Introduction

In a previous article we learned about Creating a PHP Daemon Service. Now we are going to learn how to use methods to perform IPC - Inter-Process Communication - to communicate with daemon processes.

Message Queues

In the world of UNIX, there is an incredible variety of ways to send a message or a command to a daemon script and vice versa. But first I want to talk only about message queues - "System V IPC Messages Queues".

A long time ago I learned that a queue can be either in the System V IPC implementation, or in the POSIX implementation. I want to comment only about the System V implementation, as I know it better.

Lets get started. At the "normal" operating system level, queues are stored in memory. Queue data structures are available to all system programs. Just as in the file system, it is possible to configure queues access rights and message size. Usually a queue message size is small, less than 8 KB.

This introductory part is over. Lets move on to the practice with same example scripts.queue-send.php

$key = ftok(__FILE__, 'A'); 
$queue = msg_get_queue($key);

msg_send($queue, 1, 'message, type 1');
msg_send($queue, 2, 'message, type 2');
msg_send($queue, 3, 'message, type 3');
msg_send($queue, 1, 'message, type 1');

echo "send 4 messages
";

queue-receive.php

$key = ftok('queue-send.php', 'A');
$queue = msg_get_queue($key);

for ($i = 1; $i <= 3; $i++) {
 echo "type: {$i}
";

 while ( msg_receive($queue, $i, $msgtype, 4096, $message, false, MSG_IPC_NOWAIT) ) {
 echo "type: {$i}, msgtype: {$msgtype}, message: {$message}
";
 }
}

Lets run on the first stage of the file queue-send.php, and then queue-receive.php.

u% php queue-send.php
send 4 messages
u% php queue-receive.php
type: 1
type: 1, msgtype: 1, message: s:15:"message, type 1";
type: 1, msgtype: 1, message: s:15:"message, type 1";
type: 2
type: 2, msgtype: 2, message: s:15:"message, type 2";
type: 3
type: 3, msgtype: 3, message: s:15:"message, type 3";

You may notice that the messages have been grouped. The first group gathered 2 messages of the first type, and then the remaining messages.

If we would have indicated to receive messages of type 0, you would get all messages, regardless of the type.

while (msg_receive($queue, $i, $msgtype, 4096, $message, false, MSG_IPC_NOWAIT)) {

Here it is worth noting another feature of the queues: if we do not use the constant MSG_IPC_NOWAIT in the script and run the script queue-receive.php from a terminal, and then run periodically the file queue-send.php, we see how a daemon can effectively use this to wait jobs.queue-receive-wait.php

$key = ftok('queue-send.php', 'A');
$queue = msg_get_queue($key);

while ( msg_receive($queue, 0, $msgtype, 4096, $message) ) {
 echo "msgtype: {$msgtype}, message: {$message}
";
}

Actually that is the most interesting information of all I have said. There are also functions to get statistics, disposal and checking for the existence of queues.

Lets now try to write a daemon listening to a queue:queue-daemon.php

$pid = pcntl_fork();
$key = ftok('queue-send.php', 'A');
$queue = msg_get_queue($key);

if ($pid == -1) {
 exit;
} elseif ($pid) {
 exit;
} else {
 while ( msg_receive($queue, 0, $msgtype, 4096, $message) ) {
 echo "msgtype: {$msgtype}, message: {$message}
";
 }
}

posix_setsid();

Shared Memory

We have learned to work with queues, with which you can send small system messages. But then we may certainly be faced with the task of transmitting large amounts of data. My favorite type of system, System V, has solved the problem of rapid transmission and preservation of large data in memory using a mechanism calledShared Memory.

In short, the data in the Shared Memory lives until the system is rebooted. Since the data is in memory, it works much faster than if it was stored in a database somewhere in a file, or, God forgive me on a network share.

Lets try to write a simple example of data storage.shared-memory-write-base.php

$id = ftok(__FILE__, 'A');


$shmId = shm_attach($id);

$var = 1;

if (shm_has_var($shmId, $var)) {
 $data = (array) shm_get_var($shmId, $var);
} else {
 $data = array();
}

$data[time()] = file_get_contents(__FILE__);

shm_put_var($shmId, $var, $data);

Run this script several times to save the value in memory. Now lets write a script only to read from the memory.shared-memory-read-base.php

$id = ftok(__DIR__ . '/shared-memory-write-base.php', 'A');
$shmId = shm_attach($id);
$var = 1; 

if (shm_has_var($shmId, $var)) {
 $data = (array) shm_get_var($shmId, $var);
} else {
 $data = array();
}

foreach ($data as $key => $value) {
 $path = "/tmp/$key.php";
 file_put_contents($path, $value);

 echo $path . PHP_EOL;
} 

Semaphores

So, in general terms, it should be clear for you by now how to work with shared memory. The only problems left to figure out are about a couple of nuances, such as: "What to do if two processes want to record one block of memory?" Or "How to store binary files of any size?".

To prevent simultaneous accesses we will use semaphores. Semaphores allow us to flag that we want to have exclusive access to some resource, like for instance a shared memory block. While that happens other processes will wait for their turn on semaphore.

In this code it explained clearly:shared-memory-semaphors.php

$id = ftok(__FILE__, 'A');

$semId = sem_get($id);

sem_acquire($semId);

$data = file_get_contents(__DIR__.'/06050396.JPG', FILE_BINARY);

$shmId = shm_attach($id, strlen($data)+4096);
$var = 1;
 
if (shm_has_var($shmId, $var)) {
 $data = shm_get_var($shmId, $var);

 $filename = '/tmp/' . time();
 file_put_contents($filename, $data, FILE_BINARY);

 shm_remove($shmId);
} else {
 shm_put_var($shmId, $var, $data); 
}

sem_release($semId); 

Now you can use the md5sum command line utility to compare two files, the original and the saved file. Or, you can open the file in image editor or whatever prefer to compare the images.

With this we are done with shared memory and semaphores. As your homework I want to ask you to write code that a demon will use semaphores to access shared memory.

