Create Grocery Example for Metrics API

.markdownlint.json

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+{
+    "default": true,
+    "line-length": {
+        "tables": false
+    }
+}
+

examples/GroceryExample/.vscode/launch.json

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+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "OS-COMMENT1": "Use IntelliSense to find out which attributes exist for C# debugging",
+            "OS-COMMENT2": "Use hover for the description of the existing attributes",
+            "OS-COMMENT3": "For further information visit https://github.com/OmniSharp/omnisharp-vscode/blob/master/debugger-launchjson.md",
+            "name": ".NET Core Launch (console)",
+            "type": "coreclr",
+            "request": "launch",
+            "preLaunchTask": "build",
+            "OS-COMMENT4": "If you have changed target frameworks, make sure to update the program path.",
+            "program": "${workspaceFolder}/bin/Debug/net5.0/GroceryExample.dll",
+            "args": [],
+            "cwd": "${workspaceFolder}",
+            "OS-COMMENT5": "For more information about the 'console' field, see https://aka.ms/VSCode-CS-LaunchJson-Console",
+            "console": "internalConsole",
+            "stopAtEntry": false
+        },
+        {
+            "name": ".NET Core Attach",
+            "type": "coreclr",
+            "request": "attach",
+            "processId": "${command:pickProcess}"
+        }
+    ]
+}

examples/GroceryExample/.vscode/tasks.json

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+{
+    "version": "2.0.0",
+    "tasks": [
+        {
+            "label": "build",
+            "command": "dotnet",
+            "type": "process",
+            "args": [
+                "build",
+                "${workspaceFolder}/GroceryExample.csproj",
+                "/property:GenerateFullPaths=true",
+                "/consoleloggerparameters:NoSummary"
+            ],
+            "problemMatcher": "$msCompile"
+        },
+        {
+            "label": "publish",
+            "command": "dotnet",
+            "type": "process",
+            "args": [
+                "publish",
+                "${workspaceFolder}/GroceryExample.csproj",
+                "/property:GenerateFullPaths=true",
+                "/consoleloggerparameters:NoSummary"
+            ],
+            "problemMatcher": "$msCompile"
+        },
+        {
+            "label": "watch",
+            "command": "dotnet",
+            "type": "process",
+            "args": [
+                "watch",
+                "run",
+                "${workspaceFolder}/GroceryExample.csproj",
+                "/property:GenerateFullPaths=true",
+                "/consoleloggerparameters:NoSummary"
+            ],
+            "problemMatcher": "$msCompile"
+        }
+    ]
+}

examples/GroceryExample/GroceryExample.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net5.0</TargetFramework>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="$(RepoRoot)\src\OpenTelemetry.Api\OpenTelemetry.Api.csproj">
+      <Project>{99f8a331-05e9-45a5-89ba-4c54e825e5b2}</Project>
+      <Name>OpenTelemetry.Api</Name>
+    </ProjectReference>
+    <ProjectReference Include="$(RepoRoot)\src\OpenTelemetry\OpenTelemetry.csproj">
+      <Project>{ae3e3df5-4083-4c6e-a840-8271b0acde7e}</Project>
+      <Name>OpenTelemetry</Name>
+    </ProjectReference>
+  </ItemGroup>
+</Project>

examples/GroceryExample/GroceryStore.cs

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+// <copyright file="GroceryStore.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.Collections.Generic;
+using OpenTelemetry.Metrics;
+using OpenTelemetry.Trace;
+
+#pragma warning disable CS0618
+
+namespace GroceryExample
+{
+    public class GroceryStore
+    {
+        private static Dictionary<string, double> priceList = new Dictionary<string, double>()
+        {
+            { "potato", 1.10 },
+            { "tomato", 3.00 },
+        };
+
+        private string storeName;
+
+        private Meter meter;
+
+        private CounterMetric<long> itemCounter;
+
+        private CounterMetric<double> cashCounter;
+
+        private BoundCounterMetric<double> boundCashCounter;
+
+        public GroceryStore(string storeName)
+        {
+            this.storeName = storeName;
+
+            // Setup Metrics
+
+            this.meter = MeterProvider.Default.GetMeter("GroceryStore", "1.0.0");
+
+            this.itemCounter = this.meter.CreateInt64Counter("item_counter");
+
+            this.cashCounter = this.meter.CreateDoubleCounter("cash_counter");
+
+            var labels = this.meter.GetLabelSet(new List<KeyValuePair<string, string>>()
+            {
+                KeyValuePair.Create("Store", "Portland"),
+            });
+
+            this.boundCashCounter = this.cashCounter.Bind(labels);
+        }
+
+        public void ProcessOrder(string customer, params (string name, int qty)[] items)
+        {
+            double totalPrice = 0;
+
+            foreach (var item in items)
+            {
+                totalPrice += item.qty * priceList[item.name];
+
+                // Record Metric
+
+                var labels = this.meter.GetLabelSet(new List<KeyValuePair<string, string>>()
+                {
+                    KeyValuePair.Create("Store", "Portland"),
+                    KeyValuePair.Create("Customer", customer),
+                    KeyValuePair.Create("Item", item.name),
+                });
+
+                this.itemCounter.Add(default(SpanContext), item.qty, labels);
+            }
+
+            // Record Metric
+
+            var labels2 = this.meter.GetLabelSet(new List<KeyValuePair<string, string>>()
+            {
+                KeyValuePair.Create("Store", "Portland"),
+                KeyValuePair.Create("Customer", customer),
+            });
+
+            this.cashCounter.Add(default(SpanContext), totalPrice, labels2);
+
+            this.boundCashCounter.Add(default(SpanContext), totalPrice);
+        }
+    }
+}

