right brace
~	Tilde

Question: How to remove special characters from string including space?

$string='test !@#ing';
echo preg_replace('/[^A-Za-z0-9\-]/', '', $string);

Question: How to remove special characters from string except space?

$string='test !@#ing';
echo preg_replace('/[^A-Za-z0-9\-\s]/', '', $string);

Question: How to replace special characters with hyphen?

$string='test !@#ing';
echo preg_replace('/[^A-Za-z0-9\-\s]/', '-', $string);

Question: How to replace multiple hyphen with single hyphen?

$string='test-----ing';
echo preg_replace('/-+/', '-',$string);

Question: How to remove special characters from array?

$array=array('test !@#ing','sdalkjsad','#$#33');
function cleanData($string){
return preg_replace('/[^A-Za-z0-9\-]/', '', $string);
}
$array = array_map('cleanData',$array);
print_r($array);

Question: How to remove all special characters from javascript?

var stringToReplace='test !@#ing';
stringToReplace=stringToReplace.replace(/[^\w\s]/gi, '')

Monday, 16 December 2019

What is CPU Usage and Memory Usage?

CPU Usage- It is the "amount of time" a CPU was used for processing the given instructions.

Memory Usage- It is the "amount of RAM" was used for processing the given instructions

Entry Processes- It is number of scripts are running at a single time. One entry process take fraction of a second to complete. So in 10 entry process you can have 10-30 visitors.

Number of Processes- It is number of process(script) can run in one time. One process take time till the execution of script.

I/O Usage- It is speed of data transfer between the hard disk and the RAM.

Question: Is high CPU usage bad?
If the CPU usage is around 100%, this means that your computer is trying to do more work than it has the capacity. Always CPU usage must be less than 90%, If so increase the CPU.

Saturday, 14 December 2019

How to add number of days to a date in PHP?

Program Example

$Date = "2020-09-19";
echo date('Y-m-d', strtotime($Date. ' + 1 days'));
echo date('Y-m-d', strtotime($Date. ' + 2 days'));

Output

2020-09-18
2020-09-19

Question: How to add number of days to a current date?

echo date('Y-m-d', strtotime("+10 days"));

It would add 10 days to the current date.

Question: How to subtract number of days to a current date?

echo date('Y-m-d', strtotime("-10 days"));

It would subtract 10 days to the current date.

Question: How to add number of days to a on given date?

$date = new DateTime('2016-12-14');
echo date('Y-m-d', ($date->getTimestamp()+ (3600*24*10) )); //3600 = 1 hour

It would add 10 days to the current date.

Question: How to subtract number of days to a given date?

$date = new DateTime('2016-12-14');
echo date('Y-m-d', ($date->getTimestamp()- (3600*24*10) )); //3600 = 1 hour

It would subtract 10 days to the current date.

Thursday, 12 December 2019

How to get the sizes of the tables in mysql database?

Question: How to get the sizes of the tables in mysql database?

SELECT table_name "Table Name",SUM( data_length + index_length ) / 1024 / 1024 "Table Size (MB)",SUM( data_free )/ 1024 / 1024 "Free Space(MB)" FROM information_schema.TABLES WHERE table_schema='mydb' GROUP BY table_name ORDER BY SUM(TABLE_ROWS) DESC

(Replace mydb with Your Database Name)

Output

Question: Get record counts for all tables along with size in MySQL database?

SELECT table_name "Table Name",SUM( data_length + index_length ) / 1024 / 1024 "Table Size (MB)",SUM( data_free )/ 1024 / 1024 "Free Space(MB)", SUM(TABLE_ROWS) AS "Total Record(S)" FROM information_schema.TABLES WHERE table_schema='mydb' GROUP BY table_name ORDER BY SUM(TABLE_ROWS) DESC

(Replace mydb with Your Database Name)

Output

Get record counts for all tables in MySQL database

How to resize images in php

Function resizeImage

    
/**
 * 
 * @param type $width
 * @param type $height
 * @param type $mode
 * @param type $imageName
 * @param type $extension
 * @return string
 */
     function resizeImage($width, $height, $mode, $imageName,$extension) {
        $docRoot = getenv("DOCUMENT_ROOT");
        