Conclusion

Exchanging data between the daemons is very simple. This article described two options for data exchange: message queues and shared memory.

Post a comment here if you have questions or comments about how to exchange data with daemon services in PHP.

Hi Guys,
I am sharing you the simple steps by which you can broadcast the web push notifications to your subscriber. In this tutorial we are making a subscriber form and saving information using Ajax and PHP and then through a server side code returning response to current logged in user and showing notification to that user.
Following are the steps to build this system

1. Create a database, I am creating db with name 'web_notifications'

Creating subscribers and notifications tables using following sql statements

CREATE TABLE IF NOT EXISTS <code>subscribers</code> (
 <code>id</code> int(11) NOT NULL,
 <code>name</code> varchar(255) NOT NULL,
 <code>email</code> varchar(255) NOT NULL,
 <code>createdAt</code> timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

ALTER TABLE <code>subscribers</code> ADD PRIMARY KEY (<code>id</code>);

ALTER TABLE <code>subscribers</code> MODIFY <code>id</code> int(11) NOT NULL AUTO_INCREMENT;



CREATE TABLE IF NOT EXISTS <code>notifications</code> (
 <code>id</code> int(11) NOT NULL,
 <code>to_user</code> int(11) NOT NULL,
 <code>title</code> varchar(255) NOT NULL,
 <code>body</code> varchar(255) NOT NULL,
 <code>url</code> varchar(255) NOT NULL,
 <code>is_sent</code> int(11) NOT NULL DEFAULT '0',
 <code>createdAt</code> timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

ALTER TABLE <code>notifications</code> ADD PRIMARY KEY (<code>id</code>);

ALTER TABLE <code>notifications</code> MODIFY <code>id</code> int(11) NOT NULL AUTO_INCREMENT;

2. Now create a db_connect.php file with following code

<?php 
session_start();
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "web_notifications";

$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
 die("Connection failed: " . $conn->connect_error);
} 
?>

3. Create a cookies.js file to read and write browser cookies

function WriteCookie(key,content) {
 var now = new Date();
 now.setMonth( now.getMonth() + 1 ); 
 document.cookie = key+"=" + escape(content) + ";";
 document.cookie = "expires=" + now.toUTCString() + ";"
}

function ReadCookie(key) {
 var allcookies = document.cookie;
 cookiearray = allcookies.split(';');
 var CookieData=Array();
 for(var i=0; i<cookiearray.length; i++) {
 k = cookiearray[i].split('=')[0];
 v = cookiearray[i].split('=')[1];
 CookieData[k]=v;
 }
 return CookieData[key];
}

4. Create a ajax file to read and mark is_sent if any notification foun to be sent in database for that user. create file with name 'fetch_notifications.php' with following content

<?php require 'db_connect.php';

$sql = "SELECT id,title,body,url FROM notifications where to_user='".@$_GET['user_id']."' and is_sent='0' ";
$result = $conn->query($sql);

$data=array();
if ($result->num_rows > 0) {
 while($row = $result->fetch_assoc()) {
 $data[]=$row;

 $upd = "update notifications set is_sent='1' where id='".$row['id']."' ";
 $conn->query($upd);

 }
}

if(count($data)>0)
{
 $response=array("status"=>1,"notification"=>$data);
}
else
{
 $response=array("status"=>0,"error"=>"No new notification!");
}

echo json_encode($response);

$conn->close(); 
?>

5. Now code index.php to show subscriber form and on submit insert record into the subscriber table

<?php require 'db_connect.php'; ?>
<!DOCTYPE html>
<html>
<head>
 <title>Web Push Notification Demo</title>
 <script src="./cookies.js" type="text/javascript"></script>
 <link href="
<script src="
<script src="
<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.1.0/css/all.css" integrity="sha384-lKuwvrZot6UHsBSfcMvOkWwlCMgc0TaWr+30HWe3a4ltaBwTZhyTEggF5tJv8tbt" crossorigin="anonymous">
<?php 
if(isset($_POST['subscribe_form']))
{
 $_SESSION['is_login']=0;
 $username=$conn->real_escape_string($_POST['username']);
 $useremail=$conn->real_escape_string($_POST['useremail']);


 $sql = "INSERT INTO subscribers set name='".$username."',email='".$useremail."' ";
 if ($conn->query($sql) === TRUE) {
 $_SESSION['is_login']=1;
 $_SESSION['Uid']= $conn->insert_id;
 $_SESSION['Uname']= $username;
 ?>
 <script type="text/javascript">
 WriteCookie("Uid","<?php echo $_SESSION['Uid']; ?>");
 </script> 
 <?php
 $msg="<p style='color:green'>You have subscribe for push notification succesfully :)</p>";
 } else {
 $msg="<p style='color:red'>Error in subscribing for notifications</p>";
 }


}

?>
<div class="container">
<?php 
if(isset($msg) && $msg!='')
{
 ?>
 <br>
 <div class="alert alert-info">
 <?php echo $msg; ?>
 </div>
 <?php
}

if(isset($_SESSION['is_login']) && $_SESSION['is_login']==1)
{
 ?>
 <h2>Welcome <?php echo $_SESSION['Uname']; ?></h2>
 <script type="text/javascript"> 

setInterval(function(){ 
 check_notification(); 
}, 10000);

function check_notification()
{ 
 var Uid=ReadCookie("Uid");
 if(Uid!==undefined)
 {
 $.ajax({url: "fetch_notifications.php?user_id="+Uid, success: function(result){ 
 var response=JSON.parse(result);
 if(response.status==1)
 {
 
 response=response.notifications;
 for (var i = response.length - 1; i >= 0; i--) {
 var url = response[i]['url'];
 var noti = new Notification(response[i]['title'], {
 icon: 'logo.png', body: response[i]['body'],
 });
 noti.onclick = function () {
 window.open(url); 
 noti.close(); 
 };
 
 };

 }
 else{
 console.log(response.error);

 }
 
 }

 }); 
 }
}

 
 </script>
 <?php
}
else
{
 ?>
 <h2 class="text-center">Subscribe for Notifications</h2>
 <div class="row justify-content-center">
 <div class="col-12 col-md-8 col-lg-6 pb-5">

