Exploring Three Ways to Consume Azure EventHub Messages

Hey everyone,

I'd like to share some insights about the challenges we may face when consuming messages from an Azure Event Hub. But first, a quick overview:

What is Azure Event Hub?

Azure Event Hub is a scalable data streaming platform and event ingestion service. It can receive and process millions of events per second, making it a reliable solution for big data applications. Event Hub enables you to collect, transform, and store data using real-time analytics and batch processing.

After reading this brief article, you'll gain an overview of three best practices for efficiently listening to your event hub. Each method will be compared by outlining the pros and cons.

Methods for Efficiently Listening to Your Event Hub:

1. Consume Messages Using Azure Serverless Functions Triggered by Event Hub
2. Use the EventHubProcessorClient Class on a Dedicated Hosted Service
3. Use the EventHubConsumerClient Class on a Dedicated Hosted Service

Key Concepts

Before diving into the methods, let's explain some keywords:

• Checkpoints: If you're familiar with RabbitMQ, you might know about acknowledgements (ack). When a consumer processes a message in RabbitMQ, it sends an ack to signal that the message was successfully processed. If something goes wrong, RabbitMQ tries to deliver the message again. In Azure Event Hub, we have a similar concept called checkpoints. A checkpoint is a way to remember the last message we successfully processed. This way, if something crashes or restarts, we don’t have to start from scratch. Checkpoints help manage message offsets and are stored in persistent storage, like Azure Blob Storage.
• Prefetch count: This helps to fetch multiple messages in advance, reducing latency and improving throughput.

Now it`s time to jump on different ways of handling the messages on Eventhub.

1. Consuming EventHub Messages with Azure Functions

Azure Function Eventhub triggered

Azure Functions is serverless, so it handles a lot for you. It also takes care of checkpoints automatically. Sounds easy, right? Well, not quite ?????

Challenges:

Automatic checkpointing: Azure Functions checkpoint automatically when a batch of messages is processed successfully. That sounds great until you realize you have no control over it.

No customization: If processing fails, Azure Functions don’t save a checkpoint, which means you might end up processing the same failed messages again.

2. Consuming EventHub Messages with EventHubProcessorClient class and a Dedicated Hosted Service

EvenHubProcessorClient docs

Since the Azure Functions are not flexible enough, so we may try a Hosted Service with EventHubProcessorClient. This gave us more control over checkpoints, but it came with its own limitations as well ??

Challenges:

Manual concurrency and threading: EventHubProcessorClient lets you manage checkpoints yourself, but you have to deal with concurrency and threading. Imagine messages flooding in like a waterfall, and you need to manage them all!

Database and memory issues: Without proper control, database connections and memory usage can get overwhelmed.

To manage the flood of messages, techniques like SemaphoreSlim can help control the concurrency.

However, the EventHubProcessorClient approach also has limitations related to partitions:

What is Partition in an Eventhub: Event Hub distributes messages across partitions. While EventHubProcessorClient handles load balancing, issues arise if one partition has older messages. This can lead to inefficiencies because you can't specify which partition to read from. Moreover, there's a limit on the number of messages you can read across partitions simultaneously.

To overcome this, we need a method to read from specific partitions more efficiently then let`s go to the third method.

3. Consuming EventHub Messages with EventHubConsumerClient

EventhubConsumerClient documents

The EventHubProcessorClient was better but still had its flaws. Enter EventHubConsumerClient. This method gives the most control, but it also requires the most effort.

EventHubConsumerClient is like a Swiss Army knife ???you have access to anything in the Event Hub. More customization, More Codes, and More Maintenance!

Challenges:

• Manual concurrency issues: You get full control of message retrieval.
• Maintaining checkpoints: Unlike the other methods, you need to explicitly manage where and how checkpoints are stored.
• Partition control: EventHubConsumerClient allows you to read from specific partitions by using a method name 'ReadEventsFromPartitionAsync' and setting custom offsets. This means you can manage partitions more efficiently, especially if one partition has older messages or by any reason you need to read from a specific partition.

Conclusion

Each method has its own strengths and weaknesses.

Azure Functions are great for simplicity and quick setup but lack flexibility.

EventHubProcessorClient class gives you more control but comes with the overhead of managing concurrency and partitions.

EventHubConsumerClient provides the most control and flexibility but requires a lot of manual work to manage offsets, concurrency, and checkpoints.

In the end, the best method depends on your specific needs and constraints. If you need quick setup and less control, Azure Functions might be the way to go. If you need more control and are willing to manage the complexities, then EventHubConsumerClient or EventHubProcessorClient are your best bet.

Hope this helps you in your journey with Azure Event Hub! Happy coding! ??

#Azure #Appsfactory #Microsoft #Eventhub #Event-driven