Using Acknowledgments

Using Acknowledgments

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The BizTalk Messaging Engine generates positive acknowledgments (ACK) and negative acknowledgments (NACK) in response to conditions encountered during the processing of a message through a port. BizTalk Server publishes a positive acknowledgment to indicate successful transmission of a message and a negative acknowledgment to indicate transmission failure and suspension of a message.

Why Use Acknowledgments?

Positive and negative acknowledgments provide strong feedback that you can use to determine if a message arrived at its destination or encountered one or more problems along the way. For example, acknowledgments are useful when:

You want to monitor a receive port for a new trading partner for schema validation and other errors.
You want to mark the status of a loan request sent out for approval as "in process" if it is successfully sent to a partner for approval or "failed" if transmission fails (for example, if the partner's server is down).
You process interchanges containing multiple purchase orders and want to track the number of orders that are transmitted or fail transmission.

You can accomplish each of these scenarios by using acknowledgments and content-based routing that uses filters.

Routing Acknowledgments

When an ACK or NACK is published, all of the message context properties from the message that caused the ACK/NACK are demoted. Any properties that were promoted do not flow to the acknowledgment. To route an acknowledgment, build a filter using the following properties from the BTS namespace:

Property name	Data type	Description
BTS.AckFailureCategory	xs:int	Identifies the ErrorCategory, which gives the place and reason for the suspension.
BTS.AckFailureCode	xs:string	Identifies the ErrorCode, which gives the place and reason for the suspension.
BTS.AckType	xs:string	Value is ACK for a positive acknowledgment and NACK for a negative acknowledgment.
BTS.AckID	xs:string	Identifies the MessageID of the original message.
BTS.AckOwnerID	xs:string	Identifies the instance ID from the original message.
BTS.CorrelationToken	xs:string	Identifies the correlation token from the original message if one is present.
BTS.AckDescription	xs:string	Identifies the ErrorDescription, which gives the place and reason for the suspension.
BTS.AckSendPortID	xs:string	Identifies the SendPortID from the original message.
BTS.AckSendPortName	xs:string	Identifies the SendPortName from the original message.
BTS.AckOutboundTransportLocation	xs:string	Identifies the OutboundTransportLocation from the original message.
BTS.AckReceivePortID	xs:string	Identifies the ReceivePortID from the original message.
BTS.AckReceivePortName	xs:string	Identifies the ReceivePortName from the original message.
BTS.AckInboundTransportLocation	xs:string	Identifies the InboundTransportLocation from the original message.

Note
The properties that contain error information are not present in ACKs because they signal a positive delivery.

Negative Acknowledgment Message Body

Much of the important information about a positive or negative acknowledgment is contained in the context properties. In addition to the context properties, NACKs also contain a message body part containing a SOAP fault. The format of the SOAP fault is as follows:

<?xml version="1.0" encoding="utf-8"?>
<SOAP:Envelope xmlns:SOAP="http://schemas.xmlsoap.org/soap/envelope/" SOAP:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
  <SOAP:Body>
    <SOAP:Fault>
      <faultcode>Microsoft BizTalk Server Negative Acknowledgment </faultcode>
      <faultstring>An error occurred while processing the message, refer to the details section for more information </faultstring>
      <faultactor>C:\Projects\Sample\Locations\Response\FM_%MessageID%.xml</faultactor>
      <detail>
        <ns0:NACK Type="NACK" xmlns:ns0="http://schema.microsoft.com/BizTalk/2003/NACKMessage.xsd">
          <NAckID>{FFB1A60B-E593-4620-8897-4E9C7030A937}</NAckID>
          <ErrorCode>0xc0c01658</ErrorCode>
          <ErrorCategory>0</ErrorCategory>
          <ErrorDescription>There was a failure executing the send pipeline: "Microsoft.BizTalk.DefaultPipelines.XMLTransmit, Microsoft.BizTalk.DefaultPipelines, Version=3.0.1.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" Source: "XML assembler" Send Port: "Failed Message" URI: "C:\Projects\Sample\Locations\Response\FM_%MessageID%.xml" Reason: This Assembler cannot retrieve a document specification using this type: "http://Sample#Unknown".  </ErrorDescription>
        </ns0:NACK>
      </detail>
    </SOAP:Fault>
  </SOAP:Body>
</SOAP:Envelope>

The exception message raised by the adapter is in the SOAP Detail section in the ErrorDescription element.

Accessing the Message Body from an Orchestration

If you have an orchestration port that requires delivery notification, the DeliveryFailureException that is thrown on a transmission failure is deserialized from the SOAP fault that is contained in the NACK message body. To access the exception message string from within your orchestration, cast the DeliveryFailureException to a SoapException and then access the InnerXml as shown in the following code:

// Cast the DeliveryFailureException to a SoapException…
System.Web.Services.Protocols.SoapException se = (System.Web.Services.Protocols.SoapException)e.InnerException;
System.Diagnostics.Trace.WriteLine(se.Detail.InnerXml);
//e is an Microsoft.XLANGs.BaseTypes.DeliveryFailureException
//object type created in an Exception handler

The preceding code sample returns an XML fragment similar to the following:

<?xml version="1.0" encoding="utf-8"?>
<ns0:NACK Type="NACK" xmlns:ns0="http://schema.microsoft.com/BizTalk/2003/NACKMessage.xsd">
  <NAckID>{FFB1A60B-E593-4620-8897-4E9C7030A937}</NAckID>
  <ErrorCode>0xc0c01658</ErrorCode>
  <ErrorCategory>0</ErrorCategory>
  <ErrorDescription>There was a failure executing the send pipeline: "Microsoft.BizTalk.DefaultPipelines.XMLTransmit, Microsoft.BizTalk.DefaultPipelines, Version=3.0.1.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" Source: "XML assembler" Send Port: "Failed Message" URI: "C:\Projects\Sample\Locations\Response\FM_%MessageID%.xml" Reason: This Assembler cannot retrieve a document specification using this type: "http://Sample#Unknown".</ErrorDescription>
</ns0:NACK>

When Is an Acknowledgment Published?

Both positive (ACK) and negative (NACK) acknowledgments are published to the MessageBox database at the point of failure provided there is at least one matching subscription. For example, if BizTalk Server cannot find a matching schema for a message read from a receive port and there are no NACK subscriptions, it suspends the message (if failed message routing has not been enabled) and does not publish a NACK

Concepts

Using Failed Message Routing

Other Resources

Error Handling