version: '3' # '0' is not allowed

services:

  talerdb:
    build: ./images/postgres
    ports:
      - 8888:5432
  exchange:
    build: ./images/exchange
    depends_on:
      - talerdb
    ports:
      - 5555:80
  merchant:
    build: ./images/merchant
    depends_on:
      - talerdb
    ports:
      - 5556:80