Prometheus exporter (#39)

* skeleton of premetheus exporter

* almost ready

* added skeleton for prometheus exporter

* escabing of labels

Author: SergeyKanzhelev

CHANGELOG.md

@@ -1,5 +1,6 @@
 # Unreleased
 
+- Initial implementation of Prometheus exporter.
 - Initial version of Application Insights exporter implemented.
 - Zipkin exporter implemented.
 - Initial version of SDK published. It is based on contribution from Pivotal

OpenCensus.sln

@@ -37,6 +37,7 @@ EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "OpenCensus.Exporter.ApplicationInsights", "src\OpenCensus.Exporter.ApplicationInsights\OpenCensus.Exporter.ApplicationInsights.csproj", "{4493F5D9-874E-4FBF-B2F3-37890BD910E0}"
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Samples", "src\Samples\Samples.csproj", "{C58393EB-32E2-4AC6-9170-697B36306E15}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "OpenCensus.Exporter.Prometheus", "src\OpenCensus.Exporter.Prometheus\OpenCensus.Exporter.Prometheus.csproj", "{A86AF35D-9E84-4B12-AA0E-1C558DC2EE1C}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -64,6 +65,10 @@ Global
 		{C58393EB-32E2-4AC6-9170-697B36306E15}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{C58393EB-32E2-4AC6-9170-697B36306E15}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{C58393EB-32E2-4AC6-9170-697B36306E15}.Release|Any CPU.Build.0 = Release|Any CPU
+		{A86AF35D-9E84-4B12-AA0E-1C558DC2EE1C}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{A86AF35D-9E84-4B12-AA0E-1C558DC2EE1C}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{A86AF35D-9E84-4B12-AA0E-1C558DC2EE1C}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{A86AF35D-9E84-4B12-AA0E-1C558DC2EE1C}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

