Azure Blob Trigger Function triggering only once when file is updated with NLog

Question

I am using NLog to log the messages in azure blob storage with blob name as dd-mm-yyyy.log. For each and every message which I inserted into "dd-mm-yyyy.log" file, I want to call/trigger the azure blob trigger function.

For Example, if I insert 3 message in one request one after the other, then azure blob trigger function should trigger 3 times. Curranty it is trigging only 1 time.

But if I insert 3 message with 1 min difference (i.e. 1 message at 1 min), then the azure blob trigger function triggering 3 times.

Below is the Nlog code:

try
{
    //Some logic
}
catch (Exception ex)
{
    LoggingHelper.Fatal($"Exception : {Convert.ToString(ex)}");
    LoggingHelper.Fatal($"InnerException : {Convert.ToString(ex.InnerException)}");
    LoggingHelper.Fatal($"Exception StackTrace: {ex.StackTrace}");
}

Azure Blob trigger code:

[FunctionName("Function1")]
public static async Task Run([BlobTrigger("poccontainer/{name}", Connection = "")] Stream myBlob, string name, 
    ILogger log, ExecutionContext context, BlobProperties Properties)
{
    log.LogInformation($"Blob Name:{name}");
    //Logic to process the file data
}

I want to trigger the azure blob trigger function every time when I insert a message into dd-mm-yyyy.log.

Solution which I tried but no use: I have added below code in the host.json file but no use.

{
  "version": "2.0",
  "extensions": {
    "queues": {
      "batchSize": 1
    }
  }
}

Any help is really appreciated.

Answer 1

I suggest not using the Azure Blob Trigger for the Function at all. The blob trigger relies on a polling mechanism so timing might be the issue in your case. From the docs:

[...] There's no guarantee that all events are captured. Under some conditions, logs may be missed.

If you require faster or more reliable blob processing, consider creating a queue message when you create the blob. Then use a queue trigger instead of a blob trigger to process the blob. Another option is to use Event Grid; see the tutorial Automate resizing uploaded images using Event Grid.

I would definitely check the Event Grid Trigger in your case. Or, if order is important, the queue based trigger.