 <div class="card border-primary rounded-0">
 <div class="card-header p-0">
 <div class="bg-info text-white text-center py-2">
 <h3><i class="fa fa-envelope"></i> Information</h3>
 <p class="m-0">provide your information</p>
 </div>
 </div>
 <div class="card-body p-3">
 <form method="post">
 <!--Body-->
 <div class="form-group">
 <div class="input-group mb-2">
 <div class="input-group-prepend">
 <div class="input-group-text"><i class="fa fa-user text-info"></i></div>
 </div>
 <input type="text" class="form-control" id="username" name="username" placeholder="Input Your Name Here" required>
 </div>
 </div>
 <div class="form-group">
 <div class="input-group mb-2">
 <div class="input-group-prepend">
 <div class="input-group-text"><i class="fa fa-envelope text-info"></i></div>
 </div>
 <input type="text" class="form-control" id="useremail" name="useremail" pattern="[^@\s]+@[^@\s]+\.[^@\s]+" title="Invalid email address" placeholder="[email protected]" required>
 </div>
 </div>

 <div class="text-center">
 <input type="submit" value="Subscribe" name="subscribe_form" class="btn btn-info btn-block rounded-0 py-2">
 </div>
 </form>
 </div>

 </div>
 


 </div>
 </div>
<?php }?>
</div>



</head>
<body>

</body>
</html>
<?php 
$conn->close(); 
?>

The frontend of your subscription page (index.php) should look like this:




Now we are ready to receive notification in frontend, but we still need to create an admin page from where we can send notification to subscriber(s).

6. Create a table for admin user

CREATE TABLE IF NOT EXISTS <code>admin</code> (
 <code>id</code> int(11) NOT NULL,
 <code>username</code> varchar(255) NOT NULL,
 <code>password</code> varchar(255) NOT NULL,
 <code>createdAt</code> timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

ALTER TABLE <code>admin</code> ADD PRIMARY KEY (<code>id</code>);

ALTER TABLE <code>admin</code> MODIFY <code>id</code> int(11) NOT NULL AUTO_INCREMENT;

INSERT INTO <code>web_notifications</code>.<code>admin</code> (<code>id</code>, <code>username</code>, <code>password</code>, <code>createdAt</code>) VALUES (NULL, 'admin', MD5('123456'), CURRENT_TIMESTAMP);

Following is the code for admin.php to add the notifications to subscriber(s) account also i have inserted following login credentials for admin in admin table:
username:admin
password:123456

7. Now put following code in admin.php

<?php require 'db_connect.php'; ?>
<!DOCTYPE html>
<html>
<head>
 <title>ADMIN PAGE</title> 
 <link href="
<script src="
<script src="
<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.1.0/css/all.css" integrity="sha384-lKuwvrZot6UHsBSfcMvOkWwlCMgc0TaWr+30HWe3a4ltaBwTZhyTEggF5tJv8tbt" crossorigin="anonymous">
<?php 
if(isset($_POST['login']))
{
 $_SESSION['admin_login']=0;
 $username=$conn->real_escape_string($_POST['username']);
 $password=$conn->real_escape_string($_POST['password']);
 $sql = "SELECT * FROM admin where username='".$username."' and password='".md5($password)."' ";
 $result = $conn->query($sql);
 if ($result->num_rows > 0) {
 $_SESSION['admin_login']=1;
 $msg="<p style='color:green'>Admin Logged-in Successfully :)</p>";
 }
 else {
 $msg="<p style='color:red'>INVALID CREDENTIALS FOR ADMIN</p>";
 } 


}
if(isset($_POST['add_notification']))
{ 
 $title=$conn->real_escape_string($_POST['title']);
 $body=$conn->real_escape_string($_POST['body']);
 $url=$conn->real_escape_string($_POST['url']);
 $users=$_POST['users'];

 foreach ($users as $user_id) {
 $ins = "insert into notifications set to_user='".$user_id."' , title='".$title."', url='".$url."', body='".$body."' ";
 $conn->query($ins);
 }
 $msg="<p style='color:green'>Notification(s) added to subscribers account.</p>";
 
}

?>
<div class="container">
<?php 
if(isset($msg) && $msg!='')
{
 ?>
 <br>
 <div class="alert alert-info">
 <?php echo $msg; ?>
 </div>
 <?php
}

if(isset($_SESSION['admin_login']) && $_SESSION['admin_login']==1)
{
 ?>
 <h2>Welcome Admin, Send notification to Subscriber(s)</h2>

<form method="post">
 
 

<div class="form-group">
 <label for="sel1">Select Subscriber(s):</label>
 <select multiple="multiple" required="required" class="form-control" id="users" name="users[]">
 <?php
$sql = "SELECT id,name FROM subscribers";
$result = $conn->query($sql);

$data=array();
if ($result->num_rows > 0) {
 while($row = $result->fetch_assoc()) {
 echo "<option value='".$row['id']."'>".$row['name']."</option>";
 }
}
?>
 </select>
</div>

 <div class="form-group">
 <label for="email">Title</label>
 <input type="text" required class="form-control" placeholder="notification title here" name="title" id="title">
 </div>
 
 <div class="form-group">
 <label for="email">Message</label>
 <textarea required class="form-control" placeholder="notification message here" name="body" id="body"></textarea> 
 </div>

 <div class="form-group">
 <label for="email">Url</label>
 <input type="url" required class="form-control" placeholder="notification landing/click url here" name="url" id="url">
 </div>
 
 <input type="submit" class="btn btn-primary btn-block" name="add_notification" value="Submit" />

</form>


 <?php
}
else
{
 ?>
 <h2 class="text-center">ADMINISTRATOR</h2>
 <div class="row justify-content-center">
 <div class="col-12 col-md-8 col-lg-6 pb-5">

