How to create a Traefik v2.x ReplacePath label in a simple docker-compose file? - traefik

Question

Given the following url's, I'm trying to create some routers with Traefik v2.x
Route forwards to
-----------------------------
/users -> /users
/users/* -> /users/*
/users/swagger -> /swagger
So in these examples, my webserver is has some endpoints for users GET /users, GET /users/1, POST /users, DELETE /users/1, etc.. but also has a Swagger/OpenApi definition/docs located /swagger.
So I'm trying to access these endpoints through Traefik.
I'm under the impression that I need to create labels that use the routers + PathPrefex and routers + Path for the endpoint matching ... but use middleware for the replace.
I'm too sure how to do this properly.
Here's what I'm trying to do...
version: '3.5'
services:
users-api:
image: spike.openapi/users.api
build:
context: ./
dockerfile: src/Users/Dockerfile
ports:
- "80"
networks:
- backend
container_name: users.api
labels:
- "traefik.enable=true"
- "traefik.http.routers.users-api.rule=PathPrefix(`/users`)"
- "traefik.http.routers.users-api.rule=Path(`/users/swagger`)"
- "traefik.http.routers.users-api.entrypoints=web"
reverse-proxy:
image: traefik
<snipped>
...

Answer 1

Without the Host rule, traefik will not know on which backend to redirect the request so the first thing you are missing might be that. I think following should work.
services:
users-api:
...
labels:
# /users/swagger -> /swagger
traefik.http.middlewares.replacepath-middleware.replacepath.path: /swagger
traefik.http.routers.swagger-router.rule: Host(`your-domain.net`) && PathPrefix(`/users/swagger`)
traefik.http.routers.swagger-router.entrypoints: http
traefik.http.routers.swagger-router.middlewares: replacepath-middleware
# everything else (/users -> /users)
traefik.http.routers.base-router.entrypoints: http
traefik.http.routers.base-router.rule: Host(`your-domain.net`)
You could also use the stripprefix middleware to achieve the exact same thing
services:
users-api:
...
labels:
# /users/swagger -> /swagger
traefik.http.middlewares.stripprefix-middleware.stripprefix.prefixes: /users
traefik.http.routers.swagger-router.rule: Host(`your-domain.net`) && PathPrefix(`/users/swagger`)
traefik.http.routers.swagger-router.entrypoints: http
traefik.http.routers.swagger-router.middlewares: stripprefix-middleware
# everything else (/users -> /users)
traefik.http.routers.base-router.entrypoints: http
traefik.http.routers.base-router.rule: Host(`your-domain.net`)
I noticed traefik redirect the request (http 304). If what you want is some kind of url rewriting, I don't think traefik can handle it - this should be your backend's job, users-api in your case.
IMO understanding traefik middleware behaviours is not easy. I tried to reproduce your setup with a simple nginx backend. Have a try at it:
version: '3.7'
services:
traefik:
image: traefik:v2.1
ports:
- 80:80
command:
- --entrypoints.http.address=:80
- --providers.docker.exposedByDefault=false
- --log.level=DEBUG
volumes:
- /var/run/docker.sock:/var/run/docker.sock
nginx:
image: nginx:1.16.1
labels:
traefik.enable: 'true'
# /users/swagger -> /swagger
traefik.http.middlewares.replacepath-middleware.replacepath.path: /swagger
traefik.http.routers.swagger-router.rule: Host(`127.0.0.1`) && PathPrefix(`/users/swagger`)
traefik.http.routers.swagger-router.entrypoints: http
traefik.http.routers.swagger-router.middlewares: replacepath-middleware
# everything else (/users -> /users)
traefik.http.routers.base-router.entrypoints: http
traefik.http.routers.base-router.rule: Host(`127.0.0.1`)
Run the following commands first to create the folder and dummy pages:
docker-compose up -d
docker-compose exec nginx mkdir /usr/share/nginx/html/swagger
docker-compose exec nginx mkdir /usr/share/nginx/html/users
docker-compose exec nginx sh -c "echo 'users page here' > /usr/share/nginx/html/users/index.html" bbouchereau#bbouchereau
docker-compose exec nginx sh -c "echo 'swagger page here' > /usr/share/nginx/html/swagger/index.html"
The results:
http://127.0.0.1/users/ -> users page here
http://127.0.0.1/users/swagger/ -> redirect to http://127.0.0.1/swagger/ -> swagger page here