About Document Acknowledgements for a webMethods Messaging Trigger

When a trigger service finishes processing a guaranteed document, Integration Server returns an acknowledgement to the messaging provider. Upon receipt of the acknowledgement, the messaging provider removes its copy of the document from storage. By default, Integration Server returns an acknowledgement for a guaranteed document as soon as it finishes processing the document.

Note:Integration Server returns acknowledgements for guaranteed documents only. Integration Server does not return acknowledgements for volatile documents.

You can increase the number of document acknowledgements returned at one time by changing the value of the Acknowledgement queue size property. The acknowledgement queue is a queue that contains pending acknowledgements for guaranteed documents processed by the webMethods messaging trigger. When the acknowledgement queue size is greater than one, a server thread places a document acknowledgement into the acknowledgement queue after it finishes executing the trigger service. Acknowledgements collect in the queue until a background thread returns them as a group to the sending resource.

If the Acknowledgement queue size is set to one, acknowledgements will not collect in the acknowledgement queue. Instead, Integration Server returns an acknowledgement to the sending resource immediately after the trigger service finishes executing.

If a resource or connection failure occurs before acknowledgements are sent or processed, the transport redelivers the previously processed, but unacknowledged documents. The number of documents redelivered to a webMethods messaging trigger depends on the size on the number of guaranteed documents that were processed but not acknowledged before failure occurred. If exactly-once processing is configured for the webMethods messaging trigger, Integration Server detects the redelivered, guaranteed documents as duplicates and discards them without re-processing them. For more information about exactly-once processing, see Exactly-Once Processing for webMethods Messaging Triggers.

Increasing the size of a webMethods messaging trigger’s acknowledgement queue can provide the following benefits:

Reduces network traffic. Returning acknowledgements one at a time for each guaranteed document that is processed can result in a high volume of network traffic. Configuring the webMethods messaging trigger so that Integration Server returns several document acknowledgements at once can reduce the amount of network traffic.

Increases server thread availability. If the size of the acknowledgement queue is set to 1 (the default), Integration Server releases the server thread used to process the document only after returning the acknowledgement. If the size of the acknowledgement queue is greater than 1, Integration Server releases the server thread used to process the document immediately after the thread places the acknowledgement into the acknowledgement queue. When acknowledgements collect in the queue, server threads can be returned to the thread pool more quickly.