Azure IoT Hub trigger for Azure Functions

The following example shows a C# function that logs the message body of the event hub trigger.

[FunctionName("EventHubTriggerCSharp")]
public static void Run([EventHubTrigger("samples-workitems", Connection = "EventHubConnectionAppSetting")] string myEventHubMessage, ILogger log)
{
    log.LogInformation($"C# function triggered to process a message: {myEventHubMessage}");
}

To get access to event metadata in function code, bind to an EventData object (requires a using statement for Microsoft.Azure.EventHubs). You can also access the same properties by using binding expressions in the method signature. The following example shows both ways to get the same data:

[FunctionName("EventHubTriggerCSharp")]
public static void Run(
    [EventHubTrigger("samples-workitems", Connection = "EventHubConnectionAppSetting")] EventData myEventHubMessage,
    DateTime enqueuedTimeUtc,
    Int64 sequenceNumber,
    string offset,
    ILogger log)
{
    log.LogInformation($"Event: {Encoding.UTF8.GetString(myEventHubMessage.Body)}");
    // Metadata accessed by binding to EventData
    log.LogInformation($"EnqueuedTimeUtc={myEventHubMessage.SystemProperties.EnqueuedTimeUtc}");
    log.LogInformation($"SequenceNumber={myEventHubMessage.SystemProperties.SequenceNumber}");
    log.LogInformation($"Offset={myEventHubMessage.SystemProperties.Offset}");
    // Metadata accessed by using binding expressions in method parameters
    log.LogInformation($"EnqueuedTimeUtc={enqueuedTimeUtc}");
    log.LogInformation($"SequenceNumber={sequenceNumber}");
    log.LogInformation($"Offset={offset}");
}

To receive events in a batch, make string or EventData an array.

[FunctionName("EventHubTriggerCSharp")]
public static void Run([EventHubTrigger("samples-workitems", Connection = "EventHubConnectionAppSetting")] EventData[] eventHubMessages, ILogger log)
{
    foreach (var message in eventHubMessages)
    {
        log.LogInformation($"C# function triggered to process a message: {Encoding.UTF8.GetString(message.Body)}");
        log.LogInformation($"EnqueuedTimeUtc={message.SystemProperties.EnqueuedTimeUtc}");
    }
}

The following example shows an event hub trigger binding in a function.json file and a C# script function that uses the binding. The function logs the message body of the event hub trigger.

The following examples show Event Hubs binding data in the function.json file.

Version 2.x and higher

{
  "type": "eventHubTrigger",
  "name": "myEventHubMessage",
  "direction": "in",
  "eventHubName": "MyEventHub",
  "connection": "myEventHubReadConnectionAppSetting"
}

Version 1.x

{
  "type": "eventHubTrigger",
  "name": "myEventHubMessage",
  "direction": "in",
  "path": "MyEventHub",
  "connection": "myEventHubReadConnectionAppSetting"
}

Here's the C# script code:

using System;

public static void Run(string myEventHubMessage, TraceWriter log)
{
    log.Info($"C# function triggered to process a message: {myEventHubMessage}");
}

To get access to event metadata in function code, bind to an EventData object (requires a using statement for Microsoft.Azure.EventHubs). You can also access the same properties by using binding expressions in the method signature. The following example shows both ways to get the same data:

#r "Microsoft.Azure.EventHubs"

using System.Text;
using System;
using Microsoft.ServiceBus.Messaging;
using Microsoft.Azure.EventHubs;

public static void Run(EventData myEventHubMessage,
    DateTime enqueuedTimeUtc,
    Int64 sequenceNumber,
    string offset,
    TraceWriter log)
{
    log.Info($"Event: {Encoding.UTF8.GetString(myEventHubMessage.Body)}");
    log.Info($"EnqueuedTimeUtc={myEventHubMessage.SystemProperties.EnqueuedTimeUtc}");
    log.Info($"SequenceNumber={myEventHubMessage.SystemProperties.SequenceNumber}");
    log.Info($"Offset={myEventHubMessage.SystemProperties.Offset}");

    // Metadata accessed by using binding expressions
    log.Info($"EnqueuedTimeUtc={enqueuedTimeUtc}");
    log.Info($"SequenceNumber={sequenceNumber}");
    log.Info($"Offset={offset}");
}

To receive events in a batch, make string or EventData an array:

public static void Run(string[] eventHubMessages, TraceWriter log)
{
    foreach (var message in eventHubMessages)
    {
        log.Info($"C# function triggered to process a message: {message}");
    }
}

The following example shows an event hub trigger binding in a function.json file and a JavaScript function that uses the binding. The function reads event metadata and logs the message.

The following examples show Event Hubs binding data in the function.json file.

