Event Hub Troubleshooting

When creating an Azure Event Hub, chances are there will be no errors. This is not always a good thing, as it may mean that the errors exist but do not appear. Maybe the event hub is sending data, but the data cannot be read by a stream analytics job. Maybe the event hub really is working, but nothing appears in the dashboard. If any of these problems sound familiar, this post should help.

Testing the Event Hub

If you don’t have a source of data, like a raspberry pi or a sensor sending data, you can use this guide to create a C# program to send data to your event hub. Chances are though, this code is going to have to be modified even more than the instructions indicate, because the data sent is not in JSON. While it is not a requirement that data sent to the event hub be in JSON, if you want to read it with stream analytics that is one of the acceptable formats needed. If you are using the code provided and you want to insert a record into a database field input01, the message needs to be changed to the following to add the double-quotes and brackets required by JSON.
var message = "{'input01':\"" + Guid.NewGuid().ToString()   + "\"}";

Validating the Event Hubs Receive Messages

To ensure that the event hub is actually receiving data, validation can only be done in the old Azure portal. The service bus icon is two down from the HDInsight elephant. Double-clicking on the service bus namespace will bring up the a list of event hubs. Double-clicking on that will show this screen. This screen picture was taken roughly at 7:10. How many messages are there at 7:00? None.


This screen print was taken at 7:17. Notice anything different about the message count at 7:00?


Oh look, there are 144 Messages which came in between 7:00 and 7:05. This means that everything really was working, I just needed to wait to see them appear. The wait time tends to vary from 10-20 minutes. Perhaps nothing is wrong. Lucky if this is you as you can stop reading

Stream Analytics with Event Hubs

If you are using an event hub to pass data to a stream analytics job, step one, make sure the stream analytics job is started. Created does not mean started as it should say Running as shown in the clip below.

The input for this stream is set to an event hub which has a standard subscription. The basic subscription, which is of course cheaper, has one default consumer group. With a standard subscription multiple consumer groups can be created and more importantly named. When setting up the inputs there is a blank for the name of the consumer group. If you have a basic subscription this will be empty. If it is empty, then the event hub won’t pass data to the stream analytics job. Perhaps there is a way to get a basic event hub to work with a stream analytics job, but I couldn’t make it happen. When I created an event hub with a standard subscription and created a consumer group and added that name to the input of a streaming analytics job, it worked.

If you have found these troubleshooting tips helpful, please subscribe to my blog, as I will be passing along more tips in my next post which will detail the steps of how to get data from the event hub to a Azure Database.


Yours Always

Ginger Grant

Data aficionado et SQL Raconteur



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