Mqtt of NLog custom target

NLog yes .Net in Most popular Logging open source projects ( One of ), it flexible 、 free 、 Open source

Official support file 、 The Internet (TCP、UDP)、 database 、 Console Equal output

Community support Elastic、Seq Wait for the log platform to output

Real time log requirements

In specific scenarios such as the industrial Internet of things Get logs in real time Information

Commonly used in the field of industrial Internet of things is mqtt agreement

Then we use NLog  Customize a Target, Output log to MqttServer

Web adopt Mqtt(websocket) Get logs in real time , and No The passage of tradition WebApi polling journal

NLog Customize Target

1. The official documentation describes how to customize Target, Can be obtained a string Log message , Unable to get structured message

2. Need to use custom Field To do this part of the job

/// <summary>
/// Additional field details
/// </summary>
[NLogConfigurationItem]
public class Field
{
    /// <summary>
    /// Name of additional field
    /// </summary>
    [RequiredParameter]
    public string Name { get; set; }

    /// <summary>
    /// Value with NLog <see cref="NLog.Layouts.Layout"/> rendering support
    /// </summary>
    [RequiredParameter]
    public Layout Layout { get; set; }

    /// <summary>
    /// Custom type conversion from default string to other type
    /// </summary>
    /// <remarks>
    /// <see cref="System.Object"/> can be used if the <see cref="Layout"/> renders JSON
    /// </remarks>
    public Type LayoutType { get; set; } = typeof(string);

    /// <inheritdoc />
    public override string ToString()
    {
        return $"Name: {Name}, LayoutType: {LayoutType}, Layout: {Layout}";
    }
}

1. rewrite Write Method

protected override void Write(LogEventInfo logEvent)
{
    //default fields
    Dictionary<string, object> logDictionary = new()
    {
        { "timestamp", logEvent.TimeStamp },
        { "level", logEvent.Level.Name },
        { "message", RenderLogEvent(Layout, logEvent) }
    };
    //customer fields
    // Here it is treated as a string , There's room for optimization 
    foreach (var field in Fields)
    {
        var renderedField = RenderLogEvent(field.Layout, logEvent);

        if (string.IsNullOrWhiteSpace(renderedField))
            continue;

        logDictionary[field.Name] = renderedField;
    }

    SendTheMessage2MqttBroker(JsonConvert.SerializeObject(logDictionary));
}

Use

The following will be used Nlog.Target.MQTT, Demonstrated through web Real-time view Application's journal .

1. establish WebApi project

2. quote NLog.Target.MQTT

1. The configuration file

<extensions>
    <add assembly="NLog.Web.AspNetCore"/>
    <!--<add assembly="NLog.Targets.MQTT"/>-->
    <add assembly="NLog.Targets.MQTT"/>
</extensions>
<!-- the targets to write to -->
<targets>
    <!-- MQTT Target  -->
    <target xsi:type="MQTT" name="mqtt" host="localhost" port="1883" username="UserName"  password="Password" topic="log"
            layout="${longdate}|${event-properties:item=EventId_Id:whenEmpty=0}|${level:uppercase=true}|${logger}|${message} ${exception:format=tostring}|url: ${aspnet-request-url}|action: ${aspnet-mvc-action}|${callsite}" >
        <field name="machine" layout="${machinename}" />
        <field name="processid" layout="${processid}" />
        <field name="threadname" layout="${threadname}" />
        <field name="logger" layout="${logger}" />
        <field name="callsite" layout="${callsite-linenumber}" />
        <field name="url" layout="${aspnet-request-url}" />
        <field name="action" layout="${aspnet-mvc-action}" />
        <field name="level" layout="${level:uppercase=true}" />
        <field name="message" layout="${message}" />
        <field name="exception" layout="${exception:format=toString}" />
    </target>
</targets>
<!-- rules to map from logger name to target -->
<rules>
    <logger name="*" minlevel="Trace" writeTo="mqtt" />
</rules>

1. To configure MQTTServer and NLog

// ...
// NLog: Setup NLog for Dependency injection
builder.Logging.ClearProviders();
builder.Logging.SetMinimumLevel(Microsoft.Extensions.Logging.LogLevel.Trace);
builder.Host.UseNLog();

//AddHostedMqttServer
builder.Services.AddHostedMqttServer(mqttServer =>
    {
        mqttServer.WithoutDefaultEndpoint();
    })
    .AddMqttConnectionHandler()
    .AddConnections();

//Config Port
builder.WebHost.UseKestrel(option =>
{
    option.ListenAnyIP(1883, l => l.UseMqtt());
    option.ListenAnyIP(80);
});
var app = builder.Build();

// ...
//UseStaticFiles html js etc.
app.UseStaticFiles();
app.UseRouting();

//Websocket Mqtt
app.UseEndpoints(endpoints =>
{
    //MqttServerWebSocket
    endpoints.MapConnectionHandler<MqttConnectionHandler>("/mqtt", options =>
    {
        options.WebSockets.SubProtocolSelector = MqttSubProtocolSelector.SelectSubProtocol;
    });
});
// ...

1. Web Connect MqttServer

// ...    
<script src="./jquery.min.js"></script>
<script src="./mqtt.min.js"></script>
<script src="./vue.js"></script>
// ...

var client = mqtt.connect('ws://' + window.location.host + '/mqtt', options);
client.on('connect',
    function() {
        client.subscribe('log',
            function(err) {
                if (!err) {
                    console.log("subed!");
                } else {
                    alert("subed error!");
                }
            });
    });
client.on('message',
    function(topic, message) {
        if (topic === 'log') {
            if (app.logs.length > 50)
                app.logs.length = 0;
            app.logs.unshift($.parseJSON(message.toString()));
        }
    });
// ...

1. Output log

// ...  
_logger.LogDebug("LogDebug!");
_logger.LogError(new Exception("Exception Message!"), "LogError!");

//new thread output log after 500ms
Thread thread = new Thread(ThreadProc);
thread.Name = "My Thread";
thread.Start();
// ...

1. Real-time view log visit /index.html

8. It can also be done through Mqtt Client subscription log  

Source code and related links

[1] Github：https://github.com/iioter/NLog.Targets.MQTT

[2] Gitee：https://gitee.com/iioter/NLog.Targets.MQTT

[3]  IoTGateway-Doc：http://iotgateway.net/blog/NLog

[4] NLog Customize Target：https://github.com/NLog/NLog/wiki/How-to-write-a-custom-target

You can pay attention to me if you are interested