AWS Load Balancer is a powerful service offered by Amazon Web Services that helps ensure high availability and scalability for your applications. By distributing incoming network traffic across multiple servers, Load Balancer can help ensure that your application remains available and able to handle increased traffic levels, even in the event of server failures or other disruptions. In this article, we will explore the key features and benefits of Load Balancer and how it can be used to ensure high availability and scalability for your applications. We will also look at the different types of Load Balancer available and how to choose the right one for your needs. Whether you are running a small web application or a large-scale enterprise system, Load Balancer can help ensure the reliability and performance of your application.
AWS Load Balancer
AWS Load Balancer is a service offered by Amazon Web Services that helps ensure high availability and scalability for your applications. By distributing incoming network traffic across multiple servers, Load Balancer can help ensure that your application remains available and able to handle increased traffic levels, even in the event of server failures or other disruptions.
One of the key benefits of using Load Balancer is its ability to ensure high availability for your applications. By distributing traffic across multiple servers, Load Balancer can help ensure that your application remains operational and accessible to users, even if one of the servers goes down. This can be particularly important for mission-critical applications that need to be available at all times.
In addition to ensuring high availability, Load Balancer can also help improve the scalability of your applications. By automatically distributing traffic across multiple servers, Load Balancer can allow your application to scale as needed to handle increased traffic levels without experiencing a decline in performance. This can be especially useful for applications that experience sudden spikes in traffic, such as those that rely on social media marketing or other forms of viral promotion.
There are two types of Load Balancer available: Classic Load Balancer and Application Load Balancer. Classic Load Balancer is suitable for simple, less advanced configuration scenarios such as directing traffic to primary or basic servers. Application Load Balancer, on the other hand, is designed for more advanced scenarios such as controlling traffic using HTTP request attribute-based routing rules.
Load Balancer can be configured to support various protocols including HTTP, HTTPS, TCP, and SSL. It can also be used to serve traffic from different geographical locations using the Global Accelerator feature.
In conclusion, AWS Load Balancer is an essential tool for ensuring the high availability and scalability of your applications. By distributing incoming traffic across multiple servers and supporting various protocols and routing algorithms, Load Balancer can help ensure that your application remains reliable and performant, even under heavy workloads.
AWS Load Balancer is available in two types: Classic Load Balancer and Application Load Balancer.
Classic Load Balancer
Classic Load Balancer is designed for simple, less advanced configuration scenarios. It supports the following protocols: HTTP, HTTPS, TCP, and SSL. Classic Load Balancer can be used to route traffic to Amazon EC2 instances, Amazon ECS tasks, and IP addresses.
Classic Load Balancer operates at the transport layer (Layer 4) of the Open Systems Interconnection (OSI) model, which means it is capable of routing traffic based on information contained in the IP header of a packet, such as the source and destination IP addresses and port numbers. It can be configured with various routing algorithms such as nearest server, least load, or least connections.
Example scenario:
You are running a small online store that sells handmade crafts. Your store’s website is hosted on two Amazon EC2 instances in a single availability zone. You want to ensure that your store remains available and able to handle increased traffic levels, even if one of the instances goes down.
To achieve this, you decide to set up Classic Load Balancer to distribute incoming traffic across the two EC2 instances. You configure the Load Balancer with the nearest server routing algorithm, which will route traffic to the EC2 instance that is geographically closest to the user.
You also set up a health check for the Load Balancer to ensure that only healthy instances receive traffic. The health check periodically sends requests to each instance to check its status, and if an instance fails the health check, the Load Balancer will stop routing traffic to it until it becomes healthy again.
With Classic Load Balancer in place, you can rest assured that your store will remain available and able to handle increased traffic levels, even if one of the EC2 instances goes down. You can also easily scale up the number of instances if necessary to handle increased traffic.
Application Load Balancer
Application Load Balancer is designed for more advanced scenarios such as controlling traffic using HTTP request attribute-based routing rules. It supports the following protocols: HTTP and HTTPS. Application Load Balancer can be used to route traffic to Amazon EC2 instances, containers, and IP addresses.
Application Load Balancer operates at the application layer (Layer 7) of the OSI model, which means it is capable of routing traffic based on information contained in the HTTP header of a request, such as the host, path, and query string. It can be configured with rules that specify how to route traffic based on the attributes of an HTTP request, such as the host header, path, or query string parameters.
In summary, Classic Load Balancer is best suited for simple routing scenarios that require support for various protocols and routing algorithms, while Application Load Balancer is better suited for advanced scenarios that require more fine-grained control over traffic routing using HTTP request attributes.
Example scenario:
You are running a web application that provides personalized recommendations to users based on their browsing history. Your application is hosted on a group of Amazon EC2 instances and is accessed via a single domain name.
To ensure that your application remains available and able to handle increased traffic levels, you decide to set up Application Load Balancer to distribute incoming traffic across the EC2 instances.
You also want to optimize the performance of your application by routing traffic to the instance that is best suited to handle the request. To do this, you configure the Load Balancer with HTTP request attribute-based routing rules that specify how to route traffic based on the host header, path, and query string parameters of the request.
