Use Azure Event Hubs from Apache Kafka applications

Event Hubs provides an endpoint compatible with the Apache Kafka® producer and consumer APIs that can be used by most existing Apache Kafka client applications as an alternative to running your own Apache Kafka cluster. Event Hubs supports Apache Kafka's producer and consumer APIs clients at version 1.0 and above.

What does Event Hubs for Kafka provide?

The Event Hubs for Apache Kafka feature provides a protocol head on top of Azure Event Hubs that is protocol compatible with Apache Kafka clients built for Apache Kafka server versions 1.0 and later and supports for both reading from and writing to Event Hubs, which are equivalent to Apache Kafka topics.

You can often use the Event Hubs Kafka endpoint from your applications without code changes compared to your existing Kafka setup and only modify the configuration: Update the connection string in configurations to point to the Kafka endpoint exposed by your event hub instead of pointing to your Kafka cluster. Then, you can start streaming events from your applications that use the Kafka protocol into Event Hubs.

Conceptually, Kafka and Event Hubs are very similar: they're both partitioned logs built for streaming data, whereby the client controls which part of the retained log it wants to read. The following table maps concepts between Kafka and Event Hubs.

Kafka and Event Hub conceptual mapping

Kafka Concept Event Hubs Concept
Cluster Namespace
Topic Event Hub
Partition Partition
Consumer Group Consumer Group
Offset Offset

Key differences between Apache Kafka and Event Hubs

While Apache Kafka is software you typically need to install and operate, Event Hubs is a fully managed, cloud-native service. There are no servers, disks, or networks to manage and monitor and no brokers to consider or configure, ever. You create a namespace, which is an endpoint with a fully qualified domain name, and then you create Event Hubs (topics) within that namespace.

For more information about Event Hubs and namespaces, see Event Hubs features. As a cloud service, Event Hubs uses a single stable virtual IP address as the endpoint, so clients don't need to know about the brokers or machines within a cluster. Even though Event Hubs implements the same protocol, this difference means that all Kafka traffic for all partitions is predictably routed through this one endpoint rather than requiring firewall access for all brokers of a cluster.

Scale in Event Hubs is controlled by how many throughput units (TUs) or processing units you purchase. If you enable the Auto-Inflate feature for a standard tier namespace, Event Hubs automatically scales up TUs when you reach the throughput limit. This feature work also works with the Apache Kafka protocol support. For a premier tier namespace, you can increase the number of processing units assigned to the namespace.

Is Apache Kafka the right solution for your workload?

Coming from building applications using Apache Kafka, it will also useful to understand that Azure Event Hubs is part of a fleet of services which also includes Azure Service Bus, and Azure Event Grid.

While some providers of commercial distributions of Apache Kafka might suggest that Apache Kafka is a one-stop-shop for all your messaging platform needs, the reality is that Apache Kafka does not implement, for instance, the competing-consumer queue pattern, does not have support for publish-subscribe at a level that allows subscribers access to the incoming messages based on server-evaluated rules other than plain offsets, and it has no facilities to track the lifecycle of a job initiated by a message or sidelining faulty messages into a dead-letter queue, all of which are foundational for many enterprise messaging scenarios.

To understand the differences between patterns and which pattern is best covered by which service, please review the Asynchronous messaging options in Azure guidance. As an Apache Kafka user, you may find that communication paths you have so far realized with Kafka, can be realized with far less basic complexity and yet more powerful capabilities using either Event Grid or Service Bus.

If you need specific features of Apache Kafka that are not available through the Event Hubs for Apache Kafka interface or if your implementation pattern exceeds the Event Hubs quotas, you can also run a native Apache Kafka cluster in Azure HDInsight.

Security and authentication

Every time you publish or consume events from an Event Hubs for Kafka, your client is trying to access the Event Hubs resources. You want to ensure that the resources are accessed using an authorized entity. When using Apache Kafka protocol with your clients, you can set your configuration for authentication and encryption using the SASL mechanisms. When using Event Hubs for Kafka requires the TLS-encryption (as all data in transit with Event Hubs is TLS encrypted). It can be done specifying the SASL_SSL option in your configuration file.

Azure Event Hubs provides multiple options to authorize access to your secure resources.

  • OAuth 2.0
  • Shared access signature (SAS)

OAuth 2.0

Event Hubs integrates with Azure Active Directory (Azure AD), which provides an OAuth 2.0 compliant centralized authorization server. With Azure AD, you can use Azure role-based access control (Azure RBAC) to grant fine grained permissions to your client identities. You can use this feature with your Kafka clients by specifying SASL_SSL for the protocol and OAUTHBEARER for the mechanism. For details about Azure roles and levels for scoping access, see Authorize access with Azure AD.

bootstrap.servers=NAMESPACENAME.servicebus.windows.net:9093
security.protocol=SASL_SSL
sasl.mechanism=OAUTHBEARER
sasl.jaas.config=org.apache.kafka.common.security.oauthbearer.OAuthBearerLoginModule required;
sasl.login.callback.handler.class=CustomAuthenticateCallbackHandler

Shared Access Signature (SAS)

Event Hubs also provides the Shared Access Signatures (SAS) for delegated access to Event Hubs for Kafka resources. Authorizing access using OAuth 2.0 token-based mechanism provides superior security and ease of use over SAS. The built-in roles can also eliminate the need for ACL-based authorization, which has to be maintained and managed by the user. You can use this feature with your Kafka clients by specifying SASL_SSL for the protocol and PLAIN for the mechanism.

