[Windows] Dockerを使用してMosquittoでMQTTサーバを構築する際に別コンテナにloalhostで接続できるようにする #Docker

TL;DR

Mosquittoを使ってMQTTサーバを立てた際にコンテナ間でlocalhostで接続できないかと調査
docker-composeでnetwork_modeを「host」にすることでホスト端末と同じIPアドレスにすることで可能とわかった
GO言語のpaho.mqtt.golangライブラリを使って接続テストを実施

環境

Windows10
Docker Desktop 2.2.0.3
docker-composeはDocker Desktopに同梱
visual studio code 1.42.1[拡張機能Remote - Containers使用]
Mosquitto 1.6.9

完成したリポジトリ

ファイル

docker-compose.tml

version: '3'

services:
    api:
        build:
            dockerfile: Dockerfile
            context: ./containers/api
        volumes:
            - ./containers/api/src:/go/api
        tty: true
        network_mode: "host"
    mqtt:
        build:
            dockerfile: Dockerfile
            context: ./containers/mqtt
        ports: 
            - "1883:1883"
        volumes:
            - mosquittodata:/mosquitto/data
            - mosquittolog:/mosquitto/log
        tty: true
        network_mode: "host"

volumes:
    mosquittodata:
        driver: "local"
    mosquittolog:
        driver: "local"

apiコンテナとmqttコンテナにnetwork_modeで「host」を設定することでホスト端末と同じIPアドレスを使用する

main.go

package main

import (
    "crypto/tls"
    "flag"
    "fmt"
    "os"
    "strconv"
    "time"

    MQTT "github.com/eclipse/paho.mqtt.golang"
)

// Que Strut.
type Que struct {
    Server    string
    Sendtopic string
    Resvtopic string
    Qos       int
    Retained  bool
    Clientid  string
    Username  string
    Password  string
    Client    MQTT.Client
    Callback  MQTT.MessageHandler
}

// Connect func .
func (q *Que) Connect() error {
    connOpts := MQTT.NewClientOptions().AddBroker(q.Server).SetClientID(q.Clientid).SetCleanSession(true)
    if q.Username != "" {
        connOpts.SetUsername(q.Username)
        if q.Password != "" {
            connOpts.SetPassword(q.Password)
        }
    }
    tlsConfig := &tls.Config{InsecureSkipVerify: true, ClientAuth: tls.NoClientCert}
    connOpts.SetTLSConfig(tlsConfig)

    client := MQTT.NewClient(connOpts)
    if token := client.Connect(); token.Wait() && token.Error() != nil {
        return token.Error()
    }
    q.Client = client

    if q.Callback != nil {
        if token := q.Client.Subscribe(q.Resvtopic, byte(q.Qos), q.Callback); token.Wait() && token.Error() != nil {
            return token.Error()
        }
        fmt.Printf("[MQTT] Subscribe to %s\n", q.Sendtopic)
    }

    fmt.Printf("[MQTT] Connected to %s\n", q.Server)

    return nil
}

// Publish func .
func (q *Que) Publish(message string) error {
    if q.Client != nil {
        token := q.Client.Publish(q.Sendtopic, byte(q.Qos), q.Retained, message)
        if token == nil {
            return token.Error()
        }
        fmt.Printf("[MQTT] Sent to %s\n", q.Sendtopic)
    }

    return nil
}

// SetSubscribe - .
func (q *Que) SetSubscribe(callback MQTT.MessageHandler) error {
    if callback != nil {
        if token := q.Client.Subscribe(q.Resvtopic, byte(q.Qos), callback); token.Wait() && token.Error() != nil {
            return token.Error()
        }
        fmt.Printf("[MQTT] Subscribe to %s\n", q.Sendtopic)
    }

    return nil
}

func onMessageReceived(client MQTT.Client, message MQTT.Message) {
    fmt.Printf("[MQTT] Received to %s [Received Message: %s]\n", message.Topic(), message.Payload())
}

func main() {
    hostname, _ := os.Hostname()

    server := flag.String("server", "tcp://localhost:1883", "The full URL of the MQTT server to connect to")
    sendtopic := flag.String("sendtopic", "MQTT/Client/Update/TEST", "Topic to publish the messages on")
    resvtopic := flag.String("resvtopic", "MQTT/+/Update/#", "Topic to publish the messages on")
    qos := flag.Int("qos", 0, "The QoS to send the messages at")
    retained := flag.Bool("retained", false, "Are the messages sent with the retained flag")
    clientid := flag.String("clientid", hostname+strconv.Itoa(time.Now().Second()), "A clientid for the connection")
    username := flag.String("username", "", "A username to authenticate to the MQTT server")
    password := flag.String("password", "", "Password to match username")
    flag.Parse()

    q := &Que{
        Server:    *server,
        Sendtopic: *sendtopic,
        Resvtopic: *resvtopic,
        Qos:       *qos,
        Retained:  *retained,
        Clientid:  *clientid,
        Username:  *username,
        Password:  *password,
        Callback:  onMessageReceived,
    }

    err := q.Connect()
    if err != nil {
        fmt.Println(err)
        os.Exit(2)
    }

    if err := q.SetSubscribe(onMessageReceived); err != nil {
        fmt.Println(err)
        os.Exit(2)
    }

    for {
        time.Sleep(5000 * time.Millisecond)
        if err := q.Publish("test massage"); err != nil {
            fmt.Println(err)
            os.Exit(2)
        }
    }
}

MQTTサーバの接続先に「tcp://localhost:1883」を指定しているが、お互いのコンテナがnetwork_modeで「host」を設定しているので接続できる

MQTT接続実行結果

実行結果

root@docker-desktop:/go/api# go run main.go 
go: downloading github.com/eclipse/paho.mqtt.golang v1.2.0
go: downloading golang.org/x/net v0.0.0-20200320220750-118fecf932d8
[MQTT] Subscribe to MQTT/Client/Update/TEST
[MQTT] Connected to tcp://localhost:1883   
[MQTT] Subscribe to MQTT/Client/Update/TEST
[MQTT] Sent to MQTT/Client/Update/TEST
[MQTT] Received to MQTT/Client/Update/TEST [Received Message: test massage]
[MQTT] Sent to MQTT/Client/Update/TEST
[MQTT] Received to MQTT/Client/Update/TEST [Received Message: test massage]
[MQTT] Sent to MQTT/Client/Update/TEST
[MQTT] Received to MQTT/Client/Update/TEST [Received Message: test massage]

まとめ

MQTTサーバをDockerで構築する際にサーバをlocalhostにできないかな、というので調査していてnetwork_mode使えばできることがわかったので記事にしてみました。