Docker-Compose file has yaml.scanner.ScannerError

Ok, I wasted around 3 hours to debug a similar issue.

If you guys ever get the below error

ERROR: yaml.scanner.ScannerError: mapping values are not allowed here
in ".\docker-compose.yml", line 2, column 9

It's because a space is needed between

version:'3' <-- this is wrong

version: '3' <-- this is correct.

Also, if you are using eclipse, do yourself a favor and install the YEdit YAML editor plugin

And I forgot : after version

version '2'

Literally found the solution seconds later. You have to remove the "discovery-microservice" after "build":

version: '2'
services:
  discovery-microservice:
    build:
      context: ./discovery-microservice/target/docker
      dockerfile: Dockerfile
    ports:
     - "8761:8761"

Also you can use "./" in context for relative paths. :)

What is wrong is that here:

    build: discovery-microservice

you start a mapping which has a key build indented by four spaces. The value for that key is a scalar that starts with discovery-microservice and possible continues to the next line, depending on whether that has a key: value pair at the same indentation level or not

What is not allowed inside such a multiline scalar is that you have an unquoted : and have that at a different indentation level. Which is exactly what you do have.

The parser seeing context indented at a different level than build assumes you are writing a scalar string discovery-microservice context which cannot be followed on the same line (as context) by a colon.

Apart from removing discovery-microservice after build as you did in your answer, what would also make this valid YAML (but with a different meaning, probably non-sense for docker compose) are:

services:
  discovery-microservice:
    build: "discovery-microservice
      context: /discovery-microservice/target/docker"

and

services:
  discovery-microservice:
    build: discovery-microservice
    context: /discovery-microservice/target/docker"

For docker-compose version 2 files, the build key expects a mapping (and not a scalar as in the "solutions" above), making your answer the correct way to solve this.