Overview

MQTT Request Response (MRR) is a library that facilitates easy request-response handling over a MQTT connection.

Installing

go get -u github.com/joescharf/mrr

Usage

Import the library into your go code with: import "github.com/joescharf/mrr"

This library currently uses the Paho MQTT Client to connect to MQTT servers

package main
import (
    MQTT "github.com/eclipse/paho.MQTT.golang"
    "github.com/joescharf/mrr"
)

func main () {

    // example device structure for custom service injection:
    dev := &devInfo{}

    // Set MQTT connection options (paho mqtt client):
    options := MQTT.NewClientOptions()
    options.AddBroker(viper.GetString("MQTT.url"))
    options.ClientID = viper.GetString("MQTT.client_id")
    options.Username = viper.GetString("MQTT.username")
    options.Password = viper.GetString("MQTT.password")

    // Create MQTT client based on options:
    mqtt := MQTT.NewClient(options)

    // Establish MRR with mqtt client:
    mrr := mrr.New(mqtt)

    // Inject the devInfo{} service for handlers:
    mrr.Map(dev)

    // Connect to MQTT Server
    mrr.Connect()
    api.SetupRoutes(mrr)

    // Add some routes & subscribe to topics
    m.Add("device/cmd/helloworld", 0, HandleHelloWorld)
    m.Add("device/cmd/open", 0, HandleDeviceOpen)

}

// Simple handler that just takes a mrr.Conversation
func HandleHelloWorld(c mrr.Conversation) error {
    c.String(200, "Hello World!!")
    return nil
}

// Another handler that also depends on the devInfo struct,
// And returns some data on a JSON payload
func HandleDeviceOpen(c *mrr.Conversation, d *devInfo) error {
    settings := d.Open()

    payload := make(map[string]interface{})
    payload["id"] = 42
    payload["settings"] = settings

    c.JSON(200, payload)
}

Request

MRR expects a JSON encoded payload and will use the following fields to determine the response topic and QOS:

• _rt - Response Topic - (string)
• _rq - Response QOS - (int)

Example:

{"payload":{"option1":123, "option2":"test"}, "_rt":"response/topic", "_rq":1}

Default Response Topic

If the response topic fields are omitted, and a response is issued using the Conversation response methods (i.e. Conversation.String()) MRR will by default use the request topic + "_response" and will match the request's QOS:

Request topic: /device/cmd/helloworld Response topic: /device/cmd/helloworld/_response

Debug Topic:

You can specify a debug topic to which all responses are published:

mrr.SetDebugTopic("device/debug")

Handlers

Mrr uses Dependency Injection to resolve dependencies in a handler's argument list modeled after Macaron Custom Services

map a service as follows:

dev := &devInfo{}
mrr := mrr.New(mqttClient)
mrr.Map(dev)

qos := 0
mrr.Add("topic/goes/here", qos, SomeHandler))

func SomeHandler(ctx *macaron.Context, d *devInfo) {
    // Do stuff
}

Mrr injects the *mrr.Conversation service and is most commonly used service in your handlers:

func SomeHandler(c *mrr.Conversation) {