Be resilient to asset-cache mutating while retrieving assets from the host #72599
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In a perf fix I made last week, I assumed _assetCache wouldn't change underneath me during execution of SynchronizeAssetsAsync. That assumption is not true. Now, if the asset cache changes such that the missingChecksums array is no longer sufficient to hold all missing checksums, then grow the array capacity such that it can hold additional entries that might now be missing.
…ynchronizeAssetsAsync' into assets
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CyrusNajmabadi
commented
Mar 19, 2024
| @@ -29,39 +29,34 @@ internal sealed partial class AssetProvider(Checksum solutionChecksum, SolutionA | |||
| private readonly SolutionAssetCache _assetCache = assetCache; | |||
| private readonly IAssetSource _assetSource = assetSource; | |||
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| private T GetRequiredAsset<T>(Checksum checksum) | |||
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this operation si fundamentally not supported. there is no way, ever, to ensure that a checksum you're asking for is actually in the asset provider (unles sit was pinned. but that's a vanishingly small number of cases).
CyrusNajmabadi
commented
Mar 19, 2024
| @@ -136,24 +131,60 @@ public async ValueTask SynchronizeProjectAssetsAsync(ProjectStateChecksums proje | |||
| missingChecksumsCount = 0; | |||
| foreach (var checksum in checksums) | |||
| { | |||
| if (!_assetCache.TryGetAsset<object>(checksum, out _)) | |||
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view with whitespace off.
CyrusNajmabadi
commented
Mar 19, 2024
CyrusNajmabadi
commented
Mar 19, 2024
| @@ -47,14 +51,17 @@ public async ValueTask SynchronizeSolutionAssetsAsync(Checksum solutionChecksum, | |||
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| solutionChecksumObject.AddAllTo(checksums); | |||
| checksums.Remove(solutionChecksumObject.Checksum); | |||
| await _assetProvider.SynchronizeAssetsAsync(assetHint: AssetHint.None, checksums, cancellationToken).ConfigureAwait(false); | |||
| await _assetProvider.SynchronizeAssetsAsync(assetHint: AssetHint.None, checksums, results: null, cancellationToken).ConfigureAwait(false); | |||
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so we could pass a dictionary here that we then read in below. but i didn't feel like it was worth it. the data will normally always stay in the asset provider. and the cahnge below to use GetAssetAsync will normally find it, or rarely then go and reretrieve it in the rare unlucky case. that saves a potentially large dictionary alloc here (even if pooled).
CyrusNajmabadi
commented
Mar 19, 2024
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| await _assetProvider.SynchronizeAssetsAsync( | ||
| assetHint: projectChecksum.ProjectId, checksums, cancellationToken).ConfigureAwait(false); | ||
| assetHint: projectChecksum.ProjectId, checksums, results: null, cancellationToken).ConfigureAwait(false); |
ToddGrun
reviewed
Mar 19, 2024
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The asset cache serves more as a weak cache of data, storing information on the server in the hopes it will be useful at future points in time. It contains a GC thread that wakes up every minute or so and flushes data it thinks isn't needed anymore. Due to that, access to the data from the cache itself is fundamentally racey and should not be trusted.