AzureEventHubsConnector
Accesses the Azure Event Hubs to send, receive, or checkpoint messages.
Typical Uses
- Receive and send messages from an event hub
- Interoperability with Big Data analytics platforms
How does it work?
The AzureEventHubsConnector connects to Azure’s Event Hubs through the Kafka protocol using the Azure Event Hub SDK. Supports publishing, receiving messages, and checkpointing messages. A message is also known in the Azure documentation as an event.
Configuration
Input Ports
This transformer accepts any feature.
Output Ports
The output of this transformer will vary depending on the action performed. Message data and metadata are presented as feature attributes.
- After a Receive action, output features represent messages received from Azure Event Hub.
- After a Send action, output features represent messages sent to Azure Event Hub.
The incoming feature is output through this port.
Features that cause the operation to fail are output through this port. An fme_rejection_code attribute, having the value ERROR_DURING_PROCESSING, will be added, along with a more descriptive fme_rejection_message attribute which contains more specific details as to the reason for the failure.
Note: If a feature comes in to the AzureEventHubsConnector already having a value for fme_rejection_code, this value will be removed.
Rejected Feature Handling: can be set to either terminate the translation or continue running when it encounters a rejected feature. This setting is available both as a default FME option and as a workspace parameter.
Parameters
Credential Source |
Required for authentication. Using a web connection integrates best with FME, but in some cases, you may wish to use one of the other sources.
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Account |
Available when the credential source is Web Connection. To create an Azure Event Hubs connection, click the 'Account' drop-down box and select 'Add Web Connection...'. The connection can then be managed via Tools -> FME Options... -> Web Connections. |
Embedded Credentials
Event Hub Connection String | Available when the Credential Source is Embedded. The connection string is found in the Azure Portal Event Hubs Namespace under Shared Access Policies. |
Action |
The type of operation to perform. Choices are:
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Event Hubs |
The event hub to connect to. |
Some parameters are variable, depending on the value of the Request > Action parameter.
Send Options
Payload |
The content of the message. This is often JSON, but can be any string, binary, integer or floating-point value. |
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Partition ID |
(Optional) The specific partition ID to send to. If empty, a message will be assigned to a random partition using round-robin. |
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Message Properties |
(Optional) Additional properties to send with each message.
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Receives messages from the front of the queue.
Checkpointing is also enabled, but optional.
Receive Options
Consumer Group |
The name of the consumer group to view the event hub stream. Consumer groups are created in the Azure portal. The default is ‘$Default’. |
Receive Mode |
Two message receiving options are available:
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Batch Size |
In Batch mode, specifies the number of messages to read per batch. |
Partition ID |
(Optional) If specified, the client will receive from this partition only. If empty, the client will receive from all partitions. It is recommended that there is only one active receiver on a partition per consumer group. |
Prefetch Count |
(Optional) The number of messages to prefetch from Azure. Default is 300. |
Starting Position |
(Optional) Start receiving from this event position if there is no checkpoint data for the partition. Checkpoint data will be used if available. Default (empty) is @latest which receives only new events. -1 starts receiving at the beginning of the stream Can be a string, integer or a datetime. |
Starting Position Mode |
Determines whether the starting position is inclusive or not. Default is exclusive. |
Checkpoint Store (Azure Blob) - Optional
See Parameters - Checkpoint Action for more details.
Container Name |
The container name for the blob store. |
Connection String |
A connection string to an Azure Storage account. |
Checkpoint Interval |
(Optional) Submits a checkpoint store to Azure blob every nth message. The default checkpoints only at the end of the stream. There will always be a checkpoint at the end of a message stream. |
The checkpoint action manually checkpoints a message using the Azure Blob checkpoint store.
This option is used if there is post-processing of a message in a workspace in which you want the checkpoint to happen later after the message is received.
