AWS Pre-Route 53 – how DNS works

 Before diving into AWS Route 53, it's important to understand how DNS works in general.

DNS (Domain Name System) is a system that translates human-readable domain names (such as www.example.com) into IP addresses that computers can understand.

When you enter a domain name in your web browser, your computer contacts a DNS resolver to get the IP address associated with that domain name.

The DNS resolver then returns the IP address to your computer, which can then connect to the web server associated with that IP address.

Here are the general steps that occur when a DNS lookup is performed:

1. Recursive DNS resolver: Your computer sends a request to a recursive DNS resolver (often provided by your Internet Service Provider). The request includes the domain name that you want to look up.

2. Root name servers: If the recursive DNS resolver doesn't have the IP address associated with the domain name in its cache, it contacts one of the 13 root name servers. These root name servers contain information about the top-level domain names (such as .com, .org, etc.) and can direct the request to the appropriate authoritative name server.

3. Authoritative name server: The authoritative name server is responsible for storing the IP address associated with the domain name. If the authoritative name server has the IP address in its cache, it returns the IP address to the recursive DNS resolver. Otherwise, it contacts other authoritative name servers until it finds the IP address.

4. Recursive DNS resolver: Once the recursive DNS resolver has the IP address, it returns the IP address to your computer, which can then connect to the web server associated with that IP address.

AWS Route 53 is a DNS service provided by Amazon Web Services that allows you to manage DNS records for your domain names.

With Route 53, you can create and manage DNS records, such as A records (which map a domain name to an IP address) and CNAME records (which map a domain name to another domain name).

In addition to managing DNS records, Route 53 also provides other features, such as traffic routing and health checks.

With traffic routing, you can configure Route 53 to route traffic to different endpoints based on geographic location, latency, or other criteria. With health checks, you can monitor the health of your resources (such as EC2 instances) and automatically route traffic away from unhealthy resources.

Overall, AWS Route 53 is a powerful tool for managing DNS for your domain names and routing traffic to your resources.

Using AWS load balancer with Auto Scaling

Create an Auto Scaling group: First, you need to create an Auto Scaling group that will automatically launch and terminate EC2 instances based on demand. You can define the minimum and maximum number of instances in the group, as well as the desired capacity.

1. Create a launch configuration: Next, you need to create a launch configuration that defines the settings for an EC2 instance, such as the AMI, instance type, and security groups. When Auto Scaling launches new instances, it uses the launch configuration to create the instances.

2. Configure load balancer: You need to configure the load balancer to distribute traffic across the instances in your Auto Scaling group. AWS provides several types of load balancers, including the Application Load Balancer and Network Load Balancer.

3. Associate Auto Scaling group with load balancer: To ensure that traffic is distributed evenly across your instances, you need to associate your Auto Scaling group with the load balancer. This can be done using the AWS Management Console or the AWS CLI.

4. Configure Auto Scaling policies: You can configure Auto Scaling policies to automatically adjust the number of instances in your Auto Scaling group based on demand. There are several types of scaling policies available, including target tracking, simple scaling, and step scaling.

5. Test your configuration: Before deploying your configuration to production, it's a good idea to test your configuration in a staging environment. This will help you ensure that your load balancer is distributing traffic evenly across your instances and that your Auto Scaling policies are working as expected.

Overall, using AWS load balancer with Auto Scaling provides a flexible and scalable solution for managing your resources. By distributing traffic across your instances and automatically adjusting the number of instances based on demand, you can ensure that your application is highly available and responsive to user requests.

Components of Auto Scaling, scaling options and policy, instance termination

The AWS Auto Scaling service consists of several components that work together to provide automated scaling of your resources:

1. Auto Scaling Group: An Auto Scaling group is a collection of EC2 instances that are launched and terminated automatically based on demand. You can define the minimum and maximum number of instances in the group, as well as the desired capacity. Auto Scaling groups can be associated with one or more availability zones.

2. Launch Configuration: A launch configuration defines the settings for an EC2 instance, such as the AMI, instance type, and security groups. When Auto Scaling launches new instances, it uses the launch configuration to create the instances.

3. Scaling Options and Policy: AWS Auto Scaling provides two scaling options:

   • Automatic scaling: This option scales your resources automatically based on demand, using pre-defined scaling policies or target tracking policies.
   • Scheduled scaling: This option allows you to schedule scaling events in advance, based on anticipated changes in demand.

   Auto Scaling policies define the conditions for scaling your resources. There are several types of scaling policies available, including:

   • Target Tracking Scaling Policy: This policy automatically adjusts the number of instances in your Auto Scaling group to maintain a target metric, such as CPU utilization or request count per target.
   • Simple Scaling Policy: This policy adds or removes a fixed number of instances when a CloudWatch alarm is triggered.
   • Step Scaling Policy: This policy adds or removes instances based on a set of predefined thresholds.

4. Instance Termination: When an instance is terminated, it is removed from the Auto Scaling group. Auto Scaling can terminate instances based on various criteria, including:

   • Instance health: Auto Scaling can terminate instances that fail health checks.
   • Availability zone: Auto Scaling can terminate instances in a specific availability zone to balance the load across all zones.
   • Age: Auto Scaling can terminate instances that have been running for a certain period of time.

In summary, AWS Auto Scaling provides a powerful and flexible toolset for scaling your resources automatically based on demand.

By defining scaling options and policies, you can ensure that your application has the right resources available at the right time, while minimizing costs.

Additionally, Auto Scaling provides advanced instance termination options to ensure that your instances are terminated in a way that minimizes disruption to your application.

The AWS Auto Scaling service provides several options for terminating instances in an Auto Scaling group, depending on your specific requirements. Here are the general steps to terminate instances using AWS Auto Scaling:

1. Determine the termination policy: When instances need to be terminated, you need to determine which termination policy to use. AWS provides several options, including:

   • OldestInstance: Terminate the oldest instance in the Auto Scaling group.
   • NewestInstance: Terminate the newest instance in the Auto Scaling group.
   • ClosestToNextInstanceHour: Terminate the instance that is closest to the next billing hour (hourly billing).

2. Set up health checks: Auto Scaling can terminate instances that fail health checks. You can configure health checks for your instances by defining a custom health check or using the default health check.

3. Set up instance protection: If you want to prevent a specific instance from being terminated, you can set up instance protection. This can be useful if you have a critical instance that should never be terminated, even if it fails health checks.

4. Configure instance termination options: Auto Scaling provides several options for configuring how instances are terminated, including:

   • Termination wait time: The amount of time to wait before terminating an instance.
   • Instance protection: Whether to protect instances from termination.
   • Termination policy: The policy to use when terminating instances.

5. Test your configuration: Before deploying your configuration to production, it's a good idea to test your configuration in a staging environment. This will help you ensure that your termination policies are working as expected and that your instances are being terminated in a way that minimizes disruption to your application.

Overall, AWS Auto Scaling provides a flexible and powerful toolset for terminating instances in an Auto Scaling group. By setting up health checks, instance protection, and termination policies, you can ensure that your instances are terminated in a way that maximizes the availability and reliability of your application.