Breadcrumbs

Sentry uses breadcrumbs to create a trail of events that happened prior to an issue. These events are very similar to traditional logs, but can record more rich structured data.

This page provides an overview of manual breadcrumb recording and customization. Learn more about the information that displays on the Issue Details page and how you can filter breadcrumbs to quickly resolve issues in Using Breadcrumbs.

Manual Breadcrumbs

You can manually add breadcrumbs whenever something interesting happens. For example, you might manually record a breadcrumb if the user authenticates or another state change occurs.

Manually record a breadcrumb:

import 'package:sentry/sentry.dart';

Sentry.addBreadcrumb(Breadcrumb(message: 'Authenticated user'));

Automatic Breadcrumbs

To track automatic Breadcrumbs for HTTP requests, you can add a Sentry wrapper that does it automatically for you.

This is only possible if you are using the http.Client class from the http library.

The SentryHttpClient can be used as a standalone client like this:

import 'package:http/http.dart' as http;
import 'package:sentry/sentry.dart';

final client = SentryHttpClient();
try {
  final url = 'https://example.com/whatsit/create';
  final response = await client.post(url, body: {
    'name': 'doodle',
    'color': 'blue',
  });
  print('Response body: ${response.body}');
} finally {
  client.close();
}

The SentryHttpClient can also be used as a wrapper for your own HTTP Client:

import 'package:http/http.dart' as http;
import 'package:sentry/sentry.dart';

final myClient = http.Client();
final client = SentryHttpClient(client: myClient);
try {
  final url = 'https://example.com/whatsit/create';
  final response = await client.post(url, body: {
    'name': 'doodle',
    'color': 'blue',
  });
  print('Response body: ${response.body}');
} finally {
  client.close();
}

Customize Breadcrumbs

SDKs allow you to customize breadcrumbs through the beforeBreadcrumb hook.

This hook is passed an already assembled breadcrumb and, in some SDKs, an optional hint. The function can modify the breadcrumb or decide to discard it entirely by returning null:

import 'package:sentry/sentry.dart';

Breadcrumb beforeBreadcrumb(Breadcrumb breadcrumb, {Hint? hint}) {
  return 'a.spammy.Logger' == breadcrumb.category ? null : breadcrumb;
}

Future<void> main() async {
  await Sentry.init((options) => options.beforeBreadcrumb = beforeBreadcrumb);
}

For information about what can be done with the hint, see Filtering Events.