 <div class="card border-primary rounded-0">
 <div class="card-header p-0">
 <div class="bg-info text-white text-center py-2">
 <h3><i class="fa fa-envelope"></i> LOGIN</h3>
 <p class="m-0">provide admin login credentials</p>
 </div>
 </div>
 <div class="card-body p-3">
 <form method="post">
 <!--Body-->
 <div class="form-group">
 <div class="input-group mb-2">
 <div class="input-group-prepend">
 <div class="input-group-text"><i class="fa fa-user text-info"></i></div>
 </div>
 <input type="text" class="form-control" id="username" name="username" placeholder="Input username here" required>
 </div>
 </div>
 <div class="form-group">
 <div class="input-group mb-2">
 <div class="input-group-prepend">
 <div class="input-group-text"><i class="fa fa-key text-info"></i></div>
 </div>
 <input type="password" class="form-control" id="password" name="password" placeholder="your password here" required>
 </div>
 </div>

 <div class="text-center">
 <input type="submit" value="Login" name="login" class="btn btn-info btn-block rounded-0 py-2">
 </div>
 </form>
 </div>

 </div>
 


 </div>
 </div>
<?php }?>
</div>



</head>
<body>

</body>
</html>
<?php 
$conn->close(); 
?>

The admin page will ask login credentials first then it will look like following screenshot:



Now in your project if you open index.php you have a frontend where user will register themselves to receive notifications, and admin.php is your backend where you can send notifications to users or subscribers


If you face any problem in setup this small project please just let me know in the comments below, or by messaging me.

Today I am going write a blog on how to Monitor Memory and Disk custom metrics and creating alarm in Ubuntu.

To do this, we can use Amazon CloudWatch, which provides a flexible, scalable and reliable solution for monitoring our server.

Amazon Cloud Watch will allow us to collect the custom metrics from our applications that we will monitor to troubleshoot any issues, spot trends, and configure operational performance. CloudWatch functions display alarms, graphs, custom metrics data and including statistics.

Installing the Scripts

Before we start installing the scripts for monitoring, we should install all the dependent packages need to perform on Ubuntu.

First login to your AWS server, and from our terminal, install below packages

sudo apt-get update
sudo apt-get install unzip
sudo apt-get install libwww-perl libdatetime-perl

Now Install the Monitoring Scripts

Following are the steps to download and then unzip we need to configure the Cloud Watch Monitoring scripts on our server:
1. In the terminal, we need to change our directory and where we want to add our monitoring scripts.
2. Now run the below command and download the source:

curl https://aws-cloudwatch.s3.amazonaws.com/downloads/CloudWatchMonitoringScripts-1.2.2.zip -O

3. Now uncompress the currently downloaded sources using the following commands

unzip CloudWatchMonitoringScripts-1.2.2.zip && \

rm CloudWatchMonitoringScripts-1.2.2.zip && \

cd aws-scripts-mon

The directory will contain Perl scripts, because of the execution of these scripts only report memory run and disk space utilization metrics will run in our Ubuntu server.
Currently, our folder will contain the following files:
mon-get-instance-stats.pl - This Perl file is used to displaying the current utilization statistics reports for our AWS instance on which these file scripts will be executed.
mon-put-instance-data.pl - This Perl script file will be used for collecting the system metrics on our ubuntu server and which will send them to the Amazon Cloud Watch.
awscreds.template - This Perl script file will contain an example for AWS credentials keys and secret access key named with access key ID.
CloudWatchClient.pm - This Perl script file module will be used to simplify by calling Amazon Cloud Watch from using other scripts.
LICENSE.txt – This file contains the license details for Apache 2.0.
NOTICE.txt – This file contains will gives us information about Copyright notice.
4. For performing the Cloud Watch operations, we need to confirm that whether our scripts have corresponding permissions for the actions:

If we are associated with an IAM role with our EC2 Ubuntu instance, we need to verify that which will grant the permissions to perform the below-listed operations:

cloudwatch:GetMetricStatistics

cloudwatch:PutMetricData

ec2:DescribeTags

cloudwatch:ListMetrics

Now we need to copy the ‘awscreds.template’ file into ‘awscreds.conf’ by using the command below and which will update the file with details of the AWS credentials.

cp awscreds.template awscreds.conf

AWSAccessKeyId = my_access_key_id

AWSSecretKey = my_secret_access_key

Now we completed the configuration.

mon-put-instance-data.pl

This Perl script file will collect memory, disk space utilization data and swap the current system details and then it makes handling a remote call to Amazon Cloud Watch to reports details to the collected cloud watch data as a custom metrics.

We can perform a simple test run, by running the below without sending data to Amazon CloudWatch

./mon-put-instance-data.pl --mem-util --verify --verbose

Now we are going to set a cron for scheduling our metrics and we will send them to Amazon CloudWatch
1. Now we need to edit the crontab by using below command:

 crontab -e

2. Now we will update the file using the following query which will disk space utilization and report memory for particular paths to Amazon CloudWatch in every five minutes:

*/5 * * * * ~/STORAGE/cloudwatch/aws-scripts-mon/mon-put-instance-data.pl --mem-util --mem-avail --mem-used --disk-space-util --disk-space-avail --disk-space-used --disk-path=/ --disk-path=/STORAGE --from-cron

If there is an error, the scripts will write an error message in our system log.

Use of Options

--mem-used
The above command will collect the information about used memory and which will send the details of the reports in MBs into the MemoryUsed metrics. This will give us information about the metric counts memory allocated by applications and the OS as used.
--mem-util
The above command will collect the information about memory utilization in percentages and which will send the details of the Memory Utilization metrics and it will count the usage of the memory applications and the OS.
--disk-space-util
The above command will collect the information to collect the current utilized disk space and which will send the reports in percentages to the DiskSpaceUtilization for the metric and for the selected disks.
--mem-avail
The above command will collect the information about the available memory and which will send the reports in MBs to the MemoryAvailable metrics details. This is the metric counts memory allocated by the applications and the OS as used.
--disk-path=PATH
The above command will collect the information and will point out the which disk path to report disk space.
--disk-space-avail
The above command will collect the information about the available disk space and which will send the reports in GBs to the DiskSpaceAvailable metric for the selected disks.
--disk-space-used
The above command will collect the information about the disk space used and which will send the reports in GBs to the DiskSpaceUsed metric for the selected disks.

