TDM 40200: Project 13 — 2023

Motivation: Containers are everywhere and a very popular method of packaging an application with all of the requisite dependencies. In the previous series of projects you’ve built a web application. While right now it may be easy to share and run your application with another individual, as time goes on and packages are updated, this is less and less likely to be the case. Containerizing your application ensures that the application will have the proper versions of the proper packages available in the proper location to run.

Context: This is a third of a series of projects focused on containers. The end goal of this series is to solidify the concept of a container, and enable you to "containerize" the application you’ve spent the semester building. You will even get the opportunity to deploy your containerized application!

Scope: Python, containers, UNIX

Learning Objectives

  • Improve your mental model of what a container is and why it is useful.

  • Use docker to build a container image.

  • Understand the difference between the ENTRYPOINT and CMD commands in a Dockerfile.

  • Use docker to run a container.

  • Use docker to run a shell inside of a container.

  • Use docker to containerize your dashboard application.

Make sure to read about, and use the template found here, and the important information about projects submissions here.

Questions

Question 1

The end goal of this project is to containerize your frontend and backend (into two different containers), and make sure that they can communicate with each other. The following is a rough sketch of the steps involved in this process, so you have a general idea what is next at each step.

  1. On Anvil, launch and connect to your VM with Docker pre-installed.

  2. Copy the frontend and backend code from Anvil to your VM.

  3. Create a Dockerfile (or, what can more generically be referred to as a Containerfile) for each of the frontend and backend.

  4. Use Docker to build a container image for each of the frontend and backend.

  5. Run the containers and make sure they can communicate with each other.

Ultimately, in the next project, you will be deploying your frontend and backend on a Kubernetes cluster, Geddes, behind a URL! So, at the very end of this project, we will ask you to verify your access to Geddes (which you’ve hopefully already been granted).

For this question, simply prep your working environment. Launch a SLURM job, prop up your VM, and ensure you can connect to it. The only thing you need to submit is a screenshot showing that you can connect to your VM.

  1. Get a terminal on Anvil — you may complete this part however you like. I like to use ssh to connect to Anvil from my local machine, however, you may also use ondemand.anvil.rcac.purdue.edu, launch a Jupyter Lab session, and launch a terminal from within Jupyter Lab. Either works equally as well as the other.

  2. Clear out any potential SLURM environment variables:

    for i in $(env | awk -F= '/SLURM/ {print $1}'); do unset $i; done;

  3. Launch SLURM job with 8 cores and about 16 GB of memory and get a shell into the given backend node:

    salloc -A cis220051 -p shared -n 8 -c 1 -t 04:00:00

    This job will only buy you 4 hours of time on the backend node. If you need more time, you will need to re-launch the job and change the arguments to salloc to request more time.

  4. Once you have a shell on the backend node, you will need to load the qemu module:

    module load qemu

  5. Next, copy over a fresh VM image to use for this project:

    cp /anvil/projects/tdm/apps/qemu/images/alpine.qcow2 $SCRATCH

    If at any time you want to start fresh, you can simply copy over a new VM image from /anvil/projects/tdm/apps/qemu/images/alpine.qcow2 to your $SCRATCH directory. Any changes you made to the previous image will be lost. This is good to know in case you want to try something crazy but are worried about breaking something! No need to worry, you can simply re-copy the VM image and start fresh anytime!

  6. The previous command will result in a new file called alpinel.qcow2 in your $SCRATCH directory. This is the VM image you will be using for this project. Now, you will need to launch the VM:

    qemu-system-x86_64 -vnc none,ipv4 -hda $SCRATCH/alpine.qcow2 -m 8G -smp 4 -enable-kvm -net nic -net user,hostfwd=tcp::2200-:22 &

    The last part of the previous command forwards traffic from port 2200 on Anvil to port 22 on the VM. If you receive an error about port 2200 being used, you can change this number to be any other unused port number. To find an unused port you can use a utility we have available to you.

    module use /anvil/projects/tdm/opt/core
module load tdm
find_port

    The find_port command will output an unused port for you to use. If, for example, it output 12345, then you would change the qemu command to the following.

    qemu-system-x86_64 -vnc none,ipv4 -hda $SCRATCH/alpine.qcow2 -m 8G -smp 4 -enable-kvm -net nic -net user,hostfwd=tcp::12345-:22 &

  7. After launching the VM, it will be running in the background as a process (this is what the & at the end of the command does). After about 15-30 seconds, the VM will be fully booted and you can connect to the VM from Anvil using the ssh command.

    ssh -p 2200 tdm@localhost -o StrictHostKeyChecking=no

    You may be prompted for a password for the user tdm. The password is simply purdue.

    If in a previous step you changed the port from say 2200 to something like 12345, you would change the ssh command accordingly.

  8. Finally, you should be connected to the VM and have a new shell running inside the VM, great! If you were successful, contents of the terminal should look very similar to the following.

