Likely concurrency issue in CacheManager.Microsoft.Extensions.Caching.Memory

[jkernsva]

Our application is occasionally getting into a state in which its MemoryCache will throw exceptions when used. Once in this state, all further requests will fail and we must restart the process to get it into a healthy state again.

We speculate that this is related to concurrent writes to one of its internal metadata structures. Here is a partial stack trace from one of the occurences:

System.IndexOutOfRangeException: Index was outside the bounds of the array.
   at System.Collections.Generic.HashSet`1.AddIfNotPresent(T value)
   at CacheManager.MicrosoftCachingMemory.MemoryCacheExtensions.RegisterChild(MemoryCache cache, Object parentKey, Object childKey)
   at CacheManager.MicrosoftCachingMemory.MemoryCacheHandle`1.AddInternalPrepared(CacheItem`1 item)
   at CacheManager.Core.BaseCacheManager`1.AddToHandles(CacheItem`1 item, Int32 foundIndex)
   at CacheManager.Core.BaseCacheManager`1.GetCacheItemInternal(String key, String region)
   at CacheManager.Core.BaseCacheManager`1.GetOrAddInternal(String key, String region, Func`3 valueFactory)

I have submitted a pull request, #266, that I believe will address this problem. We have been testing this build internally and we have not seen the issue reoccur.

[MichaConrad]

Hi @jkernsva
Thanks for letting me know and thanks for the PR. I've seen that one already.
I'll comment on that if I find anything. But looks good overall.

[rawrspace]

I am also experiencing the same issues and the fixes @jkernsva provided in #266 appear to have resolved my problem. It would be great to see this incorporated and released as an updated NuGet package.

[tynorton]

Any idea when this will be merged / released? We are experiencing it too.

[tynorton]

Bump.

[jkernsva]

This has been resolved in #266