Data Access and Transactions
Introducing Message Queuing
For components that are not directly connected, diminished network throughput can be a severe impairment to the scalability of an application. This section discusses the use of Message Queuing to increase the reliability of transactions that use disconnected components.
Message Queuing is a fast store-and-forward service that enables applications to communicate across heterogeneous networks and systems. Applications send messages to Message Queuing, and Message Queuing ensures that the messages eventually reach their destination. Message Queuing provides guaranteed message delivery, efficient routing, security, and priority-based messaging.
Most importantly, Message Queuing also supports Component Services transactions. Because it is a resource manager under the control of the DTC, you can use Message Queuing to safely implement transaction-compliant applications that ensure that message operations either succeed or fail in conjunction with other transactions. A transactional application can send a message through Message Queuing and update a database as part of the same transaction. The transaction coordinator ensures that both actions succeed or fail together.
For instance, a single online purchase might consist of a credit card validation, an adjustment to inventory on hand, and a notification to an external supplier. Of course, the external suppliers system may be temporarily offline, which prevents the system from notifying the external supplier. In the context of a transaction, failures such as this dictate that the entire process be aborted, whether or not the inventory was available and in spite of a successful credit card debit.
A better solution is to use Message Queuing, which guarantees that the vendor will be notified eventually. In this way, Message Queuing enables systems to respond more flexibly to factors that can cause transaction failures; as a result, this effectively eliminates errors caused by server outages and long pauses caused by network latency, making Message Queuing ideal for time-independent transactions.
See the following: