Guaranteed delivery (GD) is a delivery mechanism that guarantees data is processed from a stream to an adapter.
GD ensures that data continues to be processed when:
- The Server fails.
- The destination (third-party server) fails.
- The destination (third-party server) does not respond for a period of time.
Persistent subscribe pattern (PSP) is used to implement GD in output adapters. Input adapters support GD using facilities provided by the source rather than using PSP. The WebSphereMQ Input and Output adapter, all JMS Input and Output adapters, and the TIBCO Rendezvous adapter all support GD. These adapters have specific PSP and GD parameters that are unique to them. Examples for enabling GD in one of the JMS CSV Output adapters and the WebSphere Output adapter are located <ESP_HOME>/examples/ccl/JmsOutBoundAdapterWithGDSupport and <ESP_HOME>/examples/ccl/WsmqOutBoundAdapterWithGDSupport respectively.
PSP works through a combination of a window (input, output), a control window, and a Flex operator with a log store. The window and control window plug into the Flex operator. Data from the window on which PSP is enabled is entered into the flex operator, which generates a sequence number and opcode from the data, and places them at the beginning of each row of data. The Flex operator sends this data to the adapter that is attached to it, and the adapter passes the information on to the control window. Finally, the control window informs the Flex operator of the data that has been processed by the adapter, and the Flex operator removes this data from the log store.
