Distributing Traffic
Problem with load/stress on the application
- Generally web servers when accessed create a load on cpu and memory for every request. As number of request increase one server will not be able to solve the problem/execute the request. On a broader note we have two options
- Horizontal scaling: Increase number of servers running the application
- Vertical Scaling: Increase the server resources such as CPU/Memory etc.
- If the number of servers are many then we cant share all the ips to requster. To solve this we need to understand the concept of Proxy Servers
Proxy Server
Reverse Proxy Server
Load Balancers
- Load Balancers serve incoming traffic to a application and distribute it across servers
- Load Balancers major functionality is around
- Distributing an application traffic so that the individual servers do not become overloaded
- Types of Load Balancers (functionality)
- Layer 4 load balancer
- Layer 7 load balancer
- Type of Load Balancers (creation)
- Hardware load balancer
- Software load balancer
- Virtual load balancer
OSI Networking Model
- Model overview
- Each layer adds functionality
- Now layer 4 loadbalancing can make load balancing decisions on the basis of
- ip address
- port
- protocol (TCP/UDP)
- Layer 7 has knowledge of http in addition to layer 4
Layer 4 scenario in Cloud
- In cloud generally we have two types of load balancing
- internal load balancing
- internet facing/public load balancing
-
Terms:
- inbound: where the users will hit the load balancer
- outbound: where the load balancer needs to send the traffic
-
Azure Layer 4 Load Balancer
- AWS Layer 4 Load Balancer
- Mapping name to public address of Load Balancer is done in DNS zone
Load Balancing Algorithms
- Refer Here for load balancer algorithms
DMZ (De-militarized Zone)
Lab setup for Load Balancing
- Create a ubuntu vm/ec2 instance with 80 port and 22 port opened
- steps
sudo apt update
sudo apt install apache2 -y
sudo apt install stress -y
- Create a file in
/var/www/html/index.htmlwith following content
<!DOCTYPE html>
<html>
<body style="background-color:powderblue;">
<h1>Welcome to Load Balancing</h1>
<p>This is for learning</p>
</body>
</html>
- Now access
http://<public ip> - shutdown this instance
