Understanding Azure Function App — Queue Trigger vs Timer Trigger | 2024

4 min readJul 6, 2024

→ This article is dedicated to understanding the serverless functions of Azure Cloud.

→ Azure Cloud has various types of function applications such as HTTP trigger, Queue trigger, Durable function trigger (i.e. for creating orchestrator), timer trigger, etc.

→ We have been recently working on creating a queue trigger and timer trigger in a production-specific application. Let us understand in layman’s language.

What is Queue Trigger?

→ In today’s time we are using Microservice based architecture to keep application light and independent maintainable

→ The simple idea is whenever some message is in a queue a serverless function triggers i.e. some function executes.

→ By message we mean data eg. objects.

→ Think like there are two apps — App A, and App B all independent microservices.

→ Now if we send some message to App A to a queue, some logic in its connected function will run App B.

How Queue Trigger Works?

Queue: Think of a queue as a list where messages wait to be processed.
Trigger: When a new message is added to the list, the trigger acts like a doorbell ringing.
Function: This ringing (trigger) starts a function (a piece of code) to handle what needs to be done.

Why is Queue Trigger used?

Automation: It saves you from manually checking for new messages and starting processes.
Scalability: It can handle many messages and tasks without you needing to do anything extra.
Reliability: It ensures that every message gets processed, even if it arrives when you’re not around.

Example Scenario 1: Processing Orders

Scenario: Imagine an online store where customers place orders.

Step 1: A customer places an order.
Step 2: The order details are added as a message to a queue (think of it as a to-do list).
Step 3: Azure Queue trigger detects this new message in the queue.
Step 4: It automatically runs code to process the order — like confirming it, updating inventory, or sending a receipt email.

Example Scenario 2: Image Processing

Scenario: A company that allows users to upload images for editing.

Step 1: A user uploads an image for editing.
Step 2: A message with the image details is placed in a queue.
Step 3: Azure Queue trigger sees this new message.
Step 4: It automatically runs a code to process the image — such as applying filters or resizing it.

What is a Timer Trigger?

→ The timer trigger is the same as the queue trigger with one difference. Instead of running at the same time, it will run at some interval eg. 1 minute or 1 day.

→ Assuming the function app is set to run after every 30 seconds

→ Usually, the message remains in the queue and after 30 seconds all queue messages will process at once.

Why is Timer Trigger used?

→ If your application runs a lot of serverless applications i.e. function apps. It will lead to more RU consumption simply meaning more cost.

→ Some areas in the application that can be run in bulk:

Example Scenario 1: Daily Backup

Scenario: A company needs to back up its data every night.

Step 1: Set the timer trigger to 2 AM every day.
Step 2: At 2 AM, the timer trigger activates.
Step 3: It automatically runs code that backs up the company’s data to a secure location.

Example Scenario 2: Sending Reminders

Scenario: An app sends weekly reminders to users.

Step 1: Configure the timer trigger for every Monday at 9 AM.
Step 2: On Mondays at 9 AM, the timer trigger kicks in.
Step 3: It runs a code to send reminder emails or notifications to users.

Example Scenario 3: Regular Data Cleanup

Scenario: A service that needs to clean up old records every month.

Step 1: Schedule the timer trigger for the first day of each month.
Step 2: On the first of the month, the timer trigger activates.
Step 3: It runs a code to delete or archive old data, keeping the system clean and efficient.

How Timer Trigger Works: Simplified

Timer Trigger: Think of it as setting an alarm clock.
Schedule: You choose the time or interval for the alarm.
Action: When the alarm goes off, it runs a specific task or function automatically.

Conclusion:

We now understand the difference between a Queue trigger and a Timer trigger. Both have different use cases.

For instant code execution, we use the Queue trigger and for code executing in some time or interval we use the Timer trigger.

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