.NET Cache Research

What's this

一个对.NET平台下缓存解决方案的探索关于:

MemoryCache: .NET自定义的内存缓存实现。
CacheManager：一个开源的.NET内存缓存实现。

Microsoft MemoryCache

MemoryCache是.NET唯一实现了ObjectCache的类，可以使用它来在内存中缓存任意类型对象。
MemoryCache.Default是默认的MemoryCache实例，.NET建议使用它而不是创建任意多个缓存对象。

Add Cache

Add方法会在已存在相同Key的缓存时返回false，所以不会重复添加。


MemoryCache.Default.Add(Warehouse.CACHE_KEY, Warehouse.Warehouses, DateTimeOffset.Now.AddSeconds(2));
var warehousesFromCache = MemoryCache.Default.Get(Warehouse.CACHE_KEY) as List<Warehouse>;
Assert.That(warehousesFromCache, Is.Not.Null);
Assert.That(warehousesFromCache.Count, Is.EqualTo(2));

Add Or Get Existing

返回新添加或已存在相同Key的缓存Value。


MemoryCache.Default.Add(Warehouse.CACHE_KEY, Warehouse.Warehouses, MemoryCache.InfiniteAbsoluteExpiration);
var caches = MemoryCache.Default.AddOrGetExisting(Warehouse.CACHE_KEY, Warehouse.Warehouses.Where(o => o.WarehouseNumber == "07").ToList(), MemoryCache.InfiniteAbsoluteExpiration) as List<Warehouse>;
Assert.That(caches.Count, Is.Not.EqualTo(1));
Assert.That(caches.Count, Is.EqualTo(2));

Update Cache

更新（替换）缓存。


MemoryCache.Default.Add(Warehouse.CACHE_KEY, Warehouse.Warehouses, MemoryCache.InfiniteAbsoluteExpiration);
var specialWarehouse = Warehouse.Warehouses.Where(o => o.WarehouseNumber == "07").ToList();
MemoryCache.Default.Set(Warehouse.CACHE_KEY, specialWarehouse, MemoryCache.InfiniteAbsoluteExpiration);
var caches = MemoryCache.Default.Get(Warehouse.CACHE_KEY) as List<Warehouse>;
Assert.That(caches, Is.Not.Null);
Assert.That(caches.Count, Is.EqualTo(1));
Assert.That(caches[0].WarehouseNumber == "07");

Cache Expire

有两种缓存过期策略：

AbsoluteExpiration：绝对时间过期。在指定的时间间隔后过期，缓存移除、丢失。
SlidingExpiration：滑动时间过期。在指定的时间间隔后若未命中过该缓存，则移除、丢失；否则，则顺延指定的时间间隔，缓存不移除。


MemoryCache.Default.Add(Warehouse.CACHE_KEY+"1", Warehouse.Warehouses, DateTimeOffset.Now.AddSeconds(2));
Thread.Sleep(2000);
var warehousesFromCache = MemoryCache.Default.Get(Warehouse.CACHE_KEY+"1") as List<Warehouse>;
Assert.That(warehousesFromCache, Is.Null);

Cache Refresh

当Cache丢失前，MemoryCache会回掉一个Callback委托进行通知，此时，为了让应用程序没有该缓存真空期，我们应该立即刷新缓存，保持最新的同时防止客户端出现缓存未命中（缓存丢失）的现象发生。


[Test]
public void CacheShouldRefreshSuccessAfterExpired()
{
    MemoryCache.Default.Set(Warehouse.CACHE_KEY, Warehouse.Warehouses, new CacheItemPolicy()
    {
        AbsoluteExpiration = DateTimeOffset.Now.AddSeconds(2),
        UpdateCallback = this.CacheRefreshCallback
    });

