prometheus_client 0.3.0

Dart implementation of the Prometheus client library providing metrics and a shelf integration.

prometheus_client

This is a simple Dart implementation of the Prometheus client library, similar to to libraries for other languages. It supports the default metric types like gauges, counters, summaries, or histograms. Metrics can be exported using the text format. To expose them in your server application the package comes with a shelf handler. In addition, it comes with some plug-in ready metrics for the Dart runtime and shelf.

You can find the latest updates in the changelog.

Usage

A simple usage example:

import 'package:prometheus_client/prometheus_client.dart';
import 'package:prometheus_client/runtime_metrics.dart' as runtime_metrics;
import 'package:prometheus_client/shelf_handler.dart';
import 'package:shelf/shelf.dart' as shelf;
import 'package:shelf/shelf_io.dart' as io;
import 'package:shelf_router/shelf_router.dart';

main() async {
  // Register default runtime metrics
  runtime_metrics.register();
  
  // Create a metric of type counter. 
  // Always register your metric, either at the default registry or a custom one.
  final greetingCounter =
      Counter('greetings_total', 'The total amount of greetings')..register();
  final app = Router();

  app.get('/hello', (shelf.Request request) {
    // Every time the hello is called, increase the counter by one 
    greetingCounter.inc();
    return shelf.Response.ok('hello-world');
  });
  
  // Register a handler to expose the metrics in the Prometheus text format
  app.get('/metrics', prometheusHandler());

  var handler = const shelf.Pipeline()
      .addHandler(app.handler);
  var server = await io.serve(handler, 'localhost', 8080);

  print('Serving at http://${server.address.host}:${server.port}');
}

Start the example application and access the exposed metrics at http://localhost:8080/metrics. For a full usage example, take a look at example/prometheus_client.example.dart.

Planned features

To achieve the requirements from the Prometheus Writing Client Libraries documentation, some features still have to be implemented:

• Split out shelf support into own package to avoid dependencies on shelf.

Features and bugs

Please file feature requests and bugs at the issue tracker.