improve metrics tutorial (#2453)

docs/metrics/extending-the-sdk/MyExporterExtensions.cs

@@ -0,0 +1,32 @@
+// <copyright file="MyExporterExtensions.cs" company="OpenTelemetry Authors">
+// Copyright The OpenTelemetry 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 the License 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>
+
+using System;
+using OpenTelemetry;
+using OpenTelemetry.Metrics;
+
+internal static class MyExporterExtensions
+{
+    public static MeterProviderBuilder AddMyExporter(this MeterProviderBuilder builder)
+    {
+        if (builder == null)
+        {
+            throw new ArgumentNullException(nameof(builder));
+        }
+
+        return builder.AddReader(new BaseExportingMetricReader(new MyExporter()));
+    }
+}

docs/metrics/extending-the-sdk/MyReader.cs

@@ -15,6 +15,7 @@
 // </copyright>
 
 using System;
+using System.Text;
 using OpenTelemetry;
 using OpenTelemetry.Metrics;
 
@@ -29,7 +30,18 @@ internal class MyReader : MetricReader
 
     protected override bool ProcessMetrics(Batch<Metric> metrics, int timeoutMilliseconds)
     {
-        Console.WriteLine($"{this.name}.ProcessMetrics(metrics={metrics}, timeoutMilliseconds={timeoutMilliseconds})");
+        var sb = new StringBuilder();
+        foreach (var record in metrics)
+        {
+            if (sb.Length > 0)
+            {
+                sb.Append(", ");
+            }
+
+            sb.Append($"{record}");
+        }
+
+        Console.WriteLine($"{this.name}.ProcessMetrics(metrics=[{sb}], timeoutMilliseconds={timeoutMilliseconds})");
         return true;
     }
 

docs/metrics/extending-the-sdk/Program.cs

@@ -24,29 +24,36 @@ using OpenTelemetry.Metrics;
 public class Program
 {
     private static readonly Meter MyMeter = new Meter("MyCompany.MyProduct.MyLibrary", "1.0");
+    private static readonly Counter<long> MyFruitCounter = MyMeter.CreateCounter<long>("MyFruitCounter");
+
+    static Program()
+    {
+        var process = Process.GetCurrentProcess();
+
+        MyMeter.CreateObservableGauge<long>(
+            "MyProcessWorkingSetGauge",
+            () => new List<Measurement<long>>()
+            {
+                new(process.WorkingSet64, new("process.id", process.Id), new("process.bitness", IntPtr.Size << 3)),
+            });
+    }
 
     public static void Main(string[] args)
     {
         using var meterProvider = Sdk.CreateMeterProviderBuilder()
             .AddSource("MyCompany.MyProduct.MyLibrary")
-            .AddReader(new MyReader())
-            /** /
+            /*
             TODO: revisit once this exception is removed "System.InvalidOperationException: Only one Metricreader is allowed.".
-            .AddReader(new BaseExportingMetricReader(new MyExporter()))
-            /**/
+            .AddReader(new MyReader())
+            */
+            .AddMyExporter()
             .Build();
 
-        var process = Process.GetCurrentProcess();
-        MyMeter.CreateObservableGauge<long>(
-            "MyGauge",
-            () => new List<Measurement<long>>()
-            {
-                new(process.WorkingSet64, new("process.id", process.Id), new("process.bitness", IntPtr.Size << 3)),
-            });
-
-        var counter = MyMeter.CreateCounter<long>("MyCounter");
-
-        counter.Add(1, new("tag1", "value1"), new("tag2", "value2"));
-        counter.Add(2, new("tag1", "value1"), new("tag2", "value2"));
+        MyFruitCounter.Add(1, new("name", "apple"), new("color", "red"));
+        MyFruitCounter.Add(2, new("name", "lemon"), new("color", "yellow"));
+        MyFruitCounter.Add(1, new("name", "lemon"), new("color", "yellow"));
+        MyFruitCounter.Add(2, new("name", "apple"), new("color", "green"));
+        MyFruitCounter.Add(5, new("name", "apple"), new("color", "red"));
+        MyFruitCounter.Add(4, new("name", "lemon"), new("color", "yellow"));
     }
 }

docs/metrics/getting-started/Program.cs

@@ -21,7 +21,7 @@ using OpenTelemetry.Metrics;
 public class Program
 {
     private static readonly Meter MyMeter = new Meter("MyCompany.MyProduct.MyLibrary", "1.0");
-    private static readonly Counter<long> MyCounter = MyMeter.CreateCounter<long>("MyFruitCounter");
+    private static readonly Counter<long> MyFruitCounter = MyMeter.CreateCounter<long>("MyFruitCounter");
 
     public static void Main(string[] args)
     {
@@ -30,11 +30,11 @@ public class Program
             .AddConsoleExporter()
             .Build();
 
-        MyCounter.Add(1, new("name", "apple"), new("color", "red"));
-        MyCounter.Add(2, new("name", "lemon"), new("color", "yellow"));
-        MyCounter.Add(1, new("name", "lemon"), new("color", "yellow"));
-        MyCounter.Add(2, new("name", "apple"), new("color", "green"));
-        MyCounter.Add(5, new("name", "apple"), new("color", "red"));
-        MyCounter.Add(4, new("name", "lemon"), new("color", "yellow"));
+        MyFruitCounter.Add(1, new("name", "apple"), new("color", "red"));
+        MyFruitCounter.Add(2, new("name", "lemon"), new("color", "yellow"));
+        MyFruitCounter.Add(1, new("name", "lemon"), new("color", "yellow"));
+        MyFruitCounter.Add(2, new("name", "apple"), new("color", "green"));
+        MyFruitCounter.Add(5, new("name", "apple"), new("color", "red"));
+        MyFruitCounter.Add(4, new("name", "lemon"), new("color", "yellow"));
     }
 }

docs/metrics/learning-more-instruments/Program.cs

@@ -24,6 +24,16 @@ using OpenTelemetry.Metrics;
 public class Program
 {
     private static readonly Meter MyMeter = new Meter("MyCompany.MyProduct.MyLibrary", "1.0");
+    private static readonly Histogram<long> MyHistogram = MyMeter.CreateHistogram<long>("MyHistogram");
+
+    static Program()
+    {
+        var process = Process.GetCurrentProcess();
+
+        MyMeter.CreateObservableCounter<double>("Thread.CpuTime", () => GetThreadCpuTime(process), "seconds");
+
+        MyMeter.CreateObservableGauge<int>("Thread.State", () => GetThreadState(process));
+    }
 
     public static void Main(string[] args)
     {
@@ -32,17 +42,10 @@ public class Program
             .AddConsoleExporter()
             .Build();
 
-        var process = Process.GetCurrentProcess();
-
-        MyMeter.CreateObservableCounter<double>("Thread.CpuTime", () => GetThreadCpuTime(process), "seconds");
-
-        MyMeter.CreateObservableGauge<int>("Thread.State", () => GetThreadState(process));
-
         var random = new Random();
-        var histogram = MyMeter.CreateHistogram<long>("MyHistogram");
         for (int i = 0; i < 1000; i++)
         {
-            histogram.Record(random.Next(1, 1000));
+            MyHistogram.Record(random.Next(1, 1000));
         }
     }