use multiple compose files

Author: JaimeSalas

01-contenedores/contenedores-vi/docker-compose-extension/demos/02-env-variables.md

@@ -30,4 +30,208 @@ app.use("/api", router);
 
 ```
 
-Create `docker-compose.envs.yml`
+Create `docker-compose.envs.yml`
+
+```yml
+services:
+  frontend:
+    build:
+      context: ./frontend
+    deploy:
+      replicas: 1
+    ports:
+      - 3000:8080
+    profiles: [frontend]
+
+  backend:
+    build:
+      context: ./backend
+    ports:
+      - 8080:8080
+    depends_on:
+      - mongodb
+    profiles: [debug]
+    # diff #
+    environment:
+      - DEBUG="my hard coded value"
+    # diff #
+
+  mongodb:
+    image: mongo:latest
+```
+
+```bash
+docker compose -f docker-compose.envs.yml --profile debug up --build
+```
+
+```bash
+curl http://localhost:8080/api/setup
+```
+
+Instead of using hard coded values, we can use variables declare in shell. Let's try it:
+
+```bash
+docker compose -f docker-compose.envs.yml --profile debug down
+```
+
+Update `my-app/docker-compose.envs.yml`
+
+```diff
+  backend:
+    build:
+      context: ./backend
+    ports:
+      - 8080:8080
+    depends_on:
+      - mongodb
+    profiles: [debug]
+    environment:
+-     - DEBUG="my hard coded value"
++     - DEBUG
+```
+
+```bash
+export DEBUG="from shell"
+```
+
+```bash
+docker compose -f docker-compose.envs.yml --profile debug up
+```
+
+```bash
+curl http://localhost:8080/api/setup
+```
+
+```bash
+docker compose -f docker-compose.envs.yml --profile debug down
+```
+
+We can also use a `.env` file, `docker compose` will look for this file in order to set up the ennvironment variables.
+
+```bash
+unset DEBUG
+```
+
+Create `my-app/.env`
+
+```ini
+DEBUG="from .env file"
+```
+
+```bash
+docker compose -f docker-compose.envs.yml --profile debug up
+```
+
+```bash
+curl http://localhost:8080/api/setup
+```
+
+What happens when the environment variables is not set? Let's remove the `.env` file, and see what happens.
+
+```bash
+docker compose -f docker-compose.envs.yml --profile debug down
+```
+
+```bash
+rm my-app/.env
+```
+
+```bash
+docker compose -f docker-compose.envs.yml --profile debug up
+```
+
+```bash
+curl http://localhost:8080/api/setup
+```
+
+> No value is provided
+
+```bash
+docker compose -f docker-compose.envs.yml --profile debug down
+```
+
+It would be nice if docker compose notice us, that the environment variable is not set up, that is where [interpolation](https://docs.docker.com/compose/how-tos/environment-variables/variable-interpolation/#interpolation-syntax) comes in place.
+
+Update `my-app/docker-compose.envs.yml`
+
+```diff
+....
+  backend:
+    build:
+      context: ./backend
+    ports:
+      - 8080:8080
+    depends_on:
+      - mongodb
+    profiles: [debug]
+    environment:
+-     - DEBUG
++     - DEBUG=${DEBUG}
+....
+```
+
+```bash
+docker compose -f docker-compose.envs.yml --profile debug up
+```
+
+```bash
+docker compose -f docker-compose.envs.yml --profile debug down
+```
+
+For last we can also use `env_file` attribute. The [env_file attribute](https://docs.docker.com/reference/compose-file/services/#env_file) lest use multiple `.env` files.
+
+Update `my-app/docker-compose.envs.yml`
+
+```diff
+  backend:
+    build:
+      context: ./backend
+    ports:
+      - 8080:8080
+    depends_on:
+      - mongodb
+    profiles: [debug]
+-   environment:
+-     - DEBUG=${DEBUG}
++   env_file:
++     - path: ./default.env
++       required: true
++     - path: ./override.env
++       required: false
+```
+
+Create `my-app/default.env`
+
+```ini
+DEBUG="value from default.env"
+```
+
+```bash
+docker compose -f docker-compose.envs.yml --profile debug up
+```
+
+```bash
+curl http://localhost:8080/api/setup
+```
+
+```bash
+docker compose -f docker-compose.envs.yml --profile debug down
+```
+
+Create `my-app/override.env`
+
+```ini
+DEBUG="value from override.env"
+```
+
+```bash
+docker compose -f docker-compose.envs.yml --profile debug up
+```
+
+```bash
+curl http://localhost:8080/api/setup
+```
+
+```bash
+docker compose -f docker-compose.envs.yml --profile debug down
+```

01-contenedores/contenedores-vi/docker-compose-extension/demos/03-use-multiple-compose-files.md

@@ -0,0 +1 @@
+DEBUG="value from default.env"

01-contenedores/contenedores-vi/docker-compose-extension/my-app/default.env

@@ -16,6 +16,13 @@ services:
     depends_on:
       - mongodb
     profiles: [debug]
+    # environment:
+    #   - DEBUG=${DEBUG}
+    env_file:
+      - path: ./default.env
+        required: true
+      - path: ./override.env
+        required: false
 
   mongodb:
     image: mongo:latest

01-contenedores/contenedores-vi/docker-compose-extension/my-app/docker-compose.envs.yml

@@ -0,0 +1 @@
+DEBUG="value from override.env"