Logs and errors/Browser SDK

Browser SDK

Installing @accelerup-llc/web-monitor, and the two production mistakes worth knowing about first.

@accelerup-llc/web-monitor reports browser errors, warnings, network failures and spans to AccelerUp.

Install

bash

npm install @accelerup-llc/web-monitor

import { init } from '@accelerup-llc/web-monitor';

init({
  ingestUrl: 'https://monitoring.qrdev.org/ingest',
  key: 'YOUR_INGEST_KEY',
  release: process.env.NEXT_PUBLIC_RELEASE,   // ties errors to a release
  environment: 'production',
  sampleRate: 1.0,
});

Option	Purpose
`ingestUrl`	The `/ingest` base
`key`	Ingest key — see Ingest endpoints
`release`	Set this. It is what links an error group to the release that introduced it
`environment`	Keeps staging noise out of production
`sampleRate`	1.0 while you are establishing a baseline

Two production mistakes

These both happened. Neither is obvious, and both were expensive to diagnose.

The traceparent leak

The SDK adds a traceparent header for distributed tracing. On a cross-origin request to a third party that does not allow that header, the browser's preflight fails — and the request never happens.

Caution

The symptom is not an error in your code. It is a third-party integration silently not loading: a payment iframe that never appears, a social login that does nothing. Configure the SDK to add traceparent only to your own origins.

CORS on the ingest endpoint

If ALLOWED_ORIGINS does not include the site the SDK runs on, every ingest request fails preflight. The SDK then reports nothing at all — and an SDK reporting nothing looks exactly like an application with no errors.

Tip

After deploying the SDK, deliberately throw an error in a staging build and confirm it appears in Error groups. An SDK that is not reporting is indistinguishable from healthy code.

Source maps

Upload the map for each build so stacks resolve to your source:

bash

curl -X POST https://monitoring.qrdev.org/ingest/sourcemaps \
     -H "X-Ingest-Key: $KEY" \
     -F "release=$RELEASE" \
     -F "file=@dist/main.js.map"

Do this in the build, not by hand. A map that does not match the deployed bundle resolves to the wrong lines, which sends people to code that is not running.

Privacy

Set WEB_INGEST_SCRUB_PII and WEB_INGEST_SCRUB_IP server-side. Scrubbing happens before the first write, so a scrubbed field was never stored.

What it reports

	Appears in
Uncaught errors and rejections	Error groups
`console.warn` / `console.error`	Error groups
Failed network requests	Network errors
Performance spans	APM
Session metadata	Session context on each error

Feature flags

The same package carries the feature-flag client, so a page that already has the SDK can evaluate flags without a second dependency.

Where this behaviour lives: backend/internal/handler/web_ingest_handler.go. If the code and this page disagree, the code is right — please fix the page.

Part of Logs and errors — What the software said about itself, and what was unusual about it.