EventHubConsumerClient Class

The EventHubConsumerClient class defines a high level interface for receiving events from the Azure Event Hubs service.

The main goal of EventHubConsumerClient is to receive events from all partitions of an EventHub with load-balancing and checkpointing.

When multiple EventHubConsumerClient instances are running against the same event hub, consumer group and checkpointing location, the partitions will be evenly distributed among them.

To enable load-balancing and persisted checkpoints, checkpoint_store must be set when creating the EventHubConsumerClient. If a checkpoint store is not provided, the checkpoint will be maintained internally in memory.

An EventHubConsumerClient can also receive from a specific partition when you call its method receive() or receive_batch() and specify the partition_id. Load-balancing won't work in single-partition mode. But users can still save checkpoints if the checkpoint_store is set.

Inheritance
azure.eventhub.aio._client_base_async.ClientBaseAsync
EventHubConsumerClient

Constructor

Parameters

fully_qualified_namespace
str

The fully qualified host name for the Event Hubs namespace. The namespace format is: .servicebus.windows.net.

eventhub_name
str

The path of the specific Event Hub to connect the client to.

consumer_group
str

Receive events from the event hub for this consumer group.

credential
<xref:azure.core.credentials.TokenCredential>

The credential object used for authentication which implements a particular interface for getting tokens. It accepts EventHubSharedKeyCredential, or credential objects generated by the azure-identity library and objects that implement the *get_token(self, scopes) method.

logging_enable
bool

Whether to output network trace logs to the logger. Default is False.

auth_timeout
float

The time in seconds to wait for a token to be authorized by the service. The default value is 60 seconds. If set to 0, no timeout will be enforced from the client.

user_agent
str

The user agent that should be appended to the built-in user agent string.

retry_total
int

The total number of attempts to redo a failed operation when an error occurs. Default value is 3. The context of retry_total in receiving is special: The receive method is implemented by a while-loop calling internal receive method in each iteration. In the receive case, retry_total specifies the numbers of retry after error raised by internal receive method in the while-loop. If retry attempts are exhausted, the on_error callback will be called (if provided) with the error information. The failed internal partition consumer will be closed (on_partition_close will be called if provided) and new internal partition consumer will be created (on_partition_initialize will be called if provided) to resume receiving.

idle_timeout
float

Timeout, in seconds, after which this client will close the underlying connection if there is no further activity. By default the value is None, meaning that the client will not shutdown due to inactivity unless initiated by the service.

transport_type
TransportType

The type of transport protocol that will be used for communicating with the Event Hubs service. Default is TransportType.Amqp.

http_proxy
dict

HTTP proxy settings. This must be a dictionary with the following keys: 'proxy_hostname' (str value) and 'proxy_port' (int value). Additionally the following keys may also be present: 'username', 'password'.

checkpoint_store
CheckpointStore

A manager that stores the partition load-balancing and checkpoint data when receiving events. The checkpoint store will be used in both cases of receiving from all partitions or a single partition. In the latter case load-balancing does not apply. If a checkpoint store is not provided, the checkpoint will be maintained internally in memory, and the EventHubConsumerClient instance will receive events without load-balancing.

load_balancing_interval
float

When load-balancing kicks in. This is the interval, in seconds, between two load-balancing evaluations. Default is 10 seconds.

partition_ownership_expiration_interval
float

A partition ownership will expire after this number of seconds. Every load-balancing evaluation will automatically extend the ownership expiration time. Default is 6 * load_balancing_interval, i.e. 60 seconds when using the default load_balancing_interval of 10 seconds.

load_balancing_strategy
str or LoadBalancingStrategy

When load-balancing kicks in, it will use this strategy to claim and balance the partition ownership. Use "greedy" or LoadBalancingStrategy.GREEDY for the greedy strategy, which, for every load-balancing evaluation, will grab as many unclaimed partitions required to balance the load. Use "balanced" or LoadBalancingStrategy.BALANCED for the balanced strategy, which, for every load-balancing evaluation, claims only one partition that is not claimed by other EventHubConsumerClient. If all partitions of an EventHub are claimed by other EventHubConsumerClient and this client has claimed too few partitions, this client will steal one partition from other clients for every load-balancing evaluation regardless of the load balancing strategy. Greedy strategy is used by default.

