Azure Functions Trigger Types

Azure Functions provide a variety of trigger types that allow your functions to execute in response to different events. Understanding these triggers is crucial for designing efficient and event-driven serverless applications.

Common Trigger Types

HTTP Trigger

Executes your function in response to an HTTP request. This is ideal for building web APIs, microservices, or webhooks.

Example Usage: REST APIs, webhook endpoints.

HttpRequest

Timer Trigger

Executes your function on a schedule, defined by a CRON expression. Useful for background tasks, scheduled jobs, or recurring operations.

Example Usage: Daily data cleanup, scheduled reports.

TimerInfo

Blob Trigger

Executes your function when a blob is added, updated, or deleted in an Azure Storage Blob container. Perfect for processing file uploads or changes.

Example Usage: Image resizing upon upload, data processing from new files.

CloudBlockBlob

Queue Trigger

Executes your function when a new message arrives in an Azure Storage Queue. Great for decoupling applications and processing work items asynchronously.

Example Usage: Order processing, background task queuing.

QueueMessage

Service Bus Trigger

Executes your function in response to messages on an Azure Service Bus Queue or Topic. Offers advanced messaging features like sessions, dead-lettering, and transactions.

Example Usage: Enterprise messaging, reliable message processing.

ServiceBusReceivedMessage

Event Hubs Trigger

Executes your function when events are received by an Azure Event Hub. Designed for high-throughput, real-time data streaming scenarios.

Example Usage: IoT data ingestion, real-time analytics.

EventData

Cosmos DB Trigger

Executes your function in response to changes in an Azure Cosmos DB collection. Useful for reacting to data modifications or implementing change feed processing.

Example Usage: Real-time dashboard updates, data synchronization.

Document

Configuring Triggers

Triggers are typically configured in the function.json file for each function. The configuration specifies the trigger type, its settings, and any associated input/output bindings.

Here's an example of a function.json for an HTTP trigger:

                
{
  "scriptFile": "run.py",
  "bindings": [
    {
      "authLevel": "function",
      "type": "httpTrigger",
      "direction": "in",
      "name": "req",
      "methods": [
        "get",
        "post"
      ]
    },
    {
      "type": "http",
      "direction": "out",
      "name": "res"
    }
  ]
}

Each trigger has specific properties that need to be configured, such as connection strings, queue names, CRON expressions, or event hub paths. Refer to the official Azure Functions documentation for detailed configuration options for each trigger type.