How do I debug Azure EventHubs?

Question

I am trying to send data to an azure event hub later to be consumed by stream analytics and PowerBI.

My C# application is sending a simple test string (JSON formatted) while I am testing the Event Hub, but when I want to process the data in the event hub it tells me no data has been sent.

I am unsure how to debug the hub to see why the message does not show up, I tried google for a debug document but found none when searching for debugging azure event hubs

How can I find any error messages about this?

My C# code is simplified like this for testing purposes

private async Task SendMessageToEventHub(string messageToSend)
{
    var connectionStringBuilder = new EventHubsConnectionStringBuilder(EventHubConnectionString)
    {
        EntityPath = EventHubName
    };

    eventHubClient = EventHubClient.CreateFromConnectionString(connectionStringBuilder.ToString());

    try
    {
        await eventHubClient.SendAsync(new EventData(Encoding.UTF8.GetBytes(messageToSend)));
    } catch (Exception exception) {
        _logger.LogInformation($"-PimLog- -ProductInfoController- {DateTime.Now}, > Exception: {exception.Message} ");
    }

    _logger.LogInformation($"-PimLog- -ProductInfoController- {DateTime.Now}, EventHub Message Sent Successfully ");
}

I do see the log message that Message Sent Successfully so no obvious error is there.

When I try and run the query in the azure portal I get the following message

There is no data from input 'pimhub'. Please make sure the input source has data and then try again.

How can I debug further?

SELECT * INTO [OutputAlias] FROM [pimhub] I mean this when I click on process data and then explore — Matt Douhan

ElettroAle ElettroAle · Accepted Answer · 2019-08-16T15:05:37

In my experience, i've always used Azure portal metrics to debug the Event Hub and stream Analytics chain.

First of all, you should go to the event hub overview and check if the output requests has the same amount as input requests, as shown in the picture below

Morehover, check the User Errors and Server Errors metrics to see if events are sent with no errors. If all metrics are normal, you should check the Stream Analytics. Use metrics to check if there are one of the following errors

Data Conversion Erorrs --> Errors when Stream Analytics Try to save to te output
Input Deserialization Errors --> Most of the time are Query Errors
Runtime Errors --> Have to investigate

I also noticed that many times the portal can't capture events from the EH in order to test the ASA query (as you mentioned). Honestly speacking i don't know why, but a trick may be to copy the json object you would send in a file, then test the query through the portal using the option "Upload Sample Data From File" (ASA --> Query --> Inputs).

Hope it helps

How do I debug Azure EventHubs?

3 Answers