ecaecd21bb
Sends a keepalive/heartbeat signal across RPC while a game is running. Server-side this enables the ability to manage play session state with realtime information instead of hoping that the client will stop the play session. Keepalives are tracked in server cache allowing for future potential horizontally-scaled server instances.
50 lines
2.2 KiB
C#
50 lines
2.2 KiB
C#
using ZiggyCreatures.Caching.Fusion;
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namespace LANCommander.Server.Services;
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/// <summary>
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/// Tracks the last time each active play session was heard from via the RPC keepalive. Backed by
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/// <see cref="IFusionCache"/> so it works across instances when a distributed (e.g. Redis) backend
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/// is configured. The sweep consults this to end sessions that have gone stale, ending them at the
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/// last known-alive time so recorded playtime isn't inflated.
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/// </summary>
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public sealed class PlaySessionKeepAliveTracker(
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IFusionCache cache,
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SettingsProvider<Settings.Settings> settingsProvider)
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{
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private static string GetCacheKey(Guid gameId, Guid userId) => $"PlaySessions/KeepAlive/{gameId}/{userId}";
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// Keep entries alive well past the staleness timeout so the sweep can still read the last
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// keepalive time when ending a stale session, rather than losing it to expiration.
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private TimeSpan EntryDuration =>
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TimeSpan.FromSeconds(Math.Max(1, settingsProvider.CurrentValue.Server.GameServers.KeepAliveTimeout) * 3);
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/// <summary>Records that the session for this game/user was heard from just now.</summary>
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public async Task TouchAsync(Guid gameId, Guid userId) =>
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await cache.SetAsync(GetCacheKey(gameId, userId), DateTime.UtcNow, EntryDuration);
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/// <summary>
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/// Returns the last-seen time for the session, seeding it with the current time if we have no
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/// record yet (e.g. a session that predates a restart with no distributed backend). Seeding
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/// grants a fresh grace window rather than immediately reaping a session we haven't observed yet.
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/// </summary>
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public async Task<DateTime> GetOrSeedAsync(Guid gameId, Guid userId)
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{
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var cacheKey = GetCacheKey(gameId, userId);
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var lastSeen = await cache.TryGetAsync<DateTime>(cacheKey);
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if (lastSeen.HasValue)
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return lastSeen.Value;
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var now = DateTime.UtcNow;
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await cache.SetAsync(cacheKey, now, EntryDuration);
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return now;
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}
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/// <summary>Stops tracking the session (it ended normally or was swept).</summary>
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public async Task RemoveAsync(Guid gameId, Guid userId) =>
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await cache.RemoveAsync(GetCacheKey(gameId, userId));
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}
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