Scaling
- Scaling is of two types
- Horizontal: Increasing number of servers with same application to distribute the load
- Veritical Scaling: Increasing systems resources like cpu, ram etc. In Aws, you can do this changing instance size
- Why scaling ?
- Because you might need more performance, availiability, load increased etc
Scenario:
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Our Organization (QT) has an ecommerce application with the folowing architecture
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Due to offers on your ecommerce application load increased, when load increases it is better to increase virtual machine (ec2 instances)
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How to do this in AWS?
- EC2 Auto Scaling
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Autoscaling relys on
- AMI’s: To create a new instance with same software/application we would need AMI’s first
- Auto Scaling Group: Each Auto Scaling group represents an application component (webserver/appserver). Auto scaling group will have following information
- Minimum number of ec2
- Desired Capacity of ec2
- Maximum number of ec2 instances
- Cloudwatch metrics/alerts: These help in deciding when to scale.
Lets do this practically
- Creating an ubuntu image with lamp stack installed based out of steps from here.
- In this scenario i will be creating an artifical load and for that i will be using a tool called as stress
- commands executed after ssh into ec2 ubuntu instance
sudo apt-get update
sudo apt-get install apache2 -y
sudo apt install php libapache2-mod-php php-mysql -y
sudo systemctl restart apache2
sudo systemctl enable apache2
sudo apt install php-cli -y
sudo vi /var/www/html/info.php =>
<?php
phpinfo();
?>
sudo systemctl restart apache2
sudo apt-get install stress -y
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Create an AMI of the Ec2 instance
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Assume you need to increase your ec2 instances by 1 when the cpu utilization average is greater than 75% for atleast 5 mins and decrease your ec2 instances by 1 when the cpu utilization is less that 50% for atleast 5 mins
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Now Navigate to the Autoscaling section
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Autoscaling groups requires launch configuration or launch template
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Click on Create Autoscaling group
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Create a new launch configuration and select AMI
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Choose the size which fits your application. (I use t2.micro for demo)
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Create launch configuration and select storage, security group (create)
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Create a Autoscaling group for a launch configuration
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Select scaling policies
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For this case we have decided "increase your ec2 instances by 1 when the cpu utilization average is greater than 75% for atleast 5 mins and decrease your ec2 instances by 1 when the cpu utilization is less that 50% for atleast 5 mins", so lets implement
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Add Notificiations if required
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Review the settings and create autoscaling group to see instances to be created (in action)
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Now have a look at ec2 instance autoscaling group view
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Wait till Desired (Expected) reaches the current count
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Now find the instance id and navigate to it
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Now find public ip and navigate to “`http://publicip/info.php“
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If you want to do the same from cli refer here
Next topics
- How to scale and load balance
