azure-eventhub-dotnet

Author's original introduction

Azure Event Hubs SDK for .NET. Use for high-throughput event streaming: sending events (EventHubProducerClient, EventHubBufferedProducerClient), receiving events (EventProcessorClient with checkpointing), partition management, and real-time data ingestion. Triggers: "Event Hubs", "event streaming", "EventHubProducerClient", "EventProcessorClient", "send events", "receive events", "checkpointing", "partition".

SkillPi interpretation

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azure-eventhub-dotnet

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This azure-eventhub-dotnet package contains Microsoft Azure SDK documentation and examples, not a runtime-verified installer. Check SDK names/versions, tenant/subscription and actual endpoints; grant only task-specific least privilege. Never put administrator credentials or real secrets in samples, logs or commits. Connected cloud services may receive selected text, documents, audio, messages, logs or other input and incur charges; confirm scope, redaction and costs first. Ask the user to confirm each resource creation/update/deletion, key/access change or outbound message and test with disposable resources before production. Replace and verify placeholder endpoints and samples. SkillPi checked pinned source, complete attachments and static/antivirus evidence only; it did not run the SDK, verify service compatibility or authorize cloud access.

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This azure-eventhub-dotnet package contains Microsoft Azure SDK documentation and examples, not a runtime-verified installer. Check SDK names/versions, tenant/subscription and actual endpoints; grant only task-specific least privilege. Never put administrator credentials or real secrets in samples, logs or commits. Connected cloud services may receive selected text, documents, audio, messages, logs or other input and incur charges; confirm scope, redaction and costs first. Ask the user to confirm each resource creation/update/deletion, key/access change or outbound message and test with disposable resources before production. Replace and verify placeholder endpoints and samples. SkillPi checked pinned source, complete attachments and static/antivirus evidence only; it did not run the SDK, verify service compatibility or authorize cloud access.

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Original SKILL.md

---
name: azure-eventhub-dotnet
description: |
  Azure Event Hubs SDK for .NET. Use for high-throughput event streaming: sending events (EventHubProducerClient, EventHubBufferedProducerClient), receiving events (EventProcessorClient with checkpointing), partition management, and real-time data ingestion. Triggers: "Event Hubs", "event streaming", "EventHubProducerClient", "EventProcessorClient", "send events", "receive events", "checkpointing", "partition".
license: MIT
metadata:
  author: Microsoft
  version: "1.0.0"
  package: Azure.Messaging.EventHubs
---

# Azure.Messaging.EventHubs (.NET)

High-throughput event streaming SDK for sending and receiving events via Azure Event Hubs.

## Installation

```bash
# Core package (sending and simple receiving)
dotnet add package Azure.Messaging.EventHubs

# Processor package (production receiving with checkpointing)
dotnet add package Azure.Messaging.EventHubs.Processor

# Authentication
dotnet add package Azure.Identity

# For checkpointing (required by EventProcessorClient)
dotnet add package Azure.Storage.Blobs
```

**Current Versions**: Azure.Messaging.EventHubs v5.12.2, Azure.Messaging.EventHubs.Processor v5.12.2

## Environment Variables

```bash
EVENTHUB_FULLY_QUALIFIED_NAMESPACE=<namespace>.servicebus.windows.net  # Required: Event Hubs fully qualified namespace
EVENTHUB_NAME=<event-hub-name>  # Required: Event Hub name
BLOB_STORAGE_CONNECTION_STRING=<storage-connection-string>  # Alternative to Entra ID auth
BLOB_CONTAINER_NAME=<checkpoint-container>  # Required: checkpoint container name
EVENTHUB_CONNECTION_STRING=Endpoint=sb://<namespace>.servicebus.windows.net/;SharedAccessKeyName=...  # Alternative to Entra ID auth
AZURE_TOKEN_CREDENTIALS=prod  # Required only if DefaultAzureCredential is used in production
```

## Authentication

```csharp
using Azure.Identity;
using Azure.Messaging.EventHubs;
using Azure.Messaging.EventHubs.Producer;

// Local dev: DefaultAzureCredential. Production: set AZURE_TOKEN_CREDENTIALS=prod or AZURE_TOKEN_CREDENTIALS=<specific_credential>
var credential = new DefaultAzureCredential(
    DefaultAzureCredential.DefaultEnvironmentVariableName
);
// Or use a specific credential directly in production:
// See https://learn.microsoft.com/dotnet/api/overview/azure/identity-readme?view=azure-dotnet#credential-classes
// var credential = new ManagedIdentityCredential();

var fullyQualifiedNamespace = Environment.GetEnvironmentVariable("EVENTHUB_FULLY_QUALIFIED_NAMESPACE");
var eventHubName = Environment.GetEnvironmentVariable("EVENTHUB_NAME");

var producer = new EventHubProducerClient(
    fullyQualifiedNamespace,
    eventHubName,
    credential);
```

