unkin-agent
91655fcb0a
Jellyfin:ScanLeader:Enabled defaults to false and nothing sets it, so leader election never runs and every replica executes the timer-driven library tasks concurrently - the exact behaviour the lease prevents. - Enable gating by default when a Redis connection string is configured - Honour an explicit Enabled setting either way - Carry the effective decision onto the bound options the task worker reads - Log at startup whether gating is active - Warn when gating is enabled but no Redis connection string is configured
72 lines
3.1 KiB
C#
72 lines
3.1 KiB
C#
using System;
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using Emby.Server.Implementations.ScheduledTasks;
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using MediaBrowser.Controller.ScheduledTasks;
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using Microsoft.Extensions.Configuration;
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using Microsoft.Extensions.DependencyInjection;
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using Microsoft.Extensions.Logging;
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namespace Jellyfin.Server.Extensions;
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/// <summary>
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/// Extensions for registering the scan-leader lease.
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/// </summary>
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public static class ScanLeaderServiceCollectionExtensions
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{
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private const string RedisConnectionStringKey = "Jellyfin:TranscodeStore:RedisConnectionString";
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/// <summary>
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/// Registers the scan-leader lease and reports at <see cref="LogLevel.Information"/> whether
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/// timer-driven library tasks are gated to a single instance.
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/// </summary>
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/// <remarks>
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/// Gating is on by default once a Redis connection string is configured: that is only set for a
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/// multi-instance deployment, which is the only shape where running library scans on every
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/// instance is wrong. Single-instance installs have no Redis and keep running every task locally.
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/// </remarks>
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/// <param name="serviceCollection">The service collection.</param>
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/// <param name="configuration">The configuration to read <c>Jellyfin:ScanLeader</c> from.</param>
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/// <param name="logger">The logger to report the gating decision on.</param>
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/// <returns>The updated service collection.</returns>
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public static IServiceCollection AddScanLeaderLease(
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this IServiceCollection serviceCollection,
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IConfiguration configuration,
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ILogger logger)
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{
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ArgumentNullException.ThrowIfNull(configuration);
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ArgumentNullException.ThrowIfNull(logger);
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serviceCollection.Configure<ScanLeaderOptions>(configuration.GetSection(ScanLeaderOptions.ConfigurationSection));
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var redisConfigured = !string.IsNullOrEmpty(configuration[RedisConnectionStringKey]);
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var requested = bool.TryParse(configuration[ScanLeaderOptions.EnabledKey], out var explicitChoice)
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? explicitChoice
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: redisConfigured;
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var active = requested && redisConfigured;
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// The task worker reads Enabled from the bound options, so the effective decision has to land
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// there as well as on the lease registration below.
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serviceCollection.PostConfigure<ScanLeaderOptions>(options => options.Enabled = active);
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if (active)
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{
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logger.LogInformation(
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"Scan-leader gating is active: timer-driven library tasks run only on the instance holding the Redis scan-leader lease.");
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return serviceCollection.AddSingleton<IScanLeaderLease, RedisScanLeaderLease>();
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}
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if (requested)
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{
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logger.LogWarning(
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"Scan-leader gating is enabled but no Redis connection string is configured ({Key}), so it cannot run: timer-driven library tasks run on every instance.",
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RedisConnectionStringKey);
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}
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else
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{
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logger.LogInformation("Scan-leader gating is off: timer-driven library tasks run on every instance.");
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}
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return serviceCollection.AddSingleton<IScanLeaderLease, NullScanLeaderLease>();
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}
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}
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