Function execution model in Azure - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the basic idea of the Azure Function execution model?

Azure Functions run small pieces of code in response to events without managing servers. The platform automatically handles scaling and execution.

beginner

How does Azure Functions handle scaling when many events occur?

Azure Functions automatically creates more instances of the function to handle increased events, scaling out to meet demand.

beginner

What triggers can start an Azure Function execution?

Triggers include HTTP requests, timers, messages in queues, changes in storage, and events from other Azure services.

intermediate

What happens if an Azure Function fails during execution?

Azure Functions can retry automatically based on configuration, and failures can be logged for troubleshooting.

intermediate

Explain the difference between Consumption Plan and Premium Plan in Azure Functions execution.

Consumption Plan runs functions on demand with automatic scaling and billing per execution. Premium Plan provides pre-warmed instances for faster start and supports more powerful hardware.

What automatically triggers an Azure Function?

A An event like an HTTP request or timer

B Manual server restart

C User login to Azure portal

D Scheduled OS updates

Azure Functions start automatically when an event such as an HTTP request or timer occurs.

How does Azure Functions scale when demand increases?

A It limits requests to one instance

B It queues requests until manual scaling

C It requires user to add servers

D It creates more function instances automatically

Azure Functions automatically scale out by creating more instances to handle increased events.

Which plan charges you only when your function runs?

A Premium Plan

B Consumption Plan

C Dedicated Plan

D Enterprise Plan

The Consumption Plan bills based on actual function executions, charging only when functions run.

What is a common trigger for Azure Functions?

A HTTP request

B Manual code deployment

C Azure portal login

D Database backup

HTTP requests are a common trigger that starts Azure Functions.

What happens if an Azure Function fails during execution?

A It deletes all data

B It shuts down the entire service

C It can retry automatically based on settings

D It requires manual restart every time

Azure Functions can be configured to retry automatically on failure to improve reliability.

Describe how Azure Functions execute code in response to events and how scaling works.

Think about how a waiter serves more tables when the restaurant gets busy.

Explain the difference between the Consumption Plan and Premium Plan for Azure Functions.

Consider paying for a taxi only when you ride versus renting a car all day.

Practice

1. What triggers an Azure Function to run?

easy

A. Only when the server restarts

B. Manual start from the Azure portal only

C. An event like an HTTP request or timer

D. When a user logs into Azure

Solution

1. Step 1: Understand Azure Function triggers

   Azure Functions start running when an event happens, such as an HTTP request or a timer firing.

2. Step 2: Eliminate incorrect options

   Manual starts, server restarts, or user logins are not triggers for Azure Functions.

3. Final Answer:

   An event like an HTTP request or timer -> Option C

4. Quick Check:

   Azure Functions run on events = A [OK]

Hint: Azure Functions run on events, not manual or login actions [OK]

Common Mistakes:

• Thinking functions run only manually
• Confusing server restart with trigger
• Assuming user login triggers function

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": "out", "schedule": "0 */5 * * * *"}]}

C. {"bindings": [{"type": "queueTrigger", "direction": "in", "queueName": "myqueue"}]}

D. {"bindings": [{"type": "httpOutput", "direction": "in"}]}

Solution

1. Step 1: Identify HTTP trigger binding

   The correct binding for an HTTP trigger uses "type": "httpTrigger", "direction": "in", and specifies methods like "get".

2. Step 2: Check other options for errors

   {"bindings": [{"type": "timerTrigger", "direction": "out", "schedule": "0 */5 * * * *"}]} is a timer trigger with wrong direction; {"bindings": [{"type": "queueTrigger", "direction": "in", "queueName": "myqueue"}]} is a queue trigger; {"bindings": [{"type": "httpOutput", "direction": "in"}]} uses invalid "httpOutput" type with wrong direction.

3. Final Answer:

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

4. Quick Check:

   HTTP trigger binding = {"bindings": [{"type": "httpTrigger", "direction": "in", "authLevel": "function", "methods": ["get"]}]} [OK]

Hint: HTTP triggers use "httpTrigger" type with "in" direction [OK]

Common Mistakes:

• Confusing trigger type with output binding
• Using wrong direction for triggers
• Mixing trigger types like queue or timer

3. Given this Azure Function code snippet triggered by an HTTP request:

module.exports = async function (context, req) {
  context.log('Function started');
  context.res = { status: 200, body: 'Hello ' + (req.query.name || 'world') };
};

What will be the HTTP response body if the request URL is http://example.com/api?name=Alice?

medium

A. "Error: name not found"

B. "Hello world"

C. "Hello undefined"

D. "Hello Alice"

Solution

1. Step 1: Understand the code logic

   The function reads the query parameter "name" from the request. If "name" exists, it uses it; otherwise, it defaults to "world".

2. Step 2: Apply the input URL query

   The URL has "name=Alice", so the response body becomes "Hello Alice".

3. Final Answer:

   "Hello Alice" -> Option D

4. Quick Check:

   Query name present = "Hello Alice" [OK]

Hint: Check if query parameter exists; else use default [OK]

Common Mistakes:

• Ignoring query parameters
• Assuming default always used
• Confusing response body with error

4. You deployed an Azure Function with a timer trigger but it never runs. Which of these is the most likely cause?

medium

A. The schedule expression in function.json is incorrect

B. The function app is running and healthy

C. The HTTP trigger is missing

D. The function code has no output binding

Solution

1. Step 1: Check timer trigger configuration

   If the schedule expression is wrong, the timer never fires, so the function won't run.

2. Step 2: Evaluate other options

   Running app is good; missing HTTP trigger is irrelevant for timer trigger; output binding absence doesn't stop trigger execution.

3. Final Answer:

   The schedule expression in function.json is incorrect -> Option A

4. Quick Check:

   Wrong schedule = no timer run [OK]

Hint: Check cron schedule syntax for timer triggers [OK]

Common Mistakes:

• Confusing trigger types
• Ignoring schedule format errors
• Assuming output binding affects trigger

5. You want an Azure Function to process messages from a queue and then send results to a database without writing extra code to connect to the database. Which feature should you use to achieve this?

hard

A. Manually call the database API from the function

B. Use an output binding for the database

C. Use a timer trigger to poll the database

D. Write database connection code inside the function

Solution

1. Step 1: Understand output bindings

   Output bindings let functions send data to other services automatically without extra connection code.

2. Step 2: Match requirement to feature

   Using an output binding for the database allows sending results directly after processing queue messages.

3. Final Answer:

   Use an output binding for the database -> Option B

4. Quick Check:

   Output binding sends data without extra code [OK]

Hint: Output bindings connect services without manual code [OK]

Common Mistakes:

• Thinking manual code is always needed
• Confusing triggers with output bindings
• Using timer triggers incorrectly