RabbitMQ output binding for Azure Functions overview

A C# function can be created by using one of the following C# modes:

• In-process class library: Compiled C# function that runs in the same process as the Functions runtime.
• Isolated worker process class library: Compiled C# function that runs in a worker process that's isolated from the runtime. Isolated worker process is required to support C# functions running on LTS and non-LTS versions .NET and the .NET Framework.
• C# script: Used primarily when you create C# functions in the Azure portal.

        [Function(nameof(RabbitMQFunction))]
        [RabbitMQOutput(QueueName = "destinationQueue", ConnectionStringSetting = "RabbitMQConnection")]
        public static string Run([RabbitMQTrigger("queue", ConnectionStringSetting = "RabbitMQConnection")] string item,
            FunctionContext context)
        {
            var logger = context.GetLogger(nameof(RabbitMQFunction));

            logger.LogInformation(item);

            var message = $"Output message created at {DateTime.Now}";
            return message;
        }

[FunctionName("RabbitMQOutput")]
[return: RabbitMQ(QueueName = "outputQueue", ConnectionStringSetting = "rabbitMQConnectionAppSetting")]
public static string Run([TimerTrigger("0 */5 * * * *")] TimerInfo myTimer, ILogger log)
{
    log.LogInformation($"C# Timer trigger function executed at: {DateTime.Now}");
    return $"{DateTime.Now}";
}

[FunctionName("RabbitMQOutput")]
public static async Task Run(
[RabbitMQTrigger("sourceQueue", ConnectionStringSetting = "rabbitMQConnectionAppSetting")] string rabbitMQEvent,
[RabbitMQ(QueueName = "destinationQueue", ConnectionStringSetting = "rabbitMQConnectionAppSetting")]IAsyncCollector<string> outputEvents,
ILogger log)
{
     // send the message
    await outputEvents.AddAsync(JsonConvert.SerializeObject(rabbitMQEvent));
}

namespace Company.Function
{
    public class TestClass
    {
        public string x { get; set; }
    }
    public static class RabbitMQOutput{
        [FunctionName("RabbitMQOutput")]
        public static async Task Run(
        [RabbitMQTrigger("sourceQueue", ConnectionStringSetting = "rabbitMQConnectionAppSetting")] TestClass rabbitMQEvent,
        [RabbitMQ(QueueName = "destinationQueue", ConnectionStringSetting = "rabbitMQConnectionAppSetting")]IAsyncCollector<TestClass> outputPocObj,
        ILogger log)
        {
            // send the message
            await outputPocObj.AddAsync(rabbitMQEvent);
        }
    }
}

The following Java function uses the @RabbitMQOutput annotation from the Java RabbitMQ types to describe the configuration for a RabbitMQ queue output binding. The function sends a message to the RabbitMQ queue when triggered by a TimerTrigger every 5 minutes.

@FunctionName("RabbitMQOutputExample")
public void run(
@TimerTrigger(name = "keepAliveTrigger", schedule = "0 */5 * * * *") String timerInfo,
@RabbitMQOutput(connectionStringSetting = "rabbitMQConnectionAppSetting", queueName = "hello") OutputBinding<String> output,
final ExecutionContext context) {
    output.setValue("Some string");
}

The following example shows a RabbitMQ output binding in a function.json file and a JavaScript function that uses the binding. The function reads in the message from an HTTP trigger and outputs it to the RabbitMQ queue.

Here's the binding data in the function.json file:

{
    "bindings": [
        {
            "type": "httpTrigger",
            "direction": "in",
            "authLevel": "function",
            "name": "input",
            "methods": [
                "get",
                "post"
            ]
        },
        {
            "type": "rabbitMQ",
            "name": "outputMessage",
            "queueName": "outputQueue",
            "connectionStringSetting": "rabbitMQConnectionAppSetting",
            "direction": "out"
        }
    ]
}

Here's JavaScript code:

module.exports = async function (context, input) {
    context.bindings.outputMessage = input.body;
};

The following example shows a RabbitMQ output binding in a function.json file and a Python function that uses the binding. The function reads in the message from an HTTP trigger and outputs it to the RabbitMQ queue.

Here's the binding data in the function.json file:

{
    "scriptFile": "__init__.py",
    "bindings": [
        {
            "authLevel": "function",
            "type": "httpTrigger",
            "direction": "in",
            "name": "req",
            "methods": [
                "get",
                "post"
            ]
        },
        {
            "type": "http",
            "direction": "out",
            "name": "$return"
        },​​
        {
            "type": "rabbitMQ",
            "name": "outputMessage",
            "queueName": "outputQueue",
            "connectionStringSetting": "rabbitMQConnectionAppSetting",
            "direction": "out"
        }
    ]
}

In _init_.py:

import azure.functions as func

def main(req: func.HttpRequest, outputMessage: func.Out[str]) -> func.HttpResponse:
    input_msg = req.params.get('message')
    outputMessage.set(input_msg)
    return 'OK'

Attributes

Both in-process and isolated worker process C# libraries use the attribute to define the function. C# script instead uses a function.json configuration file.

The attribute's constructor takes the following parameters:

        [Function(nameof(RabbitMQFunction))]
        [RabbitMQOutput(QueueName = "destinationQueue", ConnectionStringSetting = "RabbitMQConnection")]
        public static string Run([RabbitMQTrigger("queue", ConnectionStringSetting = "RabbitMQConnection")] string item,
            FunctionContext context)
        {

[FunctionName("RabbitMQOutput")]
public static async Task Run(
[RabbitMQTrigger("SourceQueue", ConnectionStringSetting = "TriggerConnectionString")] string rabbitMQEvent,
[RabbitMQ("DestinationQueue", ConnectionStringSetting = "OutputConnectionString")]IAsyncCollector<string> outputEvents,
ILogger log)
{
    ...
}

Annotations

The RabbitMQOutput annotation allows you to create a function that runs when a RabbitMQ message is created.

The annotation supports the following configuration settings:

See the output binding example for more detail.

Configuration

The following table explains the binding configuration properties that you set in the function.json file.

When you're developing locally, add your application settings in the local.settings.json file in the Values collection.

The parameter type supported by the RabbitMQ trigger depends on the Functions runtime version, the extension package version, and the C# modality used.

For a complete example, see C# example.

Use the following parameter types for the output binding:

• byte[] - If the parameter value is null when the function exits, Functions doesn't create a message.
• string - If the parameter value is null when the function exits, Functions doesn't create a message.
• POJO - If the parameter value isn't formatted as a Java object, an error will be received.

The queue message is available via context.bindings.<NAME> where <NAME> matches the name defined in function.json. If the payload is JSON, the value is deserialized into an object.

Refer to the Python example.