Deadlettering Messages in a Receiving Application
It is also possible for a receiving application to
deadletter messages if they are formatted incorrectly or fail to comply with
business rules.
The brokered message class contains the following methods
for deadlettering messages.
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public void DeadLetter()
public void DeadLetter(string
deadLetterReason, string
deadLetterErrorDescription)
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The QueueClient, SubscriptionClient and MessageReceiver
classes provide the following messages.
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public void DeadLetter(Guid
lockToken)
public void DeadLetter
(Guid lockToken, string
deadLetterReason, string
deadLetterErrorDescription)
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When values are passed for the deadLetterReason and deadLetterErrorDescription
parameters they will be added to the message properties collection with the
names of DeadLetterReason and DeadLetterErrorDescription respectively. This
will help a deadletter processing application to determine the cause of the
failure.
Suppose the receiving application can only process order
statistics for the UK, United States and Sweden.
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List<string> validRegions = new
List<string>()
{
"UK", "US",
"SE"
};
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When a message is received a check could be performed to
verify that the order statistics are for a valid region, if this validation
check fails the message can be deadlettered by the receiving application.
Explicitly deadlettering a message in the receiving application will save the
message from being processed reputedly until it is deadlettered by the queue.
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OrderStat stat = msg.GetBody<OrderStat>();
if
(!validRegions.Contains(stat.Region))
{
string errorDescription = string.Format("Region
{0} is not known.", stat.Region);
Console.WriteLine(errorDescription);
msg.DeadLetter("Unknown region",
errorDescription);
msg.Dispose();
}
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It is also possible for the receiving application to check
the DeliveryCount property of a message and decide weather it should be
abandoned or deadlettered.
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if
(msg.DeliveryCount < 3)
{
msg.Abandon();
msg.Dispose();
}
else
{
msg.DeadLetter();
msg.Dispose();
}
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