For example, you might set up a rule that routes traffic to a specific group of instances based on the host header of the request, or a rule that routes traffic to a different group of instances based on the path and query string parameters of the request.
With Application Load Balancer in place, you can fine-tune the routing of traffic to your application based on the specific needs of your users, helping to ensure that your application remains performant and responsive. You can also easily scale up the number of instances as needed to handle increased traffic.
Differences between scenario for classic and application load balancer:
- Protocols: Classic Load Balancer supports a wider range of protocols (HTTP, HTTPS, TCP, SSL), while Application Load Balancer is limited to HTTP and HTTPS.
- Routing algorithms: Classic Load Balancer can be configured with various routing algorithms such as nearest server, least load, or least connections, while Application Load Balancer uses HTTP request attribute-based routing rules to route traffic.
- Layer of the OSI model: Classic Load Balancer operates at the transport layer (Layer 4) of the OSI model, while Application Load Balancer operates at the application layer (Layer 7).
- Target types: Both Classic Load Balancer and Application Load Balancer can be used to route traffic to Amazon EC2 instances, but only Application Load Balancer can be used to route traffic to containers.
- Health checks: Both Classic Load Balancer and Application Load Balancer support health checks to ensure that only healthy targets receive traffic, but the specifics of how health checks are configured may differ.
Overall, the main difference between Classic Load Balancer and Application Load Balancer is the level of control and customization they offer for traffic routing. Classic Load Balancer is suitable for simple, less advanced routing scenarios, while Application Load Balancer is better suited for more advanced scenarios that require more fine-grained control over traffic routing using HTTP request attributes.
Examples:
You can use CloudFormation to set up and manage your Load Balancer resources. Here is an example CloudFormation template for creating an Application Load Balancer:
Resources:
MyLoadBalancer:
Type: AWS::ElasticLoadBalancingV2::LoadBalancer
Properties:
Name: my-load-balancer
Type: application
IpAddressType: ipv4
Scheme: internet-facing
SecurityGroups:
- !Ref MySecurityGroup
Subnets:
- !Ref MySubnet1
- !Ref MySubnet2
MyLoadBalancerListener:
Type: AWS::ElasticLoadBalancingV2::Listener
Properties:
LoadBalancerArn: !Ref MyLoadBalancer
Port: 80
Protocol: HTTP
DefaultActions:
- Type: forward
TargetGroupArn: !Ref MyTargetGroup
In this example, we are creating an Internet-facing Application Load Balancer with an HTTP listener on port 80. We are also specifying the security group and subnets for the Load Balancer, as well as the target group to which it will forward traffic.
You can use the AWS .NET SDK to programmatically interact with Load Balancer in your .NET applications. Here is an example of how to create a Load Balancer and a target group using the .NET SDK:
using Amazon.ElasticLoadBalancingV2;
using Amazon.ElasticLoadBalancingV2.Model;
// Create a Load Balancer client
var client = new AmazonElasticLoadBalancingV2Client();
// Create a Load Balancer
var createLoadBalancerResponse = client.CreateLoadBalancer(new CreateLoadBalancerRequest
{
Name = "my-load-balancer",
Type = LoadBalancerTypeEnum.Application,
IpAddressType = IpAddressTypeEnum.Ipv4,
Scheme = LoadBalancerSchemeEnum.InternetFacing,
SecurityGroups = new List<string> { "sg-12345678" },
Subnets = new List<string> { "subnet-12345678", "subnet-87654321" }
});
var loadBalancerArn = createLoadBalancerResponse.LoadBalancerArn;
// Create a target group
var createTargetGroupResponse = client.CreateTargetGroup(new CreateTargetGroupRequest
{
Name = "my-target-group",
Protocol = ProtocolEnum.Http,
Port = 80,
VpcId = "vpc-12345678",
HealthCheckProtocol = ProtocolEnum.Http,
HealthCheckPort = "traffic-port",
HealthCheckPath = "/healthcheck",
HealthCheckIntervalSeconds = 30,
HealthCheckTimeoutSeconds = 5,
HealthyThresholdCount = 5,
UnhealthyThresholdCount = 2
});
var targetGroupArn = createTargetGroupResponse.TargetGroups[0].TargetGroupArn;
// Create a listener for the Load Balancer
var createListenerResponse = client.CreateListener(new CreateListenerRequest
{
LoadBalancerArn = loadBalancerArn,
Protocol = ProtocolEnum.Http,
Port = 80,
DefaultActions = new List<Action>
{
new Action
{
Type = ActionTypeEnum.Forward,
TargetGroupArn = targetGroupArn
}
}
});
In this example, we are creating an Internet-facing Application Load Balancer with an HTTP listener on port 80. We are also specifying the security group and subnets for the Load Balancer, as well as the target group to which it will forward traffic. We are also setting up a basic health check for the target group to ensure that only healthy targets receive traffic.
AWS documentation:
https://docs.aws.amazon.com/AmazonECS/latest/developerguide/load-balancer-types.html