Examples

Create a new instance of the EventHubConsumerClient.


   import os
   from azure.eventhub.aio import EventHubConsumerClient, EventHubSharedKeyCredential

   fully_qualified_namespace = os.environ['EVENT_HUB_HOSTNAME']
   eventhub_name = os.environ['EVENT_HUB_NAME']
   shared_access_policy = os.environ['EVENT_HUB_SAS_POLICY']
   shared_access_key = os.environ['EVENT_HUB_SAS_KEY']

   consumer = EventHubConsumerClient(fully_qualified_namespace=fully_qualified_namespace,
                                     consumer_group='$Default',
                                     eventhub_name=eventhub_name,
                                     credential=EventHubSharedKeyCredential(shared_access_policy, shared_access_key))

Methods

close

Stop retrieving events from the Event Hub and close the underlying AMQP connection and links.

from_connection_string

Create an EventHubConsumerClient from a connection string.

get_eventhub_properties

Get properties of the Event Hub.

Keys in the returned dictionary include:

  • eventhub_name (str)

  • created_at (UTC datetime.datetime)

  • partition_ids (list[str])

get_partition_ids

Get partition IDs of the Event Hub.

get_partition_properties

Get properties of the specified partition.

Keys in the properties dictionary include:

  • eventhub_name (str)

  • id (str)

  • beginning_sequence_number (int)

  • last_enqueued_sequence_number (int)

  • last_enqueued_offset (str)

  • last_enqueued_time_utc (UTC datetime.datetime)

  • is_empty (bool)

receive

Receive events from partition(s), with optional load-balancing and checkpointing.

receive_batch

Receive events from partition(s) in batches, with optional load-balancing and checkpointing.

close

Stop retrieving events from the Event Hub and close the underlying AMQP connection and links.

close() -> None

Return type

Examples

Close down the client.


   import os

   event_hub_connection_str = os.environ['EVENT_HUB_CONN_STR']
   eventhub_name = os.environ['EVENT_HUB_NAME']

   from azure.eventhub.aio import EventHubConsumerClient
   consumer = EventHubConsumerClient.from_connection_string(
       conn_str=event_hub_connection_str,
       consumer_group='$Default',
       eventhub_name=eventhub_name  # EventHub name should be specified if it doesn't show up in connection string.
   )

   logger = logging.getLogger("azure.eventhub")

   async def on_event(partition_context, event):
       # Put your code here.
       # If the operation is i/o intensive, async will have better performance.
       logger.info("Received event from partition: {}".format(partition_context.partition_id))

   # The receive method is a coroutine which will be blocking when awaited.
   # It can be executed in an async task for non-blocking behavior, and combined with the 'close' method.

   recv_task = asyncio.ensure_future(consumer.receive(on_event=on_event))
   await asyncio.sleep(3)  # keep receiving for 3 seconds
   recv_task.cancel()  # stop receiving

   # Close down the consumer handler explicitly.
   await consumer.close()

from_connection_string

Create an EventHubConsumerClient from a connection string.

Parameters

conn_str
str
Required

The connection string of an Event Hub.

consumer_group
str
Required

Receive events from the Event Hub for this consumer group.

eventhub_name
str
Required

The path of the specific Event Hub to connect the client to.

logging_enable
bool
Required

Whether to output network trace logs to the logger. Default is False.

http_proxy
dict
Required

HTTP proxy settings. This must be a dictionary with the following keys: 'proxy_hostname' (str value) and 'proxy_port' (int value). Additionally the following keys may also be present: 'username', 'password'.

auth_timeout
float
Required

The time in seconds to wait for a token to be authorized by the service. The default value is 60 seconds. If set to 0, no timeout will be enforced from the client.