examples/GroceryExample/Misc/MyMetricExporter.cs

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+// <copyright file="MyMetricExporter.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 System.Collections.Generic;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using OpenTelemetry.Metrics.Export;
+
+#pragma warning disable CS0618
+
+namespace GroceryExample
+{
+    public class MyMetricExporter : MetricExporter
+    {
+        public override Task<ExportResult> ExportAsync(IEnumerable<Metric> metrics, CancellationToken cancellationToken)
+        {
+            return Task.Run<ExportResult>(() =>
+            {
+                StringBuilder sb = new StringBuilder();
+
+                sb.AppendLine("Exporting...");
+                foreach (var m in metrics)
+                {
+                    sb.AppendLine($"[{m.MetricNamespace}:{m.MetricName}]");
+
+                    foreach (var data in m.Data)
+                    {
+                        sb.Append("    ");
+
+                        string val = "-";
+                        if (data is DoubleSumData doublesum)
+                        {
+                            val = $"Sum={doublesum.Sum}";
+                        }
+                        else if (data is Int64SumData int64sum)
+                        {
+                            val = $"Sum={int64sum.Sum}";
+                        }
+                        else
+                        {
+                            val = data.ToString();
+                        }
+
+                        sb.Append($"Data: {val}, ");
+
+                        sb.Append("Labels: ");
+                        foreach (var l in data.Labels)
+                        {
+                            sb.Append($"{l.Key}={l.Value}, ");
+                        }
+
+                        sb.AppendLine();
+                    }
+                }
+
+                Console.WriteLine(sb.ToString());
+
+                return ExportResult.Success;
+            });
+        }
+    }
+}

examples/GroceryExample/Program.cs

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+// <copyright file="Program.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 System.Threading.Tasks;
+using OpenTelemetry.Metrics;
+using OpenTelemetry.Metrics.Export;
+
+#pragma warning disable CS0618
+
+namespace GroceryExample
+{
+    public class Program
+    {
+        public static void Main(string[] args)
+        {
+            // Create Metric Pipeline
+
+            var sdk = OpenTelemetry.Sdk.CreateMeterProviderBuilder()
+                .SetPushInterval(TimeSpan.FromMilliseconds(1000))
+
+                // Need to have a processor to move Metrics through pipeline
+                .SetProcessor(new UngroupedBatcher())
+
+                .SetExporter(new MyMetricExporter())
+
+                .Build()
+                ;
+
+            // Need to set for the Default provider
+            MeterProvider.SetDefault(sdk);
+
+            var store = new GroceryStore("Portland");
+
+            store.ProcessOrder("customerA", ("potato", 2), ("tomato", 3));
+            store.ProcessOrder("customerB", ("tomato", 10));
+            store.ProcessOrder("customerC", ("potato", 2));
+            store.ProcessOrder("customerA", ("tomato", 1));
+
+            // Wait for stuff to run
+            Task.Delay(5000).Wait();
+
+            // Shutdown Metric Pipeline
+            // sdk.Shutdown();
+        }
+    }
+}

examples/GroceryExample/readme.md

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+# Overview
+
+The goal of this Grocery example is to try and instrument the code. From this
+excersize we hope to discover and learn additional topics for discussions.
+
+We are focus only on the API side at the moment.  It is known that SDK
+implementation will likely affect how the API is designed, but we will make our
+best judgement to tolerate the situation at this time.
+
+## Topics for discussions
+
+- Need some kind of concrete LabelSet() in API.  Access to LabelSetSdk() is
+unavailable from API side.
+
+- It is inconvenient to have to pass a default(SpanContext) when we don't care
+about spans. Need additional prototypes to make SpanContext optional.
+
+- We create instrument with CreateInt64Counter() but it returns a generic
+Counter<long>. Seems like it should return a Int64Counter instead.
+
+- It's not allowed to new MeterProvider().  Thus, the only way to access is via
+the Default property. We can probably simplify MeterProvider.Default.GetMeter()
+to simply MeterProvider.GetMeter().
+
+- Bound counters does not allow adding more labels.  Ideally, we would bind
+Store, but still allow passing in additional lables (i.e. Customer) when
+recording measurements.
+
+- Need shutdown() for SDK