Azure Event Hubs

Since Camel 3.5

Both producer and consumer are supported

The Azure Event Hubs used to integrate Azure Event Hubs using AMQP protocol. Azure EventHubs is a highly scalable publish-subscribe service that can ingest millions of events per second and stream them to multiple consumers.

Besides AMQP protocol support, Event Hubs as well supports Kafka and HTTPS protocols. Therefore, you can use as well Camel Kafka component to produce and consume to Azure Event Hubs. You can lean more here.

Prerequisites

You must have a valid Windows Azure Event Hubs account. More information is available at Azure Documentation Portal.

Maven users will need to add the following dependency to their pom.xml for this component:

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-azure-eventhubs</artifactId>
    <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

URI Format

azure-eventhubs://[namespace/eventHubName][?options]

In case you supply the connectionString, namespace and eventHubName are not required as these options already included in the connectionString

Configuring Options

Camel components are configured on two separate levels:

  • component level

  • endpoint level

Configuring Component Options

The component level is the highest level which holds general and common configurations that are inherited by the endpoints. For example a component may have security settings, credentials for authentication, urls for network connection and so forth.

Some components only have a few options, and others may have many. Because components typically have pre configured defaults that are commonly used, then you may often only need to configure a few options on a component; or none at all.

Configuring components can be done with the Component DSL, in a configuration file (application.properties|yaml), or directly with Java code.

Configuring Endpoint Options

Where you find yourself configuring the most is on endpoints, as endpoints often have many options, which allows you to configure what you need the endpoint to do. The options are also categorized into whether the endpoint is used as consumer (from) or as a producer (to), or used for both.

Configuring endpoints is most often done directly in the endpoint URI as path and query parameters. You can also use the Endpoint DSL and DataFormat DSL as a type safe way of configuring endpoints and data formats in Java.

A good practice when configuring options is to use Property Placeholders, which allows to not hardcode urls, port numbers, sensitive information, and other settings. In other words placeholders allows to externalize the configuration from your code, and gives more flexibility and reuse.

The following two sections lists all the options, firstly for the component followed by the endpoint.

Component Options

The Azure Event Hubs component supports 24 options, which are listed below.

Name Description Default Type

amqpRetryOptions (common)

Sets the retry policy for EventHubAsyncClient. If not specified, the default retry options are used.

AmqpRetryOptions

amqpTransportType (common)

Sets the transport type by which all the communication with Azure Event Hubs occurs. Default value is AmqpTransportType#AMQP.

Enum values:

  • Amqp

  • AmqpWebSockets

AMQP

AmqpTransportType

configuration (common)

The component configurations.

EventHubsConfiguration

blobAccessKey (consumer)

In case you chose the default BlobCheckpointStore, this sets access key for the associated azure account name to be used for authentication with azure blob services.

String

blobAccountName (consumer)

In case you chose the default BlobCheckpointStore, this sets Azure account name to be used for authentication with azure blob services.

String

blobContainerName (consumer)

In case you chose the default BlobCheckpointStore, this sets the blob container that shall be used by the BlobCheckpointStore to store the checkpoint offsets.

String

blobStorageSharedKeyCredential (consumer)

In case you chose the default BlobCheckpointStore, StorageSharedKeyCredential can be injected to create the azure client, this holds the important authentication information.

StorageSharedKeyCredential

bridgeErrorHandler (consumer)

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

false

boolean

checkpointBatchSize (consumer)

Sets the batch size between each checkpoint updates. Works jointly with checkpointBatchTimeout.

500

int

checkpointBatchTimeout (consumer)

Sets the batch timeout between each checkpoint updates. Works jointly with checkpointBatchSize.

5000

int

checkpointStore (consumer)

Sets the CheckpointStore the EventProcessorClient will use for storing partition ownership and checkpoint information. Users can, optionally, provide their own implementation of CheckpointStore which will store ownership and checkpoint information. By default it set to use com.azure.messaging.eventhubs.checkpointstore.blob.BlobCheckpointStore which stores all checkpoint offsets into Azure Blob Storage.