bootstrap.servers=NAMESPACENAME.servicebus.windows.net:9093
security.protocol=SASL_SSL
sasl.mechanism=PLAIN
sasl.jaas.config=org.apache.kafka.common.security.plain.PlainLoginModule required username="$ConnectionString" password="{YOUR.EVENTHUBS.CONNECTION.STRING}";

Important

Replace {YOUR.EVENTHUBS.CONNECTION.STRING} with the connection string for your Event Hubs namespace. For instructions on getting the connection string, see Get an Event Hubs connection string. Here's an example configuration: sasl.jaas.config=org.apache.kafka.common.security.plain.PlainLoginModule required username="$ConnectionString" password="Endpoint=sb://mynamespace.servicebus.windows.net/;SharedAccessKeyName=RootManageSharedAccessKey;SharedAccessKey=XXXXXXXXXXXXXXXX";

Note

When using SAS authentication with Kafka clients, established connections aren't disconnected when the SAS key is regenerated.

Samples

For a tutorial with step-by-step instructions to create an event hub and access it using SAS or OAuth, see Quickstart: Data streaming with Event Hubs using the Kafka protocol.

For more samples that show how to use OAuth with Event Hubs for Kafka, see samples on GitHub.

Other Event Hubs features

The Event Hubs for Apache Kafka feature is one of three protocols concurrently available on Azure Event Hubs, complementing HTTP and AMQP. You can write with any of these protocols and read with any another, so that your current Apache Kafka producers can continue publishing via Apache Kafka, but your reader can benefit from the the native integration with Event Hubs' AMQP interface, such as Azure Stream Analytics or Azure Functions. Reversely, you can readily integrate Azure Event Hubs into AMQP routing networks as an target endpoint, and yet read data through Apache Kafka integrations.

Additionally, Event Hubs features such as Capture, which enables extremely cost efficient long term archival via Azure Blob Storage and Azure Data Lake Storage, and Geo Disaster-Recovery also work with the Event Hubs for Kafka feature.

Apache Kafka feature differences

The goal of Event Hubs for Apache Kafka is to provide access to Azure Event Hub's capabilities to applications that are locked into the Apache Kafka API and would otherwise have to be backed by an Apache Kafka cluster.

As explained above, the Azure Messaging fleet provides rich and robust coverage for a multitude of messaging scenarios, and although the following features are not currently supported through Event Hubs' support for the Apache Kafka API, we point out where and how the desired capability is available.

Transactions

Azure Service Bus has robust transaction support that allows receiving and settling messages and sessions while sending outbound messages resulting from message processing to multiple target entities under the consistency protection of a transaction. The feature set not only allows for exactly-once processing of each message in a sequence, but also avoids the risk of another consumer inadvertently reprocessing the same messages as it would be the case with Apache Kafka. Service Bus is the recommended service for transactional message workloads.

Compression

The client-side compression feature of Apache Kafka compresses a batch of multiple messages into a single message on the producer side and decompresses the batch on the consumer side. The Apache Kafka broker treats the batch as a special message.

This feature is fundamentally at odds with Azure Event Hubs' multi-protocol model, which allows for messages, even those sent in batches, to be individually retrievable from the broker and through any protocol.

The payload of any Event Hub event is a byte stream and the content can be compressed with an algorithm of your choosing. The Apache Avro encoding format supports compression natively.

Log Compaction

Apache Kafka log compaction is a feature that allows evicting all but the last record of each key from a partition, which effectively turns an Apache Kafka topic into a key-value store where the last value added overrides the previous one. This feature is presently not implemented by Azure Event Hubs. The key-value store pattern, even with frequent updates, is far better supported by database services like Azure Cosmos DB. Please refer to the Log Projection topic in the Event Hubs federation guidance for more details.

Kafka Streams

Kafka Streams is a client library for stream analytics that is part of the Apache Kafka open source project, but is separate from the Apache Kafka event stream broker.

The most common reason Azure Event Hubs customers ask for Kafka Streams support is because they are interested in Confluent's "ksqlDB" product. "ksqlDB" is a proprietary shared source project that is licensed such that no vendor "offering software-as-a-service, platform-as-a-service, infrastructure-as-a-service or other similar online services that competes with Confluent products or services" is permitted to use or offer "ksqlDB" support. Practically, if you use ksqlDB, you must either operate Kafka yourself or you must use Confluent’s cloud offerings. The licensing terms might also affect Azure customers who offer services for a purpose excluded by the license.

Standalone and without ksqlDB, Kafka Streams has fewer capabilities than many alternative frameworks and services, most of which have built-in streaming SQL interfaces, and all of which integrate with Azure Event Hubs today:

The listed services and frameworks can generally acquire event streams and reference data directly from a diverse set of sources through adapters. Kafka Streams can only acquire data from Apache Kafka and your analytics projects are therefore locked into Apache Kafka. To use data from other sources, you are required to first import data into Apache Kafka with the Kafka Connect framework.

If you must use the Kafka Streams framework on Azure, Apache Kafka on HDInsight will provide you with that option. Apache Kafka on HDInsight provides full control over all configuration aspects of Apache Kafka, while being fully integrated with various aspects of the Azure platform, from fault/update domain placement to network isolation to monitoring integration.

Next steps

This article provided an introduction to Event Hubs for Kafka. To learn more, see Apache Kafka developer guide for Azure Event Hubs.