nginx-headerbased-routing

Sample configuration to route traffic based on header values

The backend-server

Supports a rest endpoint at /hello that will mirror the headers received and the value of the environment Value "BACKEND".

The frontend-server

Supports a rest endpoint at /hello that will add a header configured as header.name and use a comma separated value list as header-values configured as header.values. Will forward every request to the nginx instance configured as backend.server.

Each time the hello-service is called, the frontend will use another value from the headers list.

The nginx reverse proxy

The nginx reverse proxy uses the header values in a map to route to the matching backend servers.

It is purely coincidential that the backend servers are named identical to the Header-value, yet, since the backends are attached as upstream configurations, which are actually loadbalancers, the the name of the upstreams should follow the header name to keep things simple.

The list of servers in the upstream will be set as required by your infrastructure and can even be ip addresses.

Building and running

1. install maven (3.6)
2. install jdk 11
3. run cd backend-server && mvnw package && cd ..
4. run cd frontend-server && mvnw package && cd ..
5. run cd nginx
6. run docker-compose build
7. run docker-compose up

When running, the docker-compose will consume the following ports on your host:

port	server
8000	frontend-server
9000	nginx
9010	backend customerA
9020	backend customerB
9030	backend customerC
9040	backend customerD
9050	backend default

The nginx Configuration sees the internal ports of all containers and uses 8080 in all upstream configurations

Testing

Call a backend through the frontend:

curl http://localhost:8000/hello (http://localhost:8000/hello)

                                        Header=        +---------------+
                                      +---------------+|               |
                                      | customerA      |   backendA    |
                                      |                |               |
                                      |                |               |
                                      |                +---------------+
                                      | Header=        +---------------+
                                      +---------------+|               |
                                      | customerB      |   backendB    |
     +---------+           +---------+|                |               |
     |         |  X-COMPOSE|         ||                |               |
     | frontend|+---------+|         |+                +---------------+
     |         | Header    | nginx   || Header=        +---------------+
     |:8000    |           | :9000   ||---------------+|               |
     +---------+           +---------+| customerC      |   backendC    |
                                      |                |               |
                                      |                |               |
                                      |                +---------------+
                                      | Header=        +---------------+
                                      |---------------+|               |
                                      | customerD      |   backendD    |
                                      |                |               |
                                      |                |               |
                                      |                +---------------+
                                      | Header=        +---------------+
                                      +----------------+ backendDefault|
                                        *alles andere  |               |
                                                       |               |
                                                       +---------------+