BlobCheckpointStore

CheckpointStore

consumerGroupName (consumer)

Sets the name of the consumer group this consumer is associated with. Events are read in the context of this group. The name of the consumer group that is created by default is \{code $Default}.

$Default

String

eventPosition (consumer)

Sets the map containing the event position to use for each partition if a checkpoint for the partition does not exist in CheckpointStore. This map is keyed off of the partition id. If there is no checkpoint in CheckpointStore and there is no entry in this map, the processing of the partition will start from \{link EventPosition#latest() latest} position.

Map

prefetchCount (consumer)

Sets the count used by the receiver to control the number of events the Event Hub consumer will actively receive and queue locally without regard to whether a receive operation is currently active.

500

int

lazyStartProducer (producer)

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

boolean

partitionId (producer)

Sets the identifier of the Event Hub partition that the events will be sent to. If the identifier is not specified, the Event Hubs service will be responsible for routing events that are sent to an available partition.

String

partitionKey (producer)

Sets a hashing key to be provided for the batch of events, which instructs the Event Hubs service to map this key to a specific partition. The selection of a partition is stable for a given partition hashing key. Should any other batches of events be sent using the same exact partition hashing key, the Event Hubs service will route them all to the same partition. This should be specified only when there is a need to group events by partition, but there is flexibility into which partition they are routed. If ensuring that a batch of events is sent only to a specific partition, it is recommended that the \{link #setPartitionId(String) identifier of the position be specified directly} when sending the batch.

String

producerAsyncClient (producer)

Autowired Sets the EventHubProducerAsyncClient.An asynchronous producer responsible for transmitting EventData to a specific Event Hub, grouped together in batches. Depending on the options specified when creating an {linkEventDataBatch}, the events may be automatically routed to an available partition or specific to a partition. Use by this component to produce the data in camel producer.

EventHubProducerAsyncClient

autowiredEnabled (advanced)

Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.

true

boolean

connectionString (security)

Instead of supplying namespace, sharedAccessKey, sharedAccessName …​ etc, you can just supply the connection string for your eventHub. The connection string for EventHubs already include all the necessary information to connection to your EventHub. To learn on how to generate the connection string, take a look at this documentation: https://docs.microsoft.com/en-us/azure/event-hubs/event-hubs-get-connection-string.

String

credentialType (security)

Determines the credential strategy to adopt.

Enum values:

  • AZURE_IDENTITY

  • CONNECTION_STRING

  • TOKEN_CREDENTIAL

CONNECTION_STRING

CredentialType

sharedAccessKey (security)

The generated value for the SharedAccessName.

String

sharedAccessName (security)

The name you chose for your EventHubs SAS keys.

String

tokenCredential (security)

Still another way of authentication (beside supplying namespace, sharedAccessKey, sharedAccessName or connection string) is through Azure-AD authentication using an implementation instance of TokenCredential.

TokenCredential

Endpoint Options

The Azure Event Hubs endpoint is configured using URI syntax:

azure-eventhubs:namespace/eventHubName

with the following path and query parameters:

Path Parameters (2 parameters)

Name Description Default Type

namespace (common)

EventHubs namespace created in Azure Portal.

String

eventHubName (common)

EventHubs name under a specific namespace.

String

Query Parameters (24 parameters)

Name Description Default Type

amqpRetryOptions (common)

Sets the retry policy for EventHubAsyncClient. If not specified, the default retry options are used.

AmqpRetryOptions

amqpTransportType (common)

Sets the transport type by which all the communication with Azure Event Hubs occurs. Default value is AmqpTransportType#AMQP.

Enum values:

  • Amqp

  • AmqpWebSockets

AMQP

AmqpTransportType

blobAccessKey (consumer)

In case you chose the default BlobCheckpointStore, this sets access key for the associated azure account name to be used for authentication with azure blob services.

