Detecting Deadletters with Hints

A deadletter is an unclaimed published document. If there are no subscribers for a document that is published, the webMethods Broker returns an acknowledgement to the publisher and then discards the document. If, however, a deadletter subscription exists for the document, the webMethods Broker deposits the document in the queue containing the deadletter subscription.

A deadletter subscription allows you to trap unclaimed documents. Detecting and trapping deadletters is a valuable way to quickly identify and resolve discrepancies between a published document and the filtering criteria specified by a subscriber.

You create a deadletter subscription by inserting the DeadLetterOnly hint to the subscription filter. For more information about creating deadletter subscriptions using the DeadLetterOnly hint, see Using Hints in Filters.

When using the DeadLetterOnly hint, keep the following points in mind:

If the DeadLetterOnly hint is used in a filter that contains other expressions, the other expressions are ignored by the webMethods Broker. Consider the following example:

%city% L_EQUALS "Fairfax" {hint:DeadLetterOnly=true} {hint:LocalOnly=true}

webMethods Broker will ignore the expression %city% L_EQUALS "Fairfax" in the filter and will trap only those documents that do not have a subscriber and that originate from the webMethods Broker to which the Integration Server is connected.

If the filter is registered on Integration Server but not on the webMethods Broker, the DeadLetterOnly subscription traps only the documents that are rejected by Integration Server. The filter does not trap the documents rejected by the webMethods Broker unless the filter is registered on the webMethods messaging trigger.

Both the LocalOnly and IncludeDeliver hints are implied.

Note:
If you are using Universal Messaging you can configure a dead events store. For more information, see the Universal Messaging documentation.