user_agent
str
Required

The user agent that should be appended to the built-in user agent string.

retry_total
int
Required

The total number of attempts to redo a failed operation when an error occurs. Default value is 3. The context of retry_total in receiving is special: The receive method is implemented by a while-loop calling internal receive method in each iteration. In the receive case, retry_total specifies the numbers of retry after error raised by internal receive method in the while-loop. If retry attempts are exhausted, the on_error callback will be called (if provided) with the error information. The failed internal partition consumer will be closed (on_partition_close will be called if provided) and new internal partition consumer will be created (on_partition_initialize will be called if provided) to resume receiving.

idle_timeout
float
Required

Timeout, in seconds, after which this client will close the underlying connection if there is no further activity. By default the value is None, meaning that the client will not shutdown due to inactivity unless initiated by the service.

transport_type
TransportType
Required

The type of transport protocol that will be used for communicating with the Event Hubs service. Default is TransportType.Amqp.

checkpoint_store
CheckpointStore
Required

A manager that stores the partition load-balancing and checkpoint data when receiving events. The checkpoint store will be used in both cases of receiving from all partitions or a single partition. In the latter case load-balancing does not apply. If a checkpoint store is not provided, the checkpoint will be maintained internally in memory, and the EventHubConsumerClient instance will receive events without load-balancing.

load_balancing_interval
float
Required

When load-balancing kicks in. This is the interval, in seconds, between two load-balancing evaluations. Default is 10 seconds.

partition_ownership_expiration_interval
float
Required

A partition ownership will expire after this number of seconds. Every load-balancing evaluation will automatically extend the ownership expiration time. Default is 6 * load_balancing_interval, i.e. 60 seconds when using the default load_balancing_interval of 10 seconds.

load_balancing_strategy
str or LoadBalancingStrategy
Required

When load-balancing kicks in, it will use this strategy to claim and balance the partition ownership. Use "greedy" or LoadBalancingStrategy.GREEDY for the greedy strategy, which, for every load-balancing evaluation, will grab as many unclaimed partitions required to balance the load. Use "balanced" or LoadBalancingStrategy.BALANCED for the balanced strategy, which, for every load-balancing evaluation, claims only one partition that is not claimed by other EventHubConsumerClient. If all partitions of an EventHub are claimed by other EventHubConsumerClient and this client has claimed too few partitions, this client will steal one partition from other clients for every load-balancing evaluation regardless of the load balancing strategy. Greedy strategy is used by default.

Return type

Examples

Create a new instance of the EventHubConsumerClient from connection string.


   import os
   from azure.eventhub.aio import EventHubConsumerClient
   event_hub_connection_str = os.environ['EVENT_HUB_CONN_STR']
   eventhub_name = os.environ['EVENT_HUB_NAME']
   consumer = EventHubConsumerClient.from_connection_string(
       conn_str=event_hub_connection_str,
       consumer_group='$Default',
       eventhub_name=eventhub_name  # EventHub name should be specified if it doesn't show up in connection string.
   )

get_eventhub_properties

Get properties of the Event Hub.

Keys in the returned dictionary include:

  • eventhub_name (str)

  • created_at (UTC datetime.datetime)

  • partition_ids (list[str])

get_eventhub_properties() -> typing.Dict[str, typing.Any]

Return type

get_partition_ids

Get partition IDs of the Event Hub.

get_partition_ids() -> typing.List[str]

Return type

get_partition_properties

Get properties of the specified partition.

Keys in the properties dictionary include:

  • eventhub_name (str)

  • id (str)

  • beginning_sequence_number (int)

  • last_enqueued_sequence_number (int)

  • last_enqueued_offset (str)

  • last_enqueued_time_utc (UTC datetime.datetime)

  • is_empty (bool)

get_partition_properties(partition_id: str) -> typing.Dict[str, typing.Any]

Parameters

partition_id
str
Required

The target partition ID.

Return type

Exceptions

receive

Receive events from partition(s), with optional load-balancing and checkpointing.

