OutputCaching middleware memory leak

[narcis-ro]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

OutputCacheEntry is renting an ArrayPool that never gets returned to the pool, in method: CopyHeadersFrom

aspnetcore/src/Middleware/OutputCaching/src/OutputCacheEntry.cs

Line 105 in b7fcd33

Headers = new(arr, 0, index);

P.S the dispose is empty and is never released in any other place

Expected Behavior

ArrayPool rented should be returned

Steps To Reproduce

Normal usage of Output caching, behavior happens if there are headers to cache

Exceptions (if any)

No response

.NET Version

No response

Anything else?

No response

[narcis-ro]

Could also be related: #55890

[BrennanConroy]

@mgravell

Could also be related: #55890

Don't know what that issue is about, but can't be related as the PinnedBlockMemoryPool and ArrayPool are completely different.

[sebastienros]

I don't think this would lead to a memory leak. Once the entry is released, the Headers and its array will be GC'ed. I believe the goal of this implementation is to tentatively create an array to manipulate headers, then if it's useless return it quickly for reuse. But if the array actually needs to be used for longer then it's kept in memory like any other array. This is not a memory leak, it's just using the pool as an allocator.

[narcis-ro]

I don't think this would lead to a memory leak. Once the entry is released, the Headers and its array will be GC'ed. I believe the goal of this implementation is to tentatively create an array to manipulate headers, then if it's useless return it quickly for reuse. But if the array actually needs to be used for longer then it's kept in memory like any other array. This is not a memory leak, it's just using the pool as an allocator.

Yes I can now see in docs https://learn.microsoft.com/en-us/dotnet/api/system.buffers.arraypool-1.rent?view=net-9.0

Failure to return a rented buffer is not a fatal error. However, it may lead to decreased application performance, as the pool may need to create a new buffer to replace the lost one.

I was used with other pools that would keep need to have Return called