Kong load balance where upstream has different root paths?

Question

I'm using Kong OSS (not container or k8s deployed) trying to load balance a backend two backend services for testing. My challenge is one requires authentication and different backend path port, whereas the other does not.

Frontend 1 - Kong API Gateway frontend

Host: localhost
Port: 8000
Authentication: none
Root Path: /
Example Request: POST http://localhost:8000/ {JSON Data}

I'm expecting this front-end to have following backend

Backend A - local API service for testing

Host: localhost
Port: 80
Authentication: none
Root Path: /
Example Request: POST http://localhost:80/ {JSON Data}

Backend B - hosted SaaS API service

Host: s1.example.com
Port: 443
Authentication: API Key
Root Path: /v7/guid/
Example Request: POST https://s1.example.com/v7/guid/ {JSON Data}

Following the documentation, it seems I need to create 1 service to 2 upstream/targets, but not sure how to handle different upstream root paths?

Can the upstream config dynamically change the backend path based on selected upstream/target? Or maybe instead create a single route that load-balances between two services?

I'm trying to create 1 route with 1 service that has 2 upstream targets with different root paths and request-transformers for specific upstream targets

You cannot root based on the listening port see https://github.com/Kong/kong/discussions/7273 — Ôrel, Jan 26 '22 at 19:30
I'm not trying to route based on port. I'm trying to change the backend route prefix based on selected target, while backends can live on different ports, they apparently must have the same root url path — The Unique Paul Smith, Jan 28 '22 at 22:06

score 1 · Accepted Answer · answered Feb 23 '22 at 04:35

You can create two services, each service with one route. Both routes uses the same path,

Service 1: http://httpbin.org

curl --location --request POST 'http://localhost:8001/services/' \
--form 'name="httpbin"' \
--form 'url="http://httpbin.org"'

Route 1: /path

curl --location --request POST 'http://localhost:8001/services/httpbin/routes/' \
--form 'paths[]="/testPath"' \
--form 'name="httpbinget"' \
--form 'hosts[]="httpbin.org"'

Service 2: http://mockbin.org

curl --location --request POST 'http://localhost:8001/services/' \
--form 'name="mockbin-secure"' \
--form 'url="https://mockbin.org"'

Route 2: /testpath

curl --location --request POST 'http://localhost:8001/services/mockbin-secure/routes/' \
--form 'paths[]="/testPath"' \
--form 'name="mockbin-get"' \
--form 'hosts[]="mockbin.org"'

Test the API Gateway proxy /testPath

curl --location --request GET 'http://localhost:8000/testPath/' \
--header 'Accept: application/vnd.yang.data+json' \
--header 'Host: httpbin.org'

curl --location --request GET 'http://localhost:8000/testPath/' \
--header 'Accept: application/vnd.yang.data+json' \
--header 'Host: mockbin.org'

The 2nd request is expected to fail if it requires authentication, the last step will be to enable authentication plugin on this particular service

curl -X POST http://localhost:8001/services/mockbin-secure/plugins \
    --data "name=key-auth"  \
    --data "config.key_names=apikey" \
    --data "config.key_in_body=false" \
    --data "config.key_in_header=true" \
    --data "config.key_in_query=true" \
    --data "config.hide_credentials=false" \
    --data "config.run_on_preflight=true"

the apikey needs to be provided when testing the proxy

curl --location --request GET 'http://localhost:8000/testPath/' \
--header 'Accept: application/vnd.yang.data+json' \
--header 'Host: httpbin.org' \
--header 'api-key: somekey'

I don't have a secure service to test with now, I hope that might help.

Kong load balance where upstream has different root paths?

1 Answers1