APIs & Networking

Learning Objectives

• Describe the relationship between a client and a server
• Define what an API is
• List potential uses for an API
• Use the Network Tab to inspect a network call in Chrome
• List the common HTTP response codes and recall what they mean
• List the common HTTP methods and describe an example of when they would be used

Pre-work

Copy and paste the command below into Slack

/prework APIs & Networking

Research

Task

Research the following questions:

1. What is a client?
2. What is a server?
3. What is an API?
4. What is the HTTP(S) protocol?

Research

Task

Research common HTTP status codes. What do 403, 404, 500, and 201 signify?

Explore

GitHub provides an API that allows programmatic access to their systems.

Task

Using the GitHub API documentation, find the URL and HTTP method required to:

1. List all repositories for a named organisation
2. Delete a named repository for a named user

Answer

Task

Write your response for each task in the prework thread on Slack.

Workshop

Intro (15 mins)

Elicit questions from the trainees about client/servers, APIs and HTTP

Explain that the internet we use is made up of networks, on top of which we have protocols (HTTP), on top of which we have programs (APIs)

Ask specific trainees to answer the following questions:

• What’s a client in the context of computing?

• What’s a server in the context of computing?

• What is an API?

  • What role does it play? Why is it important?
  • What might be some examples of an API?
  • What is an endpoint?

• What is HTTP?

  • What is a HTTP status code?
  • What is a HTTP method?

Draw out a diagram that shows the client/server nature of the internet

Explain what a HTTP request is

Use the Network Tab to inspect a network call in Chrome

Ask the trainees to find and explain the status codes for the request

Talk through some of the most common status codes

• 1XX is just informational
• 2XX is a success
• 3XX is a redirection
• 4XX is a client error
• 5XX is a server error

Explore the GitHub API.

Show the API reference and how to navigate it.

Request different attributes from this API using:

1. Chrome with the JSON Viewer add-on to pretty print the JSON response
2. curl with curl -v to view the headers

Consider also using curl to request a website (google.com) to show how the request is the same but it will return the html of the page.

Read the following as a group and complete the exercises

Endpoint Examples

For each HTTP method, URL and response code, you should provide a reasonable guess at the semantic meaning of the request and response from the server. You should write out this meaning in plain English. Remember, everything is built on convention, so there's no reason why:

POST www.example.com/cakes 201

Couldn't return a picture of a cat or launch a rocket. However, by convention, POST creates a resource, and 201 indicates a resource was successfully created. So we can infer:

"We're trying to add a new cake to example.com. The cake seems to have been successfully added."

Similarly, for:

GET www.example.com/students 404

"We're trying to get a list of students from example.com, but the resource that we're looking for could not be found. This could be because it's been deleted or because we're trying to request something that doesn't exist."

Ask the trainees to infer the meaning of these endpoints

1. POST www.example.com/students 400
2. GET www.example.com/students 200
3. GET www.example.com/students/alice 401
4. GET www.example.com/students 500
5. PUT www.example.com/students/alice 408
6. DELETE www.example.com/students/alice 429
7. GET www.example.com/learners 301
8. GET www.example.com/coaches 503
9. POST www.example.com/coaches 413
10. POST www.example.com/lessons 418

Finally, in pairs, ask the trainees to research the following information from the Github API

1. The username of the fifth-ever GitHub user
2. The number of followers for user kozyrkov
3. The location of the github organisation