CODEWITHSUNDEEP
dockerdocker-compose
george
george

Reputation: 705

docker-compose.yml content - How can i avoid "must be a mapping not a string" error message?

Problem: the below content returns "service 'image' must be a mapping not a string." I tried using YAML Parser(http://yaml-online-parser.appspot.com/), but it returned no error. 

version: 
     "2.0"

services:

 blog:

 image: 
  abc/defg
 environment:
  APPLICATION_SECRET:
   82xxxxxxx

  ports: -"9000:9000"

working version:

version: "2.1"
services:
 blog:
  image:  abc/defg
  environment:
   APPLICATION_SECRET:
    82xxx
  ports: 
   - "9000:9000"
networks:
  default:
    external:
      name: nat

Upvotes: 0

Views: 5970

Answers (1)

Anthon
Anthon

Reputation: 76952

If you look at the Python output that you get from the online parser, you can see that you get 

'ports': '-"9000:9000"'

which doesn't look like a list of port numbers.

A sequence element is indicated by a dash followed by a space, and if you input that space after the dash following ports:

ports: - "9000:9000"

You actually do get an error, as block sequences that are values cannot start after the key, but must start on a line of their own:

ports:
- "9000:9000"

Although the element in the sequence have to be indented, the dash doesn't have to be, it just needs to be separated from the element by at least one space.

Upvotes: 1

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