Version 2.x and higher

{
  "type": "eventHubTrigger",
  "name": "myEventHubMessage",
  "direction": "in",
  "eventHubName": "MyEventHub",
  "connection": "myEventHubReadConnectionAppSetting"
}

Version 1.x

{
  "type": "eventHubTrigger",
  "name": "myEventHubMessage",
  "direction": "in",
  "path": "MyEventHub",
  "connection": "myEventHubReadConnectionAppSetting"
}

Here's the JavaScript code:

module.exports = function (context, myEventHubMessage) {
    context.log('Function triggered to process a message: ', myEventHubMessage);
    context.log('EnqueuedTimeUtc =', context.bindingData.enqueuedTimeUtc);
    context.log('SequenceNumber =', context.bindingData.sequenceNumber);
    context.log('Offset =', context.bindingData.offset);

    context.done();
};

To receive events in a batch, set cardinality to many in the function.json file, as shown in the following examples.

Version 2.x and higher

{
  "type": "eventHubTrigger",
  "name": "eventHubMessages",
  "direction": "in",
  "eventHubName": "MyEventHub",
  "cardinality": "many",
  "connection": "myEventHubReadConnectionAppSetting"
}

Version 1.x

{
  "type": "eventHubTrigger",
  "name": "eventHubMessages",
  "direction": "in",
  "path": "MyEventHub",
  "cardinality": "many",
  "connection": "myEventHubReadConnectionAppSetting"
}

Here's the JavaScript code:

module.exports = function (context, eventHubMessages) {
    context.log(`JavaScript eventhub trigger function called for message array ${eventHubMessages}`);

    eventHubMessages.forEach((message, index) => {
        context.log(`Processed message ${message}`);
        context.log(`EnqueuedTimeUtc = ${context.bindingData.enqueuedTimeUtcArray[index]}`);
        context.log(`SequenceNumber = ${context.bindingData.sequenceNumberArray[index]}`);
        context.log(`Offset = ${context.bindingData.offsetArray[index]}`);
    });

    context.done();
};

The following example shows an event hub trigger binding in a function.json file and a Python function that uses the binding. The function reads event metadata and logs the message.

The following examples show Event Hubs binding data in the function.json file.

{
  "type": "eventHubTrigger",
  "name": "event",
  "direction": "in",
  "eventHubName": "MyEventHub",
  "connection": "myEventHubReadConnectionAppSetting"
}

Here's the Python code:

import logging
import azure.functions as func


def main(event: func.EventHubEvent):
    logging.info(f'Function triggered to process a message: {event.get_body().decode()}')
    logging.info(f'  EnqueuedTimeUtc = {event.enqueued_time}')
    logging.info(f'  SequenceNumber = {event.sequence_number}')
    logging.info(f'  Offset = {event.offset}')

    # Metadata
    for key in event.metadata:
        logging.info(f'Metadata: {key} = {event.metadata[key]}')

The following example shows an Event Hub trigger binding which logs the message body of the Event Hub trigger.

@FunctionName("ehprocessor")
public void eventHubProcessor(
  @EventHubTrigger(name = "msg",
                  eventHubName = "myeventhubname",
                  connection = "myconnvarname") String message,
       final ExecutionContext context )
       {
          context.getLogger().info(message);
 }

In the Java functions runtime library, use the EventHubTrigger annotation on parameters whose value would come from Event Hub. Parameters with these annotations cause the function to run when an event arrives. This annotation can be used with native Java types, POJOs, or nullable values using Optional<T>.

In C# class libraries, use the EventHubTriggerAttribute attribute.

The attribute's constructor takes the name of the event hub, the name of the consumer group, and the name of an app setting that contains the connection string. For more information about these settings, see the trigger configuration section. Here's an EventHubTriggerAttribute attribute example:

[FunctionName("EventHubTriggerCSharp")]
public static void Run([EventHubTrigger("samples-workitems", Connection = "EventHubConnectionAppSetting")] string myEventHubMessage, ILogger log)
{
    ...
}

For a complete example, see Trigger - C# example.

Attributes are not supported by C# Script.

Attributes are not supported by JavaScript.

Attributes are not supported by Python.

From the Java functions runtime library, use the EventHubTrigger annotation on parameters whose value would come from Event Hub. Parameters with these annotations cause the function to run when an event arrives. This annotation can be used with native Java types, POJOs, or nullable values using Optional<T>.

Default

You can use the following parameter types for the triggering Event Hub:

• string
• byte[]
• POCO
• EventData - The default properties of EventData are provided in the for the Microsoft.Azure.EventHubs namespace.

Additional types

Apps using the 5.0.0 or higher version of the Event Hub extension use the EventData type in Azure.Messaging.EventHubs instead of the one in Microsoft.Azure.EventHubs namespace. This version drops support for the legacy Body type in favor of the following types:

• EventBody

Default

You can use the following parameter types for the triggering Event Hub:

• string
• byte[]
• POCO
• EventData - The default properties of EventData are provided in the for the Microsoft.Azure.EventHubs namespace.

Additional types

Apps using the 5.0.0 or higher version of the Event Hub extension use the EventData type in Azure.Messaging.EventHubs instead of the one in Microsoft.Azure.EventHubs namespace. This version drops support for the legacy Body type in favor of the following types:

• EventBody

Refer to the Java trigger example for details.

Refer to the Javascript trigger example for details.

Refer to the Python trigger example for details.