Functions with HTTP triggers in Azure - Mini Project: Build & Apply

Create an Azure Function with HTTP Trigger

📖 Scenario: You are building a simple Azure Function that responds to HTTP requests. This function will greet users by name when they send a request with their name.

🎯 Goal: Build an Azure Function with an HTTP trigger that reads a name parameter from the query string and returns a greeting message.

📋 What You'll Learn

Create a function named HttpTriggerFunction with an HTTP trigger.

Configure the function to accept GET requests.

Read the name parameter from the query string.

Return a greeting message including the name parameter.

💡 Why This Matters

🌍 Real World

Azure Functions with HTTP triggers are commonly used to build serverless APIs that respond to web requests without managing servers.

💼 Career

Understanding how to create and configure HTTP-triggered Azure Functions is essential for cloud developers and DevOps engineers working with serverless architectures.

1

Create the function.json file with HTTP trigger

Create a file named function.json with an HTTP trigger binding. Set the authLevel to function and allowed methods to ["get"].

Azure

{
  // Define the HTTP trigger binding here
  // Your code here
}

Hint

The function.json file defines the trigger and output bindings for your Azure Function.

2

Create the function code file with the main function

Create a file named __init__.py and define a function named main that accepts parameters req and context. Import func from azure.functions.

Azure

import azure.functions as func

# Define the main function with parameters req and context
# Your code here

Hint

The main function is the entry point for your Azure Function.

3

Read the 'name' parameter from the HTTP request

Inside the main function, read the name parameter from the query string using req.params.get('name'). Store it in a variable called name.

Azure

import azure.functions as func

def main(req: func.HttpRequest, context: func.Context) -> func.HttpResponse:
    # Get the 'name' parameter from the query string
    # Your code here

Hint

Use req.params.get('name') to get the query parameter.

4

Return a greeting message in the HTTP response

Complete the main function to return an HttpResponse with the message "Hello, {name}!" if name is provided. If name is missing, return "Please pass a name on the query string." with status code 400.

Azure

import azure.functions as func

def main(req: func.HttpRequest, context: func.Context) -> func.HttpResponse:
    name = req.params.get('name')
    # Return greeting or error message
    # Your code here

Hint

Use an if statement to check if name exists and return the appropriate HttpResponse.

Practice

1. What does an HTTP trigger do in an Azure Function?

easy

A. It stores data for the function to use later.

B. It runs the function when it receives a web request.

C. It schedules the function to run at specific times.

D. It sends emails automatically when triggered.

Solution

1. Step 1: Understand the role of HTTP triggers

   HTTP triggers start a function when a web request is received.

2. Step 2: Compare with other triggers

   Other triggers like timers schedule functions, but HTTP triggers respond to web calls.

3. Final Answer:

   It runs the function when it receives a web request. -> Option B

4. Quick Check:

   HTTP trigger = runs on web request [OK]

Hint: HTTP trigger means function runs on web request [OK]

Common Mistakes:

• Confusing HTTP trigger with timer trigger
• Thinking HTTP trigger stores data
• Assuming HTTP trigger sends emails

2. Which of the following is the correct way to define an HTTP trigger in an Azure Function's function.json file?

easy

A. "bindings": [{ "type": "httpTrigger", "direction": "in", "authLevel": "function", "methods": ["get"] }]

B. "bindings": [{ "type": "timerTrigger", "direction": "in", "schedule": "0 */5 * * * *" }]

C. "bindings": [{ "type": "blobTrigger", "direction": "in", "path": "samples-workitems/{name}" }]

D. "bindings": [{ "type": "queueTrigger", "direction": "in", "queueName": "myqueue-items" }]

Solution

1. Step 1: Identify HTTP trigger binding

   The correct binding type for HTTP trigger is "httpTrigger" with direction "in".

2. Step 2: Check authLevel and methods

   authLevel "function" and methods ["get"] are valid properties for HTTP triggers.

3. Final Answer:

   "bindings": [{ "type": "httpTrigger", "direction": "in", "authLevel": "function", "methods": ["get"] }] -> Option A

4. Quick Check:

   HTTP trigger binding = type "httpTrigger" [OK]

Hint: HTTP trigger binding uses type "httpTrigger" in function.json [OK]

Common Mistakes:

• Using timerTrigger or blobTrigger instead of httpTrigger
• Missing authLevel property
• Wrong direction value

3. Given this Azure Function code snippet, what will be the HTTP response body when a GET request is sent?

import logging
import azure.functions as func

def main(req: func.HttpRequest) -> func.HttpResponse:
    name = req.params.get('name')
    if not name:
        return func.HttpResponse("Please pass a name", status_code=400)
    return func.HttpResponse(f"Hello, {name}!")

medium

A. Hello, Alice!

B. Hello, World!

C. Error 404 Not Found

D. Please pass a name

Solution

1. Step 1: Check request parameter handling

   The function looks for 'name' in query parameters. If missing, it returns a 400 response with message "Please pass a name".

