Question

我有以下代码用于从缓存中获取信息。我不知道我的应用程序是否打开了太多连接，或者只是这个错误是由于azure redis缓存上的瞬时故障造成的。

这是堆栈跟踪

[RedisConnectionException：没有连接可用于此服务   操作：GET UserProfileInformation |globaladmin@xx.onmicrosoft.com]   StackExchange.Redis.ConnectionMultiplexer.ExecuteSyncImpl（消息   消息，ResultProcessor 1 processor, ServerEndPoint server) in c:\TeamCity\buildAgent\work\3ae0647004edff78\StackExchange.Redis\StackExchange\Redis\ConnectionMultiplexer.cs:1922 StackExchange.Redis.RedisBase.ExecuteSync(Message message, ResultProcessor 1处理器，ServerEndPoint服务器）   C：\ TeamCity的\ buildAgent \工作\ 3ae0647004edff78 \ StackExchange.Redis \ StackExchange \ Redis的\ RedisBase.cs：80   StackExchange.Redis.RedisDatabase.StringGet（RedisKey key，CommandFlags   旗帜）   C：\ TeamCity的\ buildAgent \工作\ 3ae0647004edff78 \ StackExchange.Redis \ StackExchange \ Redis的\ RedisDatabase.cs：1431   xx.Utils.SampleStackExchangeRedisExtensions.Get（IDatabase缓存，   字符串键）   C：\ PROYECTOS \ XX \ XX \ utils的\ SampleStackExchangeRedisExtensions.cs：20
  xx.Cache.UserProfile.GetUserProfile（String identityname）in   C：\ PROYECTOS \ XX \ XX \缓存\ UserProfile.cs：22个
  x.Controllers.UserProfileController.GetPropertiesForUser（）in   C：\ PROYECTOS \ XX \ XX \ \控制器UserProfileController.cs：16
  lambda_method（Closure，ControllerBase，Object []）+61
  System.Web.Mvc.ActionMethodDispatcher.Execute（ControllerBase   controller，Object []参数）+14

这是代码

   public static Models.UserProfile GetUserProfile(string identityname)
        {
            /// It needs to be cached for every user because every user can have different modules enabled.

            var cachekeyname = "UserProfileInformation|" + identityname;
            IDatabase cache = CacheConnectionHelper.Connection.GetDatabase();
            Models.UserProfile userProfile = new Models.UserProfile();
            object obj = cache.Get(cachekeyname);
            string userProfileString;
            if (obj != null)
            {
                //get string from cache
                userProfileString = obj.ToString();

                //conver string to our object
                userProfile = JsonConvert.DeserializeObject<Models.UserProfile>(userProfileString);
                return userProfile;
            }
            else
            {
                #region Get User Profile from AD
                Uri serviceRoot = new Uri(SettingsHelper.AzureAdGraphApiEndPoint);
                var token = AppToken.GetAppToken();

                ActiveDirectoryClient adClient = new ActiveDirectoryClient(
                 serviceRoot,
                 async () => await AppToken.GetAppTokenAsync());

                string userObjectID = ClaimsPrincipal.Current.FindFirst("http://schemas.microsoft.com/identity/claims/objectidentifier").Value;

                Microsoft.Azure.ActiveDirectory.GraphClient.Application app = (Microsoft.Azure.ActiveDirectory.GraphClient.Application)adClient.Applications.Where(
                    a => a.AppId == SettingsHelper.ClientId).ExecuteSingleAsync().Result;
                if (app == null)
                {
                    throw new ApplicationException("Unable to get a reference to application in Azure AD.");
                }

                string requestUrl = string.Format("https://graph.windows.net/{0}/users/{1}?api-version=1.5", SettingsHelper.Tenant, identityname);
                HttpClient hc = new HttpClient();
                hc.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);
                HttpResponseMessage hrm = hc.GetAsync(new Uri(requestUrl)).Result;

                if (hrm.IsSuccessStatusCode)
                {
                    Models.UserProfile currentUserProfile = JsonConvert.DeserializeObject<Models.UserProfile>(hrm.Content.ReadAsStringAsync().Result);

