OK, as to your specific design question here is how I would do it:

A) Add a table like this:

CREATE TABLE PreProcessingLog

(

CustomerIDint,

CompletionTypeint,

--Types are 1=UserRequest, 2=DocType1, 4=DocType2, 8=DocType3

Primary Key Clustered (CustomerID, CompletionType)

)

B) When the User request is issued or at the completion of each Document Type's pre-processing, INSERT the appropriate record into this table, then send the corresponding message to your service broker service.

C) The queue activation procedure should do the following:

-- 1. Begin a transaction

-- 2. Read the message from the queue

-- 3. Execute the following check:

IF (

SELECT SUM(CompletionType)

FROM PreProcessingLog

WHERE CustomerID = @RecvdCustID

) 15

BEGIN

COMMIT TRANSACTION

RETURN 0

END

-- 4. Otherwise, continue to do the post-processing

-- 5. Delete all of the CustomerID=@RecvdCustID rows from PreProcessingLog

-- 6. Commit the transaction & return.

Now you can also throttle the intensity of the post-processing by limiting the number of concurrent queue activations.