For an application to achieve guaranteed processing, every system component must handle the logic and communication with its neighbor components that ensure guaranteed delivery.
When implementing a guaranteed processing application, you must address every component of the application, not just the Sybase CEP Engine components. The following diagram illustrates the components of an end-to-end application incorporating Sybase CEP Engine:
Messages travel through the application as follows:
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From the external data source to an input adapter. The adapter may poll the external source or register for notifications or use some other mechanism to receive data.
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The input adapter publishes messages to one or more data streams.
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The stream(s) feed projects and query module(s).
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The query module(s) publish to one or more streams.
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The stream(s) feed an output adapter.
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The output adapter subscribes to the stream(s), processes the messages, converts the data to a format suitable for the final destination, and then transmits the data.
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The destination receives the data and performs whatever actions it is designed to do.
If just one of the components uses some other methodology, then the system as a whole will not perform guaranteed processing. For example, if the data source provides events on a best-effort basis, the entire system can only be categorized as best-effort. Similarly, if the output adapter uses at-least-once processing (messages are never dropped but may be duplicated), then the application as a whole must be considered an at-least-once processor.