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Change difficulty cache storage type to nullable

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The recent changes related to adding support for working beatmap load
cancellation exposed a flaw in the beatmap difficulty cache. With the
way the difficulty computation logic was written, any error in the
calculation process (including beatmap load timeout, or cancellation)
would result in a 0.00 star rating being permanently cached in memory
for the given beatmap.

To resolve, change the difficulty cache's return type to nullable.
In failure scenarios, `null` is returned, rather than
`default(StarDifficulty)` as done previously.
This commit is contained in:
Bartłomiej Dach
2021-11-20 16:54:58 +01:00
parent b1fcb840a9
commit 15feb17da8
7 changed files with 40 additions and 25 deletions
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26
osu.Game/Beatmaps/BeatmapDifficultyCache.cs
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@ -27,7 +27,7 @@ namespace osu.Game.Beatmaps
/// A component which performs and acts as a central cache for difficulty calculations of beatmap/ruleset/mod combinations.
/// Currently not persisted between game sessions.
/// </summary>
public class BeatmapDifficultyCache : MemoryCachingComponent<BeatmapDifficultyCache.DifficultyCacheLookup, StarDifficulty>
public class BeatmapDifficultyCache : MemoryCachingComponent<BeatmapDifficultyCache.DifficultyCacheLookup, StarDifficulty?>
{
// Too many simultaneous updates can lead to stutters. One thread seems to work fine for song select display purposes.
private readonly ThreadedTaskScheduler updateScheduler = new ThreadedTaskScheduler(1, nameof(BeatmapDifficultyCache));
@ -120,9 +120,13 @@ namespace osu.Game.Beatmaps
/// <param name="rulesetInfo">The <see cref="IRulesetInfo"/> to get the difficulty with.</param>
/// <param name="mods">The <see cref="Mod"/>s to get the difficulty with.</param>
/// <param name="cancellationToken">An optional <see cref="CancellationToken"/> which stops computing the star difficulty.</param>
/// <returns>The <see cref="StarDifficulty"/>.</returns>
public virtual Task<StarDifficulty> GetDifficultyAsync([NotNull] IBeatmapInfo beatmapInfo, [CanBeNull] IRulesetInfo rulesetInfo = null,
[CanBeNull] IEnumerable<Mod> mods = null, CancellationToken cancellationToken = default)
/// <returns>
/// The requested <see cref="StarDifficulty"/>, if non-<see langword="null"/>.
/// A <see langword="null"/> return value indicates that the difficulty process failed or was interrupted early,
/// and as such there is no usable star difficulty value to be returned.
/// </returns>
public virtual Task<StarDifficulty?> GetDifficultyAsync([NotNull] IBeatmapInfo beatmapInfo, [CanBeNull] IRulesetInfo rulesetInfo = null,
[CanBeNull] IEnumerable<Mod> mods = null, CancellationToken cancellationToken = default)
{
// In the case that the user hasn't given us a ruleset, use the beatmap's default ruleset.
rulesetInfo ??= beatmapInfo.Ruleset;
@ -134,13 +138,13 @@ namespace osu.Game.Beatmaps
if (localBeatmapInfo == null || localBeatmapInfo.ID == 0 || localRulesetInfo == null)
{
// If not, fall back to the existing star difficulty (e.g. from an online source).
return Task.FromResult(new StarDifficulty(beatmapInfo.StarRating, (beatmapInfo as IBeatmapOnlineInfo)?.MaxCombo ?? 0));
return Task.FromResult<StarDifficulty?>(new StarDifficulty(beatmapInfo.StarRating, (beatmapInfo as IBeatmapOnlineInfo)?.MaxCombo ?? 0));
}
return GetAsync(new DifficultyCacheLookup(localBeatmapInfo, localRulesetInfo, mods), cancellationToken);
}
protected override Task<StarDifficulty> ComputeValueAsync(DifficultyCacheLookup lookup, CancellationToken cancellationToken = default)
protected override Task<StarDifficulty?> ComputeValueAsync(DifficultyCacheLookup lookup, CancellationToken cancellationToken = default)
{
return Task.Factory.StartNew(() =>
{
@ -151,6 +155,8 @@ namespace osu.Game.Beatmaps
}, cancellationToken, TaskCreationOptions.HideScheduler | TaskCreationOptions.RunContinuationsAsynchronously, updateScheduler);
}
protected override bool CacheNullValues => false;
public Task<List<TimedDifficultyAttributes>> GetTimedDifficultyAttributesAsync(IWorkingBeatmap beatmap, Ruleset ruleset, Mod[] mods, CancellationToken cancellationToken = default)
{
return Task.Factory.StartNew(() => ruleset.CreateDifficultyCalculator(beatmap).CalculateTimed(mods, cancellationToken),
@ -260,7 +266,7 @@ namespace osu.Game.Beatmaps
// We're on a threadpool thread, but we should exit back to the update thread so consumers can safely handle value-changed events.
Schedule(() =>
{
if (!cancellationToken.IsCancellationRequested)
if (!cancellationToken.IsCancellationRequested && t.Result != null)
bindable.Value = t.Result;
});
}, cancellationToken);
@ -272,7 +278,7 @@ namespace osu.Game.Beatmaps
/// <param name="key">The <see cref="DifficultyCacheLookup"/> that defines the computation parameters.</param>
/// <param name="cancellationToken">The cancellation token.</param>
/// <returns>The <see cref="StarDifficulty"/>.</returns>
private StarDifficulty computeDifficulty(in DifficultyCacheLookup key, CancellationToken cancellationToken = default)
private StarDifficulty? computeDifficulty(in DifficultyCacheLookup key, CancellationToken cancellationToken = default)
{
// In the case that the user hasn't given us a ruleset, use the beatmap's default ruleset.
var beatmapInfo = key.BeatmapInfo;
@ -293,11 +299,11 @@ namespace osu.Game.Beatmaps
if (rulesetInfo.Equals(beatmapInfo.Ruleset))
Logger.Error(e, $"Failed to convert {beatmapInfo.OnlineID} to the beatmap's default ruleset ({beatmapInfo.Ruleset}).");
return new StarDifficulty();
return null;
}
catch
{
return new StarDifficulty();
return null;
}
}