Orchard源码分析 - 缓存管理

DefaultCacheManager(Type component/*此类型是缓存服务消费者的类型名称,在CacheModule中配置注册,

其主要作用是在CacheHolder中创建一个cacheKey,cacheKey使用三元组(Tuple)数组结构,使cacheKey免于冲突,(component类型+用户Key类型+返回值类型)保证cacheKey的唯一性*/

, ICacheHolder cacheHolder)

public ICache<TKey, TResult> GetCache<TKey, TResult>(Type component) {
var cacheKey = new CacheKey(component, typeof(TKey), typeof(TResult));
var result = _caches.GetOrAdd(cacheKey, k => new Cache<TKey, TResult>(_cacheContextAccessor));
return (Cache<TKey, TResult>)result;
}

    ICache (最小缓存单元)                                

private CacheEntry UpdateEntry(CacheEntry currentEntry, TKey k, Func<AcquireContext<TKey>, TResult> acquire) {
//在此检测currentEntry中令牌列表中是否有任一令牌过期,如果有一个过期了,则重建CacheEntry,否则CacheEntry保持原样.
var entry = (currentEntry.Tokens.Any(t => t != null && !t.IsCurrent)) ? CreateEntry(k, acquire) : currentEntry;
PropagateTokens(entry);
return entry;
}

public IEnumerable<StereotypeDescription> GetStereotypes() {
return _cacheManager.Get("ContentType.Stereotypes", context => {
//此处调用Monitor方法的本质是在对应的CacheEntry中的令牌列表中添加一个令牌项
context.Monitor(_clock.WhenUtc(_clock.UtcNow.AddMinutes(1)));
return _providers.SelectMany(x => x.GetStereotypes());
});

}

namespace Orchard.Caching {
//所有实现此空接口的类都被视为令牌提供器
public interface IVolatileProvider : ISingletonDependency {
}
}

RegisterVolatileProvider<WebSiteFolder, IWebSiteFolder>(builder);
RegisterVolatileProvider<AppDataFolder, IAppDataFolder>(builder);
RegisterVolatileProvider<DefaultLockFileManager, ILockFileManager>(builder);
RegisterVolatileProvider<Clock, IClock>(builder);
RegisterVolatileProvider<DefaultDependenciesFolder, IDependenciesFolder>(builder);
RegisterVolatileProvider<DefaultExtensionDependenciesManager, IExtensionDependenciesManager>(builder);
RegisterVolatileProvider<DefaultAssemblyProbingFolder, IAssemblyProbingFolder>(builder);
RegisterVolatileProvider<DefaultVirtualPathMonitor, IVirtualPathMonitor>(builder);
RegisterVolatileProvider<DefaultVirtualPathProvider, IVirtualPathProvider>(builder);

_cacheDuration = _cacheManager.Get("CacheSettingsPart.Duration",
context => {
//监视一个信号,如果此信号被Trigger(触发),则当前令牌被标识过期
context.Monitor(_signals.When(CacheSettingsPart.CacheKey));
return _workContext.CurrentSite.As<CacheSettingsPart>().DefaultCacheDuration;
}
);

//标识令牌过期
_signals.Trigger("MediaProcessing_Saved_" + filter.ImageProfilePartRecord.Name);

引用相等的示例( 基础知识 )

void Main()
{
var a=new Person{N="我是a"};
var b=new Person{N="我是b"};
var c=new Person{N="我是c"};
var dic=new Dictionary<string,object>();
dic.Add("a",a);
dic.Add("b",b);
dic.Add("c",c);
var list=new List<Object>();
list.Add(a);
list.Add(b);
list.Add(c);
object o;
dic.TryGetValue("a",out o);
((Person)o).N="你好";
//字典中与链表中的值  引用是相等的
Console.Write(System.Object.ReferenceEquals(o,list[0]));   //输出 True
//因此改变字典中的值, 链表的值也会改变
Console.Write(list[0].N);   //输出 "你好"
}
class Person
{
public string N;
}

public void QueueWorkItem() {
// Start a work item to collect tokens in our internal array
ThreadPool.QueueUserWorkItem(state => {
try {
_task(token => _taskTokens.Add(token));
}
catch (Exception e) {
Logger.Error(e, "Error while monitoring extension files. Assuming extensions are not current.");
_taskException = e;
}
finally {
_isTaskFinished = true;
}
});
}

extensionEntry = _cacheManager.Get(extensionId, ctx => {
var entry = BuildEntry(extensionDescriptor);
if (entry != null) {
ctx.Monitor(_asyncTokenProvider.GetToken(monitor => {
//此方法体将在线程池中异步执行

//monitor调用时将会向AsyncVolativeToken实例的内部的List<IVolatileToken>中添加token
foreach (var loader in _loaders) {
loader.Monitor(entry.Descriptor, token => monitor(token));
}
}));
}
return entry;
});

_cacheManager.Get("CacheSettingsPart.Duration",
context => {
//这个方法仅在Cache中ConcurrentDictionary字典中未找到缓存项才执行,

//我称此方法体为[ 缓存获取方法体 ]
return  XXXXXX;
}
);

IEnumerable<TResult> RunInParallel<T, TResult>(IEnumerable<T> source, Func<T, TResult> selector);

// Run tasks in parallel and combine results immediately
var result = tasks
.AsParallel() // prepare for parallel execution
.AsOrdered() // preserve initial enumeration order
.Select(task => task.Execute()) // prepare tasks to run in parallel
.ToArray(); // force evaluation