Message Queuing Middleware

1. Message Queuing Middleware • Message queuing is asynchronous communication • Most distributed apps use synchronous communication • Sender must wait for response • Can require more hardware to handle peak workload • With queuing, make request and then move on • No guarantee on when receiver will process request • Usually good response time

2. Fundamental Challenges • Conventional communication technologies require Tx and Rx application: • Online at the same time • Able to communicate over network at the same time • Reality is: • Apps do not run at same time • WANs not always reliable and available • Change that requires other side to change not practical • Distributed transactions can impact availability and performance

3. Role of Message Queuing Middleware • MQM satisfies four important conditions • No simultaneous connection is required • Extremely strong request and response delivery guarantees • Request and responses can be translated and reformatted • Business models must promote adoption by ISVs

4. Communicating Via MQM • Applications communicate via messages • MQM provider keep messages in queues

5. MQM Benefits to Programmers • Applications can send to non running or unreachable apps • MQM will deliver waiting messages when app is available • MQM uses proven technologies to provide reliability for mission critical apps • Providers can reroute messages around failure points

6. MQM and Distributed Applications • Examine MQM in a series of scenarios • Store and forward communication • Defensive communication • Concurrent communication • Journaled communication • Connectionless communication

7. Downside of MQM • Distributed communications falls into three categories • A response is required immediately and no response will cause application to hang • A response is needed in time period set by business policy • Sender trusts the system to deliver and no response is required

8. MSMQ Objects • Objects include Machines, Queues, Messages • Using the MSMQ API, you can: • Create queue objects • Locate queue objects • Open and delete queue objects • Set and get queue object properties • Send and receive message objects • Get machine object properties

9. Types of Queues • Application Created Queues • Message • Administration • Response • MSMQ or System Created Queues • Journal • Dead Letter • Report

10. MSMQ Messages • Most messages contain application data • Other are MSMQ generated, acknowledgement • Each message contains an MSMQ generated identifier • Property also identifies message

11. MQM Transactions • This model shows two transactions • One to send messages to Queue • One to retrieve message from Queue

12. Using the MSMQ API Functions • Creating a Queue • Locating a Public Queue • Opening a Queue • Closing a Queue • Deleting a Queue • Sending Authenticated Messages • Sending Messages to a Queue • Sending Messages that Request Acknowledgments • Sending Messages that Request a Response • Sending Private Messages • Sending Messages Using an Internal Transaction • Sending Messages Using an MS DTC External Transaction • Reading Messages Synchronously • Reading Messages Asynchronously • Reading Messages Using a Cursor • Reading Messages in a Dead Letter Queue • Reading Messages in a Machine Journal • Reading Messages in a Queue Journal • Returning an Acknowledgment Message by a Connector Application • Retrieving a Queue's Properties • Setting a Queue's Properties Using API Functions • Setting Access Control Security for a Queue • Using Transactions