Skip to main content

Sinks

A sink is an output destination that implements LogSink. You can register multiple sinks on the same StructureLogger — every event is delivered to all of them.

Built-in sinks​

SimpleLineSink​

Prints a readable line to the terminal, interpolating template placeholders from data:

logger.addSink(SimpleLineSink());
InputOutput
mt: "User {id} logged in", data: {id: 7}User 7 logged in

Placeholders without a matching key in data are replaced with an empty string.

DefaultSink​

Sends the serialized event to the Dart developer log (dart:developer):

logger.addSink(DefaultSink());

Useful in Flutter DevTools and during flutter run debugging.

SinkSeq​

Sends events in CLEF format to a Seq server:

logger.addSink(SinkSeq(
  'https://seq.example.com',
  apiKey: 'your-api-key',
  deviceIdentifier: 'my-device',
));

See the Seq integration guide for configuration and lifecycle details.

Multiple sinks​

It is common to combine sinks for development and production:

final logger = StructureLogger();

if (kDebugMode) {
  logger.addSink(SimpleLineSink());
  logger.addSink(DefaultSink());
}

logger.addSink(SinkSeq(
  seqUrl,
  apiKey: apiKey,
  deviceIdentifier: deviceId,
));

Custom sink​

Implement LogSink and register with addSink. See the custom sink guide.