Establish Reliability with ServiceNow API Integrations Using the Circuit Breaker Pattern

[BillMartin]

Introduction for ServiceNow Developers & Architects

API failures can be frustrating, especially when integrating external services into ServiceNow. If an API becomes unresponsive or slow, multiple retry attempts can overload ServiceNow, degrade performance, and cause unnecessary failures.

The Circuit Breaker Pattern prevents this by tracking failures, temporarily blocking requests to failing APIs, and automatically resuming operations when the service recovers. In this article, we’ll explore how to implement Circuit Breaker Pattern in ServiceNow using GlideAjax, Script Includes, and RESTMessageV2.

Why Use a Circuit Breaker in ServiceNow?

It prevents excessive API calls when an external service is down, improves system performance by stopping repetitive failures, automatically resumes operations when the API recovers, and enhances logging and debugging for better troubleshooting. This is essential for ITSM, HR, and asset management integrations, where reliability and performance are critical.

How the Circuit Breaker Works in ServiceNow

A client script (using GlideAjax) requests API data. The request is processed by EmployeeAjax and BaseAjaxProcessor. CircuitBreakerManager checks if API failures exceed the threshold. If failures exceed the limit, the request is blocked, and an error is returned. If the API recovers, the Circuit Breaker resets automatically. This approach ensures that ServiceNow doesn’t waste resources on failing API calls while improving response times for end users.

Key Components of the Circuit Breaker Pattern Implementation

CircuitBreakerManager tracks failures and blocks requests when API downtime is detected. EmployeeRepository calls the external API and records failures when requests fail. EmployeeService handles business logic and checks Circuit Breaker before making API calls. EmployeeAjax and BaseAjaxProcessor ensure structured responses for client-side requests. AjaxClient (UI Script) handles API requests and displays results in ServiceNow. By structuring API integrations with modular components, we improve reusability, maintainability, and system reliability.

Real-World Use Cases for Circuit Breaker Pattern in ServiceNow

HR system integration prevents failures when fetching employee data from an external HR system. Incident management stops repeated failed API calls when integrating with monitoring tools. Financial transactions prevent excessive retries when payment processing APIs are down. Asset management reduces API failures when connecting to an external CMDB.

How to Monitor Circuit Breaker Activity in ServiceNow

To track Circuit Breaker events, filter logs using:

Failures Recorded: [CircuitBreakerManager.recordFailure] Failure recorded for EmployeeService. Total Failures: 3
Circuit Breaker Activation: [CircuitBreakerManager.isCircuitOpen] Circuit Breaker is OPEN. Blocking requests.
Circuit Breaker Reset (Service Recovery): [CircuitBreakerManager.resetCircuit] Circuit Breaker reset. Service is available again.

By monitoring these logs in System Logs → All, you can track failures, API recovery, and performance improvements.

Watch the Live Demo!

We’ve covered the best practices, but seeing it in action makes a huge difference. Watch our full breakdown of Circuit Breaker in ServiceNow, where we demonstrate the implementation step by step.

Have you faced API failures in ServiceNow? Share your experiences and questions in the comments! Let’s solve it together.