Disable profiler bootstrap process for .NET Core (#314)

* Disable profiler bootstrap process for .NET Core

* Update src/OpenTelemetry.ClrProfiler.Native/cor_profiler.cpp

Fixes spelling error.

Co-authored-by: Paulo Janotti <pjanotti@splunk.com>

* Update tests to use startup hook bootstrapping.

* Add test to validate startup hook is necessary

* Log if startup hook is not configured correctly.

* Add native tests for the startup hook validation.

* Update const and pass by ref for variables and parameters for startup hook functions

* Updating test and sample apps to use the startup hook.

* Updating scripts to set startup hook environment variable.

* Shutdown profiler if startup hook not configured correctly.

* Use const ref for all startup hook params and use OTEL_ naming convention.

Co-authored-by: Paulo Janotti <pjanotti@splunk.com>

defaults.env

@@ -1,5 +1,6 @@
 export CORECLR_ENABLE_PROFILING=1
 export CORECLR_PROFILER='{918728DD-259F-4A6A-AC2B-B85E1B658318}'
 export CORECLR_PROFILER_PATH=/opt/opentelemetry-dotnet-autoinstrumentation/OpenTelemetry.ClrProfiler.Native.so
+export DOTNET_STARTUP_HOOKS=/opt/opentelemetry-dotnet-autoinstrumentation/OpenTelemetry.Instrumentation.StartupHook.dll
 export OTEL_INTEGRATIONS=/opt/opentelemetry-dotnet-autoinstrumentation/integrations.json
 export OTEL_DOTNET_TRACER_HOME=/opt/opentelemetry-dotnet-autoinstrumentation

dev/envvars.sh

@@ -53,6 +53,7 @@ then
     export CORECLR_PROFILER_PATH_64="${CURDIR}/bin/tracer-home/win-x64/OpenTelemetry.ClrProfiler.Native.${SUFIX}"
     export CORECLR_PROFILER_PATH_32="${CURDIR}/bin/tracer-home/win-x86/OpenTelemetry.ClrProfiler.Native.${SUFIX}"
 fi
+export DOTNET_STARTUP_HOOKS="${CURDIR}/bin/tracer-home/netcoreapp3.1/OpenTelemetry.Instrumentation.StartupHook.dll"
 
 # Configure OpenTelemetry Tracer 
 export OTEL_DOTNET_TRACER_HOME="${CURDIR}/bin/tracer-home"

samples/Samples.AspNetCoreMvc31/Controllers/HomeController.cs

@@ -22,7 +22,7 @@ namespace Samples.AspNetCoreMvc.Controllers
             ViewBag.ClrProfilerAssemblyLocation = instrumentationType?.Assembly.Location;
             ViewBag.StackTrace = StackTraceHelper.GetUsefulStack();
 
-            var prefixes = new[] { "COR_", "CORECLR_", "OTEL_" };
+            var prefixes = new[] { "COR_", "CORECLR_", "DOTNET_", "OTEL_" };
 
             var envVars = from envVar in Environment.GetEnvironmentVariables().Cast<DictionaryEntry>()
                           from prefix in prefixes

samples/Samples.AspNetCoreMvc31/Properties/launchSettings.json

@@ -16,10 +16,11 @@
 
         "CORECLR_ENABLE_PROFILING": "1",
         "CORECLR_PROFILER": "{918728DD-259F-4A6A-AC2B-B85E1B658318}",
-        "CORECLR_PROFILER_PATH": "$(ProjectDir)$(OutputPath)profiler-lib\\OpenTelemetry.ClrProfiler.Native.dll",
+        "CORECLR_PROFILER_PATH": "$(SolutionDir)bin\\tracer-home\\win-x64\\OpenTelemetry.ClrProfiler.Native.dll",
+        "DOTNET_STARTUP_HOOKS": "$(SolutionDir)bin\\tracer-home\\netcoreapp3.1\\OpenTelemetry.Instrumentation.StartupHook.dll",
 
-        "OTEL_DOTNET_TRACER_HOME": "$(ProjectDir)$(OutputPath)profiler-lib",
+        "OTEL_DOTNET_TRACER_HOME": "$(SolutionDir)bin\\tracer-home",
-        "OTEL_INTEGRATIONS": "$(ProjectDir)$(OutputPath)profiler-lib\\integrations.json",
+        "OTEL_INTEGRATIONS": "$(SolutionDir)bin\\tracer-home\\integrations.json",
         "OTEL_SERVICE_NAME": "Samples.AspNetCoreMvc31",
         "OTEL_EXPORTER": "jaeger",
         "OTEL_EXPORTER_JAEGER_AGENT_HOST": "localhost",
@@ -36,10 +37,11 @@
 
