C# 如何使用ConcurrentQueue处理线程<;T>;
我正在尝试找出处理队列的最佳方式。我有一个返回数据表的进程。每个数据表依次与前一个数据表合并。有一个问题,太多的记录要保存到最终的大容量拷贝(OutOfMemory) 因此,我决定应该立即处理每个传入的数据表。考虑一下C# 如何使用ConcurrentQueue处理线程<;T>;,c#,multithreading,queue,concurrent-collections,C#,Multithreading,Queue,Concurrent Collections,我正在尝试找出处理队列的最佳方式。我有一个返回数据表的进程。每个数据表依次与前一个数据表合并。有一个问题,太多的记录要保存到最终的大容量拷贝(OutOfMemory) 因此,我决定应该立即处理每个传入的数据表。考虑一下ConcurrentQueue…但我不知道writequeueeddata()方法如何将表出列并写入数据库 例如: public class TableTransporter { private ConcurrentQueue<DataTable> tableQ
ConcurrentQueue
…但我不知道writequeueeddata()
方法如何将表出列并写入数据库
例如:
public class TableTransporter
{
private ConcurrentQueue<DataTable> tableQueue = new ConcurrentQueue<DataTable>();
public TableTransporter()
{
tableQueue.OnItemQueued += new EventHandler(WriteQueuedData); // no events available
}
public void ExtractData()
{
DataTable table;
// perform data extraction
tableQueue.Enqueue(table);
}
private void WriteQueuedData(object sender, EventArgs e)
{
BulkCopy(e.Table);
}
}
关于这个实现有什么问题吗?根据我对这个问题的理解,您缺少了一些东西 并发队列是一种数据结构,旨在接受多个线程对队列的读写,而无需显式锁定数据结构。(所有jazz都是在幕后处理的,或者集合的实现方式不需要锁定。) 考虑到这一点,您尝试使用的模式似乎是“产品/消费者”。首先,您有一些任务生成工作(并将项目添加到队列)。第二个任务是消耗队列中的东西(并清除项目)
所以您确实需要两个线程:一个添加项目,另一个删除项目。因为您使用的是并发集合,所以可以有多个线程添加项目,也可以有多个线程删除项目。但显然,并发队列上的争用越多,成为瓶颈的速度就越快。这是我提出的完整解决方案:
public class TableTransporter
{
private static int _indexer;
private CustomQueue tableQueue = new CustomQueue();
private Func<DataTable, String> RunPostProcess;
private string filename;
public TableTransporter()
{
RunPostProcess = new Func<DataTable, String>(SerializeTable);
tableQueue.TableQueued += new EventHandler<TableQueuedEventArgs>(tableQueue_TableQueued);
}
void tableQueue_TableQueued(object sender, TableQueuedEventArgs e)
{
// do something with table
// I can't figure out is how to pass custom object in 3rd parameter
RunPostProcess.BeginInvoke(e.Table,new AsyncCallback(PostComplete), filename);
}
public void ExtractData()
{
// perform data extraction
tableQueue.Enqueue(MakeTable());
Console.WriteLine("Table count [{0}]", tableQueue.Count);
}
private DataTable MakeTable()
{ return new DataTable(String.Format("Table{0}", _indexer++)); }
private string SerializeTable(DataTable Table)
{
string file = Table.TableName + ".xml";
DataSet dataSet = new DataSet(Table.TableName);
dataSet.Tables.Add(Table);
Console.WriteLine("[{0}]Writing {1}", Thread.CurrentThread.ManagedThreadId, file);
string xmlstream = String.Empty;
using (MemoryStream memstream = new MemoryStream())
{
XmlSerializer xmlSerializer = new XmlSerializer(typeof(DataSet));
XmlTextWriter xmlWriter = new XmlTextWriter(memstream, Encoding.UTF8);
xmlSerializer.Serialize(xmlWriter, dataSet);
xmlstream = UTF8ByteArrayToString(((MemoryStream)xmlWriter.BaseStream).ToArray());
using (var fileStream = new FileStream(file, FileMode.Create))
fileStream.Write(StringToUTF8ByteArray(xmlstream), 0, xmlstream.Length + 2);
}
filename = file;
return file;
}
private void PostComplete(IAsyncResult iasResult)
{
string file = (string)iasResult.AsyncState;
Console.WriteLine("[{0}]Completed: {1}", Thread.CurrentThread.ManagedThreadId, file);
