PatchItemAsync sometimes does not update the document in the Cosmos but returns an OK StatusCode

Question

PatchItemAsync sometimes does not update the document in the Cosmos but returns an OK StatusCode

Althea U Guerra 0

I have a durable function that accepts list of objects and chains two activities:

Activity 1: Process and send this list of objects to a third party system one by one and returns back an id to be updated in the object's property
Activity 2: Update this list of updated objects into Azure Cosmos Db within for loop using PatchItemAsync

Issue: Most of the time, there will be an object/document (item count is very random, there will be one, sometimes 4 or more and sometimes all are successfully updated) in the list of objects that will not be updated but the ItemResponse from PatchItemAsync is OK. But if the function receives one, object is always updated successfully.

What could be the root cause of this issue?

Programming Language: C# .Net

MayankBargali-MSFT 71,016 Reputation points Moderator

2024-02-07T05:41:22.17+00:00

@Althea U Guerra Thanks for reaching out. Did you see any error/expectation on your durable function? You can review the application insights logs to know more details on the error/exception or Diagnose and solve problems blade on your function to know more details if there are any runtime exception due to which you are observing this behavior. Based on the information it looks like this might be a concurrency issue with updating the objects in Azure Cosmos DB. It is possible that multiple instances of the function are trying to update the same object at the same time, causing conflicts and resulting in some objects not being updated but it would not be possible to know the root cause of the issue without reviewing the function logs. In case if you couldn't find much information on the logs at your end using application insights/diagnose and solve problem then this would need to be further reviewed from the logs at our end.
Althea U Guerra 0 Reputation points

2024-02-07T20:55:54.2866667+00:00

thanks @MayanBargali-MSFT for your response. I have added some custom logs everytime I call this update activity. I could only see 1 set for each item (specifically for an item that encountered the non-updating issue). I could not see any exceptions. I could also see a change on the _ts but the properties have not been updated.
MayankBargali-MSFT 71,016 Reputation points Moderator

2024-02-08T10:30:41.67+00:00

@Althea U Guerra What about the application insights logs or Diagnose and solve problems blade on your function. Did you see any insights there?
Althea U Guerra 0 Reputation points

2024-02-08T15:58:37.1833333+00:00

@MayanBargali-MSFT is there any specific blade you want me to check? As far as my knowledge on Azure, I have checked the Availability and Performance in the Diagnose and solve problems and in the traces and exceptions in Application Insights, but no error or exceptions logged.
Althea U Guerra 0 Reputation points

2024-02-08T16:01:54.3266667+00:00

@MayanBargali-MSFT is there any specific blade that you want me to check? I have checked the Availability and Performance on the Diagnose and solve problems but no error in it. Also in the exceptions and traces in the Application Insights, no errors/exceptions in it.
Althea U Guerra 0 Reputation points

2024-02-08T18:10:51.1133333+00:00

@MayanBargali-MSFT is there any way to explicitly force the functionApp to run only in 1 instance? I would like to test this and see if this issue would still occur
MayankBargali-MSFT 71,016 Reputation points Moderator

2024-02-09T10:49:07.3366667+00:00

@Althea U Guerra You can define the Singleton attribute below on your function method. [Singleton(Mode = SingletonMode.Function)]
Althea U Guerra 0 Reputation points

2024-02-09T22:21:16.3266667+00:00

@MayanBargali-MSFT I have tried and tested with the Singleton on the function but issue still occurred.
MayankBargali-MSFT 71,016 Reputation points Moderator

2024-02-12T05:45:19.15+00:00

@Althea U Guerra I will suggest to engage us over one on one support request to review this further. In case if you don't have the support plan then please refer to the private message on this question. For more details about private messages please refer to this.