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Build A Container Image

The target for your first image is a simple web app written in Go. Go compiles to standalone binaries which are well suited to producing smaller container images.

Run the following snippet in the terminal to download the source code for your app which is contained in a single file.

mkdir -p ~/environment/echo-frontend/src/1.0/
wget https://raw.githubusercontent.com/${EKS_GITHUB_USER}/eks-demos/main/echo-frontend/src/1.0/main.go \
  -O ~/environment/echo-frontend/src/1.0/main.go

Open ~/environment/echo-frontend/src/1.0/main.go in Cloud9 IDE to review the code.

You can launch your app from the terminal session using the following.

go run ~/environment/echo-frontend/src/1.0/main.go

Your webserver app will tie up this first Cloud9 terminal session until its process is stopped. Leave the webserver running and select Window -> New Terminal to make a second terminal session available.

In the second terminal session, use the curl command to send an HTTP GET request to the webserver as follows.

curl http://localhost:8080

As you do so, observe that the recorded value of hostname is synonymous with the value of ec2IP in this execution context.

NOTE the use of Instance Metadata (169.254.169.254) within the source code is an indication that your app is tailor-made for deployment on EC2 instances.

Return to the first terminal session and use ctrl+c to quit the app and recover your command prompt.

Each Cloud9 instance has the Docker daemon installed with a set of images pre-loaded. Remove them as they are not required.

for i in $(docker ps -q); do docker kill $i; done
docker system prune --all --force

Run the following snippet in the terminal to download the Dockerfile for your app.

wget https://raw.githubusercontent.com/${EKS_GITHUB_USER}/eks-demos/main/echo-frontend/src/1.0/Dockerfile \
  -O ~/environment/echo-frontend/src/1.0/Dockerfile

Open ~/environment/echo-frontend/src/1.0/Dockerfile in Cloud9 IDE to review the code.

Build the Docker image from the Cloud9 terminal then run the newly containerized app.

docker build -t echo-frontend:1.0 ~/environment/echo-frontend/src/1.0/ # build the container image
docker images                                                          # see what you produced
docker ps                                                              # nothing running ...
container_id=$(docker run --detach --rm -p 8081:80 echo-frontend:1.0)  # ask docker to instantiate a single container as a background process
docker ps                                                              # ... now one container running

Invoke the webserver from inside the container.

docker exec -it ${container_id} curl http://localhost:80

Invoke the webserver from outside the container.

curl http://localhost:8081

The response for the two previous curl requests are identical because it is the same operation, only the perspective is different. Observe that the recorded values of hostname and ec2IP have now diverged. This is because your app is now containerized and running inside its own namespace.

We are done with running images in Docker for now so stop the container (which will be terminated because you ran it with the --rm flag).

docker stop ${container_id}

Next: Main Menu | Push Container Image To ECR