Docker compose watch

Compose watch lets you define how a service reacts to file changes in the host.

It can be used as an alternative to bind mounts to sync code between host and container for development.
It can used to trigger images to be rebuilt if there are changes to dependencies.
It can be used to trigger containers to be restarted, which is useful for changes to configuration files.

Examples:

Alternative to bind mount

services:
  web:
    build: .
    ports:
      - "8000:5000"
    develop:
      watch:
        - action: sync
          path: .
          target: /code
  redis:
    image: "redis:alpine"

Trigger image to be rebuilt

The image is rebuilt if there are changes to package.json
In this example another interesting feature being shown is the ability to excluce certain paths, in this case node_modules.

services:
  web:
    build: .
    command: npm start
    develop:
      watch:
        - action: sync
          path: ./web
          target: /src/web
          ignore:
            - node_modules/
        - action: rebuild
          path: package.json

Sync and restart container

The container restarts if there are changes to nginx.conf

services:
  web:
    build: .
    command: npm start
    develop:
      watch:
        - action: sync
          path: ./web
          target: /app/web
          ignore:
            - node_modules/
        - action: sync+restart
          path: ./proxy/nginx.conf
          target: /etc/nginx/conf.d/default.conf

  backend:
    build:
      context: backend
      target: builder

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