如何在 Docker yml 文件中运行 curl 命令？

Question

I have 2 docker containers that are run in docker-compose, but are no longer talking to one another (connection refused error, when trying to perform a GraphQL mutation). To debug this I want to replace one of them with a simple curl command.

Original yml:

services:
  backend_container:
    container_name: backend_container
    image: backend_container:latest
    command: parm1 parm2
    volumes:
      - /c/path_to_data:/data/in
    ports:
      - 19777:19777
    depends_on:
      - ui_container
    
  ui_container:
    container_name: ui_container
    image: ui_container:latest
    ports:
      - 801:8080

proposed yml:

services: 
  test_ui:
    container_name: test_ui
    volumes:
      - /c/path_to_data:/data/in
         depends_on:
      - ui_container
    command: 
    bash -c 'curl -X POST --data-binary \"@/data/in/my_query.txt\" -H \"Content-Type: application/json\" -H 
       \"Accept: application/json\" 
       http://ui_container:8080/graphql'

  ui_container:
    same as before

I am new docker so I have a couple of questions:

1. Does this make sense to do this (have a curl as a service)?
2. I have tried to escape the quotes and colon in the curl command but I get an error ScannerError: mapping values are not allowed here pointing at the colon after 'Accept'.

Answer 1

1. Does it make sense to [...] have curl as a service?

Not really. For very short-term debugging, possibly, but in general a single command that will exit immediately doesn't make a good Compose service. A better approach might be to docker-compose run a similarly-configured container with an alternate command:

docker-compose run backend_container \
  curl --data-binary @/data/in/my_query.txt ...

2. I have tried to escape the quotes and colon in the curl command....

YAML has several ways to quote and escape strings. Here I would probably use a folded block scalar : you can write a string across multiple lines, and it will get collapsed down into one line separated by spaces. This particular call does not need a sh -c wrapper (you'd only need it if you had shell redirections or environment variable references) and skipping that also saves a level of quoting.

command: >-
  curl
  -X POST
  --data-binary @/data/in/my_query.txt
  -H "Content-Type: application/json"
  -H "Accept: application/json"
   http://ui_container:8080/graphql

Another good approach here is to use the list form of command . Again, you can't use shell constructs here, but you can (and have to) explicitly specify what "words" are.

command:
  - curl
  - -X
  - POST
  - --data-binary
  - @/data/in/my_query.txt
  - -H
  - "Content-Type: application/json" # <-- YAML string quoting
  - -H
  - "Accept: application/json"
  - "http://ui_container:8080/graphql"