Enable.Azure.WebJobs.Extensions.Mqtt

// TODO Adapt code to follow: https://github.com/Azure/azure-webjobs-sdk/wiki/Creating-custom-input-and-output-bindings.

MQTT bindings for Azure Functions and WebJobs.

MQTT is a messaging system designed for for high-latency or unreliable networks. This project adds WebJobs bindings for MQTT messaging with similar semantics to how you bind to Azure Queues or Azure Service Bus Queues.

Simple example

Here's a basic example of bindings. Just as with [Queue] bindings, the bindings will automatically JSON-serialized the user-defined type, Payload, to and from the native type, MqttMessage. SendEvents() will emit one message to the event hub. Trigger() will listen on one event and emit a new event with an incremented counter.

Note this sample is binding against EventHubs without ever referring directly to the event hubs SDK.

using Enable.Azure.WebJobs.Mqtt;

namespace Enable.Azure.WebJobs.Extensions.MQTT.Sample
{
    public class BasicTest
    {
        public class Payload
        {
            public int Counter { get; set; }
        }

        public static void SendEvents([Mqtt("TopicName")] out Payload input)
        {
            input = new Payload { Counter = 0 };
        }

        public static void Trigger(
            [MqttTrigger("TopicName")] Payload input,
            [Mqtt("TopicName")] out Payload output)
        {
            input.Counter++;
            output = input;
        }
    }
}

Configuration

Provide the MQTT connection settings to the initial JobHostConfiguration object

var config = new JobHostConfiguration{
    DashboardConnectionString = "UseDevelopmentStorage=true",
    StorageConnectionString = "UseDevelopmentStorage=true"
};


var mqttConfiguration = new MqttConfiguration
{
    Host = "{Enter hostname here}",
    Port = 1234,
    UserName = "{Enter username here}",
    Password = "{Enter password here}"
}

config.UseEventHub(eventHubConfig);

var host = new JobHost(config);

Receiving events

Use the [MqttTrigger] attribute to listen on topics.

Examples of bindings to receive one event:

void Handle([MqttTrigger("TopicName")] MqttMessage message);
void Handle([MqttTrigger("TopicName")] string message); // As a string.
void Handle([MqttTrigger("TopicName")] byte[] message); // As a byte array.
void Handle([MqttTrigger("TopicName")] MyUserType message); // As a PCOC, via JSON serialization.

// TODO Support receiving a batch of events. This is important if you need to handle a high volume of events.

Sending Events

Use the [Mqtt] attribute to send messages out to an MQTT topic.

Binding via out parameters to send a single message:

void Send([Mqtt("TopicName")] out MqttMessage message);
void Send([Mqtt("TopicName")] out string message);
void Send([Mqtt("TopicName")] out MyUserType message);

Binding via an out-array to send multiple events

void SendBatch([Mqtt("TopicName")] out MqttMessage[] output);
void SendBatch([Mqtt("TopicName")] out string[] output);
void SendBatch([Mqtt("TopicName")] out MyUserType[] output);

Binding via collector interfaces:

Task SendBatchAsync([Mqtt("TopicName")] IAsyncCollector<MqttMessage> output);
void SendBatch([Mqtt("TopicName")] ICollector<MqttMessage> output);

Task SendBatchAsync([Mqtt("TopicName")] IAsyncCollector<string> output);
void SendBatch([Mqtt("TopicName")] ICollector<MyUserType> output);