Microsoft Azure provides many ways to trigger Azure functions, including schedules and events. These triggers act as the entry point for an Azure Function, determining how and when it will run. An understanding of these concept have a vital role when preparing for the “PL-400 Microsoft Power Platform Developer” examination.
Scheduled Triggers Using Cron Expressions
A timer trigger launches an Azure function at specific times. It uses a scheduling pattern called Cron syntax which allows for much more complex schedules than are conceivable through simple interval timings.
For instance, if you want to schedule an Azure function to run at 9 AM every day, your Cron expression in the function.json file would look like this:
{
"bindings": [
{
"name": "myTimer",
"type": "timerTrigger",
"direction": "in",
"schedule": "0 0 9 * * *"
}
]
}
This configures your function to run at 9 AM daily, as dictated by the Cron expression (0 0 9 * * *).
Event-Driven Triggers
Event-driven triggers launch Azure functions in response to specific events. Azure offers a multitude of triggers tied to different services, such as the Blob trigger, HTTP trigger, and Cosmos DB trigger.
For example, to create an HTTP-triggered function, the function.json file would look like this:
{
"bindings": [
{
"authLevel": "function",
"type": "httpTrigger",
"direction": "in",
"name": "req",
"methods": [
"get",
"post"
]
},
{
"type": "http",
"direction": "out",
"name": "res"
}
]
}
This sets up an Azure function that triggers whenever an HTTP GET or POST request is sent to the function’s endpoint.
Scheduled vs. Event-Driven Triggers
| Trigger Type | Use Case | Example |
|---|---|---|
| Scheduled | When you need to run a function at specific intervals | Backing up a database every day at a specific time |
| Event-Driven | When you need to execute a function in response to an event | Resizing an image after it’s uploaded to a blob storage |
In conclusion, Azure Functions provides a flexible serverless platform for executing event-driven and scheduled tasks. Projects might use a combination of scheduled and event-triggers according to their needs. For the PL-400 Microsoft Power Platform Developer exam, it is crucial to understand how to configure these triggers within your Azure Functions to structure your applications effectively.
Practice Test
True or False: Azure Functions can be triggered by specific events such as changes in data or responding to web requests.
- True
- False
Answer: True
Explanation: Azure Functions is capable of being event-driven, meaning it can start running in response to a variety of occurrences, including changes in data, web requests, etc.
Which Azure service can be used as an event source to trigger Azure Functions?
- A. Azure Traffic Manager
- B. Azure SQL Database
- C. Azure Stream Analytics
- D. Azure Logic Apps
Answer: D. Azure Logic Apps
Explanation: Azure Logic Apps can be used to trigger Azure Functions in response to specific events, such as receiving a new email, a new tweet, etc.
True or False: Azure Functions cannot be scheduled to run at specific times.
- True
- False
Answer: False
Explanation: Azure Functions can be scheduled to run at specific times using time-based triggers.
Single Select: Which trigger type in Azure Functions makes the function run on a schedule?
- A. Blob trigger
- B. Timer trigger
- C. Queue trigger
- D. Event Hub trigger
Answer: B. Timer trigger
Explanation: Timer trigger in Azure Functions causes the function to run on a schedule.
True or False: In Azure Functions, an Event Hub triggered function cannot respond to events delivered by Azure Event Hubs.
- True
- False
Answer: False
Explanation: An Event Hub triggered function in Azure can indeed respond to events delivered by Azure Event Hubs.
Single Select: Which of the following languages can be used to write serverless Azure functions?
- A. Swift
- B. Python
- C. Ruby
- D. PHP
Answer: B. Python
Explanation: Azure Functions support several programming languages such as C#, Java, JavaScript, PowerShell, and Python.
What type of trigger in Azure Functions reacts to events within a storage blob?
- A. Queue trigger
- B. Blob trigger
- C. Event Grid trigger
- D. HTTPS trigger
Answer: B. Blob trigger
Explanation: A Blob Trigger in Azure Functions reacts to any changes to blobs in the Azure storage account.
True or False: In Azure Functions, a function cannot be triggered by an external system’s API call.
- True
- False
Answer: False
Explanation: Azure Functions can be triggered by an HTTP request, which could be from an API call of an external system.
Single Select: Which of these is not a binding type in Azure Functions?
- A. Blob
- B. Service Bus
- C. Twilio
- D. Telegram
Answer: D. Telegram
Explanation: Blob, Service Bus, and Twilio are all binding types in Azure Functions, but Telegram is not.
