In complex integration scenarios, especially those involving asynchronous messaging and multiple related messages, the ability to correlate and aggregate messages is essential. SAP Cloud Platform Integration (CPI) provides powerful features to handle these patterns, enabling integration developers to manage message sequences effectively and consolidate multiple message parts into a single meaningful output.
This article explores the concepts of correlation and aggregation within CPI and guides you through implementing these capabilities to build robust integration flows.
¶ Understanding Correlation and Aggregation
Correlation is the process of identifying and grouping related messages so they can be processed together. For example, when multiple messages are part of the same business transaction or process instance, a correlation key is used to link them.
Aggregation is the act of combining multiple related messages into a single message. After correlation identifies related messages, aggregation collects and merges them to produce a consolidated result.
Together, correlation and aggregation enable handling scenarios such as:
- Combining multiple order line items into one order.
- Collecting multiple status updates before sending a summary.
- Waiting for all parts of a split message before continuing processing.
¶ How CPI Supports Correlation and Aggregation
SAP CPI supports these patterns primarily through:
- CPI allows defining correlation properties using headers or message content.
- The correlation key ensures messages are grouped by a unique identifier (e.g., Order ID, Customer ID).
- It is used in aggregation and message processing to link related messages.
- The Aggregator is a built-in integration process step designed to collect messages based on correlation keys.
- It buffers incoming messages until a completion condition is met (e.g., number of messages received, timeout).
- After aggregation completes, a single consolidated message is emitted downstream.
¶ Implementing Correlation and Aggregation: Step-by-Step
Scenario: You receive multiple shipment updates per order and want to aggregate them into one comprehensive shipment status message.
- Extract the Order ID or Shipment Batch ID from the incoming message payload or headers.
- Use a Content Modifier or script to store this value as a correlation property.
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Insert the Aggregator step into your integration flow.
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Set the Correlation Key to the property holding the Order ID.
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Define the Completion Criteria:
- Message Count: Number of messages to aggregate.
- Timeout: Maximum wait time before aggregating available messages.
- Custom Conditions: Optional scripting to define complex completion rules.
- Design a script or mapping to combine multiple messages into one.
- For example, merge individual shipment statuses into a single XML or JSON structure.
- After aggregation, route the combined message to the next step, such as sending it to an ERP system or triggering an alert.
¶ Best Practices for Correlation and Aggregation in CPI
- Use Unique and Stable Correlation Keys: Keys must uniquely identify related messages and remain consistent.
- Handle Timeouts Gracefully: Define timeouts in the Aggregator to avoid indefinite waiting for missing messages.
- Consider Message Volume: Large volumes of messages may require optimization to avoid performance bottlenecks.
- Test Thoroughly: Use CPI trace and monitoring tools to validate correlation and aggregation behavior under different scenarios.
Correlation and aggregation are vital patterns in SAP Cloud Platform Integration that help manage complex message sequences and consolidate data for streamlined processing. CPI’s built-in Aggregator step, combined with correlation keys, allows integration developers to design resilient flows that handle asynchronous messaging with ease.
By understanding and implementing these features, you can significantly enhance the robustness and intelligence of your integration solutions on SAP Cloud Platform.