从BackgroundWorker转向TPL以获取日志记录类

时间:2015-08-26 14:58:00

标签: c# multithreading task-parallel-library backgroundworker

我目前在旧Backgroundworker类的视图中编写了一个简单的事件记录器。我试图将其转换为TPL实现。

我没有足够的使用C#中的线程来真正优先于另一个,但我知道TPL正变得越来越受欢迎,我想尽可能地坚持下去。另一个原因是,使用当前代码,我找不到一种简单的方法来使EventLog类线程安全。我发现自己使用BeginInvoke从非UI线程写入日志,这对我来说似乎很麻烦。

所以这是原始代码。

public class EventLog
{
    public String LogPath { get; set; }
    public List<LogEvent> Events { get; private set; }

    public static EventLog Instance { get { return lazyInstance.Value; } }
    private static readonly Lazy<EventLog> lazyInstance = new Lazy<EventLog>(() => new EventLog());

    private EventLog()
    {
        Events = new List<LogEvent>();
        LogPath = Assembly.GetExecutingAssembly().CodeBase;
        LogPath = Path.GetDirectoryName(LogPath);
        LogPath = LogPath.Replace("file:\\", "");
        LogPath = LogPath + "\\Log.txt";
    }

    public override void publish(LogEvent newEvent)
    {
        Events.Add(newEvent);
        if (!LogEventWriter.Instance.IsBusy)
            LogEventWriter.Instance.RunWorkerAsync(LogPath);
        LogEventWriter.Instance.LogEvents.Add(newEvent);
    }
}

internal class LogEventWriter : BackgroundWorker
{
    public BlockingCollection<LogEvent> LogEvents { get; set; }

    public static LogEventWriter Instance { get { return lazyInstance.Value; } }
    private static readonly Lazy<LogEventWriter> lazyInstance = new Lazy<LogEventWriter>(() => new LogEventWriter());

    private LogEventWriter()
    {
        WorkerSupportsCancellation = true;
        LogEvents = new BlockingCollection<LogEvent>();
    }

    protected override void OnDoWork(DoWorkEventArgs e)
    {
        if (e.Argument != null && e.Argument is String)
        {
            String logPath = (String)e.Argument;
            using (StreamWriter logFile = new StreamWriter(logPath, true))
            {
                while (!CancellationPending)
                {
                    LogEvent anEvent = LogEvents.Take();
                    logFile.WriteLine(anEvent.Message);
                    logFile.Flush();
                    if (anEvent.Message.Contains("Application Terminated"))
                        break;
                }
                logFile.Close();
            }
        }
        e.Cancel = true;
    }
}

我对日志的当前思路是在系统出现故障时尽快将日志写入文件,以便日志尽可能多地获取信息。这就是Backgroundworker的用途。我还在List<LogEvent>类中保留EventLog,以便用户可以在当前日志中搜索特定事件(未完全实现/抛光)。

这是我目前的TPL解决方案。我尽力将日志记录功能包装到Task中,但我仍然认为我应该有一个类似于publish的函数而不必直接将LogEvent放入一个BlockingCollection<>,以便我可以在主UI上的单独线程上运行日志记录。

还有一种更简洁的方法来阻止Task s而不必发送&#34;特殊&#34; LogEvent他们从他们的循环到break

public class EventLog
{
    public static EventLog Instance { get { return lazyInstance.Value; } }
    private static readonly Lazy<EventLog> lazyInstance = new Lazy<EventLog>(() => new EventLog());

    public String LogPath { get; set; }
    public ConcurrentQueue<LogEvent> Events { get; set; }

    private EventLog()
    {
        Events = new ConcurrentQueue<LogEvent>();
        WriteQueue = new BlockingCollection<LogEvent>();
        LogEventQueue = new BlockingCollection<LogEvent>();

        LogPath = Assembly.GetExecutingAssembly().CodeBase;
        LogPath = Path.GetDirectoryName(LogPath);
        LogPath = LogPath.Replace("file:\\", "");
        LogPath = LogPath + "\\LogASDF.txt";

        StartManager();
        StartWriter();
    }

    public BlockingCollection<LogEvent> LogEventQueue { get; set; }
    private void StartManager()
    {
        var writeTask = Task.Factory.StartNew(() =>
        {
            while (true)
            {
                LogEvent anEvent = LogEventQueue.Take();
                Events.Enqueue(anEvent);
                WriteQueue.Add(anEvent);
                if (anEvent.Message.Contains("Application Terminated"))
                    break;
            }
        });
    }

    private BlockingCollection<LogEvent> WriteQueue { get; set; }
    private void StartWriter()
    {
        var writeTask = Task.Factory.StartNew(() =>
        {
            using (StreamWriter logFile = new StreamWriter(LogPath, true))
            {
                while(true)
                {
                    LogEvent anEvent = WriteQueue.Take();
                    logFile.WriteLine(anEvent.Message);
                    logFile.Flush();
                    if (anEvent.Message.Contains("Application Terminated"))
                        break;
                }
                logFile.Close();
            }
        });
    }
}
  1. 如何正确使用CancellationToken取消这两项任务?我不知道如果BlockingCollection阻塞,我总是要&#34;脉冲&#34;该集合让它解除封锁。
  2. 是否有&#34;清洁剂&#34;将LogEvent插入日志的方式,而不必直接将其插入LogEventQueue

1 个答案:

答案 0 :(得分:1)

以下是使用.net 4.5处理此问题的方法。对事件队列的所有访问都是同步的,因此不需要锁定或同步:

public class EventLog
{
    public String LogPath { get; set; }
    public List<LogEvent> Events {get;set;}
    private isProcessing = false;
    public CancellationTokenSource cts = new CancellationTokenSource();
    private CancellationToken _token;

    public static EventLog Instance { get { return lazyInstance.Value; } }
    private static readonly Lazy<EventLog> lazyInstance = new Lazy<EventLog>(() => new EventLog());

    private EventLog()
    {
        Events = new List<LogEvent>();
        Events.CollectionChanged += Events_CollectionChanged;
        LogPath = Assembly.GetExecutingAssembly().CodeBase;
        LogPath = Path.GetDirectoryName(LogPath);
        LogPath = LogPath.Replace("file:\\", "");
        LogPath = LogPath + "\\Log.txt";
        _token = cts.Token; 
    }

    public override void publish(LogEvent newEvent)
    {
        Events.Add(newEvent);
        if (!isProcessing)
            ProcessLog();
    }

    private async void ProcessLog()
    {
        while (Events.Count > 0)
        {
            isProcessing = true;
            LogEvent e = EventLogs.First();
            await Task.Run (() => { WriteLog(e,token); },_token);
            EventLogs.Remove(e);
            if (_token.IsCancellationRequested == true)
                EventLogs.Clear();
        }
        isProcessing = false;
    }

    private void WriteLog(LogEvent e,CancellationToken token)
    {
        using (StreamWriter logFile = new StreamWriter(LogPath, true))
        {
            if (token.IsCancellationRequested == false)
            {
                logFile.WriteLine(e.Message);
                logFile.Flush();
            }
        }
    }
}

编辑:添加了取消令牌。 编辑2:添加了WriteLog功能。