过期后不会删除ServiceStack Ormlite缓存项

Question

我们将serviceStack缓存与OrmLite提供者(MySql)结合使用。我们注意到，当我们创建带有到期日期的缓存密钥时，这些密钥在到期日期之后不会被删除。相反，它们在“ExpiryDate”列中获得空值。因此，在计算Cache.GetTimeToLive()时会产生奇怪的值。

这是serviceStack中的一个bug，还是键创建代码中的错误？我们使用的是ServiceStack版本(4.5.4)和OrmLite版本(4.5.4)

        IAppSettings appSettings = new AppSettings();

        var userConsultsPerHourLimit = appSettings.Get<int>("throttling:consultations:requests:perHourLimit");
        var userConsultsPerDayLimit = appSettings.Get<int>("throttling:consultations:requests:perDayLimit");
        var userConsultsPerMonthLimit = appSettings.Get<int>("throttling:consultations:requests:perMonthLimit");

        var userConsultsMadePerHour = Cache.GetOrCreate<int>(UserConsultPerHourCacheKey, TimeSpan.FromHours(1), () => { return 0; });
        var userConsultsMadePerDay = Cache.GetOrCreate<int>(UserConsultPerDayCacheKey, TimeSpan.FromDays(1), () => { return 0; });
        var userConsultsMadePerMonth = Cache.GetOrCreate<int>(UserConsultPerMonthCacheKey, (new DateTime(DateTime.UtcNow.Year, DateTime.UtcNow.Month, 1).AddMonths(1).AddDays(-1) - DateTime.UtcNow), () => { return 0; });

        string retryAfter = System.Threading.Thread.CurrentThread.CurrentCulture.Name == "ar-SA" ? "يوم" : "day";

        bool shouldThrottleRequest = false;
        bool didExceedMonthlyLimit = false;

        if (userConsultsMadePerHour >= userConsultsPerHourLimit)
        {
            shouldThrottleRequest = true;
            TimeSpan? timeToLive = Cache.GetTimeToLive(UserConsultPerHourCacheKey);
            if (timeToLive.HasValue)
                retryAfter = Humanizer.TimeSpanHumanizeExtensions.Humanize(timeToLive.Value, 2, System.Threading.Thread.CurrentThread.CurrentUICulture);
        }
        else if (userConsultsMadePerDay >= userConsultsPerDayLimit)
        {
            shouldThrottleRequest = true;
            TimeSpan? timeToLive = Cache.GetTimeToLive(UserConsultPerDayCacheKey);
            if (timeToLive.HasValue)
                retryAfter = Humanizer.TimeSpanHumanizeExtensions.Humanize(timeToLive.Value, 2, System.Threading.Thread.CurrentThread.CurrentUICulture);
        }
        else if (userConsultsMadePerMonth >= userConsultsPerMonthLimit)
        {
            shouldThrottleRequest = true;
            TimeSpan? timeToLive = Cache.GetTimeToLive(UserConsultPerMonthCacheKey);
            if (timeToLive.HasValue)
                retryAfter = Humanizer.TimeSpanHumanizeExtensions.Humanize(timeToLive.Value, 3, System.Threading.Thread.CurrentThread.CurrentUICulture);
            didExceedMonthlyLimit = true;
        }

Answer 1

我想我们找到了真相..。这是由于我们一方对缓存API的误用造成的。我们在其他不同的地方发现了对"Increment“和”deleted“API的API调用，导致删除密钥(那些已经超过到期日期的密钥)(通过内部调用验证方法)，然后从头重新创建(但没有终止日期)。解决方案是在调用Increment/ date之前调用GetOrCreate，以确保密钥确实存在，如果不存在，则使用新的过期日期值重新创建它。

Answer 2

这是按预期工作，在ServiceStack的最新版本中，在获取过期的缓存条目后删除行：

var ormliteCache = Cache as OrmLiteCacheClient;
var key = "int:key";

var value = Cache.GetOrCreate(key, TimeSpan.FromMilliseconds(100), () => 1);
var ttl = Cache.GetTimeToLive(key);

using (var db = ormliteCache.DbFactory.OpenDbConnection())
{
    var row = db.SingleById<CacheEntry>(key);
    Assert.That(row, Is.Not.Null);
    Assert.That(row.ExpiryDate, Is.Not.Null);
}

Assert.That(value, Is.EqualTo(1));
Assert.That(ttl.Value.TotalMilliseconds, Is.GreaterThan(0));

Thread.Sleep(200);
value = Cache.Get<int>(key);
ttl = Cache.GetTimeToLive(key);

Assert.That(value, Is.EqualTo(0));
Assert.That(ttl, Is.Null);

using (var db = ormliteCache.DbFactory.OpenDbConnection())
{
    var row = db.SingleById<CacheEntry>(key);
    Assert.That(row, Is.Null);
}

我们注意到，当我们创建带有到期日期的缓存密钥时，这些密钥在到期日期之后不会被删除。

关系数据库管理系统不会按日期自动过期缓存条目，但是当解析缓存条目时，OrmLiteCacheClient将自动删除过期条目(如上文所示)，因此它将永远不会返回过期的条目。

相反，它们在“ExpiryDate”列中获得空值。

这是不可能的只有在创建或替换现有条目时才填充ExpiryDate，它在过期时从未设置为null。当条目过期时，整个条目将被删除。