         "CORECLR_ENABLE_PROFILING": "1",
         "CORECLR_PROFILER": "{918728DD-259F-4A6A-AC2B-B85E1B658318}",
-        "CORECLR_PROFILER_PATH": "$(ProjectDir)$(OutputPath)profiler-lib\\OpenTelemetry.ClrProfiler.Native.dll",
+        "CORECLR_PROFILER_PATH": "$(SolutionDir)bin\\tracer-home$(OutputPath)\\OpenTelemetry.ClrProfiler.Native.dll",
+        "DOTNET_STARTUP_HOOKS": "$(SolutionDir)bin\\tracer-home\\netcoreapp3.1\\OpenTelemetry.Instrumentation.StartupHook.dll",
 
-        "OTEL_DOTNET_TRACER_HOME": "$(ProjectDir)$(OutputPath)profiler-lib",
+        "OTEL_DOTNET_TRACER_HOME": "$(SolutionDir)bin\\tracer-home",
-        "OTEL_INTEGRATIONS": "$(ProjectDir)$(OutputPath)profiler-lib\\integrations.json",
+        "OTEL_INTEGRATIONS": "$(SolutionDir)bin\\tracer-home\\integrations.json",
 
         "OTEL_SERVICE_NAME": "Samples.AspNetCoreMvc31",
         "OTEL_EXPORTER": "jaeger",

src/OpenTelemetry.ClrProfiler.Native/OpenTelemetry.ClrProfiler.Native.vcxproj

@@ -202,6 +202,7 @@
     <ClInclude Include="module_metadata.h" />
     <ClInclude Include="pal.h" />
     <ClInclude Include="rejit_handler.h" />
+    <ClInclude Include="startup_hook.h" />
     <ClInclude Include="stats.h" />
     <ClInclude Include="string.h" />
     <ClInclude Include="util.h" />

src/OpenTelemetry.ClrProfiler.Native/cor_profiler.cpp

@@ -17,6 +17,7 @@
 #include "module_metadata.h"
 #include "pal.h"
 #include "resource.h"
+#include "startup_hook.h"
 #include "stats.h"
 #include "util.h"
 #include "version.h"
@@ -119,6 +120,10 @@ HRESULT STDMETHODCALLTYPE CorProfiler::Initialize(IUnknown* cor_profiler_info_un
     if (SUCCEEDED(hr))
     {
         Logger::Debug("Interface ICorProfilerInfo10 found.");
+        // .NET Core applications should use the dotnet startup hook to bootstrap OpenTelemetry so that the
+        // necessary dependencies will be available. Bootstrapping with the profiling APIs occurs too early
+        // and the necessary dependencies are not available yet.
+        use_dotnet_startuphook_bootstrapper = true;
     }
     else
     {
@@ -135,6 +140,17 @@ HRESULT STDMETHODCALLTYPE CorProfiler::Initialize(IUnknown* cor_profiler_info_un
         }
     }
 
+    if (use_dotnet_startuphook_bootstrapper)
+    {
+        const auto home_path = GetEnvironmentValue(environment::profiler_home_path);
+        const auto startup_hooks = GetEnvironmentValue(environment::dotnet_startup_hooks);
+        if (!IsStartupHookEnabled(startup_hooks, home_path))
+        {
+          Logger::Error("The required startup hook was not configured correctly. No telemetry will be captured.");
+          return E_FAIL;
+        }
+    }
+
     if (IsAzureAppServices())
     {
         Logger::Info("Profiler is operating within Azure App Services context.");
@@ -742,7 +758,7 @@ HRESULT STDMETHODCALLTYPE CorProfiler::JITCompilationStarted(FunctionID function
 {
     auto _ = trace::Stats::Instance()->JITCompilationStartedMeasure();
 
-    if (!is_attached_ || !is_safe_to_block)
+    if (!is_attached_ || !is_safe_to_block || use_dotnet_startuphook_bootstrapper)
     {
         return S_OK;
     }

src/OpenTelemetry.ClrProfiler.Native/cor_profiler.h

@@ -29,6 +29,7 @@ private:
 