2. Step 2: Analyze given request

   The question states a GET request is sent but does not mention a 'name' parameter, so name will be None.

3. Final Answer:

   Please pass a name -> Option D

4. Quick Check:

   No name param = "Please pass a name" response [OK]

Hint: If no 'name' param, function returns error message [OK]

Common Mistakes:

• Assuming default name is 'Alice' or 'World'
• Ignoring the 400 status code response
• Confusing request body with query parameters

4. You have this function.json snippet for an HTTP triggered Azure Function:

{
  "bindings": [
    {
      "type": "httpTrigger",
      "direction": "in",
      "authLevel": "anonymous",
      "methods": ["post"]
    },
    {
      "type": "httpTrigger",
      "direction": "out"
    }
  ]
}

What is the error in this configuration?

medium

A. The output binding type should be "http" not "httpTrigger".

B. The output binding type "http" is invalid; it should be "httpResponse".

C. The output binding type "http" is invalid; it should be "httpTrigger".

D. The output binding type should be "http" with direction "in".

Solution

1. Step 1: Review input and output bindings

   The input binding uses "httpTrigger" which is correct for HTTP triggers.

2. Step 2: Identify output binding error

   The output binding incorrectly uses "httpTrigger"; it should be "http" with direction "out" for HTTP responses.

3. Final Answer:

   The output binding type should be "http" not "httpTrigger". -> Option A

4. Quick Check:

   HTTP output binding = type "http" [OK]

Hint: HTTP output binding uses type "http", not "httpTrigger" [OK]

Common Mistakes:

• Using "httpTrigger" as output binding type incorrectly
• Confusing input and output binding types
• Setting wrong direction for output binding

5. You want to create an Azure Function with an HTTP trigger that only allows calls with a function key (authLevel set to "function") and responds with JSON containing a greeting message using the "name" query parameter and returns a JSON error message if the "name" query parameter is missing. Which of the following code snippets correctly implements this behavior?

hard

A. import azure.functions as func

def main(req: func.HttpRequest) -> func.HttpResponse:
name = req.params.get('name')
if not name:
return func.HttpResponse('Missing name', status_code=400)
return func.HttpResponse(f'{"message": "Hello, {name}!"}', mimetype='application/json')

B. import azure.functions as func

def main(req: func.HttpRequest) -> func.HttpResponse:
name = req.get_json().get('name')
if not name:
return func.HttpResponse('Missing name', status_code=400)
return func.HttpResponse(f'Hello, {name}!')

C. import azure.functions as func
import json

def main(req: func.HttpRequest) -> func.HttpResponse:
name = req.params.get('name')
if not name:
return func.HttpResponse(json.dumps({'error': 'Missing name'}), status_code=400, mimetype='application/json')
return func.HttpResponse(json.dumps({'message': f'Hello, {name}!'}), mimetype='application/json')

D. import azure.functions as func
import json

def main(req: func.HttpRequest) -> func.HttpResponse:
name = req.params.get('name')
return func.HttpResponse(json.dumps({'message': f'Hello, {name}!'}), mimetype='text/plain')

Solution

1. Step 1: Check authLevel and input handling

   authLevel "function" is set in function.json (not shown), so code must handle query param 'name' safely.

2. Step 2: Validate JSON response and error handling

   import azure.functions as func import json def main(req: func.HttpRequest) -> func.HttpResponse: name = req.params.get('name') if not name: return func.HttpResponse(json.dumps({'error': 'Missing name'}), status_code=400, mimetype='application/json') return func.HttpResponse(json.dumps({'message': f'Hello, {name}!'}), mimetype='application/json') uses json.dumps to create proper JSON for both error ({'error': 'Missing name'}) and success ({'message': f'Hello, {name}!'}), with mimetype='application/json' and status_code=400 for errors.

3. Step 3: Compare other options

   A returns plain text error and f-string JSON-like string; C uses get_json() instead of params; D uses text/plain mimetype.

4. Final Answer:

   Uses json.dumps and mimetype='application/json' for both success and error JSON responses. -> Option C

5. Quick Check:

   json.dumps for JSON error and success with application/json mimetype [OK]

Hint: Use json.dumps and mimetype 'application/json' for JSON responses [OK]

Common Mistakes:

• Returning JSON as plain string without json.dumps
• Using wrong mimetype for JSON
• Reading JSON body instead of query parameters