Homework 05

Due Date: Tuesday, Feb 28, by 11:00am CST

Undone (The Sweater Container)

Scenario: The API you developed for the ISS positional and velocity data (in homework 04) is a great start! But, there are many improvements we could make in order to make the API more useful. And, we can use some smart software engineering & design strategies to make our app more portable.

PART 1

Start a new directory for this homework (called homework05) and copy the Flask app from homework 04 into this new directory. If it isn’t already, please name the file iss_tracker.py. Add the following new features to the Flask app:

• Add query parameters offset and limit to the /epochs route. The offset query parameter should offset the start point by an integer. For example, offset=0 would begin printing at the first Epoch, offset=1 would begin printing at the second Epoch, etc. The limit query parameter controls how many results are returned. For example limit=10 would return 10 Epochs, limit=100 would return 100 Epochs, etc. Putting them together, the route /epochs?limit=20&offset=50 would return Epochs 51 through 70 (20 total).

• Add a /help route that returns a human readable string to the screen. The string should give brief descriptions of all available routes (plus their methods) for your API. The returned text should be similar output to a command line tool. For example, look at the output returned when you type git --help or docker --help

• Add a /delete-data route that deletes everything from the in-memory dictionary of ISS data. Make sure to use a DELETE method for this route. After curling the /delete-data route, other routes (e.g /epochs) should return no data.

• Add a /post-data route that restores the data to the ISS dictionary by performing a new GET request using the Python requests library. Although inside this route you will be performing a GET request, the route itself should only accept a POST method.

After completing the above, your app should have the following routes:

Route	Method	What it should do
/	GET	Return entire data set
/epochs	GET	Return list of all Epochs in the data set
/epochs?limit=int&offset=int	GET	Return modified list of Epochs given query parameters
/epochs/<epoch>	GET	Return state vectors for a specific Epoch from the data set
/epochs/<epoch>/speed	GET	Return instantaneous speed for a specific Epoch in the data set (math required!)
/help	GET	Return help text (as a string) that briefly describes each route
/delete-data	DELETE	Delete all data from the dictionary object
/post-data	POST	Reload the dictionary object with data from the web

Please use defensive programming strategies for your routes. Assume we will try to break your routes by doing naughty things like sending non-integers into your query parameters, or querying routes after deleting all the data. Your routes should use exception handling to catch and handle these bad requests.

PART 2

Write a Dockerfile to containerize your iss_tracker.py script. The image should contain the same version of Python as you are using on the Jetream VM, plus any other dependencies (i.e. non-standard Python libraries). The default command should launch the Flask app in a standard way. Build an image with the version tag similar to username/iss_tracker:hw05 and push it to your namespace in Docker Hub.

PART 3

You’ve written the code, you’ve containerized it, now you need to tell other people how to use it. The problem is that you are not quite sure how people will want to use this code. In the real world, developers and end users will find your repo, and some of them will want to use your pre-built Docker image to run the code, while others will want to start from your Dockerfile and build their own image. The challenge is to write a README that caters to all audiences.

Write a README with the standard sections from previous homeworks: there should be a descriptive title, there should be a high level description of the project, there should be concise descriptions of the main files within, and you should be using Markdown styles and formatting to your advantage.

The section of the README with run instructions will be a little more challenging. Please make sure to include instructions to (at a minimum):

• Pull and use your existing image from Docker Hub

• Build a new image from your Dockerfile

• Run the containerized Flask app being careful to map ports correctly

• Give example API query commands and expected outputs in code blocks

Finally, your README should also have a section to describe the ISS data. Please give enough information for others to understand what data they are seeing and what it means (including units). Please cite the data appropriately as well.

What to Turn In

A sample Git repository may contain the following new files after completing homework 05:

my-coe332-hws/
├── homework01
│   └── ...
├── ...
├── homework04
│   └── ...
├── homework05
│   ├── Dockerfile
│   ├── iss_tracker.py       # please use this name for your file
│   └── README.md
└── README.md

Additional Resources

• NASA Data Set

• Please find us in the class Slack channel if you have any questions!