I’m going to provide step by step instructions to use AWS to remotely build docker containers using rancher compose

Requirements

Install the following software on your development machine

  • docker
  • rancher-compose

Create a free account with Amazon Web Services

You need to first define your application using docker-compose.yml

For this exercise, let us choose a simple application. I’ll just use the example from docker compose documentation here.

create a directory called composetest.

In that directory create a file named docker-compose.yml and fill in with :-

web:
    build: .
    ports:
        - "5000:5000"
    links:
        - redis
redis:
    image: redis

The above compose file defines a service called web, that opens up port 5000 of the container running it to the host. It also has a service link to redis, therefore the application running inside the web container will be able to reach the redis container by its hostname - redis.

Let us define the rancher-compose.yml file for it. This file will let you enhance your applciation definition by providing additional directives to it, like sparinkling sugar on sweets.

web: 
    scale: 3

This file says that run this service on 3 different containers.

Next, we need to write the application itself and the steps to build it.

Create a file named app.py and fill it with

from flask import Flask
from redis import Redis

app = Flask(__name__)
redis = Redis(host='redis', port=6379)

@app.route('/')
def hello():
    redis.incr('hits')
    return 'Hello World! I have been seen %s times.' % redis.get('hits')

if __name__ == "__main__":
    app.run(host="0.0.0.0", debug=True)

This application talks to a host called redis, which is expected to be running a redis KV store, and increments the value of a key in the store called hits, and retrieves it.

This application depends on two libraries. Create a file called requirements.txt and fill it with

flask
redis

Now, let us define the steps to build it.

Create a file called Dockerfile and fill it with 

FROM python:2.7
ADD . /code
WORKDIR /code
RUN pip install -r requirements.txt
CMD python app.py

These instruction define how the application container should be built

Now, start up your rancher-server 

docker run -d -p 8080:8080 --restart=always rancher/server

This will start up rancher/server on your localhost:8080

NOTE: If you’re running boot2docker on a mac, then run 

open http://$(boot2docker ip):8080

to access the UI. Also, replace localhost with the result of 

boot2docker ip

Now open a browser and go to localhost:8080

Open the Infrastructure tab, and then under the Hosts subtab, click on Add Hosts

If you’re prompted to perform Host Registration, then assign an address that is routable from your local dev box (the $(boot2docker ip):8080 or localhost:8080 will work just fine)

Click on the Custom tile and then copy-paste the command provided into your terminal. This will start a rancher-agent on your dev box, effectively emulating the cloud setup.

Now, from the same composetest folder, run the following command to create a S3 build for your web application

RANCHER_URL=http://localhost:8080/v1/projects/1a5/schema AWS_ACCESS_KEY_ID=$(aws-access-key) AWS_SECRET_ACCESS_KEY=$(aws-secret-key) rancher-compose up

Obviously, replace the symbols inside the dollars to actual values.

This will start the web container on the remote host(in this case, it is your development box). It first uploads the current directory to s3 (verify it by going to s3 UI, and checking for a new upload). Then, it downloads it from the remote host, where it builds the container using the files you provided. On successful build, it starts the container. Which means, if all went well, your web container must be running on your machine. Using a browser, Go to remote_ip:5000 to verify that your app is actually running.