Cache image reponses are not disposed

[deanmarcussen]

Prerequisites

• I have written a descriptive issue title
• I have verified that I am running the latest version of ImageSharp.Web
• I have verified if the problem exist in both DEBUG and RELEASE mode
• I have searched open and closed issues to ensure it has not already been reported

Description

There is a couple of reported memory related issues, and while I know there is some tracking in ImageSharp itself about releasing retained resources, there looks to be another issue here (easily resolved) regarding stream usage.

Reported here on Orchard Core OrchardCMS/OrchardCore#9060
and likely related to this discussion #161

Performance testing locally this causes memory usage to grow dramatically - got as high as 15Gb before I stopped it.

Collecting manually doesn't drop it, so I suspect that's why there's reported app service failures.

Steps to Reproduce

This line doesn't dispose of the cache file streams

ImageSharp.Web/src/ImageSharp.Web/Middleware/ImageSharpMiddleware.cs

Line 476 in 8f67aae

await imageContext.SendAsync(stream ?? await cacheResolver.OpenReadAsync(), metadata);

adding a dispose

                    using (var stream = await cacheResolver.OpenReadAsync())
                    {
                        await imageContext.SendAsync(stream, metadata);
                    }

and everything gets collected when the GC runs, and memory usage is as one would expect.

I've seen some (difficult to reproduce) issues with file locks on the cache images, but I am hoping this might explain those as well.

Off for the covid jab in a minute, so pr to come

System Configuration

Just locally.

[deanmarcussen]

Note: that sample code doesn't match well as I'm working of this pr at the moment for testing #160

[JimBobSquarePants]

Great catch! I have time so will PR right now.

[JimBobSquarePants]

Fixed by #160