Docker: Using COPY when the Dockerfile is located

I'm building an app using multiple dockerfiles (one for each service). My app's directory structure is as follows:

app
├── dockerfiles
│   ├── webserver
│   │   └── Dockerfile
│   └── database
│       └── Dockerfile
├── public
    └── <frontend>
├── db
    └── <data>
  [...]
├── LICENSE
├── README.md
└── docker-compose.yml

In my webserver's Dockerfile, I want to copy in my existing code using the COPY command:

# Dockerfile
COPY ./public /var/www/html

And I want to deploy the app using my docker-compose.yml file:

# docker-compose.yml
version: "3"
services:
   webserver:
      build: ./dockerfiles/webserver
      image: webserver:php-apache

However, when I run docker-compose from the working directory (app), I get the following error:

Building webserver
Step 1/2 : FROM php:7.1.11-apache-jessie
 ---> cb6a5015ad72
Step 2/2 : COPY ./public /var/www/html
Service 'webserver' failed to build: COPY failed: stat /var/lib/docker/tmp/docker-builder193736188/public: no such file or directory

This error disappears if I move my webserver's Dockerfile to the app's root, so I know that it's being caused by a paths or build context issue.

And knowing this, we can fix the problem one of two ways, by either:

(1) Using one Dockerfile for the entire app (in the app's root), or

app
└── Dockerfile

(2) Using multiple Dockerfiles for each service (in the app's root).

app
├── Dockerfile.webserver
└── Dockerfile.database

These solutions are bad because using one dockerfile/container for everything is not best practice (1), and having multiple dockerfiles organized in this way just looks messy (2).

So, My Question is:

How do we fix this problem without changing our original directory structure?

What changes need to be made to the dockerfiles, to docker-compose.yml, or to the basic runtime commands?
Is there a better way to organize everything?
What about the WORKDIR command?

Ideally, the best solution should work for both dev (local) and production (remote) environments, so let's avoid volumes for now...

回答1:

All you need to do here is add context: . and dockerfile in your build section inside your docker-compose.yml file so that your service understands the complete directory structure.

# docker-compose.yml
version: "3"
services:
  webserver:
    build:
      context: .
      dockerfile: ./dockerfiles/webserver/Dockerfile
    image: webserver:php-apache

回答2:

The scope for the COPY instruction is the folder where Dockerfile is. My suggestion is to change your Dockerfile to public folder and change the instruction to COPY . /var/www/html.