String

blobAccountName (consumer)

In case you chose the default BlobCheckpointStore, this sets Azure account name to be used for authentication with azure blob services.

String

blobContainerName (consumer)

In case you chose the default BlobCheckpointStore, this sets the blob container that shall be used by the BlobCheckpointStore to store the checkpoint offsets.

String

blobStorageSharedKeyCredential (consumer)

In case you chose the default BlobCheckpointStore, StorageSharedKeyCredential can be injected to create the azure client, this holds the important authentication information.

StorageSharedKeyCredential

checkpointBatchSize (consumer)

Sets the batch size between each checkpoint updates. Works jointly with checkpointBatchTimeout.

500

int

checkpointBatchTimeout (consumer)

Sets the batch timeout between each checkpoint updates. Works jointly with checkpointBatchSize.

5000

int

checkpointStore (consumer)

Sets the CheckpointStore the EventProcessorClient will use for storing partition ownership and checkpoint information. Users can, optionally, provide their own implementation of CheckpointStore which will store ownership and checkpoint information. By default it set to use com.azure.messaging.eventhubs.checkpointstore.blob.BlobCheckpointStore which stores all checkpoint offsets into Azure Blob Storage.

BlobCheckpointStore

CheckpointStore

consumerGroupName (consumer)

Sets the name of the consumer group this consumer is associated with. Events are read in the context of this group. The name of the consumer group that is created by default is \{code $Default}.

$Default

String

eventPosition (consumer)

Sets the map containing the event position to use for each partition if a checkpoint for the partition does not exist in CheckpointStore. This map is keyed off of the partition id. If there is no checkpoint in CheckpointStore and there is no entry in this map, the processing of the partition will start from \{link EventPosition#latest() latest} position.

Map

prefetchCount (consumer)

Sets the count used by the receiver to control the number of events the Event Hub consumer will actively receive and queue locally without regard to whether a receive operation is currently active.

500

int

bridgeErrorHandler (consumer (advanced))

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

false

boolean

exceptionHandler (consumer (advanced))

To let the consumer use a custom ExceptionHandler. Notice if the option bridgeErrorHandler is enabled then this option is not in use. By default the consumer will deal with exceptions, that will be logged at WARN or ERROR level and ignored.

ExceptionHandler

exchangePattern (consumer (advanced))

Sets the exchange pattern when the consumer creates an exchange.

Enum values:

  • InOnly

  • InOut

ExchangePattern

partitionId (producer)

Sets the identifier of the Event Hub partition that the events will be sent to. If the identifier is not specified, the Event Hubs service will be responsible for routing events that are sent to an available partition.

String

partitionKey (producer)

Sets a hashing key to be provided for the batch of events, which instructs the Event Hubs service to map this key to a specific partition. The selection of a partition is stable for a given partition hashing key. Should any other batches of events be sent using the same exact partition hashing key, the Event Hubs service will route them all to the same partition. This should be specified only when there is a need to group events by partition, but there is flexibility into which partition they are routed. If ensuring that a batch of events is sent only to a specific partition, it is recommended that the \{link #setPartitionId(String) identifier of the position be specified directly} when sending the batch.

String

producerAsyncClient (producer)

Autowired Sets the EventHubProducerAsyncClient.An asynchronous producer responsible for transmitting EventData to a specific Event Hub, grouped together in batches. Depending on the options specified when creating an {linkEventDataBatch}, the events may be automatically routed to an available partition or specific to a partition. Use by this component to produce the data in camel producer.

EventHubProducerAsyncClient

lazyStartProducer (producer (advanced))

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

boolean

connectionString (security)

Instead of supplying namespace, sharedAccessKey, sharedAccessName …​ etc, you can just supply the connection string for your eventHub. The connection string for EventHubs already include all the necessary information to connection to your EventHub. To learn on how to generate the connection string, take a look at this documentation: https://docs.microsoft.com/en-us/azure/event-hubs/event-hubs-get-connection-string.

String

credentialType (security)

Determines the credential strategy to adopt.

