ELB Flashcards
What is ELB?
Elastic Load Balancer. Used to help balance the load across several different servers.
What are the 3 types of ELB?
1) Application Load Balancer
2) Network Load Balancer
3) Classic Load Balancer
When to use an Application Load Balancer?
Best suited for load balancing of HTTP or HTTPs traffic
- Layer 7
- Application aware
- Send specific requests to specific web server
When to use a Network Load Balancer?
Best for TCP traffic where need extreme performance
- Layer 4
- Can handle millions of requests per sec while maintain ultra low latency
- MOST EXPENSIVE
When to use a Classic Load Balancer?
- Legacy app
- Load balance HTTP/HTTPS apps
- Layer 7 specific features such as X Forward and Stick Sessions
- Also use strict layer 4 for apps that rely solely on TCP protocol
NOT AS GOOD as application load balancer
What does it mean if you receive a 504 error from a Classic ELB?
Either webserver or database layer has an issue. It is something below the load balancer experiencing the error.
To fix try scaling the app up or out.
How to perform TLS encryption with ALB?
Perform TLS termination on the ALB to ensure data is encrypted in transit between VPC and the customer who is accessing it.
How to get an IPv4 address of the end user with a ELB?
Look for the X-Forwarded-For header
Services that can use ELB?
EC2 instances
ECS containers
Lambda functions
IP addresses
in multiple availability zones
What is Cross Zone Load Balancing?
distributes traffic across registered targets in all enabled Availability Zones.
Does ELB support load balancer-generated cookies?
Yes, but only for sticky sessions.
Monitoring Services for ELB
ALL
CloudWatch
CloudWatch Logs
Network
VPC Flow Logs
Application
Access Logs
Request Tracing
Classic
Access Logs
What are Stick Sessions?
Way to route requests to the same target within a target group. This could be set in seconds. This is great for stateful applications.
