Concepts
Elastic Load Balancing (ELB) is an essential component of any highly available, scalable application on AWS, helping distribute incoming application traffic across multiple targets, such as Amazon EC2 instances. Amazon Route 53 is a scalable and highly available Domain Name System (DNS) web service that routes end-user requests to infrastructure running in AWS, such as instances behind an ELB.
Configuring ELB with Route 53 health checks ensures that traffic is routed to healthy instances, improving the reliability and availability of your application. Here’s how you can configure ELB and set up Route 53 health checks as an AWS Certified SysOps Administrator:
Configuring Elastic Load Balancing (ELB)
- Sign in to the AWS Management Console and open the Amazon EC2 console.
- In the navigation pane, under Load Balancing, select Load Balancers.
- Click Create Load Balancer and choose the type of ELB you need for your application – Application Load Balancer for HTTP/HTTPS traffic, Network Load Balancer for TCP/UDP traffic, or Classic Load Balancer for simple load balancing of requests.
- Configure the load balancer settings:
- Basic Configuration: Assign a name, select the VPC, and if necessary, enable the dual-stack to support IPv4 and IPv6 addresses.
- Listeners: Set up listeners that define how your load balancer routes requests to its registered targets.
- Configure security settings by selecting appropriate security groups and setting up SSL certificates if you’re using HTTPS listeners.
- Configure routing to define a target group, which is a set of targets, such as EC2 instances, that you route traffic to.
- Review and create the load balancer, and then add targets to the target group.
Configuring Health Checks for Your ELB Target Groups
- On the Target Group’s page, under Health Checks, you can configure and adjust the settings such as:
- Health Check Protocol: HTTP, HTTPS, or TCP.
- Port: The port used for the health check.
- Path: The destination for health checks, typically a URI like /health or /ping.
- Healthy and Unhealthy Thresholds: The number of consecutive health check successes to consider an unhealthy target healthy, and conversely the number of consecutive health check failures to consider a healthy target unhealthy.
- Interval: The time between health checks.
- Save the changes to the health check configuration.
Configuring Amazon Route 53 Health Checks
- Open the Route 53 console, and in the navigation pane, select Health Checks.
- Click Create Health Check, and set up your health check:
- Name: Enter a name that helps you identify the health check.
- What to Monitor: Choose whether to monitor an endpoint, a status of a CloudWatch alarm, or other health checks.
- Specify Endpoint: If endpoint monitoring, provide the IP address or domain name of the endpoint to check, and select the port and type (HTTP, HTTPS, TCP).
- Specify request and failure details:
- For HTTP/HTTPS health checks, set the path to a resource that is always available when the endpoint is healthy.
- Decide how many health checkers should report an instance as unhealthy before the endpoint is considered unhealthy (failure threshold).
- Configure advanced features as needed like string matching or SNI.
- Click Create Health Check to finish.
Route 53 Health Checks Integration With ELB
- When creating Route 53 health checks, select the option Yes under the Associate with Health Check section of the ELB.
- Route 53 will configure health checks that in turn use the health checks defined for the ELB’s target groups, providing an additional layer of health monitoring.
- The Route 53 DNS will then only route traffic to the load balancer if the health checks pass.
By combining ELB with Route 53 health checks, AWS users can ensure traffic is only sent to healthy instances, thus increasing the overall availability and reliability of the deployed applications. Remember to monitor and adjust configurations as required to maintain optimum application performance and health status visibility.
Answer the Questions in Comment Section
True/False: Elastic Load Balancing automatically distributes incoming application traffic across multiple targets, such as Amazon EC2 instances, containers, and IP addresses.
- True
Elastic Load Balancing automatically distributes incoming application traffic across multiple targets, ensuring fault tolerance and scalability.
True/False: Amazon Route 53 does not support health checking and DNS failover for endpoints in a private hosted zone.
- True
Route 53 health checks are not available for endpoints in a private hosted zone as they are meant to monitor publicly accessible endpoints.
Which feature of Amazon Route 53 can detect if an application is reachable, available, and functional?
- A) DNSSEC
- B) Health Checks
- C) Traffic Flow
- D) Geolocation routing
Answer: B) Health Checks
Route 53 Health Checks monitor the health of your application endpoints and are used in conjunction with DNS failover to reroute traffic if an endpoint fails.
True/False: Sticky Sessions cannot be enabled in an Elastic Load Balancer to bind a user’s session to a specific target.
- False
Sticky Sessions can be enabled in an Elastic Load Balancer to bind a user’s session to a specific target for the duration of the session.
Which of the following is a benefit of using Elastic Load Balancing?
- A) Reduces the security of EC2 instances.
- B) Auto Scaling is not required anymore.
- C) Disproportionate load distribution.
- D) High availability and fault tolerance.
Answer: D) High availability and fault tolerance.
Elastic Load Balancing provides high availability and fault tolerance by distributing incoming traffic across healthy targets in multiple Availability Zones.
What type of Elastic Load Balancer can be used to handle millions of requests per second with very low latencies?
- A) Network Load Balancer (NLB)
- B) Application Load Balancer (ALB)
- C) Classic Load Balancer (CLB)
- D) Both A and B
Answer: A) Network Load Balancer (NLB)
Network Load Balancers are designed to handle millions of requests per second while maintaining ultra-low latencies, making them suitable for TCP, UDP, and TLS traffic.
True/False: Cross-zone load balancing automatically balances loads across all registered instances in all Availability Zones within a region in an Application Load Balancer (ALB).
- True
Cross-zone load balancing in an ALB allows the load balancer to distribute the load evenly across all registered instances in multiple Availability Zones.
True/False: If an AWS Region that hosts the primary resource becomes unavailable, Amazon Route 53 can automatically switch traffic to a secondary location.
- True
Route 53 can be configured to perform DNS failover to automatically route traffic to a secondary location if the primary location becomes unavailable.
What is the main purpose of the health checks in Amazon Route 53?
- A) To ensure that the DNS queries return the correct IP addresses
- B) To monitor the performance of the compute resources
- C) To charge for the number of check requests
- D) To determine the availability of endpoints for request routing
Answer: D) To determine the availability of endpoints for request routing
Health checks in Route 53 are used to verify the health of endpoint resources, determining whether they are available to handle requests.
When creating a listener for your load balancer, you need to specify:
- A) The default rule actions.
- B) The SSL certificate to use.
- C) The type of load balancer.
- D) All of the above.
Answer: D) All of the above.
When creating a listener, you need to specify the default rule actions, SSL certificate (if needed, for HTTPS listeners), and the type of load balancer.
True/False: Amazon Route 53 supports health checking on HTTPS endpoints without sending the actual data in the request.
- True
Route 53 can perform health checks on HTTPS endpoints purely based on the connection success without needing to inspect the data in the request.
The Application Load Balancer operates at which layer of the OSI model?
- A) Layer 4 (Transport Layer)
- B) Layer 7 (Application Layer)
- C) Layer 3 (Network Layer)
- D) Layer 1 (Physical Layer)
Answer: B) Layer 7 (Application Layer)
The Application Load Balancer operates at the application layer of the OSI model (Layer 7), allowing for advanced request routing based on content.
This blog post on configuring ELB and Route 53 is super helpful. Thanks!
Can anyone explain how Route 53 health checks work specifically for multi-region setups?
Appreciate the detailed steps provided in this guide!
I followed the steps but my ELB health checks are failing. Any ideas why?
Thanks for this post!
The information about DNS failover using Route 53 is top notch!
What are the costs associated with using Route 53 health checks and ELB?
I wish the guide included more examples.