No Token Found error in Prometheus

Question

I want to monitor my .Net Core application with Prometheus. In order to do that I am using a .Net Prometheus Library (AppMetrics). And when I go to the link http://localhost:57057/metrics it returns me a JSON with data.

But when I go to prometheus and add this link as target it throws this error No Token Found.

level=warn ts=2018-05-22T06:52:17.5781093Z caller=scrape.go:697 component="scrape manager" scrape_pool=actibook target=http://localhost:57057/metrics msg="append failed" err="no token found"

Is it a way that I can handle this?

Anyone having trouble with this one here's the solution.

Startup.cs

//ConfigureServices
var metrics = new MetricsBuilder()
                            .OutputMetrics.AsPrometheusPlainText()
                            .OutputMetrics.AsPrometheusProtobuf().Build();
            services.AddMetrics(metrics);
            services.AddMetricsEndpoints(options =>
            {
                options.MetricsTextEndpointOutputFormatter = new MetricsPrometheusTextOutputFormatter();
                options.MetricsEndpointOutputFormatter = new MetricsPrometheusProtobufOutputFormatter();
            });
            services.AddMvc().AddMetrics();

//Configure
            app.UseMetricsAllMiddleware();
            app.UseMetricsAllEndpoints();

Program.cs

Metrics = AppMetrics.CreateDefaultBuilder()
                        .OutputMetrics.AsPrometheusPlainText()
                        .OutputMetrics.AsPrometheusProtobuf()
                        .Build();

            return WebHost.CreateDefaultBuilder(args)
                .ConfigureMetrics(Metrics)
                .UseMetrics()
                .UseStartup<Startup>()
                .Build();

appsettings.json

"MetricsOptions": {
    "DefaultContextLabel": "MyMvcApplication",
    "Enabled": true
  },
  "MetricsWebTrackingOptions": {
    "ApdexTrackingEnabled": true,
    "ApdexTSeconds": 0.1,
    "IgnoredHttpStatusCodes": [ 404 ],
    "IgnoredRoutesRegexPatterns": [],
    "OAuth2TrackingEnabled": true
  },
  "MetricEndpointsOptions": {
    "MetricsEndpointEnabled": true,
    "MetricsTextEndpointEnabled": true,
    "EnvironmentInfoEndpointEnabled": true
  }

And you can access it by /metrics-text path. Also in your prometheus.yml file should add this one:

- job_name: 'nameOfJob'
    metrics_path: '/metrics-text'
    static_configs:
      - targets: ['localhost:57057']

Answer 1

This usually means that the output is not valid Prometheus text format. Look for hyphens in metric or label names, or either of those starting with numbers - those are the most common errors.

Answer 2

Prom Tools can be used to inspect your metrics endpoints for errors.

sudo apt install prometheus
curl -L -s http://your-website.com:80/metrics | promtool check metrics

The problem for me was that the metrics endpoint was only available for logged in users.