Error Monitoring

Error Monitoring is an important part of building production-ready single-spa systems. This lesson explains what error monitoring means, how it works, and how to apply it with practical examples you can reuse.

Error Monitoring Overview

Error Monitoring is a building block you will reach for often in single-spa. It keeps related logic together and makes your intent obvious to reviewers and future maintainers.

When you learn error monitoring properly, you avoid the guesswork that leads to bugs and rework. The example below shows the shape you will use in most real single-spa projects.

import { registerApplication, start } from 'single-spa';

registerApplication({
  name: '@org/app',
  app: () => System.import('@org/app'),
  activeWhen: ['/app'],
});

start();

single-spa orchestrates multiple framework apps on one page through a root config.

Error Monitoring Example

registerApplication({
  name: '@org/app',
  app: () => System.import('@org/app'),
  activeWhen: ['/app'],
});
start();

Start from a minimal Error Monitoring example and grow it only as needed.
Keep configuration explicit so Error Monitoring behaves the same in every environment.
Name things clearly so teammates understand your Error Monitoring at a glance.
Add tests around Error Monitoring early to lock in expected behaviour.

Single-SPA Cheatsheet

Core single-spa APIs related to error monitoring.

API	Example	Purpose
registerApplication	`registerApplication({ name, app, activeWhen })`	Register a micro frontend
activeWhen	`activeWhen: ['/checkout']`	Route ownership
start	`start()`	Begin routing
bootstrap	`export async function bootstrap()`	One-time setup
mount	`export async function mount(props)`	Render the app
unmount	`export async function unmount(props)`	Clean up the app
import map	`systemjs-importmap`	Locate app bundles

How Error Monitoring Works in Single-SPA

Error Monitoring is part of how single-spa lets multiple applications — even in different frameworks — coexist on one page. A root config registers each app and controls when it is active.

single-spa orchestrates multiple framework apps on one page through a root config.

A root config registers apps and calls start().
Each app exports bootstrap, mount, and unmount lifecycles.
activeWhen decides which routes each app owns.
Import maps resolve each app's bundle at runtime.

Practical Guidance for Error Monitoring

For reliable micro frontends, error monitoring should isolate failures and keep shared state minimal. Let each team own its app end to end while agreeing on a few shared contracts.

Concern	Recommendation
Isolation	One app's crash should not break others
Shared state	Prefer shared utility modules over globals
Routing	Keep activeWhen rules explicit and non-overlapping
Deployment	Release via import-map updates per app

Common Mistakes

Copying error monitoring snippets without understanding what each line does.
Skipping error handling and edge cases when wiring up error monitoring.
Leaving error monitoring untested, so regressions slip into production.
Over-engineering error monitoring before you actually need the extra flexibility.

Key Takeaways

Error Monitoring is a core part of working effectively with single-spa.
Start small and keep error monitoring focused on a single responsibility.
Apply consistent patterns so error monitoring scales across your project.
Test and document error monitoring to keep it maintainable over time.

Pro Tip

Pair error monitoring with automated tests from day one. It is far cheaper to catch single-spa regressions in CI than in production.