Unpacking Asynchronous Integration: Execution vs. Transaction in ServiceNow

[Daxin]

When discussing integrations with ServiceNow, the concept of "asynchronous" frequently arises. A common misconception, however, is conflating asynchronous execution with asynchronous transaction processing. While both are crucial for robust integrations, they address different aspects of data exchange. Understanding this distinction is fundamental for designing efficient and scalable solutions.

Asynchronous Execution: Freeing Your Threads

In many integration scenarios, when an API call is triggered, the execution thread (e.g., a user's session or a business rule's process) is blocked, waiting for the external system's response. This can lead to:

• Poor User Experience: Users are stuck waiting for a potentially slow external system.
• Performance Bottlenecks: Long-running external calls tie up valuable ServiceNow resources.

This is where asynchronous execution comes into play. In ServiceNow, methods like RESTMessageV2.executeAsync() or SOAPMessageV2.executeAsync() enable this. When executeAsync() is called, the system does not block the current execution thread. Instead, it creates a scheduled job in the background to make the actual API call to the external system.

The key takeaway is that the initiating thread immediately proceeds with subsequent steps, without waiting for the external API's response. This pattern is vital for improving responsiveness and preventing timeouts for interactive processes.

(For more technical details on executeAsync and its implications, refer to ServiceNow KB article: KB0716391)

The other way to have this behaviour is using IntegrationHub where the API interaction happens in the Flow.

Asynchronous Integration Pattern: Decoupling Transactions

Beyond just how an API call is executed internally, an asynchronous integration pattern refers to a broader architectural approach where the sender of a message or request does not wait for an immediate, final response from the receiver. Instead, the sender continues its processing, expecting the response (if needed) to be handled later via a separate communication or callback mechanism. This pattern is all about decoupling the systems involved.

Let's explore how this pattern manifests in ServiceNow for both inbound and outbound integrations:

ServiceNow Inbound Asynchronous Processing:

When an external system sends an API request to ServiceNow, ServiceNow can immediately send back an acknowledgment of receipt (e.g., an HTTP 202 Accepted status). The actual processing of the received data occurs later, in the background.

Typically, this involves:

1. Storing the Data: ServiceNow receives the data and quickly saves it to a temporary location (like an Import Set staging table or event parameters).
2. Immediate Acknowledgment: A success response is sent back to the external system, often including a reference to the staged data.
3. Background Processing: An internal job (e.g., transform map / business rule / event) then picks up this data, processes it, and performs the transformation logic to insert/update the record in the target table.
4. Optional Callback: If configured, it might perform a callback to the originating system once the processing is complete.

A prime example is the Import Set API. By default, these APIs are asynchronous. They accept large volumes of data, send an immediate success response acknowledging receipt to the staging table, and then background processes handle the transformation to the target.

ServiceNow Outbound Asynchronous Processing (Callback Pattern):

This scenario is commonly encountered in e-bonding or other distributed workflows.

1. Initial Request: ServiceNow sends out a request to an external system (e.g., to create an incident).
2. Immediate Acknowledgment: The external system responds immediately, confirming that the request was received (e.g., "data received successfully").
3. Background Processing: The external system then processes the data internally.
4. Asynchronous Update (Callback): Later, after its internal processing is complete, the external system makes a separate API request back to ServiceNow (a callback) to update ServiceNow on the final result of the transaction (e.g., "incident successfully created, here is the external reference number").

Conclusion:

Asynchronous integration isn't just a best practice; it's essential for building scalable and robust integrations . By understanding the distinct power of asynchronous execution (which keeps your threads free and users unblocked) and leveraging asynchronous integration patterns (which decouple entire transactions for greater resilience), you can design solutions that truly enhance performance, prevent bottlenecks, and ensure seamless communication across your connected systems.