The PATH can specify to point or any of the files can be located on which are mounted point for the filesystem which needs to be reported.

If we want to points to the multiple disks, then specify both of the disks like below:

--disk-path=/ --disk-path=/home

Setting an Alarm for Custom Metrics

Before we are going to running our Perl Scripts, then we need to create an alarm that will be listed in our default metrics except for the custom metrics. You can see some default metrics are listed in below image:



Once we completed setting the cron, then the custom metrics will be located in Linux System Metrics.

Now we are going to creating the alarm for our custom metrics
1. We need to open the cloudwatch console panel at https://console.aws.amazon.com/cloudwatch/home
2. Now navigate to the navigation panel, we need to click on Alarm and we can Create Alarm.
3. This will open a popup which with the list of the CloudWatch metrics by category.
4. Now click on the Linux System Metrics . This will be listed out with custom metrics you can see in the below pictures






5. Now we need to select metric details and we need to click on the NEXT button. Now we need to navigate to Define Alarm step.



6. Now we need to define an Alarm with required fields

Now we need to enter the Alarm name for identifying them. Then we need to give a description of our alarm.

Next, we need to give the condition with the maximum limit of bytes count or percentage when it notifies the alarm. If the condition satisfies, then the alarm will start trigger.

We need to provide a piece of additional information about for our alarm.

We need to define what are the actions to be taken when our alarm changes it state.

We need to select or create a new topic with emails needed for sending notification about alarm state.
7. Finally, we need to choose the Create Alarm.

So its completed. Now the alarm is created for our selected custom metrics.

Finished!

Now the alarm will be listed out under the selected state in our AWS panel. Now we need to select an alarm from the list seen and we can see the details and history of our alarm.

Laravel introduces eloquent relationships from laravel 5.0 onwards. We all know, while we creating an application we all have foreign keys. Each table will be connected to some other. Eloquent make easy to connect each tables easily. Here we will One to one, one to many and many to many relationships. Here we will see three types of relationships,
   
. One to one relationships
    . One to many relationships
    . Many to many relationships

Why Eloquent Relationships

Here we have 2 tables, students and marks, so for join each table,

$student = student::join(‘marks’,’marks.student_id,’=’,students.id’)->where(‘students.id’,’1’)->get();

dd($student);

the above query is to long, so when we connect more tables its too tough we will be having a big query and complicated.

Model Query using Relationships

$student_marks = student::find(1);

dd($student_marks->mark1);

The above example is a simple example of eloquent relationships. We can reduce the first query into a simple one.

ONE TO ONE RELATIOSHIPS

Here we are creating 2 tables:
* Users
* Phones

Now we can see one to one relationships using hasone() and belongsto().

We need to create table using migrations

Create migrations

users table will be created by using

Schema::create('users', function (Blueprint $table) {

 $table->increments('id');

 $table->string('name');

 $table->string('email')->unique();

 $table->string('password');

 $table->rememberToken();

 $table->timestamps();

});

Phones table will be created by

Schema::create('phones', function (Blueprint $table) {

 $table->increments('id');

 $table->integer('user_id')->unsigned();

 $table->string('phone');

 $table->timestamps();

 $table->foreign('user_id')->references('id')->on('users')

 ->onDelete('cascade');

});

After that we need to create model for each tables, as we all know if the table name is laravel table name will be ending with ‘s’ and model name will be without ‘s’ of the same table name.

User model

<?php

namespace App;

use Illuminate\Notifications\Notifiable;

use Illuminate\Foundation\Auth\User as Authenticatable;



class User extends Authenticatable

{

 use Notifiable;



 

 protected $fillable = [

 'name', 'email', 'password',

 ];



 

 protected $hidden = [

 'password', 'remember_token',

 ];



 

 public function phone()

 {

 return $this->hasOne('App\Phone');

 }

}

Phone Model

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;



class Phone extends Model

{

 

 public function user()

 {

 return $this->belongsTo('App\User');

 }

}

For Creating records

$user = User::find(1);

$phone = new Phone;

$phone->phone = '9080054945';

$user->phone()->save($phone);



$phone = Phone::find(1);

$user = User::find(10);

$phone->user()->associate($user)->save();

Now we can get our records by

$phone = User::find(1)->phone;

dd($phone);



$user = Phone::find(1)->user;

dd($user);

ONE TO MANY RELATIONSHIPS

Here we will use hasMany() and belongsTo() for relationships

Now we are creating two tables, posts and comments, we will be having a foreign key towards posts table.


Migrations for posts and comments table

Schema::create('posts', function (Blueprint $table) {

 $table->increments('id');

 $table->string("name");

 $table->timestamps();

});



Schema::create('comments', function (Blueprint $table) {

 $table->increments('id');

 $table->integer('post_id')->unsigned();

 $table->string("comment");

 $table->timestamps();

 $table->foreign('post_id')->references('id')->on('posts')

 ->onDelete('cascade');

});

Now we will create Post Model and Comment Model

Post Model

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;



class Post extends Model

{

 

 public function comments()

 {

 return $this->hasMany(Comment::class);

 }

}

Comment Model

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;



class Comment extends Model

{

 

 public function post()

 {

 return $this->belongsTo(Post::class);

 }

}

Now we can create records

$post = Post::find(1);

$comment = new Comment;

$comment->comment = "Hi Harikrishnan";

$post = $post->comments()->save($comment);

$post = Post::find(1);



$comment1 = new Comment;

$comment1->comment = "How are You?";

$comment2 = new Comment;

$comment2->comment = "Where are you?";

$post = $post->comments()->saveMany([$comment1, $comment2]);



$comment = Comment::find(1);

$post = Post::find(2);

$comment->post()->associate($post)->save();

Now we can get records

$post = Post::find(1);

$comments = $post->comments;

dd($comments);



$comment = Comment::find(1);

$post = $comment->post;

dd($post);

MANY TO MANY RELATIONSHIPS

Many to many is little bit different and complicated than the above two.