Parameters

on_event
<xref:Callable>[PartitionContext, <xref:Optional>[EventData]]
Required

The callback function for handling a received event. The callback takes two parameters: partition_context which contains partition context and event which is the received event. The callback function should be defined like: on_event(partition_context, event). For detailed partition context information, please refer to PartitionContext.

max_wait_time
float
Required

The maximum interval in seconds that the event processor will wait before calling the callback. If no events are received within this interval, the on_event callback will be called with None. If this value is set to None or 0 (the default), the callback will not be called until an event is received.

partition_id
str
Required

If specified, the client will receive from this partition only. Otherwise the client will receive from all partitions.

owner_level
int
Required

The priority for an exclusive consumer. An exclusive consumer will be created if owner_level is set. A consumer with a higher owner_level has higher exclusive priority. The owner level is also know as the 'epoch value' of the consumer.

prefetch
int
Required

The number of events to prefetch from the service for processing. Default is 300.

track_last_enqueued_event_properties
bool
Required

Indicates whether the consumer should request information on the last-enqueued event on its associated partition, and track that information as events are received. When information about the partitions last-enqueued event is being tracked, each event received from the Event Hubs service will carry metadata about the partition. This results in a small amount of additional network bandwidth consumption that is generally a favorable trade-off when considered against periodically making requests for partition properties using the Event Hub client. It is set to False by default.

starting_position
str, int, datetime or dict[<xref:str,Any>]
Required

Start receiving from this event position if there is no checkpoint data for a partition. Checkpoint data will be used if available. This can be a a dict with partition ID as the key and position as the value for individual partitions, or a single value for all partitions. The value type can be str, int or datetime.datetime. Also supported are the values "-1" for receiving from the beginning of the stream, and "@latest" for receiving only new events.

starting_position_inclusive
bool or dict[<xref:str,bool>]
Required

Determine whether the given starting_position is inclusive(>=) or not (>). True for inclusive and False for exclusive. This can be a dict with partition ID as the key and bool as the value indicating whether the starting_position for a specific partition is inclusive or not. This can also be a single bool value for all starting_position. The default value is False.

on_error
<xref:Callable>[[PartitionContext, Exception]]
Required

The callback function that will be called when an error is raised during receiving after retry attempts are exhausted, or during the process of load-balancing. The callback takes two parameters: partition_context which contains partition information and error being the exception. partition_context could be None if the error is raised during the process of load-balance. The callback should be defined like: on_error(partition_context, error). The on_error callback will also be called if an unhandled exception is raised during the on_event callback.

on_partition_initialize
<xref:Callable>[[PartitionContext]]
Required

The callback function that will be called after a consumer for a certain partition finishes initialization. It would also be called when a new internal partition consumer is created to take over the receiving process for a failed and closed internal partition consumer. The callback takes a single parameter: partition_context which contains the partition information. The callback should be defined like: on_partition_initialize(partition_context).

on_partition_close
<xref:Callable>[[PartitionContext, CloseReason]]
Required

The callback function that will be called after a consumer for a certain partition is closed. It would be also called when error is raised during receiving after retry attempts are exhausted. The callback takes two parameters: partition_context which contains partition information and reason for the close. The callback should be defined like: on_partition_close(partition_context, reason). Please refer to CloseReason for the various closing reasons.

Return type

Examples

Receive events from the EventHub.


       logger = logging.getLogger("azure.eventhub")

       async def on_event(partition_context, event):
           # Put your code here.
           # If the operation is i/o intensive, async will have better performance.
           logger.info("Received event from partition: {}".format(partition_context.partition_id))

       async with consumer:
           await consumer.receive(
               on_event=on_event,
               starting_position="-1",  # "-1" is from the beginning of the partition.
           )

receive_batch

Receive events from partition(s) in batches, with optional load-balancing and checkpointing.

