- Connect to public subnets (at least 2)
- Directs traffic to the healthy points
- ALB, NLB, CLB
- Load balancers always get only DNS names, except NLB - can get static IP
- ALB
- Operates at layer 7
- Best for load balancing HTTP and HTTPS traffic
- Intelligent
- Send specified requests to specific web servers
- Can see inside the application layer
- NLB
- Load balancing of TCP traffic where extreme performance is required
- Operates at the connection level (layer 4)
- Can handle millions of requests per second - while maintaining ultra low latency
- CLB
- Can load balance HTTP/HTTPS appplications and use layer 7 features, such as the X-forwarded headers and sticky sessions.
- Can also use layer 4 load balancing for apps that rely purely on TCP protocol.
- Cannot look into application layer
- 504 error
- Gateway timeout
- Instance not responding
- Not a LB error
- Sticky sessions
- Can disable sticky sessions
- Happens when LB is directing traffic to just one instance
- Enables users to stic kto the same ec2 instance
- Cross zone LB
- Must be enabled otherwise cant sent traffic to another AZ
- When enabled, total traffic is divided by the number of instances, since LBs can send traffic to any LB regardless of AZ
- Path Patterns
- Must be enabled
- Path based routine
- LB can used path based rules to direct traffic to a particular direction/instance
- SSH/RDP = layer 4 - therefore needs Network Load Balancer (Layer 4), cant use ALB (Layer 7)
- NLB are expensive ish
HA Architecture
- Netflix high availability tests - Simian army
- Chaos monkley
- Chaos Gorilla
- Chaos Kong
- Janitor Monkey
- Security Monkey
- etc.
- Scaling up
- Increase resources e.g. t2.micro to small
- Scaling out
- Adding additional resources/instances e.g. new ec2 instance
Cloudfront Distros
- Use for stuff like web servers - e.g. have website images served up through cloudfront pulling out of S3
On Premise Strategies
- Database migration service (DMS)
- homogenous migration
- heterogenous migration
- Server migration service (SMS)
- AWS Application Discovery Service
- VM Import/Export