Enum values:

  • AZURE_IDENTITY

  • CONNECTION_STRING

  • TOKEN_CREDENTIAL

CONNECTION_STRING

CredentialType

sharedAccessKey (security)

The generated value for the SharedAccessName.

String

sharedAccessName (security)

The name you chose for your EventHubs SAS keys.

String

tokenCredential (security)

Still another way of authentication (beside supplying namespace, sharedAccessKey, sharedAccessName or connection string) is through Azure-AD authentication using an implementation instance of TokenCredential.

TokenCredential

Authentication Information

You have three different Credential Types: AZURE_IDENTITY, TOKEN_CREDENTIAL and CONNECTION_STRING. You can also provide a client instance yourself. To use this component, you have 3 options in order to provide the required Azure authentication information:

CONNECTION_STRING: - Provide sharedAccessName and sharedAccessKey for your Azure Event Hubs account. The sharedAccessKey can be generated through your Event Hubs Azure portal. - Provide connectionString string, if you provide the connection string, you don’t supply namespace, eventHubName, sharedAccessKey and sharedAccessName as these data already included in the connectionString, therefore is the simplest option to get started. Learn more here on how to generate the connection string.

TOKEN_CREDENTIAL: - Provide an implementation of com.azure.core.credential.TokenCredential into the Camel’s Registry, e.g. using the com.azure.identity.DefaultAzureCredentialBuilder().build(); API. See the documentation here about Azure-AD authentication.

AZURE_IDENTITY: - This will use com.azure.identity.DefaultAzureCredentialBuilder().build(); instance. This will follow the Default Azure Credential Chain. See the documentation here about Azure-AD authentication.

Client instance: - Provide a EventHubProducerAsyncClient instance which can be provided into producerAsyncClient. However, this is only possible for camel producer, for the camel consumer, is not possible to inject the client due to some design constraint by the EventProcessorClient.

Checkpoint Store Information

A checkpoint store stores and retrieves partition ownership information and checkpoint details for each partition in a given consumer group of an event hub instance. Users are not meant to implement an CheckpointStore. Users are expected to choose existing implementations of this interface, instantiate it, and pass it to the component through checkpointStore option. Users are not expected to use any of the methods on a checkpoint store, these are used internally by the client.

Having said that, if the user does not pass any CheckpointStore implementation, the component will fallback to use BlobCheckpointStore to store the checkpoint info in Azure Blob Storage account. If you chose to use the default BlobCheckpointStore, you will need to supply the following options:

  • blobAccountName: It sets Azure account name to be used for authentication with azure blob services.

  • blobAccessKey : It sets access key for the associated azure account name to be used for authentication with azure blob services.

  • blobContainerName : It sets the blob container that shall be used by the BlobCheckpointStore to store the checkpoint offsets.

Async Consumer and Producer

This component implements the async Consumer and producer.

This allows camel route to consume and produce events asynchronously without blocking any threads.

Usage

For example in order consume event from EventHub, use the following snippet:

from("azure-eventhubs:/camel/camelHub?sharedAccessName=SASaccountName&sharedAccessKey=SASaccessKey&blobAccountName=accountName&blobAccessKey=accessKey&blobContainerName=containerName")
  .to("file://queuedirectory");

Message Headers

The Azure Event Hubs component supports 8 message header(s), which is/are listed below:

Name Description Default Type

CamelAzureEventHubsPartitionKey (common)

Constant: PARTITION_KEY

(producer) Overrides the hashing key to be provided for the batch of events, which instructs the Event Hubs service to map this key to a specific partition. (consumer) It sets the partition hashing key if it was set when originally publishing the event. If it exists, this value was used to compute a hash to select a partition to send the message to. This is only present on a received EventData.

String

CamelAzureEventHubsPartitionId (common)

Constant: PARTITION_ID

(producer) Overrides the identifier of the Event Hub partition that the events will be sent to. (consumer) It sets the partition id of the Event Hub.

