Tutorial: Working with Azure Event Hubs Schema Registry

This tutorial will guide you through the process of integrating Azure Event Hubs with the Schema Registry to manage and validate event schemas. Schema Registry helps ensure data consistency and interoperability within your event streaming pipeline.

Prerequisites

Step 1: Enable and Configure Schema Registry

The Schema Registry is an optional component that can be enabled for your Event Hubs namespace. You can enable it through the Azure portal or Azure CLI.

Using Azure CLI:


az eventhubs namespace schema-registry update \
    --resource-group  \
    --namespace-name  \
    --enabled true

Replace <your-resource-group-name> and <your-eventhubs-namespace-name> with your actual resource group and namespace names.

Step 2: Create a Schema Group

Within the Schema Registry, you define schema groups. Each group can hold multiple versions of a schema for a specific event type.

Using Azure CLI:


az eventhubs schema-group create \
    --resource-group  \
    --namespace-name  \
    --schema-group-name MySchemaGroup \
    --auto-create-schema true \
    --serialization DataContractJson \
    --retention-days 7

Step 3: Register a Schema

Now, let's register your first schema for the created schema group. Schemas can be defined in JSON, Avro, or other supported formats.

Create a file named user_schema.json with the following content:


{
    "type": "object",
    "properties": {
        "userId": {"type": "string"},
        "orderId": {"type": "string"},
        "timestamp": {"type": "string", "format": "date-time"}
    },
    "required": ["userId", "orderId", "timestamp"]
}

Using Azure CLI:


az eventhubs schema-group schema create \
    --resource-group  \
    --namespace-name  \
    --schema-group-name MySchemaGroup \
    --schema-name UserSchema \
    --content user_schema.json

This command registers the schema under the name UserSchema within MySchemaGroup.

Step 4: Integrate with Event Hubs Producer

Your Event Hubs producer application can now leverage the Schema Registry. When sending events, the producer will serialize the event data according to the registered schema and include schema information.

Example (Conceptual Python):


from azure.eventhub import EventHubProducer
from azure.schemaregistry import SchemaRegistryClient
from azure.schemaregistry.encoder.avroencoder import AvroEncoder

# Connection details
eventhub_namespace = ""
eventhub_name = ""
schema_group = "MySchemaGroup"
schema_name = "UserSchema"

# Get Event Hubs connection string (e.g., from environment variable or Azure CLI)
eventhub_conn_str = ""
# Get Schema Registry credential (e.g., from Azure Identity)
# For simplicity, using connection string here. In production, use managed identity or AAD.
schemaregistry_conn_str = ""

producer = EventHubProducer.from_connection_string(eventhub_conn_str, eventhub_name)

# Initialize Schema Registry client and encoder
schema_registry_client = SchemaRegistryClient(schemaregistry_conn_str)
# Use AvroEncoder as an example, adjust based on your schema serialization
encoder = AvroEncoder(schema_registry_client)

# Event data
event_data = {
    "userId": "user123",
    "orderId": "orderABC",
    "timestamp": "2023-10-27T10:00:00Z"
}

# Encode and send
encoded_event = encoder.encode(event_data, schema_group, schema_name)

producer.send(encoded_event)

print("Event sent successfully with schema validation.")

producer.close()

Note: The actual implementation will depend on your chosen language and SDKs. You will typically obtain the Schema Registry endpoint and credentials separately.

Step 5: Integrate with Event Hubs Consumer

Your Event Hubs consumer application will receive encoded events. It can then use the Schema Registry client to decode the event data, ensuring it conforms to the expected schema.

Example (Conceptual Python):


from azure.eventhub import EventHubConsumerClient
from azure.schemaregistry import SchemaRegistryClient
from azure.schemaregistry.decoder.avrodecoder import AvroDecoder

# ... (Connection details as in producer example)

consumer = EventHubConsumerClient.from_connection_string(eventhub_conn_str, eventhub_name, consumer_group="$Default")

# Initialize Schema Registry client and decoder
schema_registry_client = SchemaRegistryClient(schemaregistry_conn_str)
# Use AvroDecoder as an example
decoder = AvroDecoder(schema_registry_client)

def process_event(partition_context, event):
    # The event object might contain schema ID and encoded data.
    # The decoder handles retrieving the schema based on the ID.
    decoded_data = decoder.decode(event.body)
    print(f"Received and decoded event: {decoded_data}")
    partition_context.update_checkpoint(event)

with consumer:
    consumer.receive(on_event=process_event)
Best Practice: Always use schema evolution capabilities carefully. Ensure that consumers can handle older versions of schemas if you make breaking changes.

Conclusion

By integrating Azure Event Hubs with the Schema Registry, you establish a robust mechanism for managing and validating your event data. This leads to more reliable and maintainable event-driven architectures.

For more advanced scenarios, explore features like schema versioning, custom schema groups, and different serialization formats.

Further Reading: