网上找FoDicom资料时, 发现dicomservice早期版本用的是ThreadPoolQueue http://blog.csdn.net/zssureqh/article/details/50637387
Dicomservice目前使用的是C#5.0引入的async和await, 之前使用的是C# 4.0引入的Task, 再之前使用的是C#1.0的Begin/End(APM)
其中Task版本用到了TaskQueue, 内部调用Task.Run(() => this.ExecuteProc(group));
APM版本用到了ThreadPoolQueue, 内部调用ThreadPool.QueueUserWorkItem(ExecuteProc, group);
ThreadPoolQueue和TaskQueue的逻辑是一样的, 只是将ThreadPool替换为了Task, 只需要看ThreadPoolQueue
可以从旧版本的Dicomservice的EndReadPDU处开始看起
EndReadPDU表示结束读取收到的PDU包1
2case 0x04: //PDataTF (带数据)
_processQueue.Queue(ProcessPDataTF, pdu);
_processQueue为ThreadPoolQueue, 其他case都是ACSE(见之前的笔记), 直接调用OnReceiveAssociationAccept等方法处理
ProcessPDataTF方法内部:1
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6if (DicomMessage.IsRequest(_dimse.Type)) ThreadPool.QueueUserWorkItem(PerformDimseCallback, _dimse);
else
_processQueue.Queue(
(_dimse as DicomResponse).RequestMessageID,
PerformDimseCallback,
_dimse);
如果_dimse是request, 则直接交由ThreadPool去执行
如果_dimse是response, 则放入ThreadPoolQueue中
看看ThreadPoolQueue的Queue方法做了什么1
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44public void Queue(WaitCallback callback, object state) {
Queue(new WorkItem {
Group = DefaultGroup,
Callback = callback,
State = state
});
}
private void Queue(WorkItem item) {
lock (_lock) {
WorkGroup group = null;
if (!_groups.TryGetValue(item.Group, out group)) {
group = new WorkGroup(item.Group);
_groups.Add(item.Group, group);
}
lock (group.Lock)
group.Items.Enqueue(item);
Execute(item.Group);//按组来执行
}
}
private void Execute(T groupKey) {
WorkGroup group = null;
lock (_lock) {
if (!_groups.TryGetValue(groupKey, out group))
return;
}
lock (group.Lock) {
if (group.Executing)
return;
if (group.Items.Count == 0 && !group.Key.Equals(DefaultGroup)) {
_groups.Remove(groupKey);
return;
}
group.Executing = true;
ThreadPool.QueueUserWorkItem(ExecuteProc, group);
}
}
ExecuteProc: 内部最终执行1
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8try {
if (item.Action != null)
item.Action();
else if (item.Callback != null)
item.Callback(item.State);
} catch {
// log this somewhere?
}
从代码中可以这样理解ThreadPoolQueue的Queue方法:
- 将Item放入queue
- 如果当前queue没有执行, 则将该queue放入线程池中执行
- 如果当前queue正在执行, 则返回
于是会出现这样一种情况: 多次调用Queue方法, 但此时queue在执行, 则item会在queue中累积
为何要这样做, 从fodicom自带的ThreadPoolQueueTest中可以看到
public void Queue_OrderOfExecutionForSameKey_ShouldBeFifo()
为何要这样设计, 对于response需要FIFO? 其中一点认识: C-Get和C-Move都是复合操作, 对于响应的顺序比较重要.