In this example, I will create users, roles, and role, users_tables, here each table will be connected each other using the foreign keys.



Using belongsToMany() we will use see a demo of Many to many relationship

Create Migrations

Schema::create('users', function (Blueprint $table) {

 $table->increments('id');

 $table->string('name');

 $table->string('email')->unique();

 $table->string('password');

 $table->rememberToken();

 $table->timestamps();

});



Schema::create('roles', function (Blueprint $table) {

 $table->increments('id');

 $table->string('name');

 $table->timestamps();

});



Schema::create('role_user', function (Blueprint $table) {

 $table->integer('user_id')->unsigned();

 $table->integer('role_id')->unsigned();

 $table->foreign('user_id')->references('id')->on('users')

 ->onDelete('cascade');

 $table->foreign('role_id')->references('id')->on('roles')

 ->onDelete('cascade');

});

Create Models

User Model

<?php

namespace App;

use Illuminate\Notifications\Notifiable;

use Illuminate\Foundation\Auth\User as Authenticatable;



class User extends Authenticatable

{

 use Notifiable;



 

 protected $fillable = [

 'name', 'email', 'password',

 ];



 

 protected $hidden = [

 'password', 'remember_token',

 ];



 

 public function roles()

 {

 return $this->belongsToMany(Role::class, 'role_user');

 }

}

Role Model

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;



class Role extends Model

{

 

 public function users()

 {

 return $this->belongsToMany(User::class, 'role_user');

 }

}

UserRole Model

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;



class UserRole extends Model

{

}

Now we can create records

$user = User::find(2); 

$roleIds = [1, 2];

$user->roles()->attach($roleIds);



$user = User::find(3); 

$roleIds = [1, 2];

$user->roles()->sync($roleIds);



$role = Role::find(1); 

$userIds = [10, 11];

$role->users()->attach($userIds);



$role = Role::find(2); 

$userIds = [10, 11];

$role->users()->sync($userIds);

Now we can retrieve records

$user = User::find(1); 

dd($user->roles);



$role = Role::find(1);

dd($role->users);

Hence laravel Eloquent is more powerful and we do relationships easily compared to native query. We will be having three more relationships in laravel. Ie.., has many, one to many polymorphic and many to many polymorphic. With eloquent relationship we can easily connect the tables each other. One to one relationships we can connect two tables with their basic functionalities. In one to many we will connect with single table with multiple options. In Many to many we will be having more tables.

Models and controllers are one of the most essential programming handlers in the Laravel MVC framework, and both are used vastly for different functional operations. Models in Laravel are created inside the app folder and are mostly used to interact with the database using Eloquent ORM, while the controllers are located inside the directory App/Http/Controllers.

As a programmer, you should have the knowledge how to keep the balance in between the programming usage of Models and controllers. As which one should be more utilized for allowing functional tasks in applications deployed on any PHP MySQL hosting.

What is the Concept of Thin Controller and FAT Models

The concept of the thin controller and fat model is that we do less work in our controllers and more work in our models. Like we use our controllers to validate our data and then pass it to the models. While in models, we define our actual functional logic and main coding operations of the desired application. This code structuring process is also a very basic concept of MVC and also the differentiating factor from the conventional complex programming which we mistakenly ignore sometimes.

Why FAT Controllers Are Bad For Handling Code

Controllers are always meant to be defined short and concise, and it should only be used for receiving requests and return responses to it. Anything else further should be programmed in Models, which is actually made for main functional operations.

Placing functional logic in controllers can be bad for many reasons for your applications deployed on anyhosting for PHP. As it not only makes code structure long but also makes it complex sometimes. Further placing code in Controllers is also not recommended because if same functionality is needed somewhere else in route, then pulling out the whole code from their becomes difficult and so its reusability in the application.

Though Laravel is an MVC framework while developing on laravel, we sometimes ignore this and write mostly all our code including the extending of App\Model and all our functional logic in controller route methods. What we can do here is we can create a sub model of our parent model. For example, our parent model is User then we can create another sub model of username in CustomerModel if you are using the same User model for all types of users. In this model, we will write all the logic related to user type Customer.

So now let's take an example of my existing blog creating comment system with laravel and vuejs. In that article, you can see I have made so much mess in my controller methods. Mostly, I have written all my comments logic in my methods, so to shorten that let's clean them in this article. Inside app folder, I will create a new file with name CommentModel.php. Inside this file, I will write my whole logic for comment functions. This is my basic file:

<?php
namespace App;

use App\Comment;
use App\CommentVote;
use App\CommentSpam;
use App\User;
use Auth;

class CommentModel
{


}

?>

Right now it contains no function but has the reference of all my models which I required for this model. Let's first add a function namedgetallcomments passing$pageId as a parameter inside it. The function will get all the comments for the given page:

public function getAllComments($pageId)
 {
 $comments = Comment::where('page_id',$pageId)->get();

 $commentsData = [];


 foreach ($comments as $key) {
 $user = User::find($key->users_id);
 $name = $user->name;
 $replies = $this->replies($key->id);
 $photo = $user->first()->photo_url;
 $reply = 0;
 $vote = 0;
 $voteStatus = 0;
 $spam = 0;
 if(Auth::user()){
 $voteByUser = CommentVote::where('comment_id',$key->id)->where('user_id',Auth::user()->id)->first();
 $spamComment = CommentSpam::where('comment_id',$key->id)->where('user_id',Auth::user()->id)->first();


 if($voteByUser){
 $vote = 1;
 $voteStatus = $voteByUser->vote;
 }

 if($spamComment){
 $spam = 1;
 }
 }


 if(sizeof($replies) > 0){
 $reply = 1;
 }

 if(!$spam){
 array_push($commentsData,[
 "name" => $name,
 "photo_url" => (string)$photo,
 "commentid" => $key->id,
 "comment" => $key->comment,
 "votes" => $key->votes,
 "reply" => $reply,
 "votedByUser" =>$vote,
 "vote" =>$voteStatus,
 "spam" => $spam,
 "replies" => $replies,
 "date" => $key->created_at->toDateTimeString()
 ]);
 } 


