Publicize required methods to allow for custom implementations of resource detectors.

docs/trace/extending-the-sdk/MyResourceDectectorExtensions.cs

@@ -0,0 +1,26 @@
+// <copyright file="MyResourceDectectorExtensions.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 OpenTelemetry.Resources;
+
+internal static class MyResourceDectectorExtensions
+{
+    internal static ResourceBuilder AddMyResourceDetector(this ResourceBuilder resourceBuilder)
+    {
+        resourceBuilder.AddDetector(new MyResourceDetector());
+        return resourceBuilder;
+    }
+}

docs/trace/extending-the-sdk/MyResourceDetector.cs

@@ -0,0 +1,55 @@
+// <copyright file="MyResourceDetector.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 OpenTelemetry.Resources;
+
+internal class MyResourceDetector : IResourceDetector
+{
+    public const string EnVarkey = "myEnVarkey";
+
+    public Resource Detect()
+    {
+        var resource = Resource.Empty;
+        if (this.LoadString(EnVarkey, out string envAttributeVal))
+        {
+            resource = new Resource(new List<KeyValuePair<string, object>>
+            {
+                new KeyValuePair<string, object>(EnVarkey, envAttributeVal),
+            });
+        }
+
+        return resource;
+    }
+
+    internal bool LoadString(string envVarKey, out string result)
+    {
+        result = null;
+
+        try
+        {
+            result = Environment.GetEnvironmentVariable(envVarKey);
+        }
+        catch (Exception ex)
+        {
+            Console.WriteLine("Exception: {0}.", ex);
+            return false;
+        }
+
+        return !string.IsNullOrEmpty(result);
+    }
+}

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

@@ -16,6 +16,7 @@
 
 using System.Diagnostics;
 using OpenTelemetry;
+using OpenTelemetry.Resources;
 using OpenTelemetry.Trace;
 
 public class Program
@@ -27,6 +28,7 @@ public static void Main()
         using var tracerProvider = Sdk.CreateTracerProviderBuilder()
             .SetSampler(new MySampler())
             .AddSource("OTel.Demo")
+            .SetResourceBuilder(ResourceBuilder.CreateEmpty().AddMyResourceDetector())
             .AddProcessor(new MyProcessor("ProcessorA"))
             .AddProcessor(new MyProcessor("ProcessorB"))
             .AddProcessor(new SimpleActivityExportProcessor(new MyExporter("ExporterX")))

docs/trace/extending-the-sdk/README.md

@@ -4,6 +4,7 @@
 * [Building your own instrumentation library](#instrumentation-library)
 * [Building your own processor](#processor)
 * [Building your own sampler](#sampler)
+* [Building your own resourceDetector](#detector)
 * [References](#references)
 
 ## Exporter
@@ -293,6 +294,16 @@ class MySampler : Sampler
 
 A demo sampler is shown [here](./MySampler.cs).
 
+## ResourceDetector
+Custom ResourceDetector can be implemented:
+
+* ResourceDetectors should inherit from 
+  `OpenTelemetry.Resources.IResourceDetector`, (which belongs 
+  to the [OpenTelemetry](../../../src/OpenTelemetry/README.md) 
+  package), and implement the `Detect` method.
+
+A demo ResourceDetector is shown [here](./MyResourceDetector.cs).
+
 ## References
 
 * [Exporter

src/OpenTelemetry/.publicApi/net461/PublicAPI.Unshipped.txt

@@ -114,6 +114,8 @@ OpenTelemetry.ReadOnlyTagCollection.GetEnumerator() -> OpenTelemetry.ReadOnlyTag
 OpenTelemetry.ReadOnlyTagCollection.ReadOnlyTagCollection() -> void
 OpenTelemetry.Resources.IResourceDetector
 OpenTelemetry.Resources.IResourceDetector.Detect() -> OpenTelemetry.Resources.Resource
+OpenTelemetry.Resources.Resource.Resource(System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string, object>> attributes) -> void
+OpenTelemetry.Resources.ResourceBuilder.AddDetector(OpenTelemetry.Resources.IResourceDetector resourceDetector) -> OpenTelemetry.Resources.ResourceBuilder
 OpenTelemetry.Trace.BatchExportActivityProcessorOptions
 OpenTelemetry.Trace.BatchExportActivityProcessorOptions.BatchExportActivityProcessorOptions() -> void
 override OpenTelemetry.BaseExportProcessor<T>.OnForceFlush(int timeoutMilliseconds) -> bool

src/OpenTelemetry/.publicApi/netstandard2.0/PublicAPI.Unshipped.txt

@@ -114,6 +114,8 @@ OpenTelemetry.ReadOnlyTagCollection.GetEnumerator() -> OpenTelemetry.ReadOnlyTag
 OpenTelemetry.ReadOnlyTagCollection.ReadOnlyTagCollection() -> void
 OpenTelemetry.Resources.IResourceDetector
 OpenTelemetry.Resources.IResourceDetector.Detect() -> OpenTelemetry.Resources.Resource
+OpenTelemetry.Resources.Resource.Resource(System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string, object>> attributes) -> void
+OpenTelemetry.Resources.ResourceBuilder.AddDetector(OpenTelemetry.Resources.IResourceDetector resourceDetector) -> OpenTelemetry.Resources.ResourceBuilder
 OpenTelemetry.Trace.BatchExportActivityProcessorOptions
 OpenTelemetry.Trace.BatchExportActivityProcessorOptions.BatchExportActivityProcessorOptions() -> void
 override OpenTelemetry.BaseExportProcessor<T>.OnForceFlush(int timeoutMilliseconds) -> bool

src/OpenTelemetry/Resources/Resource.cs

@@ -35,7 +35,7 @@ public class Resource
         /// Initializes a new instance of the <see cref="Resource"/> class.
         /// </summary>
         /// <param name="attributes">An <see cref="IEnumerable{T}"/> of attributes that describe the resource.</param>
-        internal Resource(IEnumerable<KeyValuePair<string, object>> attributes)
+        public Resource(IEnumerable<KeyValuePair<string, object>> attributes)
         {
             if (attributes == null)
             {

src/OpenTelemetry/Resources/ResourceBuilder.cs

@@ -86,9 +86,7 @@ public Resource Build()
             return finalResource;
         }
 
-        // Internal until spec is finalized.
-        // https://github.com/open-telemetry/oteps/blob/master/text/0111-auto-resource-detection.md
-        internal ResourceBuilder AddDetector(IResourceDetector resourceDetector)
+        public ResourceBuilder AddDetector(IResourceDetector resourceDetector)
         {
             Guard.ThrowIfNull(resourceDetector);