Decoupling Strategies for HTTP-Based Integrations: Exploring JMS Queue, Event-Based Platform, SOAP Adapter, and DataStore Options.

In integration scenarios where sender communication is synchronous but processing takes longer, decoupling strategies are necessary. Four options are available: JMS queue, event-based platform, SOAP adapter, and datastore. JMS queues are the recommended and most common option, allowing immediate acknowledgement and processing in a separate flow. Event-based platforms, such as SAP Event Mesh or Kafka, are suitable for event-driven architectures, while SOAP adapters are a quick-win solution for simple calls. Datastores are a fallback option for low-to-medium volume messages that can tolerate delayed processing.

In integration scenarios where sender communication is synchronous but processing takes longer, decoupling strategies are necessary to ensure efficient and reliable data flow. SAP Cloud Integration (CPI) offers several options to address this challenge, each with its unique advantages and limitations.

The most recommended and commonly used strategy is the JMS queue. This method allows for immediate acknowledgment of the HTTP request by pushing the message to a JMS queue quickly and sending an HTTP 200/202 response back to the sender within their timeout. The processing continues in a separate flow that consumes the message from the queue. JMS queues are reliable, durable, and have built-in retry mechanisms, making them a robust choice for integration flows [1].

For event-driven architectures, an event-based platform such as SAP Event Mesh or Kafka can be employed. This approach involves publishing an event to a broker and responding quickly to the sender. The processing is then handled asynchronously by a separate consumer. Event-based platforms are highly scalable and can decouple systems further, fitting well into microservice and event-driven designs. However, they may be overkill for single-use scenarios and require a complex setup [1].

SOAP adapters provide a quick-win solution for simple calls. By transforming the HTTP call into a SOAP call, this method allows for immediate response to the sender and asynchronous processing. This approach is straightforward and does not require queues or dedicated software, making it suitable for simple use cases. However, it may not be ideal for handling large payloads in non-XML format [1].

As a fallback option, datastores can be used when other methods are not feasible. Datastores persist the incoming message and respond immediately to the HTTP sender. Processing continues asynchronously in a separate, scheduled iFlow. This method is useful for low-to-medium volume messages that can tolerate delayed, batch-style processing. However, it lacks built-in retry mechanisms and requires manual polling logic, making it less suitable for high-throughput or time-sensitive processing [1].

While these decoupling strategies offer various benefits, the ideal solution would be to achieve the decoupling at the HTTP adapter itself. However, the HTTP adapter is synchronous by design and does not allow for configuration changes to alter this behavior. Workarounds such as routing the HTTP request through a parallel or sequential multicast before forwarding it to the processing iFlow have been explored but did not reliably solve the issue.

In conclusion, the choice of decoupling strategy depends on the specific requirements of the integration scenario. JMS queues are the most common and recommended option, while event-based platforms, SOAP adapters, and datastores offer alternative solutions for different use cases.

References:
[1] https://community.sap.com/t5/technology-blog-posts-by-members/decoupling-strategies-for-http-based-integrations-in-sap-cloud-integration/ba-p/14167141