Successfully connected to the VM
Figure 1. Successfully connected to the VM

If at any time you would like to "save" your progress and restart the project at a later date or time, you can do this by exiting the VM by running the exit command. Next, type jobs to find the qemu job number (probably 1). Finally, bring the qemu command to the foreground by typing either fg 1 or fg %1 followed by Ctrl+c. This will kill the VM and you can restart the project at a later date or time by simply using the same alpine.qcow2 image you used previously.
Items to submit

  • Code used to solve this problem.

  • Output from running the code.

Question 2

The next step is to copy the application /anvil/projects/tdm/etc/project13 and the database /anvil/projects/tdm/data/movies_and_tv/imdb.db to the VM (the database belongs in /home/tdm for this project). You can do this by using the scp command. scp uses ssh to securely transfer files between hosts. Remember, your VM is essentially another machine with open port 2200 for ssh (and scp). Figure out how to accomplish this task and then copy the application to the VM.

For this question, submit a screenshot of the following on the VM.

ls -la /home/tdm/project13/frontend
ls -la /home/tdm/project13/frontend/templates
ls -la /home/tdm/project13/backend/api
Items to submit

  • Code used to solve this problem.

  • Output from running the code.

Question 3

Create two Dockerfile files:

  • /home/tdm/project13/frontend/Dockerfile

  • /home/tdm/project13/backend/Dockerfile

As long as your images build and work correctly, you can use any base image you want. However, if you want the potential to get better/faster help (via Piazza), you should use the following base image: python:3.11.3-slim-bullseye (hub.docker.com/_/python/tags?page=1&name=3.11).

Here are some general guidelines for your Dockerfile files.

Frontend

  1. Use the python:3.11.3-slim-bullseye base image.

  2. Optionally use the WORKDIR command to set an internal (to the container) working directory /app.

  3. Copy the project13/frontend directory to the container, maybe in the /app workdir.

    You can use COPY . /app/ to copy the contents of the current directory (the directory where your Dockerfile lives) to the /app directory in the container.

  4. Install the required Python packages using pip.

    The following are the required Python packages: httpx and "fastapi[all]" (the double quotes are needed).

  5. Use EXPOSE to mark port 8888 as being used by the container.

  6. Use CMD or ENTRYPOINT to start the application.

    Use the --host argument to uvicorn and specify 0.0.0.0 to broadcast on all network interfaces.

    Since you are running your application from a different perspective than before, you will need to modify backend.endpoints:app to endpoints:app.

To build the image, you can use the following command.

cd /home/tdm/project13/frontend
docker build -t client .

Backend

  1. Use the python:3.11.3-slim-bullseye base image.

  2. Optionally use the WORKDIR command to set an internal (to the container) working directory /app.

  3. Copy the project13/backend directory to the container, maybe in the /app workdir.

    You can use COPY . /app/ to copy the contents of the current directory (the directory where your Dockerfile lives) to the /app directory in the container.

  4. Install the required Python packages using pip.

    The following are the required Python packages: httpx, "fastapi[all]", aiosql==7.2, and pydantic (the double quotes are needed).

  5. Use EXPOSE to mark port 7777 as being used by the container.

  6. Use VOLUME to specify a mount point inside the container. This will be where we will mount imdb.db so that our application can access the databse outside of the container. You should use the location /data.

  7. Use CMD or ENTRYPOINT to start the application.

    Use the --host argument to uvicorn and specify 0.0.0.0 to broadcast on all network interfaces.

    Since you are running your application from a different perspective than before, you will need to modify frontend.api.api:app to api.api:app.

To build the image, you can use the following command.

cd /home/tdm/project13/backend
docker build -t server .

For this question, include the contents of both of your Dockerfile files in your submission. If you make mistakes and need to modify your Dockerfile files in future questions, please update your submission for this question to be the functioning Dockerfile files.

Items to submit

  • Code used to solve this problem.

  • Output from running the code.

Question 4

Okay, awesome! You now have a couple of container images built and available on your VM, named client and server. You should be able to see these images by running the following command.

docker images

Okay, the next step is to run both of the containers, making sure that they can communicate. Our ultimate goal here is to run the following command and get the following results.

curl localhost:8888/people/nm0000148
results
<html>
    <head>
        <title>Harrison Ford</title>
        <script src="https://unpkg.com/[email protected]"></script>
    </head>
    <body>
        <div hx-target="this" hx-swap="outerHTML">
            <div>
                <label for="person_id">Person ID:</label> nm0000148
            </div>
            <div>
                <label for="name">Name:</label> Harrison Ford
            </div>
            <div>
                <label for="born">Born:</label> 1942
            </div>
            <div>
                <label for="died">Died:</label> None
            </div>
            <button hx-get="http://localhost:8888/people/nm0000148/update">Click to update</button>
        </div>
    </body>
</html>

We want those results because it demonstrates, in a single command, a variety of important things:

  1. We can access the frontend from the host machine (our VM).

  2. The frontend can access the backend.

  3. The backend can access the database.

This is enough evidence for us to say that our containers are communicating properly and are good enough to deploy (in the next project).