    Thread.Sleep(5000);
    var warehousesFromCache = MemoryCache.Default.Get(Warehouse.CACHE_KEY) as List<Warehouse>;
    Assert.That(warehousesFromCache, Is.Not.Null);
}

private void CacheRefreshCallback(CacheEntryUpdateArguments args)
{
    var cacheItem = MemoryCache.Default.GetCacheItem(args.Key);
    var cacheObj = cacheItem.Value;

    cacheItem.Value = cacheObj;
    args.UpdatedCacheItem = cacheItem;
    var policy = new CacheItemPolicy
    {
        UpdateCallback = new CacheEntryUpdateCallback(CacheRefreshCallback),
        AbsoluteExpiration = DateTimeOffset.Now.AddSeconds(2)
    };

    args.UpdatedCacheItemPolicy = policy;
}

Cache Config File

在需要缓存文件内容时适用；且当文件内容更改时自动刷新缓存。


var configFilePath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "warehouse.txt");
var contents = MemoryCache.Default.Get("WarehouseConfig");
if (contents == null)
{
    var policy = new CacheItemPolicy()
    {
        AbsoluteExpiration = DateTimeOffset.Now.AddSeconds(30),
    };

    policy.ChangeMonitors.Add(new HostFileChangeMonitor(new List<string>() { configFilePath }));
    MemoryCache.Default.Set("WarehouseConfig", File.ReadAllText(configFilePath), policy);
}

Thread.Sleep(5000);
var contentsFromCache = MemoryCache.Default.Get("WarehouseConfig");
Assert.That(contentsFromCache, Is.Not.Null);
Assert.That(contentsFromCache, Is.EqualTo("01,02,03"));

Open Source CacheManager

CacheManager是GitHub上一个开源的专注于.NET Cache领域项目，其有许多新的思想和概念是.NET MemoryCache所不具备的；相对于MemoryCache，其有以下特有feature：

代码实现、写法上更符合现如今的可读性、连续性的友好风格
缓存抽象出Layer的概念，同一份缓存数据可以同时缓存到多个Layer（CacheManager称之为'Handle'）上，有利于防止某Layer缓存意外丢失，降低客户端缓存未命中的概率，其中DictionaryHandle性能最好
每层可单独定义过期策略，并指定层与层之间当发现缓存不一致时（有的丢失了，有的还在）的更新策略
支持通过配置文件(.config)形式定义缓存策略（过期策略、缓存Handle等），就可以不修改代码来随时更改
有针对每个Layer缓存的Add、Remove、Update、Hit统计信息输出
有提供Logging接口，以记录缓存在Add、Remove、Update、Hit时的详细信息输入
有提供分布式缓存不一致的解决方案（ClientA、ClientB共享同一份缓存，同时各自缓存一份In-Process缓存在本地，当ClientA更新了本地缓存时，通过消息的方式通知ClientB更新本地缓存）

Add Cache

添加缓存；已存在时返回false。


var cacheManager = CacheFactory.Build<List<Warehouse>>(setting =>
{
    setting.WithDictionaryHandle();
    setting.WithSystemRuntimeCacheHandle();
});

cacheManager.Add(Warehouse.CACHE_KEY, Warehouse.Warehouses);
var caches = cacheManager.Get(Warehouse.CACHE_KEY);
Assert.That(caches.Count, Is.EqualTo(2));
Assert.That(cacheManager.CacheHandles.Count, Is.EqualTo(2));

Add Or Get Existing

返回新添加的或已存在相同Key的缓存。


var cacheManager = CacheFactory.Build<List<Warehouse>>(settings =>
{
    settings.WithDictionaryHandle();
});

var caches = cacheManager.GetOrAdd(Warehouse.CACHE_KEY, Warehouse.Warehouses);
Assert.That(caches.Count, Is.EqualTo(2));

Add Or Update Existing

不存在就添加，存在就更新。


var manager = CacheFactory.Build<List<Company>>(settings =>
{
    settings.WithDictionaryHandle();
});

manager.Add(Company.CACHE_KEY, Company.MovieCompanies);
manager.AddOrUpdate(Company.CACHE_KEY, Company.ITCompanies, o => Company.ITCompanies);

var caches = manager.Get(Company.CACHE_KEY);
Assert.That(caches, Is.Not.Null);
Assert.That(caches.Count, Is.EqualTo(2));
Assert.That(caches[0].CompanyType, Is.EqualTo(CompanyType.ITCompany));

Update Cache

更新缓存。


var manager = CacheFactory.Build(settings =>
{
    settings.WithDictionaryHandle();
});

manager.Add(Company.CACHE_KEY, Company.MovieCompanies);
manager.Update(Company.CACHE_KEY, o => Company.ITCompanies.Union(o as List<Company>).ToList());
var caches = manager.Get<List<Company>>(Company.CACHE_KEY);

Assert.That(caches.Count, Is.EqualTo(4));

