Service Consumer a Sends a Message with a Business Document

question 16

Multiple Choice

Service Consumer A sends a message with a business document to Service A (1) , which writes the business document to Database A (2) . Service A then forwards the business document to Service B (3) , which writes the business document to Database B (4) . Service B then responds to Service A with a message containing a failure or success code (5) after which Service A responds to Service Consumer A with a message containing a failure or success code (6) . Upon receiving the message, Service Consumer A updates a log table in Database B (7) . The log entry is comprised of the entire business document. Database A is dedicated to the Service A service architecture and Database B is a shared database. You are told that the database updates performed by Service A and Service B must be either both successful or they cannot happen at all. The database update performed by Service Consumer A must happen after it is given the outcome of the database updates performed by Service A and Service B . Given that Service Consumer A must also update Database B as part of this service composition architecture, how is it possible to fulfill these requirements?

• A) The State Repository pattern can be applied so that Service A writes the business document data to a separate state database until it receives a response message from Service B . If the response message contains a success code, Service A writes the business document to Database A. If the response contains a failure code, Service A discards the data that was written to the state database.
• B) The Service Data Replication pattern can be applied to Service Consumer A and Service B so that separate dedicated databases can be established allowing Service Consumer A to make updates independently of Service B . Service A is simply redesigned to not write the business document to Database A until after it receives a message containing a success code from Service B.
• C) The Atomic Service Transaction pattern can be applied to encompass Service A, Service B and Service Consumer A. This will guarantee that all of the actions performed by the service composition participants will either be successful or will be rolled back if anyone is not successful.
• D) None of the above.

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