Add Sdk.SuppressInstrumentation (#960)

* add Sdk.SuppressInstrumentation

* simplify the code

* fix comments

* add XML comment

Co-authored-by: Mikel Blanchard <mblanchard@macrosssoftware.com>

src/OpenTelemetry.Api/Context/AsyncLocalRuntimeContextSlot.cs

@@ -15,6 +15,7 @@
 // </copyright>
 
 #if !NET452
+using System.Runtime.CompilerServices;
 using System.Threading;
 
 namespace OpenTelemetry.Context
@@ -38,12 +39,14 @@ namespace OpenTelemetry.Context
         }
 
         /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public override T Get()
         {
             return this.slot.Value;
         }
 
         /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public override void Set(T value)
         {
             this.slot.Value = value;

src/OpenTelemetry.Api/Context/RemotingRuntimeContextSlot.cs

@@ -17,6 +17,7 @@
 #if NET452
 using System.Collections;
 using System.Reflection;
+using System.Runtime.CompilerServices;
 using System.Runtime.Remoting.Messaging;
 
 namespace OpenTelemetry.Context
@@ -50,6 +51,7 @@ namespace OpenTelemetry.Context
         }
 
         /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public override T Get()
         {
             var wrapper = CallContext.LogicalGetData(this.Name) as BitArray;
@@ -63,6 +65,7 @@ namespace OpenTelemetry.Context
         }
 
         /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public override void Set(T value)
         {
             var wrapper = new BitArray(0);

src/OpenTelemetry.Api/Context/RuntimeContext.cs

@@ -17,6 +17,7 @@
 using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
+using System.Runtime.CompilerServices;
 
 namespace OpenTelemetry.Context
 {
@@ -41,7 +42,8 @@ namespace OpenTelemetry.Context
         /// </summary>
         /// <param name="name">The name of the context slot.</param>
         /// <typeparam name="T">The type of the underlying value.</typeparam>
-        public static void RegisterSlot<T>(string name)
+        /// <returns>The slot registered.</returns>
+        public static RuntimeContextSlot<T> RegisterSlot<T>(string name)
         {
             lock (Slots)
             {
@@ -52,10 +54,23 @@ namespace OpenTelemetry.Context
 
                 var type = ContextSlotType.MakeGenericType(typeof(T));
                 var ctor = type.GetConstructor(new Type[] { typeof(string) });
-                Slots[name] = ctor.Invoke(new object[] { name });
+                var slot = (RuntimeContextSlot<T>)ctor.Invoke(new object[] { name });
+                Slots[name] = slot;
+                return slot;
             }
         }
 
+        /// <summary>
+        /// Get a registered slot from a given name.
+        /// </summary>
+        /// <param name="name">The name of the context slot.</param>
+        /// <typeparam name="T">The type of the underlying value.</typeparam>
+        /// <returns>The slot previously registered.</returns>
+        public static RuntimeContextSlot<T> GetSlot<T>(string name)
+        {
+            return (RuntimeContextSlot<T>)Slots[name];
+        }
+
         /*
         public static void Apply(IDictionary<string, object> snapshot)
         {
@@ -86,6 +101,7 @@ namespace OpenTelemetry.Context
         /// <param name="name">The name of the context slot.</param>
         /// <param name="value">The value to be set.</param>
         /// <typeparam name="T">The type of the value.</typeparam>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static void SetValue<T>(string name, T value)
         {
             var slot = (RuntimeContextSlot<T>)Slots[name];
@@ -98,6 +114,7 @@ namespace OpenTelemetry.Context
         /// <param name="name">The name of the context slot.</param>
         /// <typeparam name="T">The type of the value.</typeparam>
         /// <returns>The value retrieved from the context slot.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static T GetValue<T>(string name)
         {
             var slot = (RuntimeContextSlot<T>)Slots[name];

src/OpenTelemetry.Api/Context/ThreadLocalRuntimeContextSlot.cs

@@ -14,6 +14,7 @@
 // limitations under the License.
 // </copyright>
 
+using System.Runtime.CompilerServices;
 using System.Threading;
 
 namespace OpenTelemetry.Context
@@ -37,12 +38,14 @@ namespace OpenTelemetry.Context
         }
 
         /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public override T Get()
         {
             return this.slot.Value;
         }
 
         /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public override void Set(T value)
         {
             this.slot.Value = value;

src/OpenTelemetry/Sdk.cs

@@ -17,7 +17,9 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
+using System.Runtime.CompilerServices;
 using System.Threading;
+using OpenTelemetry.Context;
 using OpenTelemetry.Metrics;
 using OpenTelemetry.Metrics.Export;
 using OpenTelemetry.Trace;
@@ -32,7 +34,53 @@ namespace OpenTelemetry
     /// </summary>
     public static class Sdk
     {
-        private static TimeSpan defaultPushInterval = TimeSpan.FromSeconds(60);
+        private static readonly TimeSpan DefaultPushInterval = TimeSpan.FromSeconds(60);
+
+        private static readonly RuntimeContextSlot<bool> SuppressInstrumentationRuntimeContextSlot = RuntimeContext.RegisterSlot<bool>("otel.suppress_instrumentation");
+
+        /// <summary>
+        /// Gets or sets a value indicating whether automatic telemetry
+        /// collection in the current context should be suppressed (disabled).
+        /// Default value: False.
+        /// </summary>
+        /// <remarks>
+        /// Set <see cref="SuppressInstrumentation"/> to <see langword="true"/>
+        /// when you want to turn off automatic telemetry collection.
+        /// This is typically used to prevent infinite loops created by
+        /// collection of internal operations, such as exporting traces over HTTP.
+        /// <code>
+        ///    public override async Task&lt;ExportResult&gt; ExportAsync(
+        ///        IEnumerable&lt;Activity&gt; batch,
+        ///        CancellationToken cancellationToken)
+        ///    {
+        ///       var currentSuppressionPolicy = Sdk.SuppressInstrumentation;
+        ///       Sdk.SuppressInstrumentation = true;
+        ///       try
+        ///       {
+        ///          await this.SendBatchActivityAsync(batch, cancellationToken).ConfigureAwait(false);
+        ///          return ExportResult.Success;
+        ///       }
+        ///       finally
+        ///       {
+        ///          Sdk.SuppressInstrumentation = currentSuppressionPolicy;
+        ///       }
+        ///    }
+        /// </code>
+        /// </remarks>
+        public static bool SuppressInstrumentation
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                return SuppressInstrumentationRuntimeContextSlot.Get();
+            }
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            set
+            {
+                SuppressInstrumentationRuntimeContextSlot.Set(value);
+            }
+        }
 
         /// <summary>
         /// Creates MeterProvider with the configuration provided.
@@ -60,7 +108,7 @@ namespace OpenTelemetry
                 meterRegistry,
                 metricProcessor,
                 metricExporter,
-                meterBuilder.MetricPushInterval == default(TimeSpan) ? defaultPushInterval : meterBuilder.MetricPushInterval,
+                meterBuilder.MetricPushInterval == default(TimeSpan) ? DefaultPushInterval : meterBuilder.MetricPushInterval,
                 cancellationTokenSource);
 
             var meterProviderSdk = new MeterProviderSdk(metricProcessor, meterRegistry, controller, cancellationTokenSource);