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Patterns in Windows Azure Service Bus - Dynamic Router Pattern

Last time we talked about Scatter-Gather Pattern and how we can implement it using Windows Azure Service Bus. Today, we will look over Dynamic Router Pattern and how can be integrated in Windows Azure Service Bus.
First of all, let’s see what Dynamic Router is. This is a pattern that can be used when we want to register at runtime different rules and based on this rules the messages are redirected to a specific consumers. This sounds pretty simple in the first moment, but we have 2 different situations that need to be handled.
The first one is from the consumer perspective.  In any moment we need to be able to change the rules or add new rules, without stopping the system. These rules can use properties from messages that didn’t exist when the system started.
The second situations are from the producer. At runtime we need to be able to add or remove properties that can be handled by the system when the routing is made without restarting the system or affecting the consumers.
Top on this, it would be nice to be able to extract all the properties that will be used by the routing mechanism automatically, without the need to make special configuration over the system.
Of course, this pattern can be implemented with success using Windows Azure Service Bus. This pattern can be implemented using Service Bus Queues or Service Bus Topics. The secret here to have the best implementation of this pattern in Windows Azure is to create a mechanism that can extract the properties that are needed by the dynamic routing from the message that is added to the Service Bus. This solution need to be very flexible and to give us the possibility at runtime to control this.
The solution of this problem can be the promoted properties that can be found in BizTalk. This kind of properties doesn’t exist yet in Windows Azure Service Bus, but can be implemented very easily using attributes. I describe this solution in the following blog post:
In this moment we know how we can dynamically add/remove properties from a BrokeredMessage. From now one, the rest can be implemented very easily. If we are using Windows Azure Service Bus Topic, we can create custom filters over each subscription.
TopicClient topicClient = TopicClient.CreateFromConnectionString(
SqlFilter sqlFilterReviewGroup = new SqlFilter(“Groups LIKE ‘%Review%’”);
topicClient.AddSubscription(“ReviewSubscription”, sqlFilterReviewGroup);
SqlFilter sqlFilterTestGroup = new SqlFilter(“Groups LIKE ‘%Test%’”);
topicClient.AddSubscription(“ReviewSubscription”, sqlFilterTestGroup);
This pattern can be used with success when we need a dynamic routing mechanism where rules and filters attributes can change anytime. This is a case that can appear when we offer a solution that is used by other solution providers.
Last edit: A list of all patterns that can be used with Windows Azure Service Bus, that were described by me LINK.  


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