Parameters

on_event_batch
<xref:Callable>[PartitionContext, <xref:List>[EventData]]
Required

The callback function for handling a batch of received events. The callback takes two parameters: partition_context which contains partition context and event_batch, which is the received events. The callback function should be defined like: on_event_batch(partition_context, event_batch). event_batch could be an empty list if max_wait_time is not None nor 0 and no event is received after max_wait_time. For detailed partition context information, please refer to PartitionContext.

max_batch_size
int
Required

The maximum number of events in a batch passed to callback on_event_batch. If the actual received number of events is larger than max_batch_size, the received events are divided into batches and call the callback for each batch with up to max_batch_size events.

max_wait_time
float
Required

The maximum interval in seconds that the event processor will wait before calling the callback. If no events are received within this interval, the on_event_batch callback will be called with an empty list. If this value is set to None or 0 (the default), the callback will not be called until events are received.

partition_id
str
Required

If specified, the client will receive from this partition only. Otherwise the client will receive from all partitions.

owner_level
int
Required

The priority for an exclusive consumer. An exclusive consumer will be created if owner_level is set. A consumer with a higher owner_level has higher exclusive priority. The owner level is also know as the 'epoch value' of the consumer.

prefetch
int
Required

The number of events to prefetch from the service for processing. Default is 300.

track_last_enqueued_event_properties
bool
Required

Indicates whether the consumer should request information on the last-enqueued event on its associated partition, and track that information as events are received. When information about the partitions last-enqueued event is being tracked, each event received from the Event Hubs service will carry metadata about the partition. This results in a small amount of additional network bandwidth consumption that is generally a favorable trade-off when considered against periodically making requests for partition properties using the Event Hub client. It is set to False by default.

starting_position
str, int, datetime or dict[<xref:str,Any>]
Required

Start receiving from this event position if there is no checkpoint data for a partition. Checkpoint data will be used if available. This can be a a dict with partition ID as the key and position as the value for individual partitions, or a single value for all partitions. The value type can be str, int or datetime.datetime. Also supported are the values "-1" for receiving from the beginning of the stream, and "@latest" for receiving only new events.

starting_position_inclusive
bool or dict[<xref:str,bool>]
Required

Determine whether the given starting_position is inclusive(>=) or not (>). True for inclusive and False for exclusive. This can be a dict with partition ID as the key and bool as the value indicating whether the starting_position for a specific partition is inclusive or not. This can also be a single bool value for all starting_position. The default value is False.

on_error
<xref:Callable>[[PartitionContext, Exception]]
Required

The callback function that will be called when an error is raised during receiving after retry attempts are exhausted, or during the process of load-balancing. The callback takes two parameters: partition_context which contains partition information and error being the exception. partition_context could be None if the error is raised during the process of load-balance. The callback should be defined like: on_error(partition_context, error). The on_error callback will also be called if an unhandled exception is raised during the on_event callback.

on_partition_initialize
<xref:Callable>[[PartitionContext]]
Required

The callback function that will be called after a consumer for a certain partition finishes initialization. It would also be called when a new internal partition consumer is created to take over the receiving process for a failed and closed internal partition consumer. The callback takes a single parameter: partition_context which contains the partition information. The callback should be defined like: on_partition_initialize(partition_context).

on_partition_close
<xref:Callable>[[PartitionContext, CloseReason]]
Required

The callback function that will be called after a consumer for a certain partition is closed. It would be also called when error is raised during receiving after retry attempts are exhausted. The callback takes two parameters: partition_context which contains partition information and reason for the close. The callback should be defined like: on_partition_close(partition_context, reason). Please refer to CloseReason for the various closing reasons.

Return type

Examples

Receive events in batches from the EventHub.


       logger = logging.getLogger("azure.eventhub")

       async def on_event_batch(partition_context, event_batch):
           # Put your code here.
           # If the operation is i/o intensive, async will have better performance.
           logger.info(
               "{} events received from partition: {}".format(len(event_batch), partition_context.partition_id)
           )

       async with consumer:
           await consumer.receive_batch(
               on_event_batch=on_event_batch,
               starting_position="-1",  # "-1" is from the beginning of the partition.
           )