An Application Load Balancer is a load balancing option for the Elastic Load Balancing service that operates at the application layer and allows you to define routing rules based on content across multiple services or containers running on one or more Amazon Elastic Compute Cloud (Amazon EC2) instances.

Content-Based Routing
If your application is composed of several individual services, an Application Load Balancer can route a request to a service based on the content of the request.

Host-based Routing

You can route a client request based on Host field of the HTTP header allowing you to route to multiple domains from the same load balancer.

Path-based Routing

You can route a client request based on the URL path of the HTTP header.

Containerized Application Support
You can now configure an Application Load Balancer to load balance containers across multiple ports on a single EC2 instance. Amazon EC2 Container Service (ECS) allows you to specify a dynamic port in the ECS task definition, giving the container an unused port when it is scheduled on the EC2 instance. The ECS scheduler automatically adds the task to the ELB using this port.

HTTP/2 Support
HTTP/2 is a new version of the HyperText Transfer Protocol (HTTP) that uses a single, multiplexed connection to allow multiple requests to be sent on the same connection. It also compresses header data before sending it out in binary format and supports TLS connections to clients.

WebSockets Support
WebSockets allows a server to exchange real-time messages with end-users without the end users having to request (or poll) the server for an update. The WebSockets protocol provides bi-directional communication channels between a client and a server over a long-running TCP connection.

Native IPv6 Support
Application Load Balancers support native Internet Protocol version 6 (IPv6) in a VPC. This will allow clients to connect to the Application Load Balancer via IPv4 or IPv6. 

Sticky Sessions
Sticky sessions are a mechanism to route requests from the same client to the same target. The Application Load Balancer supports sticky sessions using load balancer generated cookies. If you enable sticky sessions, the same target receives the request and can use the cookie to recover the session context. Stickiness is defined at a target group level.

Health Checks
An Application Load Balancer routes traffic only to healthy targets. With an Application Load Balancer, you get improved insight into the health of your applications in two ways: (1) health check improvements that allow you to configure detailed error codes from 200-399. The health checks allow you to monitor the health of each of your services behind the load balancer; and (2) new metrics that give insight into traffic for each of the services running on an EC2 instance.

High Availability
An Application Load Balancer requires you to specify more than one Availability Zone. You can distribute incoming traffic across your targets in multiple Availability Zones. An Application load balancer automatically scales its request handling capacity in response to incoming application traffic.

Security Features
When using Amazon Virtual Private Cloud (VPC), you can create and manage security groups associated with Elastic Load Balancing to provide additional networking and security options. You can configure an Application Load Balancer to be Internet facing or create a load balancer without public IP addresses to serve as an internal (non-Internet-facing) load balancer.

Layer-7 Load Balancing
You can load balance HTTP/HTTPS applications and use layer 7-specific features, such as X-Forwarded-For headers.

HTTPS Support
An Application Load Balancer supports HTTPS termination between the clients and the load balancer. Application load balancers also offer management of SSL certificates through AWS Identity and Access Management (IAM) and AWS Certificate Manager for pre-defined security policies.

Operational Monitoring
Amazon CloudWatch reports Application Load Balancer metrics such as request counts, error counts, error types, and request latency.

Logging

You can use the Access Logs feature to record all requests sent to your load balancer, and store the logs in Amazon S3 for later analysis. The logs are compressed and have a gzip file extension. The compressed logs save both storage space and transfer bandwidth and are useful for diagnosing application failures and analyzing web traffic.

You can also use AWS CloudTrail to record Application Load Balancer API calls for your account and deliver log files. The API call history enables you to perform security analysis, resource change tracking, and compliance auditing.

Delete Protection
You can enable deletion protection on an Application Load Balancer to prevent it from being accidentally deleted.

Request Tracing
The Application Load Balancer injects a new custom identifier “X-Amzn-Trace-Id” HTTP header on all requests coming into the load balancer. Request tracing allows you to track a request by its unique ID as the request makes its way across various services that make up the your websites and distributed applications. You can use the unique trace identifier to uncover any performance or timing issues in your application stack at the granularity of an individual request.

Web Application Firewall
You can now use AWS WAF to protect your web applications on your Application Load Balancers. AWS WAF is a web application firewall that helps protect your web applications from common web exploits that could affect application availability, compromise security, or consume excessive resources.  

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  • The Application Load Balancer is only supported for use within an Amazon Virtual Private Cloud (VPC).
  • You can create up to twenty (20) load balancers per region, which includes both Classic and Application Load Balancers. Should you need to exceed these limits, please complete this form.