For event notification, the connector detects events written to a queue by an application rather than a database trigger. An event occurs when an application or other MQ-capable software generates FIX messages and stores them on the MQ message queue.
The connector uses the pollForEvents() method to poll the MQ queue at regular intervals for messages. When the connector finds a message, it retrieves it from the MQ queue and examines it to determine its format. If the format has been defined in the connector's static object, the connector passes both the message body and a new instance of the business object associated with the format to the configured data handler; the data handler is expected to populate the business object and specify a verb. If the format is not defined in the static meta-object, the connector passes only the message body to the data handler; the data handler is expected to determine, create and populate the correct business object for the message. See Error handling for event failure scenarios.
The connector processes messages by first opening a transactional session to the input queue. This transactional approach allows for a small chance that a business object could be delivered to an integration broker twice due to the connector successfully submitting the business object but failing to commit the transaction in the queue. To avoid this problem, the connector moves all messages to an in-progress queue. There, the message is held until processing is complete. If the connector shuts down unexpectedly during processing, the message remains in the in-progress queue instead of being reinstated to the original input queue.
Optionally, to support applications that want feedback on the requests they issue through WebSphere MQ, the connector for FIX Protocol issues report messages back to the applications detailing the outcome of their requests once they have been processed.
To achieve this, the connector posts the business data for such requests synchronously to the integration broker. If the business object is successfully processed, the connector sends a report back to the requestor including the return code from the integration broker and any business object changes. If the business object cannot be processed, the connector sends a report containing the appropriate error code and error message.
In either case, an application that sends a request to the connector for FIX Protocol is notified of its outcome.
If the connector for FIX Protocol receives any messages requesting positive or negative acknowledgement reports (PAN or NAN), it posts the content of the message synchronously to the integration broker and then incorporates the return code and modified business data into a report message that is sent back to the requesting application.
Table 1 shows the required structure of FIX messages that are
received and processed synchronously by the connector.
Table 1. Required structure of synchronous WebSphere MQ messages
MQMD field | Description | Supported values (multiple values should be OR'd) |
---|---|---|
MessageType | Message Type | DATAGRAM |
report | Options for report message requested |
You can specify one or both of the following:
You can specify one of the following to control how the correlation ID of the report message is to be set:
|
ReplyToQueue | Name of reply queue | The name of the queue to which the report message should be sent. |
replyToQueue Manager | Name of queue manager | The name of the queue manager to which the report message should be sent. |
Message Body |
| A serialized business object in a format compatible with the data handler configured for the connector. |
Upon receipt of a message as described in Table 1, an ICS-based connector does the following:
Table 2 shows the structure of the report that is sent back to the
requestor from the connector.
Table 2. Structure of the report returned to the requestor
MQMD field | Description | Supported values (multiple values should be OR'd) |
---|---|---|
MessageType | Message Type |
REPORT |
feedback | Type of report | One of the following:
|
Message Body |
| If the business object is successfully processed, the connector populates the message body with the business object returned by the integration broker. This default behavior can be overridden by setting the DoNotReportBusObj property to true in the static meta-data object. If the request could not be processed, the connector will populate the message body with the error message generated by the connector or the integration broker. |
Upon initialization, the connector checks the in-progress queue for messages that have not been completely processed, presumably due to a connector shutdown. The connector configuration property InDoubtEvents allows you to specify one of four options for handling recovery of such messages: fail on startup, reprocess, ignore, or log error.
With the fail on startup option, if the connector finds messages in the in-progress queue during initialization, it logs an error and immediately shuts down. It is the responsibility of the user or system administrator to examine the message and take appropriate action, either to delete these messages entirely or move them to a different queue.
With the reprocessing option, if the connector finds any messages in the in-progress queue during initialization, it processes these messages first during subsequent polls. When all messages in the in-progress queue have been processed, the connector begins processing messages from the input queue.
With the ignore option, if the connector finds any messages in the in-progress queue during initialization, the connector ignores them, but does not shut down.
With the log error option, if the connector finds any messages in the in-progress queue during initialization, it logs an error but does not shut down.
If the connector property ArchiveQueue is specified and identifies a valid queue, the connector places copies of all successfully processed messages in the archive queue. If ArchiveQueue is undefined, messages are discarded after processing. For more information on archiving unsubscribed or erroneous messages, see Error handling.