Publishing Events to Azure Event Hubs

This guide explains how to publish events to Azure Event Hubs. Publishing involves sending data records (events) to an Event Hub. You can use various SDKs and protocols to achieve this.

Example Language:

Core Concepts

Event Hub: A highly scalable data streaming platform and event ingestion service.
Publisher: An application or service that sends events to an Event Hub.
Event: A record or message containing data.
Partition Key: A value that determines which partition an event is routed to.

Using the Azure Event Hubs SDK

The recommended way to publish events is by using the official Azure SDKs. These SDKs handle connections, retries, batching, and other complexities for you.

Example: Publishing with the .NET SDK

using Azure.Messaging.EventHubs;
using Azure.Messaging.EventHubs.Producer;
using System;
using System.Collections.Generic;
using System.Text;
using System.Threading.Tasks;

async Task PublishEventsAsync()
{
    string connectionString = "";
    string eventHubName = "";

    await using var producerClient = new EventHubProducerClient(connectionString, eventHubName);

    using EventDataBatch eventBatch = await producerClient.CreateBatchAsync();

    for (int i = 1; i <= 5; i++)
    {
        var eventBody = $"{{ \"message\": \"Event number {i}\" }}";
        if (!eventBatch.TryAddMessage(new EventData(Encoding.UTF8.GetBytes(eventBody))))
        {
            // If the batch is full, send it and start a new one
            await producerClient.SendAsync(eventBatch);
            Console.WriteLine($"Sent batch with {eventBatch.Count} events.");
            eventBatch.Clear();
        }
    }

    // Send the last batch if it's not empty
    if (eventBatch.Count > 0)
    {
        await producerClient.SendAsync(eventBatch);
        Console.WriteLine($"Sent last batch with {eventBatch.Count} events.");
    }

    Console.WriteLine("All events published successfully.");
}

// Call the async method
// PublishEventsAsync().GetAwaiter().GetResult();

Note: Replace <YOUR_EVENT_HUB_CONNECTION_STRING> and <YOUR_EVENT_HUB_NAME> with your actual Event Hub connection string and name.

Example: Publishing with the Python SDK

from azure.eventhub import EventHubProducer, EventData
import os
import json

async def publish_events_async():
    connection_str = os.environ["EVENTHUB_CONNECTION_STR"]
    eventhub_name = os.environ["EVENTHUB_NAME"]

    producer = EventHubProducer(connection_str, eventhub_name)

    async with producer:
        async with producer.create_batch() as batch:
            for i in range(1, 6):
                event_body = json.dumps({"message": f"Event number {i}"})
                try:
                    batch.add(EventData(event_body.encode('utf-8')))
                except ValueError:
                    # Batch is full, send it and start a new one
                    await producer.send(batch)
                    print(f"Sent batch with {len(batch)} events.")
                    batch = await producer.create_batch() # Re-create batch

            # Send the last batch if not empty
            if len(batch) > 0:
                await producer.send(batch)
                print(f"Sent last batch with {len(batch)} events.")
    print("All events published successfully.")

# To run this async function:
# import asyncio
# asyncio.run(publish_events_async())

Example: Publishing with the Java SDK

import com.azure.messaging.eventhubs.EventData;
import com.azure.messaging.eventhubs.EventHubProducerClient;
import com.azure.messaging.eventhubs.EventHubClientBuilder;
import com.azure.messaging.eventhubs.models.CreateBatchOptions;
import com.azure.messaging.eventhubs.models.EventHubEvent;

import java.util.concurrent.ExecutionException;
import java.util.Arrays;

public class EventPublisher {

    public static void main(String[] args) {
        String connectionString = "";
        String eventHubName = "";

        EventHubProducerClient producerClient = new EventHubClientBuilder()
                .connectionString(connectionString, eventHubName)
                .buildProducerClient();

        try {
            for (int i = 0; i < 5; i++) {
                String eventBody = String.format("{\"message\": \"Event number %d\"}", i + 1);
                EventHubEvent event = new EventHubEvent(eventBody.getBytes());

                CreateBatchOptions options = new CreateBatchOptions();
                // You can set maxBytes, partitionId, etc. here if needed.

                producerClient.send(Arrays.asList(event));
                System.out.println("Sent event: " + eventBody);
            }
            System.out.println("All events published successfully.");

        } catch (Exception e) {
            System.err.println("Error publishing events: " + e.getMessage());
            e.printStackTrace();
        } finally {
            producerClient.close();
        }
    }
}

Example: Publishing with the Node.js SDK

const { EventHubProducerClient } = require("@azure/event-hubs");

async function publishEvents() {
    const connectionString = process.env.EVENTHUB_CONNECTION_STR;
    const eventHubName = process.env.EVENTHUB_NAME;

    const producerClient = new EventHubProducerClient(connectionString, eventHubName);

    let batch = await producerClient.createBatch();

    for (let i = 1; i <= 5; i++) {
        const eventBody = { message: `Event number ${i}` };
        if (!batch.tryAdd({ body: eventBody })) {
            // If batch is full, send it and create a new one
            await producerClient.send(batch);
            console.log(`Sent batch with ${batch.count} events.`);
            batch = await producerClient.createBatch();
        }
    }

    // Send the last batch if not empty
    if (batch.count > 0) {
        await producerClient.send(batch);
        console.log(`Sent last batch with ${batch.count} events.`);
    }

    console.log("All events published successfully.");
    await producerClient.close();
}

// To run this function:
// publishEvents().catch(err => console.error("Error publishing events:", err));

Publishing Strategies

When publishing events, consider the following:

Partitioning

Events are routed to specific partitions within an Event Hub. By default, the SDK might use round-robin distribution. To ensure events from the same source or related events are processed in order, use the partitionKey property when creating your EventData. This ensures all events with the same partition key are sent to the same partition.

Tip: Use a consistent and meaningful value for your partitionKey, such as a user ID, session ID, or device ID, to guarantee ordered processing for related events.

Batching

For efficiency, the SDKs often batch events before sending them to Event Hubs. This reduces network overhead. You can control batching by checking the batch size (e.g., using TryAddMessage or similar methods) and sending batches when they are full or when you've sent all your events.

Compression

For large volumes of data, consider enabling compression if supported by the SDK and your Event Hub configuration. This can significantly reduce bandwidth usage and latency.

Alternative Publishing Methods

REST API: You can publish events directly via HTTP POST requests to the Event Hubs API endpoint. This is useful for scenarios where you cannot use an SDK.
AMQP: Event Hubs supports the Advanced Message Queuing Protocol (AMQP). You can use AMQP clients to send events.

Troubleshooting

Common issues when publishing include:

Authentication errors: Ensure your connection string is correct and has the necessary permissions.
Quota exceeded: Check your Event Hubs throughput limits.
Network issues: Verify network connectivity to Azure Event Hubs endpoints.

Warning: Never hardcode sensitive connection strings directly in your application code. Use environment variables, Azure Key Vault, or other secure secret management solutions.