True or False: With Azure Functions, you can write event-driven functions that execute your code in response to events, such as timer elapsed.
- True
- False
Answer: True
Explanation: Yes, with Azure Functions, you can write serverless functions that execute your code in response to a variety of events, including timers, HTTPs requests, and more.
Single Select: Which of the following protocols are not supported by Azure HTTP trigger?
- A. GET
- B. POST
- C. DELETE
- D. CONNECT
Answer: D. CONNECT
Explanation: CONNECT method is not supported by Azure HTTP trigger. Azure HTTP triggers allow functions to respond to HTTP methods like GET, POST, DELETE, etc.
True or False: Azure Functions can’t interface with other Azure services.
- True
- False
Answer: False
Explanation: Azure Functions can interface with other Azure services and can be integrated in complex configurations with them.
Single Select: When Azure Function events are defined by data changes, which type of trigger is in use?
- A. Timer
- B. HTTP
- C. Blob Storage
- D. Queue
Answer: C. Blob Storage
Explanation: When events are defined by data changes in Azure, then Blob Storage triggers are used.
True or False: Azure functions can only be activated by event triggers.
- True
- False
Answer: False
Explanation: Apart from event triggers, Azure functions can also be triggered on a schedule (Timer Triggers) or by a direct HTTP call (HTTP Triggers).
Single Select: Which of the following is a trigger type defined in Azure Logic Apps?
- A. Recurrence
- B. Queue
- C. Blob
- D. All of the above
Answer: A. Recurrence
Explanation: Recurrence is a trigger type in Azure Logic Apps which sets off the function based on a recurring schedule or time-interval. Queue and Blob are trigger types of Azure Functions, not Logic Apps.
Interview Questions
What is the purpose of function triggers in Azure Functions?
Function triggers in Azure Functions are used to execute the function in response to specific types of events.
What is a scheduled trigger in Azure Functions?
A scheduled trigger in Azure Functions allows a function to be run based on a defined schedule, using the CRON expressions for scheduling.
What is an event-driven trigger in Azure Functions?
An event-driven trigger in Azure Functions execute the function based on specific event occurrences such as a new message on a Queue, a blob upload, or an Http Request.
How do you configure a scheduled trigger in Azure Functions?
A scheduled trigger in Azure Functions is configured by defining a schedule in the function.json file with a CRON expression under the “bindings” section.
How can one define a CRON expression for scheduling Azure Functions?
A CRON expression is a string of six fields that represent a schedule in time. The fields are {second} {minute} {hour} {day} {month} {day-of-week}. All fields are required and time is UTC.
How does Azure Functions support event-driven triggers?
Azure Functions has built-in support for triggers from various services including Blob storage, Event Hubs, Cosmos DB, HTTP requests, and more.
What does the eventGridEvent parameter represent in an Event Grid trigger function in Azure Functions?
This parameter represents the data associated with the Event Grid event.
What happens if an Azure function triggered by an event fails or times out?
The Azure Functions runtime tries to automatically retry the operation when a function that responds to a trigger fails.
How can we determine the scale of an Azure function with triggers?
The scale that function apps can reach is determined by the trigger that they’re based on. For example, a queue trigger function might scale based on the length of the queue, while a time trigger function would not scale.
Is it possible to create functions with multiple triggers in Azure Functions?
No, it’s not possible to associate multiple triggers with a single Azure Function. Each function is associated with a single trigger.
How is Trigger Binding Data used in Azure Functions?
Trigger Binding Data includes specific details about the trigger event such as the Id of a Queue message or the Path of a Blob, which is provided to the function during execution.
Is it possible to manually trigger an Azure Function?
Yes, HTTP triggered functions can be invoked manually by making an HTTP request.
Can a single Azure function be scheduled to run at multiple times?
Yes, by defining multiple CRON expressions, a single function can be scheduled to run at various times.
How long can a single execution of an Azure function last?
The maximum execution time of an Azure function depends on the hosting tier. For the Consumption tier, it’s 5 minutes by default and can be increased up to 10 minutes. For Premium and App Service plan, it can be unrestricted.
How do we configure an Azure Function to be triggered by Cosmos DB change feed?
You would need to specify Cosmos DB as the trigger in function.json file and provide the necessary connection parameters such as database name, collection name etc.
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