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U4-4931 - lock contention & potential application lockdown

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Conflicts:
	src/Umbraco.Core/Cache/ObjectCacheRuntimeCacheProvider.cs
	src/umbraco.cms/Actions/Action.cs
This commit is contained in:
Stephan
2014-05-16 16:48:31 +02:00
parent 60d6ae44b5
commit 8729156fbf
4 changed files with 64 additions and 39 deletions
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42
src/Umbraco.Core/Cache/HttpRuntimeCacheProvider.cs
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@@ -81,25 +81,36 @@ namespace Umbraco.Core.Cache
{
cacheKey = GetCacheKey(cacheKey);
// NOTE - because we don't know what getCacheItem does, how long it will take and whether it will hang,
// getCacheItem should run OUTSIDE of the global application lock else we run into lock contention and
// nasty performance issues.
// So.... we insert a Lazy<object> in the cache while holding the global application lock, and then rely
// on the Lazy lock to ensure that getCacheItem runs once and everybody waits on it, while the global
// application lock has been released.
// Note that this means we'll end up storing null values in the cache, whereas in the past we made sure
// not to store them. There's code below, commented out, to make sure we do re-compute the value if it
// was previously computed as null - effectively reproducing the past behavior - but I'm not quite sure
// it is a good idea.
Lazy<object> result;
using (var lck = new UpgradeableReadLock(Locker))
{
var result = DictionaryCache.Get(cacheKey);
if (result == null)
result = DictionaryCache.Get(cacheKey) as Lazy<object>;
if (result == null /* || (result.IsValueCreated && result.Value == null) */)
{
lck.UpgradeToWriteLock();
result = getCacheItem();
if (result != null)
{
var absolute = isSliding ? System.Web.Caching.Cache.NoAbsoluteExpiration : (timeout == null ? System.Web.Caching.Cache.NoAbsoluteExpiration : DateTime.Now.Add(timeout.Value));
var sliding = isSliding == false ? System.Web.Caching.Cache.NoSlidingExpiration : (timeout ?? System.Web.Caching.Cache.NoSlidingExpiration);
_cache.Insert(cacheKey, result, dependency, absolute, sliding, priority, removedCallback);
}
result = new Lazy<object>(getCacheItem);
var absolute = isSliding ? System.Web.Caching.Cache.NoAbsoluteExpiration : (timeout == null ? System.Web.Caching.Cache.NoAbsoluteExpiration : DateTime.Now.Add(timeout.Value));
var sliding = isSliding == false ? System.Web.Caching.Cache.NoSlidingExpiration : (timeout ?? System.Web.Caching.Cache.NoSlidingExpiration);
_cache.Insert(cacheKey, result, dependency, absolute, sliding, priority, removedCallback);
}
return result;
}
return result.Value;
}
public object GetCacheItem(string cacheKey, Func<object> getCacheItem, TimeSpan? timeout, bool isSliding = false, CacheItemPriority priority = CacheItemPriority.Normal, CacheItemRemovedCallback removedCallback = null, string[] dependentFiles = null)
@@ -124,8 +135,11 @@ namespace Umbraco.Core.Cache
/// <param name="dependency"></param>
internal void InsertCacheItem(string cacheKey, Func<object> getCacheItem, TimeSpan? timeout = null, bool isSliding = false, CacheItemPriority priority = CacheItemPriority.Normal, CacheItemRemovedCallback removedCallback = null, CacheDependency dependency = null)
{
var result = getCacheItem();
if (result == null) return;
// NOTE - here also we must insert a Lazy<object> but we can evaluate it right now
// and make sure we don't store a null value. Though I'm not sure it is a good idea.
var result = new Lazy<object>(getCacheItem);
//if (result.Value == null) return;
cacheKey = GetCacheKey(cacheKey);