'./docker-compose.yml', service must be a mapping, not a NoneType

问题

When I ran: COMPOSE_PROJECT_NAME=zk_test docker-compose up, I got error saying

"ERROR: In file './docker-compose.yml', service must be a mapping, not a NoneType.".

This is my yml file:

version: '2'
services:
zoo1:
image: zookeeper
restart: always
container_name: zoo1
ports:
- "2181:2181"
environment:
ZOO_MY_ID: 1
ZOO_SERVERS: server.1=zoo1:2888:3888 server.2=zoo2:2888:3888 server.3=zoo3:2888:3888

zoo2:
image: zookeeper
restart: always
container_name: zoo2
ports:
- "2182:2181"
environment:
ZOO_MY_ID: 2
ZOO_SERVERS: server.1=zoo1:2888:3888 server.2=zoo2:2888:3888 server.3=zoo3:2888:3888

zoo3:
image: zookeeper
restart: always
container_name: zoo3
ports:
- "2183:2181"
environment:
ZOO_MY_ID: 3
ZOO_SERVERS: server.1=zoo1:2888:3888 server.2=zoo2:2888:3888 server.3=zoo3:2888:3888

Sample Image:

回答1:

YAML is indentation dependent. This

services:
zoo1:

is a mapping with two keys that both map to null (i.e. None in Python).

Whereas:

services:
   zoo1:

is a mapping nested in a mapping. The key 'services' has as value a mapping with key zoo1 (which again has a value null).

来源：https://stackoverflow.com/questions/43452448/docker-compose-yml-service-must-be-a-mapping-not-a-nonetype