        /* Get original image x y */
        $tmpNM = $_FILES['files']['tmp_name'];
        
        list($w, $h) = getimagesize($_FILES['files']['tmp_name']);
        /* calculate new image size with ratio */
        $ratio = max($width / $w, $height / $h);
        $h = ceil($height / $ratio);
        $x = ($w - $width / $ratio) / 2;
        $w = ceil($width / $ratio);
        /* new file name */
        if ($mode == 'userphoto') {
                $path = $docRoot . '/upload/userphoto/' . $imageName;
        } 
        
 
        /* read binary data from image file */
        $imgString = file_get_contents($_FILES['files']['tmp_name']);
        /* create image from string */
        $image = imagecreatefromstring($imgString);
        $tmp = imagecreatetruecolor($width, $height);
        imagecopyresampled($tmp, $image, 0, 0, $x, 0, $width, $height, $w, $h);
        $fileTypes = array('jpg', 'jpeg', 'jpe', 'png', 'bmp', 'gif'); // File extensions
        /* Save image */
        $extension = strtolower($extension);
        switch ($extension) {
            case 'jpg':
            case 'jpeg':
            case 'jpe':
                imagejpeg($tmp, $path, 100);
                break;
            case 'png':
                imagepng($tmp, $path,0);
                break;
            case 'gif':
                imagegif($tmp, $path, 100);
                break;
            case 'bmp':
                imagewbmp($tmp, $path);
                break;
            default:
                
                exit;
                break;
        }
        return $path;
        /* cleanup memory */
        imagedestroy($image);
       imagedestroy($tmp);
    }

How to use Code
HTML Code

<form action="upload.php" enctype="multipart/form-data" method="post">
<input id="image upload" name="files" type="file" />
<input name="submit" type="submit" value="Upload Image" />

PHP Code

  
//List of thumbnails
$sizes = array(200 => 200, 150 => 150);

$files=array();
if (!empty($_FILES)) {
    //Clean the image name
    $_FILES['files']['name'] = preg_replace('/[^a-zA-Z0-9_.-]/', '', strtolower(trim($_FILES['files']['name'])));    
    
    //Temporary file, type, name
    $tmpNM = $_FILES['files']['tmp_name'];
    $imageType = $_FILES['files']['type'];
    $imageName = $_FILES['files']['name'];
    
    //Get image extension
    $imageNameType = explode(".", $_FILES['files']['name']);
    
    //Type of images support for uploading
    $fileMimeTypes = array('image/jpeg', 'image/png', 'image/bmp', 'image/gif'); // mime  extensions
    $fileTypes = array('jpg', 'jpeg', 'jpe', 'png', 'bmp', 'gif'); // File extensions
    
    if (in_array(strtolower($imageNameType[1]), $fileTypes)) {
        $fullImageName = time('his') . '_' . $_FILES['files']['name'];
        foreach ($sizes as $w => $h) {
            $files[] = $this->resizeImage($w, $h, 'userphoto', "{$w}_{$fullImageName}", $imageNameType[1]);
        }

    } 
}

Sunday, 8 December 2019

Swagger - REST API documentation tool

Question: What is swagger?
It is REST API documentation tool which is used to list the APIs and view the request and response.
In this, we need to add some annotations in your functions and then it will automatically generate a beautiful and user-friendly documentation for your APIs.

Question: Where it is used?
Whenever we develop an android, IOS (Apple) application, we need to create an APIs for them.

To check the API details (URL, Request, response), we use Swagger.

Question: Who is using swagger?
Backend Developer: developer used it while creating Or updating an API.
Team Leader: As it give List of APIs with request and response. Team leader used it review the APIs.
Android/IOS Developer: While integrating the APIs, Its quite help the developer because they can check the response of APIs with different request.

Question: What are benefits of swagger?

Its give list of APIs with short description.
Its give the Request and Response of API.
We can test the response of API with different request.
We need to integrate in application first time, after the we need to add some annotations in functions/APIs.
Can be integrate in Core PHP or Framework.
We need not to list and details of apis manually.

Question: What is Swagger Editor?
The Swagger Editor is the tool for quickly getting started with the Swagger Specification.
Create new APIs OR update existing ones in a powerful Editor which visually renders your Swagger definition and provides real time error-feedback.
http://editor.swagger.io/#/

Question: Give a Demo URL?
http://petstore.swagger.io/

Question: From where i can download?
http://swagger.io/docs/#swagger-ui-documentation-29

Question: How to Add API in swagger?
Add Following code before the class declaration

/**
 * @SWG\Resource(
 *     apiVersion="1.0",
 *     swaggerVersion="1.2",
 *     description="Search users"
 * )
 */

Question: How to add new Operation for an API?
Add Following code before the method declaration

    /**
     * @SWG\Api(
     *     path="/search",
     *     @SWG\Operation(
     *         method="POST",
     *         summary="Get users near your location",
     *         type="Users list",
     *         @SWG\Parameters(
     *             @SWG\Parameter(
     *                 name="interests",
     *                 paramType="form",
     *                 description="comma seperated looking for",
     *                 required=false,
     *                 type="string",
     *                 minimum="1.0"
     *             ),
     *             @SWG\Parameter(
     *                 name="page",
     *                 paramType="form",
     *                 description="page number",
     *                 required=true,
     *                 type="string",
     *                 minimum="1.0"
     *             ),
     *         ),
     *         @SWG\ResponseMessage(code=400, message="Invalid Data")
     *     )
     * )
     */

Difference between channel and playlist on youtube

A channel is your identity on YouTube, like your name, where your upload videos.
OR
A channel is the home page for an your youtube account.

Question: What details are available on Channel page?
--- Basic information like Your Name, Account type etc.
--- Your public videos which you have uploaded.
--- Listing of playlist.

Question: What we can do on Channel page?
--- Update your information. --- upload videos.
--- customize the color theme of your channel.
--- Others can subscribe your channel.

Question: Sample of Youtbe Channel?
https://www.youtube.com/channel/UCFPS0qKgr-GbSRAppOkdpUA

Question: What is playlist?
A playlist is a collection of videos you may saved.

Question: List of Playlist (After Login on youtube.com with your gmail.com account)
https://www.youtube.com/view_all_playlists

Create a New Playlist (After Login on youtube)
https://www.youtube.com/view_all_playlists
Click on "New Playlist", an popup will prompt, just add the your playlist name

Question: How to add videos in playlist?
Go to playlist page (Like https://www.youtube.com/playlist?list=PLREKFLRZTg5xJJHmLiKZ0VBTKpubGXksb).
Click on "Add Videos" (Middle Right side).
An Popup will prompt.
Just add the YouTube video URL (Any video which you like) and follow Steps.

Question: What you can do with your playlist?
--- Make the playlist as public/private.
--- Add notes to each videos.
--- Re-ordering the videos.
--- AutoPlay on/off for videos.
--- Share your playlist on Fb.
--- Embed your playlist videos in your website/blog.

Question: Need Playlist Sample URL
https://www.youtube.com/playlist?list=PLREKFLRZTg5xJJHmLiKZ0VBTKpubGXksb

Question: Can we earn money with playlist?
No, You can't earn money on other's video (Uploaded by other).
You can earn money with your own videos (uploaded by you)

Saturday, 7 December 2019

How to Validate email address in PHP?

Following are in built PHP function to validate the email address and Ip Address.

Validate Email - Example 1

$email='helo@gmail.com';
if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
  echo $email. ' - Invalid'; 
}else{
echo $email. ' - Valid';     
}

helo@gmail.com - Valid

Validate Email - Example 2

$email='464646@gmail.com';
if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
  echo $email. '- Invalid'; 
}else{
echo $email. ' - Valid';     
}

464646@gmail.com - Valid

Validate Email - Example 3

$email='arunkumar.com';
if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
  echo $email. ' - Invalid'; 
}else{
echo $email. ' - Valid';     
}

arunkumar.com - Invalid

Validate IP Address - Example 1
Question: How to Validate IP Address?

$ipAddress = '127.0.0.1';
if (!filter_var($ipAddress, FILTER_VALIDATE_IP)) {
    echo "$ipAddress is In-valid.";
}else{
    echo "$ipAddress is Valid.";
}

127.0.0.1 is Valid

Validate IP Address - Example 2

$ipAddress = '127.test.0.0.1';
if (!filter_var($ipAddress, FILTER_VALIDATE_IP)) {
    echo "$ipAddress is In-valid.";
}else{
    echo "$ipAddress is In-Valid.";
}

127.test.0.0.1 is Valid

Validate URL - Example 1

$ipAddress = '127.test.0.0.1';
$website = 'https://www.web-technology-experts-notes.in';
if (!preg_match("/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i",$website)) {
  echo   "Invalid URL";
}else{
echo   "Valid URL";
}

Valid URL

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