Create Cache Instance From Config

从配置文件加载缓存策略等信息。

Caches.config


<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<configSections>
  <section name="cacheManager" type="CacheManager.Core.Configuration.CacheManagerSection, CacheManager.Core" />
</configSections>

<cacheManager>
  <managers>
    <cache  name="ITCompaniesCacheConfig" updateMode="Up" enableStatistics="false" enablePerformanceCounters="false">
      <handle name="handleName" ref="systemRuntimeHandle" expirationMode="Absolute" timeout="50s"/>
    </cache>
    <cache  name="MoviesCompaniesCacheConfig" updateMode="Up" enableStatistics="false" enablePerformanceCounters="false">
      <handle name="handleName" ref="systemRuntimeHandle" expirationMode="Absolute" timeout="50s"/>
    </cache>
  </managers>
  <cacheHandles>
    <handleDef  id="systemRuntimeHandle" type="CacheManager.SystemRuntimeCaching.MemoryCacheHandle`1, CacheManager.SystemRuntimeCaching"
        defaultExpirationMode="Sliding" defaultTimeout="5m"/>
  </cacheHandles>
</cacheManager>
</configuration>

Create Cache Instance From Config


var cfg = ConfigurationBuilder.LoadConfigurationFile("Caches.config", "ITCompaniesCacheConfig");
var manager = CacheFactory.FromConfiguration<List<Company>>(cfg);
manager.Add(Company.CACHE_KEY, Company.ITCompanies);
var caches = manager.Get(Company.CACHE_KEY);

Assert.That(caches, Is.Not.Null);
Assert.That(caches.Count, Is.EqualTo(2));

Cache With Multiple Layers

将同一份数据缓存到多个Layer，会按Layer（Handle）的添加顺序去命中缓存（返回第一个命中的）。


var manager = CacheFactory.Build<List<Company>>(settings =>
 {
     settings.WithDictionaryHandle().WithExpiration(ExpirationMode.Absolute, TimeSpan.FromSeconds(1));
     settings.WithSystemRuntimeCacheHandle();
     settings.WithUpdateMode(CacheUpdateMode.None);
 });

// all cache layer hold the ITCompanies.
manager.Add(Company.CACHE_KEY, Company.ITCompanies);

Thread.Sleep(1000);

var caches = manager.Get(Company.CACHE_KEY); // ONLY When GET: If find some layer was difference from others, the "Update" strategy will be executed.

Assert.That(caches, Is.Not.Null);
Assert.That(caches.Count, Is.EqualTo(2));

Assert.That(manager.CacheHandles.Count, Is.EqualTo(2));
Assert.That(manager.CacheHandles.First().Count, Is.EqualTo(0));
Assert.That(manager.CacheHandles.Last().Count, Is.GreaterThanOrEqualTo(1));

Cache Expire

缓存过期是针对每个Layer的，可以用连续调用的方式来初始化一个带有过期策略的CacheManager。


var manager = CacheFactory.Build<List<Company>>(settings =>
{
 settings.WithDictionaryHandle().WithExpiration(ExpirationMode.Absolute, TimeSpan.FromSeconds(1));
 settings.WithSystemRuntimeCacheHandle();
 settings.WithUpdateMode(CacheUpdateMode.None);
});

注意这里的WithUpdateMode,CacheUpdateMode有三种值，分别代表：

CacheUpdateMode.None: 无论缓存首先被命中在哪一个的Layer，各个Layer存储的缓存不做任何更新即使它们彼此不一样；
CacheUpdateMode.Full: 无论缓存首先被命中在哪一个的Layer，各个Layer存储的缓存将被更新一致当它们彼此不一样时；
CacheUpdateMode.UP: 更新缓存首先被命中的那个Layer添加顺序之上的所有Layer的缓存以保持一致。

Cache Statistics

Cache在各种Operation下的次数统计信息输出。


var manager = CacheFactory.Build<List<Company>>(settings =>
{
    settings.WithDictionaryHandle().WithExpiration(ExpirationMode.Absolute,             TimeSpan.FromSeconds(1)).EnableStatistics().EnablePerformanceCounters();    
    settings.WithSystemRuntimeCacheHandle().EnableStatistics();
    settings.WithUpdateMode(CacheUpdateMode.None);
});