Checkpoint Options
Received Message ID |
The _receive_id attribute from a receiving transformer (with the Receive action) used to identify a message to checkpoint. |
Checkpoint Store (Azure blob)
Checkpoint store is optional for the Receive action and required for the Checkpoint action. It is used to store the partition load-balancing and checkpoint data when receiving events. Load balancing does not apply when receiving from a single partition.
If a checkpoint store is not provided, the checkpoint will be maintained internally in memory, and the client will receive events without load-balancing.
When used, a checkpoint store uses an Azure storage container to store offset information. The offset information is used to start receiving at the same position at the next receive.
Container Name |
The container name for the blob store. |
Connection String |
A connection string to an Azure Storage account. |
Checkpoint Interval |
(Optional) Submits a checkpoint store to Azure blob every nth message. The default checkpoints only at the end of the stream. There will always be a checkpoint at the end of a message stream. |
The following attributes can be selected for inclusion on the output features. Each output feature represents a message that was either sent or received.
_payload | The message payload. UTF-8 string if possible to decode, otherwise binary or numeric. |
_enqueued_time | The timestamp when the message was sent. |
_offset | The offset of the message. |
_partition_key | The partition of the message. |
_properties | A key, value pair of message properties. |
_receive_id | An id generated to identify the message used for the Checkpoint action. |
_sequence_number | The sequence number of the message. |
_system_properties | Metadata set by the Event Hubs Service associated with the message. |
Editing Transformer Parameters
Using a set of menu options, transformer parameters can be assigned by referencing other elements in the workspace. More advanced functions, such as an advanced editor and an arithmetic editor, are also available in some transformers. To access a menu of these options, click beside the applicable parameter. For more information, see Transformer Parameter Menu Options.
Defining Values
There are several ways to define a value for use in a Transformer. The simplest is to simply type in a value or string, which can include functions of various types such as attribute references, math and string functions, and workspace parameters. There are a number of tools and shortcuts that can assist in constructing values, generally available from the drop-down context menu adjacent to the value field.
Using the Text Editor
The Text Editor provides a convenient way to construct text strings (including regular expressions) from various data sources, such as attributes, parameters, and constants, where the result is used directly inside a parameter.
Using the Arithmetic Editor
The Arithmetic Editor provides a convenient way to construct math expressions from various data sources, such as attributes, parameters, and feature functions, where the result is used directly inside a parameter.
Conditional Values
Set values depending on one or more test conditions that either pass or fail.
Parameter Condition Definition Dialog
Content
Expressions and strings can include a number of functions, characters, parameters, and more.
When setting values - whether entered directly in a parameter or constructed using one of the editors - strings and expressions containing String, Math, Date/Time or FME Feature Functions will have those functions evaluated. Therefore, the names of these functions (in the form @<function_name>) should not be used as literal string values.
These functions manipulate and format strings. | |
Special Characters |
A set of control characters is available in the Text Editor. |
Math functions are available in both editors. | |
Date/Time Functions | Date and time functions are available in the Text Editor. |
These operators are available in the Arithmetic Editor. | |
These return primarily feature-specific values. | |
FME and workspace-specific parameters may be used. | |
Creating and Modifying User Parameters | Create your own editable parameters. |
Dialog Options - Tables
Transformers with table-style parameters have additional tools for populating and manipulating values.
Row Reordering
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Enabled once you have clicked on a row item. Choices include:
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Cut, Copy, and Paste
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Enabled once you have clicked on a row item. Choices include:
Cut, copy, and paste may be used within a transformer, or between transformers. |
Filter
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Start typing a string, and the matrix will only display rows matching those characters. Searches all columns. This only affects the display of attributes within the transformer - it does not alter which attributes are output. |
Import
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Import populates the table with a set of new attributes read from a dataset. Specific application varies between transformers. |
Reset/Refresh
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Generally resets the table to its initial state, and may provide additional options to remove invalid entries. Behavior varies between transformers. |
Note: Not all tools are available in all transformers.
Reference
Processing Behavior |
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Feature Holding |
No |
Dependencies | Microsoft Azure Account with the Event Hubs Service |
Aliases | |
History |
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