Demo application featuring RabbitMq, Spring Cloud Stream and Spring Amqp

The app does nothing useful obviously :-)

• The app checks if the payload of the input message contains the word "retry",
• if so, the app sends the message to a retry-exchange.
• Depending on the number of retries, the message will be routed to a waiting queue (1 second and 10 seconds), or a parking queue
• Before sending the message to the parking queue, the app will send a message to a "log queue" with StreamBridge

Implementation notes:

• The retry-mechanism is based on the per-queue message TTL and on dead letter exchanges
• Spring Amqp is used to set up RabbitMq queues and exchanges (Cloud Stream doesn't allow fine-grained RabbitMq configuration)
• Cloud Stream :
  • use of functional programming model
  • dynamic routing
  • use of StreamBridge
• Some tests use Spring Cloud test binder, and others are run only if a rabbit mq server is running on localhost

Notes on the retry-infrastructure (queues and exchanges):

• it can be shared across multiple applications
• adding more wait queues is easy (only requires adding a couple of properties)
• it should be easy to extract the retry features, and include them into a library