README.md

@@ -50,6 +50,35 @@ Thread.Sleep(TimeSpan.FromSeconds(1));
 span.End();
 ```
 
+### Using Prometheus exporter
+
+Configure Prometheus exporter to have stats collected by Prometheus.
+
+1. Get Prometheus using [getting started guide][prometheus-get-started].
+2. Start `PrometheusExporter` as below.
+3. See [sample][prometheus-sample] for example use.
+
+``` csharp
+var exporter = new PrometheusExporter(
+    new PrometheusExporterOptions()
+    {
+        Url = new Uri("http://localhost:9184/metrics/")
+    },
+    Stats.ViewManager);
+
+exporter.Start();
+
+try
+{
+    // record metrics
+    statsRecorder.NewMeasureMap().Put(VideoSize, values[0] * MiB).Record();
+}
+finally
+{
+    exporter.Stop();
+}
+```
+
 ### Using Application Insights exporter
 
 1. Create [Application Insights][ai-get-started] resource.
@@ -100,4 +129,6 @@ deprecate it for 18 months before removing it, if possible.
 [ai-get-started]: https://docs.microsoft.com/azure/application-insights
 [semver]: http://semver.org/
 [ai-sample]: https://github.com/census-instrumentation/opencensus-csharp/blob/develop/src/Samples/TestApplicationInsights.cs
-[zipkin-sample]: https://github.com/census-instrumentation/opencensus-csharp/blob/develop/src/Samples/TestZipkin.cs
+[zipkin-sample]: https://github.com/census-instrumentation/opencensus-csharp/blob/develop/src/Samples/TestZipkin.cs
+[prometheus-get-started]: https://prometheus.io/docs/introduction/first_steps/
+[prometheus-sample]: https://github.com/census-instrumentation/opencensus-csharp/blob/develop/src/Samples/TestPrometheus.cs

src/OpenCensus.Exporter.ApplicationInsights/ApplicationInsightsExporter.cs

@@ -31,8 +31,6 @@ public class ApplicationInsightsExporter
     {
         private const string TraceExporterName = "ApplicationInsightsTraceExporter";
 
-        private const string MetricsExporterName = "ApplicationInsightsMetricsExporter";
-
         private readonly TelemetryConfiguration telemetryConfiguration;
 
         private readonly IViewManager viewManager;
@@ -45,6 +43,8 @@ public class ApplicationInsightsExporter
 
         private CancellationTokenSource tokenSource;
 
+        private Task workerThread;
+
         /// <summary>
         /// Instantiates a new instance of an exporter from Open Census to Azure Application Insights.
         /// </summary>
@@ -79,7 +79,7 @@ public void Start()
                 CancellationToken token = this.tokenSource.Token;
 
                 var metricsExporter = new MetricsExporterThread(this.telemetryConfiguration, this.viewManager, token, TimeSpan.FromMinutes(1));
-                Task.Factory.StartNew((Action)metricsExporter.WorkerThread, TaskCreationOptions.LongRunning);
+                this.workerThread = Task.Factory.StartNew((Action)metricsExporter.WorkerThread, TaskCreationOptions.LongRunning);
             }
         }
 
@@ -97,6 +97,7 @@ public void Stop()
 
                 this.exportComponent.SpanExporter.UnregisterHandler(TraceExporterName);
                 this.tokenSource.Cancel();
+                this.workerThread.Wait();
                 this.tokenSource = null;
 
                 this.handler = null;

src/OpenCensus.Exporter.ApplicationInsights/Implementation/MetricsExporterThread.cs

@@ -140,6 +140,10 @@ internal void Export()
                         {
                             if (combined is IMeanData mean)
                             {
+                                metricTelemetry.Sum = mean.Mean * mean.Count;
+                                metricTelemetry.Count = (int)mean.Count;
+                                metricTelemetry.Max = mean.Max;
+                                metricTelemetry.Min = mean.Min;
                             }
 
                             return null;
@@ -148,7 +152,8 @@ internal void Export()
                         {
                             if (combined is IDistributionData dist)
                             {
-                                metricTelemetry.Sum = dist.Mean;
+                                metricTelemetry.Sum = dist.Mean * dist.Count;
+                                metricTelemetry.Count = (int)dist.Count;
                                 metricTelemetry.Min = dist.Min;
                                 metricTelemetry.Max = dist.Max;
                                 metricTelemetry.StandardDeviation = dist.SumOfSquaredDeviations;

src/OpenCensus.Exporter.Prometheus/Implementation/MetricsHttpServer.cs

@@ -0,0 +1,120 @@
+// <copyright file="MetricsHttpServer.cs" company="OpenCensus Authors">
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of theLicense at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// </copyright>
+
+namespace OpenCensus.Exporter.Prometheus.Implementation
+{
+    using System;
+    using System.Diagnostics;
+    using System.IO;
+    using System.Net;
+    using System.Threading;
+    using OpenCensus.Stats;
+    using OpenCensus.Stats.Aggregations;
+
+    internal class MetricsHttpServer
+    {
+        private readonly IViewManager viewManager;
+
+        private readonly CancellationToken token;
+
+        private readonly HttpListener httpListener = new HttpListener();
+
+        public MetricsHttpServer(IViewManager viewManager, PrometheusExporterOptions options, CancellationToken token)
+        {
+            this.viewManager = viewManager;
+            this.token = token;
+            this.httpListener.Prefixes.Add(options.Url.ToString());
+        }
+
+        public void WorkerThread()
+        {
+            this.httpListener.Start();
+
+            try
+            {
+                while (!this.token.IsCancellationRequested)
+                {
+                    var ctxTask = this.httpListener.GetContextAsync();
+                    ctxTask.Wait(this.token);
+
+                    var ctx = ctxTask.Result;
+
+                    ctx.Response.StatusCode = 200;
+                    ctx.Response.ContentType = PrometheusMetricBuilder.ContentType;
+
+                    using (var output = ctx.Response.OutputStream)
+                    {
+                        using (var writer = new StreamWriter(output))
+                        {
+                            foreach (var view in this.viewManager.AllExportedViews)
+                            {
+                                var data = this.viewManager.GetView(view.Name);
+
+                                var builder = new PrometheusMetricBuilder()
+                                    .WithName(data.View.Name.AsString)
+                                    .WithDescription(data.View.Description);
+
+                                builder = data.View.Aggregation.Match<PrometheusMetricBuilder>(
+                                    (agg) => { return builder.WithType("gauge"); }, // Func<ISum, M> p0
+                                    (agg) => { return builder.WithType("counter"); }, // Func< ICount, M > p1, 
+                                    (agg) => { return builder.WithType("histogram"); }, // Func<IMean, M> p2, 
+                                    (agg) => { return builder.WithType("histogram"); }, // Func< IDistribution, M > p3,
+                                    (agg) => { return builder.WithType("gauge"); }, // Func<ILastValue, M> p4,
+                                    (agg) => { return builder.WithType("gauge"); }); // Func< IAggregation, M > p6);
+
+                                foreach (var value in data.AggregationMap)
+                                {
+                                    var metricValueBuilder = builder.AddValue();
+
+                                    // TODO: This is not optimal. Need to refactor to split builder into separate functions
+                                    metricValueBuilder = value.Value.Match<PrometheusMetricBuilder.PrometheusMetricValueBuilder>(
+                                        metricValueBuilder.WithValue,
+                                        metricValueBuilder.WithValue,
+                                        metricValueBuilder.WithValue,
+                                        metricValueBuilder.WithValue,
+                                        metricValueBuilder.WithValue,
+                                        metricValueBuilder.WithValue,
+                                        metricValueBuilder.WithValue,
+                                        metricValueBuilder.WithValue);
+
+                                    for (int i = 0; i < value.Key.Values.Count; i++)
+                                    {
+                                        metricValueBuilder.WithLabel(data.View.Columns[i].Name, value.Key.Values[i].AsString);
+                                    }
+                                }
+
+                                builder.Write(writer);
+                            }
+                        }
+                    }
+                }
+            }
+            catch (OperationCanceledException)
+            {
+                // this will happen when cancellation will be requested
+            }
+            catch (Exception)
+            {
+                // TODO: report error
+            }
+            finally
+            {
+                this.httpListener.Stop();
+                this.httpListener.Close();
+            }
+        }
+    }
+}