First thing is first. By default, Docker will add any running container to the bridge network. You can see this network listed by running the following.

docker network ls
output
NETWORK ID     NAME      DRIVER    SCOPE
6c21df067202   bridge    bridge    local
8acdd7457852   host      host      local
78e8c707cf0c   none      null      local

In theory, if you ran our frontend on the network on 0.0.0.0:8888 and the server on the same network at 0.0.0.0:7777, they should be able to communicate. However, with the way we have our frontend configured in endpoints.py, it will not work. We can’t just specify localhost and move on, instead, we would need to specify the actual IP address that the server is assigned on the bridge network. This is a bit of a pain, so we are going to create a new user network and run our containers on that network. This way, we can refer to other containers on the same network by their name rather than their IP address.

Let’s create this network. We can call it anything, however, we will call it tdm-net.

docker network create tdm-net

Upon success, you should see the network in your list of networks.

docker network ls
output
NETWORK ID     NAME      DRIVER    SCOPE
6c21df067202   bridge    bridge    local
8acdd7457852   host      host      local
78e8c707cf0c   none      null      local
40574054296e   tdm-net   bridge    local

Now, in order to run our client (frontend) and server (backend) on the tdm-net network, we just need to add --net tdm-net to our docker run commands. Great!

Frontend

The -p flag is used to specify port mappings. The format is host_port:container_port. In this case, we are mapping port 8888 on the host to port 8888 on the container.

It would be best to run this container using -dit, liked discussed in the previous project.

Don’t forget to run this container on the tdm-net network!

Backend

By default, we have endpoints.py setup to target our host with name server and port 7777. For this to continue to work, you will want to specify the name (which should be "server") of the server container using the --name argument with docker run.

The -p flag is used to specify port mappings. The format is host_port:container_port. In this case, we are mapping port 7777 on the host to port 7777 on the container.

It would be best to run this container using -dit, liked discussed in the previous project.

Use the --mount argument to mount the /home/tdm/imdb.db database outside of the container to /data/imdb.db inside of the container. Remember, in the Dockerfile for the server we specified this location, /data, as a mount point for the database. The type of the mount is bind. See here for more help.

Don’t forget to run this container on the tdm-net network!

General tips

You can see if your containers are running properly by running docker ps. You should see both containers running.

If you need to tear down a running container named server, in order to run a newer version of the container, you can run the following.

docker kill server # when you use the --name server argument, this name replaces the automatically created names
docker rm server # otherwise, when trying to run a new container with the name server, you will get an error

If curl localhost:8888/people/nm0000148 does not return what you expect — you can figure out what is going on by peeking at the frontend logs. You can do this by running the following.

docker logs client # this assumes that you used the --name client argument

If you want to "pop into" a running container, for example, the client, you can do so by running the following.

docker exec -it client /bin/bash

You may be wondering why we are using VOLUME and the --mount arguments. The reason why is that, if we were to include imdb.db inside the container, via something like COPY imdb.db /data/imdb.db, then the database would not be persisted in the case where the container is stopped or restarted. This is a bad situation. To avoid this, we simply mount the imdb.db database file outside of the container, on our persistent file system, to be available inside our container. Although inside the container the database appears to be located at /data/imdb.db, it actually lives /home/tdm/imdb.db on our host, the VM.

It is very common to have a need to persist some type of data. When this is needed, look towards using VOLUME and --mount.

For this question, simply include a screenshot showing the successful curl command and output.

Items to submit

  • Code used to solve this problem.

  • Output from running the code.

Question 5

Finally, please verify that you have access to two resources for the next project (even if you don’t plan on doing it). On the Purdue VPN or on a Purdue network, please visit the following links:

geddes.rcac.purdue.edu

  1. Login using your 2-factor authentication (Purdue Login on Duo Mobile).

  2. Click on the "geddes" name under the "Clusters" section.

  3. Click on the Projects/Namespaces under the "Cluster" tab on the left-hand side.

  4. Make sure you can see something like "The Data Mine - Students (tdm-students)". If you can, take a screenshot and you are done with this part. If you cannot, please email post in Piazza with your Purdue username and specify that you could not see the Geddes project.

geddes-registry.rcac.purdue.edu

  1. Login using your Purdue alias and regular password.

  2. If you get logged in successfully, take a screenshot and you are done with this part. If you cannot, please post in Piazza with your Purdue username and specify that you could not login to the Geddes registry.

Include both screenshots for this question. If you failed on one or more of the steps, please just specify that you posted in Piazza and you will receive full credit.

Items to submit

  • Code used to solve this problem.

  • Output from running the code.

Please make sure to double check that your submission is complete, and contains all of your code and output before submitting. If you are on a spotty internet connection, it is recommended to download your submission after submitting it to make sure what you think you submitted, was what you actually submitted.

In addition, please review our submission guidelines before submitting your project.