Deadlock occurs for flag value fetching while using in memory or redis cache for flags

[Aniketsingh1]

How are you running Flagsmith

• Self Hosted with Docker
• Self Hosted with Kubernetes
• SaaS at flagsmith.com
• Some other way (add details in description below)

Describe the bug

I have added in memory or redis caching for flag values to control flagsmith API hits. But as soon as I add that the flag fetching for the first time becomes a never returning call and its like deadlock occurs.

Here is the code .
Do note that I am using the open feature sdk here for flagsmith provider.

Steps To Reproduce

// At the class level
private static readonly ConcurrentDictionary<string, (bool Value, DateTime Timestamp)> featureCache
     = new ConcurrentDictionary<string, (bool Value, DateTime Timestamp)>();`

   public static async Task<bool> GetFeatureState(string flagName, bool defaultValue, OpenFeature.Model.EvaluationContext context, string identity)
   {
       try
       {
           var CommonConfigValue = ConfigurationManager.AppSettings[flagName];
           var flagStatus = false;

           if (string.IsNullOrEmpty(CommonConfigValue) &&
               AppSettings._OpenFeatureProviderName.ToLower() == ProviderEnum.FlagSmith.ToString().ToLower())
           {
               var cacheflagName = $"{identity}:{flagName}";

               if (featureCache.TryGetValue(cacheflagName, out (bool Value, DateTime Timestamp) cachedEntry))
               {
                   SystemLogger.WriteInformation($"Found cached value for {cacheflagName}");
                   // Use cached value only if timestamp is within 30 minutes
                   if ((DateTime.Now - cachedEntry.Timestamp).TotalMinutes < 30)
                   {
                       SystemLogger.WriteInformation($"Using cached value for {cacheflagName}");
                       return cachedEntry.Value;
                   }
               }

               // Retrieve the Flagsmith client from the Application state
               var flagsmithClient = OpenFeature.Api.Instance.GetClient("FsProvider");

               // Check the feature flag asynchronously
               flagStatus = await flagsmithClient.GetBooleanValueAsync(flagName, defaultValue, context)
                                                 .ConfigureAwait(false);

               // Store value with timestamp
               featureCache[cacheflagName] = (flagStatus, DateTime.Now);
           }
           else
           {
               flagStatus = CommonConfigValue?.Trim().ToLower() == "true";
           }

           return flagStatus;
       }
       catch (Exception ex)
       {
           SystemLogger.WriteError($"Error checking feature state: {ex.Message}");
           return false;
       }
   }

Expected behavior

Flag value must be returned and stored in cache for 30 min time

Screenshots

No response

[Aniketsingh1]

This is happening inside dot net 4.8

[Aniketsingh1]

Any update on this ?

[matthewelwell]

@Aniketsingh1 I'm sorry, I don't quite follow this issue. It looks like you have built your own caching implementation so I'm not sure how this relates to our SDK? Could you provide any more information?

[Aniketsingh1]

I am trying to cache the flag and its values. Caching mechanism is mine but the call is made to flagsmith to get the values is actually going into a deadlock state and not returning anything.