TCP Routing

This document will describe how to configure FSM Gateway to load balance TCP traffic.

During the L4 load balancing process, FSM Gateway determines which backend server to distribute traffic to based mainly on network layer and transport layer information, such as IP address and port number. This approach allows the FSM Gateway to make decisions quickly and forward traffic to the appropriate server, thereby improving overall network performance.

If you want to load balance HTTP traffic, please refer to the document HTTP Routing.

Prerequisites

• Kubernetes cluster version v1.21.0 or higher.
• kubectl CLI
• FSM Gateway installed via guide doc.

Demonstration

Deploy sample

First, let’s install the example in namespace httpbin with commands below.

kubectl create namespace httpbin
kubectl apply -n httpbin -f https://raw.githubusercontent.com/flomesh-io/fsm-docs/main/manifests/gateway/tcp-routing.yaml

The command above will create Gateway and TCPRoute resources except for sample app ht tpbin.

In Gateway, there are two listener defined listening on ports 8000 and 8001.

listeners:
- protocol: TCP
  port: 8000
  name: foo
  allowedRoutes:
    namespaces:
      from: Same
- protocol: TCP
  port: 8001
  name: bar
  allowedRoutes:
    namespaces:
      from: Same 

The TCPRoute mapping to backend service httpbin is bound to the two ports defined above.

parentRefs:
- name: simple-fsm-gateway
  port: 8000
- name: simple-fsm-gateway
  port: 8001    
rules:
- backendRefs:
  - name: httpbin
    port: 8080

This means we should reach backend service via either of two ports.

Testing

Let’s record the IP address of Gateway first.

export GATEWAY_IP=$(kubectl get svc -n httpbin -l app=fsm-gateway -o jsonpath='{.items[0].status.loadBalancer.ingress[0].ip}')

Sending a request to port 8000 of gateway and it will forward the traffic to backend service.

curl http://$GATEWAY_IP:8000/headers
{
  "headers": {
    "Accept": "*/*",
    "Host": "20.24.88.85:8000",
    "User-Agent": "curl/8.1.2"
  }

With gatweay port 8081, it works fine too.

curl http://$GATEWAY_IP:8001/headers
{
  "headers": {
    "Accept": "*/*",
    "Host": "20.24.88.85:8001",
    "User-Agent": "curl/8.1.2"
  }
}

The path /headers responds all request header received. From the header Host, we can get the entrance.