RunPostProcess.EndInvoke(iasResult);
}
public static String UTF8ByteArrayToString(Byte[] ArrBytes)
{ return new UTF8Encoding().GetString(ArrBytes); }
public static Byte[] StringToUTF8ByteArray(String XmlString)
{ return new UTF8Encoding().GetBytes(XmlString); }
}
public sealed class CustomQueue : ConcurrentQueue<DataTable>
{
public event EventHandler<TableQueuedEventArgs> TableQueued;
public CustomQueue()
{ }
public CustomQueue(IEnumerable<DataTable> TableCollection)
: base(TableCollection)
{ }
new public void Enqueue (DataTable Table)
{
base.Enqueue(Table);
OnTableQueued(new TableQueuedEventArgs(Table));
}
public void OnTableQueued(TableQueuedEventArgs table)
{
EventHandler<TableQueuedEventArgs> handler = TableQueued;
if (handler != null)
{
handler(this, table);
}
}
}
public class TableQueuedEventArgs : EventArgs
{
#region Fields
#endregion
#region Init
public TableQueuedEventArgs(DataTable Table)
{this.Table = Table;}
#endregion
#region Functions
#endregion
#region Properties
public DataTable Table
{get;set;}
#endregion
}
公共类TableTransporter
{
专用静态int_索引器;
私有CustomQueue tableQueue=新CustomQueue();
私有函数RunPostProcess;
私有字符串文件名;
公共交通工具(
{
RunPostProcess=newfunc(序列化表);
tableQueue.TableQueued+=新的EventHandler(tableQueue\u TableQueued);
}
void tableQueue\u TableQueued(对象发送方,TableQueuedEventArgs e)
{
//用桌子做些什么
//我不知道如何在第三个参数中传递自定义对象
RunPostProcess.BeginInvoke(例如,表,新的异步回调(PostComplete),文件名);
}
公共数据()
{
//执行数据提取
entqueue(MakeTable());
WriteLine(“表计数[{0}]”,tableQueue.count);
}
私有数据表MakeTable()
{返回新的数据表(String.Format(“表{0}”,_indexer++);}
私有字符串序列化表(DataTable表)
{
字符串文件=Table.TableName+“.xml”;
数据集数据集=新数据集(Table.TableName);
dataSet.Tables.Add(表);
WriteLine(“[{0}]写入{1}”,Thread.CurrentThread.ManagedThreadId,文件);
string xmlstream=string.Empty;
使用(MemoryStream memstream=new MemoryStream())
{
XmlSerializer XmlSerializer=新的XmlSerializer(类型(数据集));
XmlTextWriter xmlWriter=新的XmlTextWriter(memstream,Encoding.UTF8);
serializer.Serialize(xmlWriter,dataSet);
xmlstream=UTF8ByteArrayToString(((MemoryStream)xmlWriter.BaseStream.ToArray());
使用(var fileStream=newfilestream(file,FileMode.Create))
Write(StringToUTF8ByteArray(xmlstream),0,xmlstream.Length+2);
}
文件名=文件;
返回文件;
}
私有作废完成后(IAsyncResult iasResult)
{
字符串文件=(字符串)iasResult.AsyncState;
WriteLine(“[{0}]已完成:{1}”,Thread.CurrentThread.ManagedThreadId,文件);
EndInvoke(iasResult);
}
公共静态字符串UTF8ByteArrayToString(字节[]ArrBytes)
{返回新的UTF8Encoding().GetString(ArrBytes);}
公共静态字节[]StringToUTF8ByteArray(字符串XmlString)
{返回新的UTF8Encoding().GetBytes(XmlString);}
}
公共密封类CustomQueue:ConcurrentQueue
{
公共事件EventHandler表已排队;
公共自定义队列()
{ }
公共自定义队列(IEnumerable TableCollection)
:base(TableCollection)
{ }
新的公共void排队(DataTable)
{
基本队列(表);
OnTableQueued(新的TableQueuedEventArgs(Table));
}
公共无效OnTableQueued(TableQueuedEventArgs表)
{
EventHandler=TableQueued;
if(处理程序!=null)
{
处理程序(此,表);
}
}
}
公共类TableQueuedEventArgs:EventArgs
{
#区域字段
#端区
#区域初始化
公共表QueueDeventargs(数据表)
{this.Table=Table;}
#端区
#区域功能
#端区
#区域属性
公共数据表
{get;set;}
#端区
}
作为概念的证明,它似乎工作得很好。我最多看到4个工作线程。我认为
ConcurrentQueue
只在极少数情况下有用。它的主要优点是无锁。但是,通常生产者线程必须以某种方式通知消费者线程有数据可供处理。线程之间的这种信令需要锁,并且否定了使用ConcurrentQueue