// all cache layer hold the ITCompanies.
manager.Add(Company.CACHE_KEY, Company.ITCompanies);
manager.Put(Company.CACHE_KEY, Company.MovieCompanies);
manager.Remove(Company.CACHE_KEY);
manager.Add(Company.CACHE_KEY, Company.ITCompanies);

var cachesFinal = manager.Get(Company.CACHE_KEY);
foreach (var handle in manager.CacheHandles)
{
    var stats = handle.Stats;
    Console.WriteLine(string.Format(
            "Items: {0}, Hits: {1}, Miss: {2}, Remove: {3}, ClearRegion: {4}, Clear: {5}, Adds: {6}, Puts: {7}, Gets: {8}",
                stats.GetStatistic(CacheStatsCounterType.Items),
                stats.GetStatistic(CacheStatsCounterType.Hits),
                stats.GetStatistic(CacheStatsCounterType.Misses),
                stats.GetStatistic(CacheStatsCounterType.RemoveCalls),
                stats.GetStatistic(CacheStatsCounterType.ClearRegionCalls),
                stats.GetStatistic(CacheStatsCounterType.ClearCalls),
                stats.GetStatistic(CacheStatsCounterType.AddCalls),
                stats.GetStatistic(CacheStatsCounterType.PutCalls),
                stats.GetStatistic(CacheStatsCounterType.GetCalls)
            ));
}

Cache Logging

支持Cache在各种Operation下的日志记录。


var manager = CacheFactory.Build<List<Company>>(settings =>
{
    settings.WithDictionaryHandle().WithExpiration(ExpirationMode.Absolute,  TimeSpan.FromSeconds(1)).EnableStatistics().EnablePerformanceCounters();
    settings.WithSystemRuntimeCacheHandle().EnableStatistics();
    settings.WithUpdateMode(CacheUpdateMode.None);
    settings.WithLogging(typeof(CustomerLogFactory));
});

// all cache layer hold the ITCompanies.
manager.Add(Company.CACHE_KEY, Company.ITCompanies);
manager.Put(Company.CACHE_KEY, Company.MovieCompanies);
manager.Remove(Company.CACHE_KEY);
manager.Add(Company.CACHE_KEY, Company.ITCompanies);

var caches = manager.Get(Company.CACHE_KEY);
Assert.That(caches, Is.Not.Null);

OutPut Like Below:


CacheManager.Core.BaseCacheManager<object>: Trace: Add or update: key .
CacheManager.Core.BaseCacheManager<object>: Trace: Add: key 
CacheManager.Core.BaseCacheManager<object>: Trace: Add: key  to handle redis FAILED. Evicting items from other handles.
CacheManager.Core.BaseCacheManager<object>: Trace: Evict from other handles: key : excluding handle 1.
CacheManager.Core.BaseCacheManager<object>: Trace: Evict from handle: key : on handle default.
CacheManager.Core.BaseCacheManager<object>: Trace: Add or update: key : add failed, trying to update...
CacheManager.Core.BaseCacheManager<object>: Trace: Update: key .
CacheManager.Core.BaseCacheManager<object>: Trace: Update: key : tried on handle redis: result: Success.
CacheManager.Core.BaseCacheManager<object>: Trace: Evict from handles above: key : above handle 1.
CacheManager.Core.BaseCacheManager<object>: Trace: Evict from handle: key : on handle default.
CacheManager.Core.BaseCacheManager<object>: Trace: Add to handles below: key : below handle 1.
CacheManager.Core.BaseCacheManager<object>: Trace: Add or update: key : successfully updated.

.NET Cache Research

What's this

Microsoft MemoryCache

Add Cache

Add Or Get Existing

Update Cache

Cache Expire

Cache Refresh

Cache Config File

Open Source CacheManager

Add Cache

Add Or Get Existing

Add Or Update Existing

Update Cache

Create Cache Instance From Config

Cache With Multiple Layers

Cache Expire

Cache Statistics

Cache Logging

(打赏)

If you want to pay for this
I will list your account name here.
HA HA!

What's this

Microsoft MemoryCache

Add Cache

Add Or Get Existing

Update Cache

Cache Expire

Cache Refresh

Cache Config File

Open Source CacheManager

Add Cache

Add Or Get Existing

Add Or Update Existing

Update Cache

Create Cache Instance From Config

Cache With Multiple Layers

Cache Expire

Cache Statistics

Cache Logging

(打赏)

If you want to pay for thisI will list your account name here. HA HA!

If you want to pay for this
I will list your account name here.
HA HA!