**Required RBAC Roles**:
- **Sending**: `Azure Event Hubs Data Sender`
- **Receiving**: `Azure Event Hubs Data Receiver`
- **Both**: `Azure Event Hubs Data Owner`

## Client Types

| Client | Purpose | When to Use |
|--------|---------|-------------|
| `EventHubProducerClient` | Send events immediately in batches | Real-time sending, full control over batching |
| `EventHubBufferedProducerClient` | Automatic batching with background sending | High-volume, fire-and-forget scenarios |
| `EventHubConsumerClient` | Simple event reading | Prototyping only, NOT for production |
| `EventProcessorClient` | Production event processing | **Always use this for receiving in production** |

## Core Workflow

### 1. Send Events (Batch)

```csharp
using Azure.Identity;
using Azure.Messaging.EventHubs;
using Azure.Messaging.EventHubs.Producer;

await using var producer = new EventHubProducerClient(
    fullyQualifiedNamespace,
    eventHubName,
    new DefaultAzureCredential());

// Create a batch (respects size limits automatically)
using EventDataBatch batch = await producer.CreateBatchAsync();

// Add events to batch
var events = new[]
{
    new EventData(BinaryData.FromString("{\"id\": 1, \"message\": \"Hello\"}")),
    new EventData(BinaryData.FromString("{\"id\": 2, \"message\": \"World\"}"))
};

foreach (var eventData in events)
{
    if (!batch.TryAdd(eventData))
    {
        // Batch is full - send it and create a new one
        await producer.SendAsync(batch);
        batch = await producer.CreateBatchAsync();
        
        if (!batch.TryAdd(eventData))
        {
            throw new Exception("Event too large for empty batch");
        }
    }
}

// Send remaining events
if (batch.Count > 0)
{
    await producer.SendAsync(batch);
}
```

### 2. Send Events (Buffered - High Volume)

```csharp
using Azure.Messaging.EventHubs.Producer;

var options = new EventHubBufferedProducerClientOptions
{
    MaximumWaitTime = TimeSpan.FromSeconds(1)
};

await using var producer = new EventHubBufferedProducerClient(
    fullyQualifiedNamespace,
    eventHubName,
    new DefaultAzureCredential(),
    options);

// Handle send success/failure
producer.SendEventBatchSucceededAsync += args =>
{
    Console.WriteLine($"Batch sent: {args.EventBatch.Count} events");
    return Task.CompletedTask;
};

producer.SendEventBatchFailedAsync += args =>
{
    Console.WriteLine($"Batch failed: {args.Exception.Message}");
    return Task.CompletedTask;
};

// Enqueue events (sent automatically in background)
for (int i = 0; i < 1000; i++)
{
    await producer.EnqueueEventAsync(new EventData($"Event {i}"));
}

// Flush remaining events before disposing
await producer.FlushAsync();
```

### 3. Receive Events (Production - EventProcessorClient)

```csharp
using Azure.Identity;
using Azure.Messaging.EventHubs;
using Azure.Messaging.EventHubs.Consumer;
using Azure.Messaging.EventHubs.Processor;
using Azure.Storage.Blobs;

// Blob container for checkpointing
var blobClient = new BlobContainerClient(
    Environment.GetEnvironmentVariable("BLOB_STORAGE_CONNECTION_STRING"),
    Environment.GetEnvironmentVariable("BLOB_CONTAINER_NAME"));

await blobClient.CreateIfNotExistsAsync();

// Create processor
var processor = new EventProcessorClient(
    blobClient,
    EventHubConsumerClient.DefaultConsumerGroup,
    fullyQualifiedNamespace,
    eventHubName,
    new DefaultAzureCredential());

// Handle events
processor.ProcessEventAsync += async args =>
{
    Console.WriteLine($"Partition: {args.Partition.PartitionId}");
    Console.WriteLine($"Data: {args.Data.EventBody}");
    
    // Checkpoint after processing (or batch checkpoints)
    await args.UpdateCheckpointAsync();
};

// Handle errors
processor.ProcessErrorAsync += args =>
{
    Console.WriteLine($"Error: {args.Exception.Message}");
    Console.WriteLine($"Partition: {args.PartitionId}");
    return Task.CompletedTask;
};

// Start processing
await processor.StartProcessingAsync();

// Run until cancelled
await Task.Delay(Timeout.Infinite, cancellationToken);

// Stop gracefully
await processor.StopProcessingAsync();
```