                    //convert object to json string
                    userProfileString = JsonConvert.SerializeObject(currentUserProfile);

                    cache.Set(cachekeyname, userProfileString, TimeSpan.FromMinutes(SettingsHelper.CacheUserProfileMinutes));
                    return currentUserProfile;
                }
                else
                {
                    return null;
                }
                #endregion
            }
        }




public static class SampleStackExchangeRedisExtensions
    {
        public static T Get<T>(this IDatabase cache, string key)
        {
            return Deserialize<T>(cache.StringGet(key));
        }

        public static object Get(this IDatabase cache, string key)
        {
            return Deserialize<object>(cache.StringGet(key));
        }

        public static void Set(this IDatabase cache, string key, object value, TimeSpan expiration)
        {
            cache.StringSet(key, Serialize(value), expiration);
        }

        static byte[] Serialize(object o)
        {
            if (o == null)
            {
                return null;
            }
            BinaryFormatter binaryFormatter = new BinaryFormatter();
            using (MemoryStream memoryStream = new MemoryStream())
            {
                binaryFormatter.Serialize(memoryStream, o);
                byte[] objectDataAsStream = memoryStream.ToArray();
                return objectDataAsStream;
            }
        }

        static T Deserialize<T>(byte[] stream)
        {
            BinaryFormatter binaryFormatter = new BinaryFormatter();
            if (stream == null)
                return default(T);

            using (MemoryStream memoryStream = new MemoryStream(stream))
            {
                T result = (T)binaryFormatter.Deserialize(memoryStream);
                return result;
            }
        }

问题是： 1.如何控制如图所示的连接异常，以便用户不会收到错误，如果redis不可用则转到数据库？ 2.无论如何都要重试对azure redis缓存进行瞬态故障处理吗？

Answer 1

我相信这些都是暂时的错误。在我实现简单的重试逻辑之前，我在应用程序日志中看到了很多这些。我也有很多超时。非常简单的重试逻辑，再加上syncTimeout=3000为redis连接字符串解析所有这些对我来说。

public object Get(string key)
{
    return Deserialize(Cache.StringGet(key));
}

public object GetWithRetry(string key, int wait, int retryCount)
{
    int i = 0;
    do
    {
        try
        {
            return Get(key);
        }
        catch (Exception)
        {
            if (i < retryCount + 1)
            {
                Thread.Sleep(wait);
                i++;
            }
            else throw;
        }
    }
    while (i < retryCount + 1);
    return null;
}

Answer 2

我在我的缓存存储库中使用Polly来重试此异常的所有操作。我尝试了Polly的Retry方法，但这个错误的决定现在我正在使用WaitAndRetry。使用此方法，您可以使用一些休眠时间重试操作 - 使用此功能可以将操作排入Redis

Answer 3

此外，Stack Exchange客户端具有内置的重试逻辑，客户端将在其中重试。以下是有关配置选项的更多信息。 https://azure.microsoft.com/en-us/documentation/articles/cache-faq/#what-do-the-stackexchangeredis-configuration-options-do

Answer 4

正如Rouen所说，这些可能是暂时的连接错误。这是使用Polly处理重试的完整异步示例。

        var value = await Policy 
            .Handle<RedisConnectionException>() // Possible network issue 
            .WaitAndRetryAsync(3, i => TimeSpan.FromSeconds(3)) // retry 3 times, with a 3 second delay, before giving up
            .ExecuteAsync(async () => {
                return await cache.StringGetAsync(key);
            });

Answer 5

将您的redis nuget软件包更新到最新版本，它应该像我的一样解决您的问题！

没有可用于此操作的连接：使用Azure Redis缓存时

5 个答案: