73 lines
2.4 KiB
C#
73 lines
2.4 KiB
C#
using System.Text.Json;
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using Microsoft.EntityFrameworkCore;
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using StackExchange.Redis;
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public class ThresholdCacheLoader : IHostedService
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{
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private readonly IServiceProvider _services;
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private readonly IConnectionMultiplexer _redis;
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private readonly ILogger<ThresholdCacheLoader> _logger;
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public ThresholdCacheLoader(
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IServiceProvider services,
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IConnectionMultiplexer redis,
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ILogger<ThresholdCacheLoader> logger)
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{
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_services = services;
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_redis = redis;
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_logger = logger;
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}
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public async Task StartAsync(CancellationToken cancellationToken)
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{
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using var scope = _services.CreateScope();
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var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();
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var thresholds = await db.AlertThresholds.ToListAsync(cancellationToken);
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const int maxAttempts = 3;
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int[] backoffMs = [2000, 4000, 8000];
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for (var attempt = 0; attempt < maxAttempts; attempt++)
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{
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try
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{
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var cache = _redis.GetDatabase();
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var batch = cache.CreateBatch();
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foreach (var t in thresholds)
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{
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var json = JsonSerializer.Serialize(new
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{
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t.ObservationCode,
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t.CriticalLow,
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t.WarningLow,
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t.WarningHigh,
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t.CriticalHigh
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});
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_ = batch.StringSetAsync($"threshold:{t.ObservationCode}", json);
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}
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batch.Execute();
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_logger.LogInformation("Loaded {Count} alert thresholds into Redis cache", thresholds.Count);
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return;
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}
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catch (RedisException ex)
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{
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_logger.LogWarning(ex,
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"Redis unavailable during threshold cache load — attempt {Attempt}/{Max}",
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attempt + 1, maxAttempts);
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if (attempt < maxAttempts - 1)
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await Task.Delay(backoffMs[attempt], cancellationToken);
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}
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}
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_logger.LogError(
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"Failed to load thresholds into Redis after {Max} attempts — " +
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"application will start without cache; observation ingest falls back to PostgreSQL",
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maxAttempts);
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}
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public Task StopAsync(CancellationToken cancellationToken) => Task.CompletedTask;
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} |