文件链接:
TaskQueueTest.cs
https://github.com/fo-dicom/fo-dicom/blob/b386e73e3b33c6de3bb7c4400464e0c2e010dbad/DICOM%20%5BUnit%20Tests%5D/Threading/TaskQueueTest.cs
ThreadPoolQueue.cs
https://github.com/fo-dicom/fo-dicom/blob/12f4e225b250e3107d4ecb5f9404fa12e18a3dcd/DICOM/Threading/ThreadPoolQueue.cs
ThreadPoolQueueTest.cs
https://github.com/fo-dicom/fo-dicom/blob/12f4e225b250e3107d4ecb5f9404fa12e18a3dcd/DICOM%20%5BUnit%20Tests%5D/Threading/ThreadPoolQueueTest.cs
DicomService.cs (使用ThreadPoolQueue)
https://github.com/fo-dicom/fo-dicom/blob/12f4e225b250e3107d4ecb5f9404fa12e18a3dcd/DICOM/Network/DicomService.cs
下面是单元测试程序1
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274下面是单元测试程序:
using System;
using System.Collections.Generic;
using System.Diagnostics.Contracts;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
namespace ThreadQueuePoolTest
{
public class Program
{
static void Main(string[] args)
{
Queue_OrderOfExecutionForSameKey_ShouldBeFifo();
}
static void Queue_OrderOfExecutionForSameKey_ShouldBeFifo()
{
string[] expected = { "Group 1: ", "Group 2: ", "Group 3: " };
string[] actual = { "Group 1: ", "Group 2: ", "Group 3: " };
bool[] finished = { false, false, false };
var handle = new ManualResetEventSlim(false);
var pool = new ThreadPoolQueue<int>(int.MinValue);
for (var i = 0; i < 99; ++i)
{
var group = i % 3;
expected[group] += string.Format("B{0}E{0} ", i);
pool.Queue(
group,
state =>
{
actual[group] += string.Format("B{0}", state);
Thread.Sleep(1);
actual[group] += string.Format("E{0} ", state);
Thread.Sleep(1);
if ((int)state > 96)
{
finished[group] = true;
if (finished.All(f => f)) handle.Set();
}
},
i);
}
handle.Wait(1000);
foreach (var item in expected)
{
Console.WriteLine(item);
}
Console.WriteLine("\n");
foreach (var item in actual)
{
Console.WriteLine(item);
}
Console.ReadLine();
}
}
class ThreadPoolQueue<T>
{
private class WorkItem
{
public T Group;
public Action Action;
public System.Threading.WaitCallback Callback;
public object State;
}
private class WorkGroup
{
public T Key;
public object Lock = new object();
public volatile bool Executing = false;
public Queue<WorkItem> Items = new Queue<WorkItem>();
public WorkGroup(T key)
{
Key = key;
}
}
private object _lock = new object();
private Dictionary<T, WorkGroup> _groups;
public ThreadPoolQueue(T defaultGroup = default(T))
{
_groups = new Dictionary<T, WorkGroup>();
Linger = 200;
DefaultGroup = defaultGroup;
}
/// <summary>Time in milliseconds (MS) to keep the WorkGroup alive after processing last item.</summary>
public int Linger
{
get;
set;
}
/// <summary>Value of key for default group.</summary>
public T DefaultGroup
{
get;
set;
}
public void Queue(Action action)
{
Queue(new WorkItem
{
Group = DefaultGroup,
Action = action
});
}
public void Queue(WaitCallback callback)
{
Queue(new WorkItem
{
Group = DefaultGroup,
Callback = callback
});
}
public void Queue(WaitCallback callback, object state)
{
Queue(new WorkItem
{
Group = DefaultGroup,
Callback = callback,
State = state
});
}
public void Queue(T group, Action action)
{
Queue(new WorkItem
{
Group = group,
Action = action
});
}
public void Queue(T group, WaitCallback callback)
{
Queue(new WorkItem
{
Group = group,
Callback = callback
});
}
public void Queue(T group, WaitCallback callback, object state)
{
Queue(new WorkItem
{
Group = group,
Callback = callback,
State = state
});
}
private void Queue(WorkItem item)
{
lock (_lock)
{
WorkGroup group = null;
if (!_groups.TryGetValue(item.Group, out group))
{
group = new WorkGroup(item.Group);
_groups.Add(item.Group, group);
}
lock (group.Lock)
group.Items.Enqueue(item);
Execute(item.Group);
}
}
private void Execute(T groupKey)
{
WorkGroup group = null;
lock (_lock)
{
if (!_groups.TryGetValue(groupKey, out group))
return;
}
lock (group.Lock)
{
if (group.Executing)
return;
if (group.Items.Count == 0 && !group.Key.Equals(DefaultGroup))
{
_groups.Remove(groupKey);
return;
}
group.Executing = true;
ThreadPool.QueueUserWorkItem(ExecuteProc, group);
}
}
private void ExecuteProc(object state)
{
var group = (WorkGroup)state;
do
{
WorkItem item = null;
bool empty;
lock (group.Lock)
{
empty = group.Items.Count == 0;
if (!empty)
item = group.Items.Dequeue();
}
if (empty)
{
var linger = DateTime.Now.AddMilliseconds(Linger);
while (empty && DateTime.Now < linger)
{
Thread.Sleep(0);
lock (_lock)
{
empty = group.Items.Count == 0;
if (!empty)
item = group.Items.Dequeue();
}
}
if (empty)
{
lock (_lock)
{
lock (group.Lock)
group.Executing = false;
if (!group.Key.Equals(DefaultGroup))
_groups.Remove(group.Key);
return;
}
}
}
try
{
if (item.Action != null)
item.Action();
else if (item.Callback != null)
item.Callback(item.State);
}
catch
{
// log this somewhere?
}
} while (true);
}
}
}