String

CamelAzureEventHubsOffset (consumer)

Constant: OFFSET

It sets the offset of the event when it was received from the associated Event Hub partition. This is only present on a received EventData.

Integer

CamelAzureEventHubsEnqueuedTime (consumer)

Constant: ENQUEUED_TIME

It sets the instant, in UTC, of when the event was enqueued in the Event Hub partition. This is only present on a received EventData.

Instant

CamelAzureEventHubsSequenceNumber (consumer)

Constant: SEQUENCE_NUMBER

It sets the sequence number assigned to the event when it was enqueued in the associated Event Hub partition. This is unique for every message received in the Event Hub partition. This is only present on a received EventData.

Long

CamelAzureEventHubsMetadata (consumer)

Constant: METADATA

The set of free-form event properties which may be used for passing metadata associated with the event with the event body during Event Hubs operations.

Map

CamelMessageTimestamp (consumer)

Constant: MESSAGE_TIMESTAMP

The timestamp of the message.

long

CamelAzureEventHubsCheckpointUpdatedBy (consumer)

Constant: CHECKPOINT_UPDATED_BY

It sets the reason for the checkpoint to have been updated. This is only present on a received EventData.

String

Message body type

The component’s producer expects the data in the message body to be in byte[]. This allows the user to utilize Camel TypeConverter to marshal/unmarshal data with ease. The same goes as well for the component’s consumer, it will set the encoded data as byte[] in the message body.

Automatic detection of EventHubProducerAsyncClient client in registry

The component is capable of detecting the presence of an EventHubProducerAsyncClient bean into the registry. If it’s the only instance of that type it will be used as client and you won’t have to define it as uri parameter, like the example above. This may be really useful for smarter configuration of the endpoint.

Consumer Example

The example below will unmarshal the events that was originally produced in JSON:

from("azure-eventhubs:?connectionString=RAW({{connectionString}})"&blobContainerName=containerTest&eventPosition=#eventPosition"
    +"&blobAccountName={{blobAccountName}}&blobAccessKey=RAW({{blobAccessKey}})")
.unmarshal().json(JsonLibrary.Jackson)
.to(result);

Producer Example

The example below will send events as String to EventHubs:

from("direct:start")
.process(exchange -> {
        exchange.getIn().setHeader(EventHubsConstants.PARTITION_ID, firstPartition);
        exchange.getIn().setBody("test event");
})
.to("azure-eventhubs:?connectionString=RAW({{connectionString}})"

Also, the component supports as well aggregation of messages by sending events as iterable of either Exchanges/Messages or normal data (e.g: list of Strings). For example:

from("direct:start")
.process(exchange -> {
        final List<String> messages = new LinkedList<>();
        messages.add("Test String Message 1");
        messages.add("Test String Message 2");

        exchange.getIn().setHeader(EventHubsConstants.PARTITION_ID, firstPartition);
        exchange.getIn().setBody(messages);
})
.to("azure-eventhubs:?connectionString=RAW({{connectionString}})"

Azure-AD Authentication example

The example below makes use of the Azure-AD authentication. See here about what environment variables you need to set for this to work:

@BindToRegistry("myTokenCredential")
public com.azure.core.credential.TokenCredential myTokenCredential() {
    return com.azure.identity.DefaultAzureCredentialBuilder().build();
}

from("direct:start")
.to("azure-eventhubs:namespace/eventHubName?tokenCredential=#myTokenCredential&credentialType=TOKEN_CREDENTIAL)"

Development Notes (Important)

When developing on this component, you will need to obtain your Azure accessKey in order to run the integration tests. In addition to the mocked unit tests you will need to run the integration tests with every change you make or even client upgrade as the Azure client can break things even on minor versions upgrade. To run the integration tests, on this component directory, run the following maven command:

mvn verify -DconnectionString=string -DblobAccountName=blob -DblobAccessKey=key

Whereby blobAccountName is your Azure account name and blobAccessKey is the access key being generated from Azure portal and connectionString is the eventHub connection string.