的好处。同步线程的最快方法是使用Monitor.Pulse()
,它只在锁内工作。所有其他同步工具甚至更慢
当然,使用者只需不断地检查队列中是否有某些东西,这可以在没有锁的情况下工作,但这是对处理器资源的巨大浪费。更好的一点是,如果消费者在检查之间等待
在写入队列时引发线程是一个非常糟糕的主意。使用ConcurrentQueue
来节省大约1微秒的时间将完全浪费在执行eventhandler
上,这可能需要1000个tim
public class TableTransporter
{
private static int _indexer;
private CustomQueue tableQueue = new CustomQueue();
private Func<DataTable, String> RunPostProcess;
private string filename;
public TableTransporter()
{
RunPostProcess = new Func<DataTable, String>(SerializeTable);
tableQueue.TableQueued += new EventHandler<TableQueuedEventArgs>(tableQueue_TableQueued);
}
void tableQueue_TableQueued(object sender, TableQueuedEventArgs e)
{
// do something with table
// I can't figure out is how to pass custom object in 3rd parameter
RunPostProcess.BeginInvoke(e.Table,new AsyncCallback(PostComplete), filename);
}
public void ExtractData()
{
// perform data extraction
tableQueue.Enqueue(MakeTable());
Console.WriteLine("Table count [{0}]", tableQueue.Count);
}
private DataTable MakeTable()
{ return new DataTable(String.Format("Table{0}", _indexer++)); }
private string SerializeTable(DataTable Table)
{
string file = Table.TableName + ".xml";
DataSet dataSet = new DataSet(Table.TableName);
dataSet.Tables.Add(Table);
Console.WriteLine("[{0}]Writing {1}", Thread.CurrentThread.ManagedThreadId, file);
string xmlstream = String.Empty;
using (MemoryStream memstream = new MemoryStream())
{
XmlSerializer xmlSerializer = new XmlSerializer(typeof(DataSet));
XmlTextWriter xmlWriter = new XmlTextWriter(memstream, Encoding.UTF8);
xmlSerializer.Serialize(xmlWriter, dataSet);
xmlstream = UTF8ByteArrayToString(((MemoryStream)xmlWriter.BaseStream).ToArray());
using (var fileStream = new FileStream(file, FileMode.Create))
fileStream.Write(StringToUTF8ByteArray(xmlstream), 0, xmlstream.Length + 2);
}
filename = file;
return file;
}
private void PostComplete(IAsyncResult iasResult)
{
string file = (string)iasResult.AsyncState;
Console.WriteLine("[{0}]Completed: {1}", Thread.CurrentThread.ManagedThreadId, file);
RunPostProcess.EndInvoke(iasResult);
}
public static String UTF8ByteArrayToString(Byte[] ArrBytes)
{ return new UTF8Encoding().GetString(ArrBytes); }
public static Byte[] StringToUTF8ByteArray(String XmlString)
{ return new UTF8Encoding().GetBytes(XmlString); }
}
public sealed class CustomQueue : ConcurrentQueue<DataTable>
{
public event EventHandler<TableQueuedEventArgs> TableQueued;
public CustomQueue()
{ }
public CustomQueue(IEnumerable<DataTable> TableCollection)
: base(TableCollection)
{ }
new public void Enqueue (DataTable Table)
{
base.Enqueue(Table);
OnTableQueued(new TableQueuedEventArgs(Table));
}
public void OnTableQueued(TableQueuedEventArgs table)
{
EventHandler<TableQueuedEventArgs> handler = TableQueued;
if (handler != null)
{
handler(this, table);
}
}
}
public class TableQueuedEventArgs : EventArgs
{
#region Fields
#endregion
#region Init
public TableQueuedEventArgs(DataTable Table)
{this.Table = Table;}
#endregion
#region Functions
#endregion
#region Properties
public DataTable Table
{get;set;}
#endregion
}