 }
 $collection = collect($commentsData);
 return $collection->sortBy('votes');
 }

Now I will create another function namedreplies which takes$commentId as a parameter. The function is more or less programmed in the same manner as the upper function get all comments.

protected function replies($commentId)
 {
 $comments = Comment::where('reply_id',$commentId)->get();
 $replies = [];



 foreach ($comments as $key) {
 $user = User::find($key->users_id);
 $name = $user->name;
 $photo = $user->first()->photo_url;

 $vote = 0;
 $voteStatus = 0;
 $spam = 0; 


 if(Auth::user()){
 $voteByUser = CommentVote::where('comment_id',$key->id)->where('user_id',Auth::user()->id)->first();
 $spamComment = CommentSpam::where('comment_id',$key->id)->where('user_id',Auth::user()->id)->first();

 if($voteByUser){
 $vote = 1;
 $voteStatus = $voteByUser->vote;
 }

 if($spamComment){
 $spam = 1;
 }
 }
 if(!$spam){


 array_push($replies,[
 "name" => $name,
 "photo_url" => $photo,
 "commentid" => $key->id,
 "comment" => $key->comment,
 "votes" => $key->votes,
 "votedByUser" => $vote,
 "vote" => $voteStatus,
 "spam" => $spam,
 "date" => $key->created_at->toDateTimeString()
 ]);
 }




 }


 $collection = collect($replies);
 return $collection->sortBy('votes');
 }

Now lets create a functioncreate comment which passes$array as a parameter in it:

public function createComment($arary)
 {
 $comment = Comment::create($array);


 if($comment)
 return [ "status" => "true","commentId" => $comment->id ];
 else
 return [ "status" => "false" ]; 
 }

Similarly, Now I will create all the function for comment in myCommentModel, so that all the functions gets accumulated in one model.

<?php
namespace App;

use App\Comment;
use App\CommentSpam;
use App\CommentVote;
use App\User;
use Auth;

class CommentModel
{
 public function getAllComments($pageId)
 {
 $comments = Comment::where('page_id', $pageId)->get();

 $commentsData = [];

 foreach ($comments as $key) {
 $user = User::find($key->users_id);
 $name = $user->name;
 $replies = $this->replies($key->id);
 $photo = $user->first()->photo_url;
 $reply = 0;
 $vote = 0;
 $voteStatus = 0;
 $spam = 0;
 if (Auth::user()) {
 $voteByUser = CommentVote::where('comment_id', $key->id)->where('user_id', Auth::user()->id)->first();
 $spamComment = CommentSpam::where('comment_id', $key->id)->where('user_id', Auth::user()->id)->first();

 if ($voteByUser) {
 $vote = 1;
 $voteStatus = $voteByUser->vote;
 }

 if ($spamComment) {
 $spam = 1;
 }
 }

 if (sizeof($replies) > 0) {
 $reply = 1;
 }

 if (!$spam) {
 array_push($commentsData, [
 "name" => $name,
 "photo_url" => (string) $photo,
 "commentid" => $key->id,
 "comment" => $key->comment,
 "votes" => $key->votes,
 "reply" => $reply,
 "votedByUser" => $vote,
 "vote" => $voteStatus,
 "spam" => $spam,
 "replies" => $replies,
 "date" => $key->created_at->toDateTimeString(),
 ]);
 }

 }
 $collection = collect($commentsData);
 return $collection->sortBy('votes');
 }

 protected function replies($commentId)
 {
 $comments = Comment::where('reply_id', $commentId)->get();
 $replies = [];

 foreach ($comments as $key) {
 $user = User::find($key->users_id);
 $name = $user->name;
 $photo = $user->first()->photo_url;

 $vote = 0;
 $voteStatus = 0;
 $spam = 0;

 if (Auth::user()) {
 $voteByUser = CommentVote::where('comment_id', $key->id)->where('user_id', Auth::user()->id)->first();
 $spamComment = CommentSpam::where('comment_id', $key->id)->where('user_id', Auth::user()->id)->first();

 if ($voteByUser) {
 $vote = 1;
 $voteStatus = $voteByUser->vote;
 }

 if ($spamComment) {
 $spam = 1;
 }
 }
 if (!$spam) {

 array_push($replies, [
 "name" => $name,
 "photo_url" => $photo,
 "commentid" => $key->id,
 "comment" => $key->comment,
 "votes" => $key->votes,
 "votedByUser" => $vote,
 "vote" => $voteStatus,
 "spam" => $spam,
 "date" => $key->created_at->toDateTimeString(),
 ]);
 }

 }

 $collection = collect($replies);
 return $collection->sortBy('votes');
 }

 public function createComment($arary)
 {
 $comment = Comment::create($array);

 if ($comment) {
 return ["status" => "true", "commentId" => $comment->id];
 } else {
 return ["status" => "false"];
 }

 }

 public function voteComment($commentId, $array)
 {
 $comments = Comment::find($commentId);
 $data = [
 "comment_id" => $commentId,
 'vote' => $array->vote,
 'user_id' => $array->users_id,
 ];

 if ($array->vote == "up") {
 $comment = $comments->first();
 $vote = $comment->votes;
 $vote++;
 $comments->votes = $vote;
 $comments->save();
 }

 if ($array->vote == "down") {
 $comment = $comments->first();
 $vote = $comment->votes;
 $vote--;
 $comments->votes = $vote;
 $comments->save();
 }

 if (CommentVote::create($data)) {
 return true;
 }

 }

 public function spamComment($commentId, $array)
 {
 $comments = Comment::find($commentId);

 $comment = $comments->first();
 $spam = $comment->spam;
 $spam++;
 $comments->spam = $spam;
 $comments->save();