### 4. Partition Operations

```csharp
// Get partition IDs
string[] partitionIds = await producer.GetPartitionIdsAsync();

// Send to specific partition (use sparingly)
var options = new SendEventOptions
{
    PartitionId = "0"
};
await producer.SendAsync(events, options);

// Use partition key (recommended for ordering)
var batchOptions = new CreateBatchOptions
{
    PartitionKey = "customer-123"  // Events with same key go to same partition
};
using var batch = await producer.CreateBatchAsync(batchOptions);
```

## EventPosition Options

Control where to start reading:

```csharp
// Start from beginning
EventPosition.Earliest

// Start from end (new events only)
EventPosition.Latest

// Start from specific offset
EventPosition.FromOffset(12345)

// Start from specific sequence number
EventPosition.FromSequenceNumber(100)

// Start from specific time
EventPosition.FromEnqueuedTime(DateTimeOffset.UtcNow.AddHours(-1))
```

## ASP.NET Core Integration

```csharp
// Program.cs
using Azure.Identity;
using Azure.Messaging.EventHubs.Producer;
using Microsoft.Extensions.Azure;

builder.Services.AddAzureClients(clientBuilder =>
{
    clientBuilder.AddEventHubProducerClient(
        builder.Configuration["EventHub:FullyQualifiedNamespace"],
        builder.Configuration["EventHub:Name"]);
    
    clientBuilder.UseCredential(new DefaultAzureCredential());
});

// Inject in controller/service
public class EventService
{
    private readonly EventHubProducerClient _producer;
    
    public EventService(EventHubProducerClient producer)
    {
        _producer = producer;
    }
    
    public async Task SendAsync(string message)
    {
        using var batch = await _producer.CreateBatchAsync();
        batch.TryAdd(new EventData(message));
        await _producer.SendAsync(batch);
    }
}
```

## Best Practices

1. **Use `EventProcessorClient` for receiving** — Never use `EventHubConsumerClient` in production
2. **Checkpoint strategically** — After N events or time interval, not every event
3. **Use partition keys** — For ordering guarantees within a partition
4. **Reuse clients** — Create once, use as singleton (thread-safe)
5. **Use `await using`** — Ensures proper disposal
6. **Handle `ProcessErrorAsync`** — Always register error handler
7. **Batch events** — Use `CreateBatchAsync()` to respect size limits
8. **Use buffered producer** — For high-volume scenarios with automatic batching

## Error Handling

```csharp
using Azure.Messaging.EventHubs;

try
{
    await producer.SendAsync(batch);
}
catch (EventHubsException ex) when (ex.Reason == EventHubsException.FailureReason.ServiceBusy)
{
    // Retry with backoff
    await Task.Delay(TimeSpan.FromSeconds(5));
}
catch (EventHubsException ex) when (ex.IsTransient)
{
    // Transient error - safe to retry
    Console.WriteLine($"Transient error: {ex.Message}");
}
catch (EventHubsException ex)
{
    // Non-transient error
    Console.WriteLine($"Error: {ex.Reason} - {ex.Message}");
}
```

## Checkpointing Strategies

| Strategy | When to Use |
|----------|-------------|
| Every event | Low volume, critical data |
| Every N events | Balanced throughput/reliability |
| Time-based | Consistent checkpoint intervals |
| Batch completion | After processing a logical batch |

```csharp
// Checkpoint every 100 events
private int _eventCount = 0;

processor.ProcessEventAsync += async args =>
{
    // Process event...
    
    _eventCount++;
    if (_eventCount >= 100)
    {
        await args.UpdateCheckpointAsync();
        _eventCount = 0;
    }
};
```

## Related SDKs

| SDK | Purpose | Install |
|-----|---------|---------|
| `Azure.Messaging.EventHubs` | Core sending/receiving | `dotnet add package Azure.Messaging.EventHubs` |
| `Azure.Messaging.EventHubs.Processor` | Production processing | `dotnet add package Azure.Messaging.EventHubs.Processor` |
| `Azure.ResourceManager.EventHubs` | Management plane (create hubs) | `dotnet add package Azure.ResourceManager.EventHubs` |
| `Microsoft.Azure.WebJobs.Extensions.EventHubs` | Azure Functions binding | `dotnet add package Microsoft.Azure.WebJobs.Extensions.EventHubs` |

Copyright and license notice

    MIT License

    Copyright (c) Microsoft Corporation.

    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
    in the Software without restriction, including without limitation the rights
    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    copies of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included in all
    copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
    SOFTWARE