Load Balancers Flashcards
What are the 3 kinds of Load balancers in aws?
Application Load balancer - They are application-aware and suitable to load balance http and https traffic.
Network Load balancer - They work mostly at tcp level.They are used when extreme performance is required.
Classic Load balancer - These are not intelligent,It is used for HTTP and https but it is not application-aware. It can still use X-FORWARDED-FOR for and sticky sessions.
Use this to keep costs down
What is 504 error
Blanket error is thrown by Load balancer when something goes wrong. It could be the Webserver, database server or something else. We will have to debug to find the failing bit.
What are target groups?
Target group is used to route requests to one or more registered targets. When you create each listener rule, you specify a target group and conditions. When a rule condition is met, traffic is forwarded to the corresponding target group. You can create different target groups for different types of requests. For example, create one target group for general requests and other target groups for requests to the microservices for your application
Explain auto-scaling groups?
Its a service where we can set the EC2 instances to grow or shrink based on configuration.
1) Create a launch configuration where we specify the kind of EC2 instances we want to spin-off, its start up scripts etc. Launch configuration itself doesn’t create any instances, it’s only a template.
2) Create an Autoscaling group, specify the minimum and maximum amount of instances we need, their availability zones, the condition under which we need new instances would be created (like CPU utilization) and the launch configuration created in step one.
3) Auto-scaling groups can also be configured to be associated with a load balancer
Difference between scaling up and scaling out?
Scaling out is creating auto scaling groups and additional EC2, whereas scaling up is increasing the resources inside ec2
What is cloud formation?
Bunch of templates designed by aws to launch complicated environments, very quickly.
What is elastic Beanstalk?
Aimed at developers without much knowledged about AWS.Its a way of deploying applications to cloud, where we can upload the code and AWS will create the environment for us. We can later change it to add securty groups, load balancers, scaling, health monitoring etc etc.
which TCp port is supported for Load balancing
1-65535
Is it possible to convert Classic Load Balancer to an Application Load Balancer (and vice versa
No there is no conversion, but migration is possible
Some of the parameters/conditiona to create listener rule in Load balancer and available options
The supported conditions are Host header, path, HTTP headers, methods, query parameters, and source IP CIDRs. The supported actions are redirect, fixed response, authenticate, and forward.
How to secure applications beyond load balancer
Integrating with WAF, (Web Application firewall) allows rules to be written based on IP addresses, HTTP headers, and custom URI strings
Can Load balancer route requests to Lamba methods?
Yes, when the one of teh target group fpr the load balancer is lambda function and if the incoming request matches rules to be sent to the Lambda method, the parameters are converted to JSon and passed to Lambda method and the response is sent back at http
How does billing happen in Load balancer
per hour and based on LCU(Load balancer capacity units)
An LCU defines the maximum resource consumed in any one of the dimensions (new connections, active connections, bandwidth and rule evaluations) the Application Load Balancer processes your traffic
Does cross zone data transfer incur charges in ELB?
Only for Network Load balancers
How are classic Load balancers billed?
Billed on Bandwidth and hourly rate
