loadbalancer HA Proxy

Load Balancer concepts

Two type of load balancers

• layer 4 based on ip cannot see packet single TCP connection Expensive dedicated network device Not round robit in some cases no caching

implementation

PORT=4444 node index.js

PORT=5555 node index.js

Load balancer listening on port something

brew install haproxy

tcp.cfg for layer 4 loadbalancing

haproxy -f tcp.cfg

to check for correct config

haproxy -c -f tcp.cfg

mode tcp is the key there

localhost:8888 --> localhost:4444 or localhost:5555 url doesnt change

• layer 7 software load balancer can see packet and then decide where to go round robbin mostly caching 2 TCP connections

acl app1 path_end -i /app1 acl app2 path_end -i /app2 use_backend app1servers if app1 use_backend app2servers if app2

it means that go to app1 if /app1 and app1 to use app1servers

example backend app1servers mode http server app1server1 127.0.0.1:4444 check server app1server2 127.0.0.1:6666 check

haproxy -f http.conf

localhost:9999/app1

ges to either 4444 or 6666 rounf robit

same for /app2

End of HA PROXY

PROXY VS REVERSE PROXY

Proxy : server doesnot know who the client is ______ client 1 ---------http:80 ---| | | | client 2 ---------http:80 ---|PROXY |-------http:80-----SERVER | | client 3 ---------http:80 ---|______|

firewall annonimity

Reverse Proxy: Client doesnot know which server it is connecting to

                         |      |-------http:8080-----SERVER1
                         |      |

client 1 ---------http:80 ---|reverse |PROXY |-------http:8080-----SERVER2 | | |______|-------http:8080-----SERVER3

dont know which service exist in which server loadbalancing caching isolating internal traffic

both at same time - service mesh

nginx - one of few things that acts as web server and also as load balancer