High Availability & Scalability Flashcards
What are the 4 types of Load Balancer available?
- CLB Classic Load Balancers
- ALB Application Load Balancers
- NLB Network Load Balancers
- GWLB Gateway Load Balancers
What 3 protocols does the Classic Load Balancer support?
- TCP Layer 4
- HTTP and HTTP Layer 7
What 2 protocols are the Classic Load Balancer Health Checks on?
- TCP
- HTTP
What protocol does the Application Load Balancer support?
HTTP Layer 7
What are the 4 routing options in the ALB?
- URL path
- URL hostname
- Query String
- Headers
With CLB and ALB, we get a fixed hostname, what does that look like?
xxx.region.elb.amazonaws.com
How do we retrieve the client ip, port and proto if using an ELB?
IP - X-Forwarded-For
Port - X-Forwarded-Port
Proto - X-Forwarded-Proto
What protocol does the Network Load Balancer support?
Layer 4 to allow TCP & UDP
Does the NLB have a fixed hostname?
No, it has a static IP per AZ
What is a Gateway Load Balancer used for?
To deploy, scale and manage a fleet of 3rd party network virtual appliances in AWS
What protocol does the Gateway Load Balancer support?
Layer 3 Network Layer for IP Packets
In AWS console, what protocol and port does the Gateway Load Balancer use?
GENEVE on port 6081
What are sticky sessions?
Its when the same client traffic is always redirected to the same instance behind the ELB
What are sticky sessions also known as?
Session Affinity
What is needed for sticky sessions?
A cookie which has an expiration date
What ELB is Cross Zone Load Balancing enabled on?
The ALB has it enabled by default and cannot be disabled so there is no charge
What ELBs is Cross Zone Load Balancing disabled on?
- NLB has it disabled by default and charges apply if enabled.
- CLB has it disabled by default and there are no charges if enabled
What does SSL stand for?
Secure Sockets Layer
What does TSL stand for?
Transport Layer Security
What kind of certificates does the ELB use?
X.509 certificate (SSL/TLS certificate)
What does SNI stand for?
Server Name Indication
What does SNI do?
It solves the problem of loading multiple certs onto one web server
What is Connection Draining?
It provides time to complete in-flight requests while terminating and prevents new requests being sent
What is Connection Draining also known as?
Deregistration Delay
What are 4 metrics to scale on in an Auto Scaling Group?
- CPU Utilization
- RequestCountPerTarget
- Average Network In/Out
- Any Custom Metric
What is the default cooldown period for ASGs?
300 seconds (5 minutes)
What are the 2 steps taken in the default termination policy?
- Find the AZ which has the most instances
- Delete the instance with the oldest launch configuration
