hello-world

The Docker voting app

Initialize project

In this example, we will create a single service application that deploys a web page displaying a message.

Initialize the single file project using docker-app init --single-file hello-world. A single file application contains the three sections, metadata which corresponds to metadata.yml, settings which corresponds to settings.yml and services which corresponds to docker-compose.yml.

$ ls -l
-rw-r--r-- 1 README.md
$ docker-app init --single-file hello-world
$ ls -l
-rw-r--r-- 1 README.md
-rw-r--r-- 1 hello-world.dockerapp
$ cat hello-world.dockerapp
# This section contains your application metadata.
version: 0.1.0
name: hello-world
description: ""
namespace: ""
maintainers:
- name: dimrok
  email: ""
targets:
  swarm: true
  kubernetes: true

--
# This section contains the Compose file that describes your application services.
version: "3.6"
services: {}

--
# This section contains the default values for your application settings.

Open hello-world.dockerapp with your favorite text editor.

Edit metadata

Edit the description and maintainers fields in the metadata section.

Add variables to the compose file

Add a service hello to the services section.

---

hello-world.dockerapp:

[...]
---
# This section contains the Compose file that describes your application services.
services:
  hello:
    image: hashicorp/http-echo
    command: ["-text", "${text}"]
    ports:
      - ${port}:5678

---
[...]

Give variables their default value

In the settings section, add every variables with the default value you want, e.g.:

---

hello-world.dockerapp:

[...]
---
# This section contains the default values for your application settings.
port: 8080
text: hello world!

Render

You can now render your application by running docker-app render or even personalize the rendered Compose file by running docker-app render --set text="hello user!".

Create a render directory and redirect the output of docker-app render ... to render/docker-compose.yml.

$ mkdir -p render
$ docker-app render -s text="hello user" > render/docker-compose.yml

Deploy

You directly deploy your application by running docker-app deploy --set text="hello user!" or you can use the rendered version and run docker stack deploy render/docker-compose.yml.

http://<ip_of_your_node>:8080 will display your message, e.g. http://127.0.0.1:8080 if you deployed locally.