 $data = [
 "comment_id" => $commentId,
 'user_id' => $array->users_id,
 ];

 if (CommentSpam::create($data)) {
 return true;
 }

 }
}
?>

Now we have all our required methods inCommentModel. So now let's clean upCommentController which is currently bit complex and lengthy in code structure. As right nowCommentController look like this:

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Http\Requests;
use App\Comment;
use App\CommentVote;
use App\CommentSpam;
use App\User;
use Auth;

class CommentController extends Controller
{


 
 public function index($pageId)
 {
 $comments = Comment::where('page_id',$pageId)->get();

 $commentsData = [];




 foreach ($comments as $key) {
 $user = User::find($key->users_id);
 $name = $user->name;
 $replies = $this->replies($key->id);
 $photo = $user->first()->photo_url;
 $reply = 0;
 $vote = 0;
 $voteStatus = 0;
 $spam = 0;
 if(Auth::user()){
 $voteByUser = CommentVote::where('comment_id',$key->id)->where('user_id',Auth::user()->id)->first();
 $spamComment = CommentSpam::where('comment_id',$key->id)->where('user_id',Auth::user()->id)->first();


 if($voteByUser){
 $vote = 1;
 $voteStatus = $voteByUser->vote;
 }

 if($spamComment){
 $spam = 1;
 }
 }


 if(sizeof($replies) > 0){
 $reply = 1;
 }

 if(!$spam){
 array_push($commentsData,[
 "name" => $name,
 "photo_url" => (string)$photo,
 "commentid" => $key->id,
 "comment" => $key->comment,
 "votes" => $key->votes,
 "reply" => $reply,
 "votedByUser" =>$vote,
 "vote" =>$voteStatus,
 "spam" => $spam,
 "replies" => $replies,
 "date" => $key->created_at->toDateTimeString()
 ]);
 } 


 }
 $collection = collect($commentsData);
 return $collection->sortBy('votes');
 }

 protected function replies($commentId)
 {
 $comments = Comment::where('reply_id',$commentId)->get();
 $replies = [];



 foreach ($comments as $key) {
 $user = User::find($key->users_id);
 $name = $user->name;
 $photo = $user->first()->photo_url;

 $vote = 0;
 $voteStatus = 0;
 $spam = 0; 


 if(Auth::user()){
 $voteByUser = CommentVote::where('comment_id',$key->id)->where('user_id',Auth::user()->id)->first();
 $spamComment = CommentSpam::where('comment_id',$key->id)->where('user_id',Auth::user()->id)->first();

 if($voteByUser){
 $vote = 1;
 $voteStatus = $voteByUser->vote;
 }

 if($spamComment){
 $spam = 1;
 }
 }
 if(!$spam){


 array_push($replies,[
 "name" => $name,
 "photo_url" => $photo,
 "commentid" => $key->id,
 "comment" => $key->comment,
 "votes" => $key->votes,
 "votedByUser" => $vote,
 "vote" => $voteStatus,
 "spam" => $spam,
 "date" => $key->created_at->toDateTimeString()
 ]);
 }




 }


 $collection = collect($replies);
 return $collection->sortBy('votes');
 }

 
 public function store(Request $request)
 {
 $this->validate($request, [
 'comment' => 'required',
 'reply_id' => 'filled',
 'page_id' => 'filled',
 'users_id' => 'required',
 ]);
 $comment = Comment::create($request->all());
 if($comment)
 return [ "status" => "true","commentId" => $comment->id ];
 }

 
 public function update(Request $request, $commentId,$type)
 {
 if($type == "vote"){


 $this->validate($request, [
 'vote' => 'required',
 'users_id' => 'required',
 ]);

 $comments = Comment::find($commentId);
 $data = [
 "comment_id" => $commentId,
 'vote' => $request->vote,
 'user_id' => $request->users_id,
 ];

 if($request->vote == "up"){
 $comment = $comments->first();
 $vote = $comment->votes;
 $vote++;
 $comments->votes = $vote;
 $comments->save();
 }

 if($request->vote == "down"){
 $comment = $comments->first();
 $vote = $comment->votes;
 $vote--;
 $comments->votes = $vote;
 $comments->save();
 }

 if(CommentVote::create($data))
 return "true";
 }

 if($type == "spam"){


 $this->validate($request, [
 'users_id' => 'required',
 ]);

 $comments = Comment::find($commentId);


 $comment = $comments->first();
 $spam = $comment->spam;
 $spam++;
 $comments->spam = $spam;
 $comments->save();

 $data = [
 "comment_id" => $commentId,
 'user_id' => $request->users_id,
 ];

 if(CommentSpam::create($data))
 return "true";
 }
 }

 
 public function destroy($id)
 {
 }
}?>

After cleaning up the controller it will look much simpler and easy to understand like this:

<?php

namespace App\Http\Controllers;

use App\CommentModel;
use Illuminate\Http\Request;

class CommentController extends Controller
{

 private $commentModel = null;
 private function __construct()
 {
 $this->commentModel = new CommentModel();
 }

 
 public function index($pageId)
 {
 return $this->commentModel->getAllComments($pageId);
 }

 
 public function store(Request $request)
 {
 $this->validate($request, [
 'comment' => 'required',
 'reply_id' => 'filled',
 'page_id' => 'filled',
 'users_id' => 'required',
 ]);
 return $this->commentModel->createComment($request->all());
 }

 
 public function update(Request $request, $commentId, $type)
 {
 if ($type == "vote") {

 $this->validate($request, [
 'vote' => 'required',
 'users_id' => 'required',
 ]);

 return $this->commentModel->voteComment($commentId, $request->all());
 }

 if ($type == "spam") {

 $this->validate($request, [
 'users_id' => 'required',
 ]);

 return $this->commentModel->spamComment($commentId, $request->all());
 }
 }

}
?>

Wrap Up!

So Isn't it looking much cleaner and simpler to understand now? This is what actually a thin controller and fat model looks like. We have all our logic related to Comment system programmed in ourCommentModel and our controller is now just used to transfer data from the user to our model and returning the response which is coming from our model.

So this is how the structuring of the thin controller and fat model is made. Give your thoughts in the comments below.