NLog自定义Target之MQTT

NLog是.Net中最流行的日志记录开源项目(之一)，它灵活、免费、开源

官方支持文件、网络(Tcp、Udp)、数据库、控制台等输出

社区支持Elastic、Seq等日志平台输出

实时日志需求

在工业物联网等特定场景下需要实时获取日志信息

工业物联网领域常用的是mqtt协议

那我们就使用NLog 自定义一个Target，将日志输出到MqttServer

Web通过Mqtt(websocket)实时获取日志，而不是传统的通过WebApi轮询日志

NLog自定义Target

1. 官方文档介绍了如何自定义Target，可以获取到一串日志消息，无法获取结构化消息
2. 需要时用使用自定义Field来完成这部分工作

/// 

/// Additional field details
/// 
[NLogConfigurationItem]
public class Field
{
    /// 

    /// Name of additional field
    /// 
    [RequiredParameter]
    public string Name { get; set; }

    /// 

    /// Value with NLog  rendering support
    /// 
    [RequiredParameter]
    public Layout Layout { get; set; }

    /// 

    /// Custom type conversion from default string to other type
    /// 
    /// 
    ///  can be used if the  renders JSON
    /// 
    public Type LayoutType { get; set; } = typeof(string);

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

3. 重写Write方法

protected override void Write(LogEventInfo logEvent)
{
    //default fields
    Dictionary logDictionary = new()
    {
        { "timestamp", logEvent.TimeStamp },
        { "level", logEvent.Level.Name },
        { "message", RenderLogEvent(Layout, logEvent) }
    };

    //customer fields
    //这里都处理为字符串了，有优化空间
    foreach (var field in Fields)
    {
        var renderedField = RenderLogEvent(field.Layout, logEvent);

        if (string.IsNullOrWhiteSpace(renderedField))
            continue;

        logDictionary[field.Name] = renderedField;
    }

    SendTheMessage2MqttBroker(JsonConvert.SerializeObject(logDictionary));
}

使用

下面将使用Nlog.Target.MQTT,演示通过web实时查看应用程序的日志。

1. 创建WebApi项目
2. 引用NLog.Target.MQTT

3. 配置文件

4. 配置MQTTServer和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("/mqtt", options =>
    {
        options.WebSockets.SubProtocolSelector = MqttSubProtocolSelector.SelectSubProtocol;
    });
});
// ...

5. Web连接MqttServer

// ...    



// ...

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()));
        }
    });
// ...

6. 输出日志

// ...  
_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();
// ...

7. 实时查看日志
   访问index.html

8. 通过Mqtt客户端订阅日志
   

源码

在这里NLog.Targets.MQTT:https://github.com/iioter/NLog.Targets.MQTT

相关链接

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

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

[3] NLog自定义Target:https://github.com/NLog/NLog/wiki/How-to-write-a-custom-target

交流

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