没有可用于此操作的连接:使用Azure Redis缓存时

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天蓝色redis缓存的瞬态故障造成的.

这是堆栈跟踪

[RedisConnectionException:没有可用于此操作的连接:GET UserProfileInformation|globaladmin@xx.onmicrosoft.com] 1 processor, ServerEndPoint server) in c:\TeamCity\buildAgent\work\3ae0647004edff78\StackExchange.Redis\StackExchange\Redis\ConnectionMultiplexer.cs:1922 StackExchange.Redis.RedisBase.ExecuteSync(Message message, ResultProcessorc:\ TeamCity\buildAgent\work中的StackExchange.Redis.ConnectionMultiplexer.ExecuteSyncImpl(消息消息,ResultProcessor 1处理器,ServerEndPoint服务器)\3ae0647004edff78\StackExchange.Redis\StackExchange\Redis\RedisBase.cs:80 StackExchange.Redis.RedisDatabase.StringGet(RedisKey key,CommandFlags标志)位于c:\ TeamCity\buildAgent\work\3ae0647004edff78\StackExchange.Redis\StackExchange\Redis\RedisDatabase.cs:1431 xx.Utils.SampleStackExchangeRedisExtensions.Get(IDatabase cache,String key)位于C:\ Proyectos\xx\xx\Utils\SampleStackExchangeRedisExtensions.cs:20
xx.Cache.UserProfile.GetUserProfile(String identityname)in C:\Proyectos\xx\xx\Cache\UserProfile.cs:22
x.Controllers.UserProfileController.GetPropertiesForUser()在C:\ Proyectos\xx\xx\Controllers\UserProfileController.cs:16
lambda_method(Closure,ControllerBase,Object []) +61
System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase控制器,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,重新尝试使用azure redis缓存进行瞬态故障处理？

Answer 1

我相信这些是短暂的错误.在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syncTimeout=3000上redis连接字符串解决了所有这些问题.

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;
}