Exception: System.ThrowHelper.ThrowInvalidOperationException_ConcurrentOperationsNotSupported

[ivastokic]

Hi, We were getting this error in production environment on one of our pods:

It started yesterday evening, and restarting of the pod stopped it. We followed your example how to register service, also didn't have any related changes recently. Stack pointing to this one:

public async Task TrackFeature(string featureName)
    {
      int num;
      this.AnalyticsData[featureName] = this.AnalyticsData.TryGetValue(featureName, out num) ? num + 1 : 1;
      if ((DateTime.Now - this._LastFlushed).Seconds <= this._FlushIntervalSeconds)
        return;
      await this.Flush();
    } 

Do you have any idea why this happened, could it be related to lack of thread safety?

We are using version 5.0.1

[novakzaballa]

Hi @ivastokic. Could you please provide us with more information? For example: Are you using .Net Core or .Net Framework? Which version? Also, from the info and context provided, it looks like a safe thread issue, however, it is hard to say the root cause or recommend a solution without more context. Can you generate a minimal project reproducing the issue and your current configuration?

[ivastokic]

Hi, it is .NET Core app, but is it also hard to reproduce it from out side. The change with introducing enableAnalytics ON, on registering FlagsmithClient was introduced in October 2023, and worked well so far, even when this occurred, it fail on only one of pods, fine on others. We will turn off analytics for now.

[MaximTkachenko]

It looks like you have a thread sefety issue inside AnalyticsProcessor:

• according to your documentation FlagsmithClient is used as a sigleton
• it means that AnalyticsProcessor created inside FlagsmithClient is used as a sigleton too
• inside AnalyticsProcessor you use plain dictionary for feature usage tracking without any synchronization and periodically you call Clear for this dictionary

So you read and modify this dictionary concurrently without any protection. I made a screenshot from the decompiled code:

[novakzaballa]

Thank you @MaximTkachenko and sorry about the late reply! We will take a look into this issue soon. In the mean time if you prefer you can submit a PR and We'll get that merged for you ASAP.

[novakzaballa]

While I was not able to reproduce the issue with functional tests, or automatic tests using the SDK main functions, I was able to systematically replicate the issue accessing directly the TrackFeature method of the AnalycticsProcessor class and I put a fix in place in the above PR, which is ready for review now. I will update this thread as soon as we have the fix merged.