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Fixed incorrect TTL and Retry-After values for Redis #490

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Fixed incorrect TTL and Retry-After values for Redis #490

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22 changes: 11 additions & 11 deletions src/AspNetCoreRateLimit.Redis/RedisProcessingStrategy.cs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,4 @@
using AspNetCoreRateLimit;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging;
using StackExchange.Redis;
using System;
using System.Threading;
Expand All @@ -21,8 +20,7 @@ public RedisProcessingStrategy(IConnectionMultiplexer connectionMultiplexer, IRa
_logger = logger;
}

static private readonly LuaScript _atomicIncrement = LuaScript.Prepare("local count = redis.call(\"INCRBYFLOAT\", @key, tonumber(@delta)) local ttl = redis.call(\"TTL\", @key) if ttl == -1 then redis.call(\"EXPIRE\", @key, @timeout) end return count");

static private readonly LuaScript _atomicIncrement = LuaScript.Prepare("local count = redis.call(\"INCRBYFLOAT\", @key, tonumber(@delta)) local ttl = redis.call(\"TTL\", @key) if ttl == -1 then redis.call(\"EXPIRE\", @key, @timeout) end return { 'count', count, 'ttl', ttl }");
public override async Task<RateLimitCounter> ProcessRequestAsync(ClientRequestIdentity requestIdentity, RateLimitRule rule, ICounterKeyBuilder counterKeyBuilder, RateLimitOptions rateLimitOptions, CancellationToken cancellationToken = default)
{
var counterId = BuildCounterKey(requestIdentity, rule, counterKeyBuilder, rateLimitOptions);
Expand All @@ -31,16 +29,18 @@ public override async Task<RateLimitCounter> ProcessRequestAsync(ClientRequestId

public async Task<RateLimitCounter> IncrementAsync(string counterId, TimeSpan interval, Func<double> RateIncrementer = null)
{
var now = DateTime.UtcNow;
var numberOfIntervals = now.Ticks / interval.Ticks;
var intervalStart = new DateTime(numberOfIntervals * interval.Ticks, DateTimeKind.Utc);

_logger.LogDebug("Calling Lua script. {counterId}, {timeout}, {delta}", counterId, interval.TotalSeconds, 1D);
var count = await _connectionMultiplexer.GetDatabase().ScriptEvaluateAsync(_atomicIncrement, new { key = new RedisKey(counterId), timeout = interval.TotalSeconds, delta = RateIncrementer?.Invoke() ?? 1D });
var cacheStart = DateTime.UtcNow;
var cached = await _connectionMultiplexer.GetDatabase().ScriptEvaluateAsync(_atomicIncrement, new { key = new RedisKey(counterId), timeout = interval.TotalSeconds, delta = RateIncrementer?.Invoke() ?? 1D });
var responseDict = cached.ToDictionary();
var ttlSeconds = (int)responseDict["ttl"];
if (ttlSeconds != -1)
cacheStart = cacheStart.Add(-interval).AddSeconds(ttlSeconds); // Subtract the amount of seconds the interval adds, then add the amount of seconds still left to live.
var count = (double)responseDict["count"];
return new RateLimitCounter
{
Count = (double)count,
Timestamp = intervalStart
Count = count,
Timestamp = cacheStart
};
}
}
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