     // Startup helper variables
     bool first_jit_compilation_completed = false;
+    bool use_dotnet_startuphook_bootstrapper = false;
 
     bool instrument_domain_neutral_assemblies = false;
     bool corlib_module_loaded = false;

src/OpenTelemetry.ClrProfiler.Native/dd_profiler_constants.h

@@ -26,7 +26,8 @@ const WSTRING env_vars_to_display[]{environment::tracing_enabled,
                                     environment::azure_app_services,
                                     environment::azure_app_services_app_pool_id,
                                     environment::azure_app_services_cli_telemetry_profile_value,
-                                    environment::internal_trace_profiler_path};
+                                    environment::internal_trace_profiler_path,
+                                    environment::dotnet_startup_hooks};
 
 const WSTRING skip_assembly_prefixes[]{
     WStr("Microsoft.AI"),

src/OpenTelemetry.ClrProfiler.Native/environment_variables.h

@@ -89,6 +89,12 @@ const WSTRING internal_trace_profiler_path =
 // Sets whether to enable NGEN images.
 const WSTRING clr_enable_ngen = WStr("OTEL_CLR_ENABLE_NGEN");
 
+// The list of startup hooks defined for .NET Core 3.1+ applications.
+// This is a .NET runtime environment variable. 
+// See https://github.com/dotnet/runtime/blob/main/docs/design/features/host-startup-hook.md
+// for more information about this environment variable.
+const WSTRING dotnet_startup_hooks = WStr("DOTNET_STARTUP_HOOKS");
+
 }  // namespace environment
 }  // namespace trace
 

src/OpenTelemetry.ClrProfiler.Native/pal.h

@@ -22,6 +22,12 @@
 #include "string.h" // NOLINT
 #include "util.h"
 
+#ifdef _WIN32
+#define DIR_SEPARATOR WStr('\\')
+#else
+#define DIR_SEPARATOR WStr('/')
+#endif
+
 namespace trace
 {
 
@@ -34,13 +40,7 @@ inline WSTRING GetDatadogLogFilePath(const std::string& file_name_suffix)
 
     if (directory.length() > 0)
     {
-        return directory +
+        return directory + DIR_SEPARATOR + ToWSTRING(file_name);
-#ifdef _WIN32
-               WStr('\\') +
-#else
-               WStr('/') +
-#endif
-               ToWSTRING(file_name);
     }
 
     WSTRING path = GetEnvironmentValue(TLoggerPolicy::logging_environment::log_path);

src/OpenTelemetry.ClrProfiler.Native/startup_hook.h

@@ -0,0 +1,30 @@
+#ifndef OTEL_CLR_PROFILER_STARTUP_HOOK_H_
+#define OTEL_CLR_PROFILER_STARTUP_HOOK_H_
+
+#include "string.h"  // NOLINT
+#include "pal.h"
+
+namespace trace
+{
+
+inline WSTRING GetExpectedStartupHookPath(const WSTRING& home_path) {
+    WSTRING separator = EmptyWStr;
+    if (home_path.back() != DIR_SEPARATOR) {
+        separator = DIR_SEPARATOR;
+    }
+
+    return home_path + separator + WStr("netcoreapp3.1") + DIR_SEPARATOR +
+            WStr("OpenTelemetry.Instrumentation.StartupHook.dll");
+}
+
+inline bool IsStartupHookEnabled(const WSTRING& startup_hooks, const WSTRING& home_path)
+{
+    const WSTRING expected_startup_hook = GetExpectedStartupHookPath(home_path);
+    auto n = startup_hooks.find(expected_startup_hook);
+
+    return n != WSTRING::npos;
+}
+
+}  // namespace trace
+
+#endif  // OTEL_CLR_PROFILER_STARTUP_HOOK_H_

test/OpenTelemetry.ClrProfiler.Native.Tests/OpenTelemetry.ClrProfiler.Native.Tests.vcxproj

@@ -80,6 +80,7 @@
       <PrecompiledHeader Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">Create</PrecompiledHeader>
       <PrecompiledHeader Condition="'$(Configuration)|$(Platform)'=='Release|x64'">Create</PrecompiledHeader>
     </ClCompile>
+    <ClCompile Include="startup_hook_test.cpp" />
     <ClCompile Include="version_struct_test.cpp" />
   </ItemGroup>
   <ItemGroup>

test/OpenTelemetry.ClrProfiler.Native.Tests/startup_hook_test.cpp

@@ -0,0 +1,82 @@
+#include "pch.h"
+
+#include "../../src/OpenTelemetry.ClrProfiler.Native/startup_hook.h"
+
+using namespace trace;
+
+TEST(StartupHookTest, GetExpectedStartupHookPathDoesNotAddSeparator) {
+  const auto home_path = WStr("C:\\tracer_home\\");
+  const auto expected_path = WStr("C:\\tracer_home\\netcoreapp3.1\\OpenTelemetry.Instrumentation.StartupHook.dll");
+
+  const auto startup_hook_path = GetExpectedStartupHookPath(home_path);
+
+  ASSERT_EQ(expected_path, startup_hook_path);
+}
+
+TEST(StartupHookTest, GetExpectedStartupHookPathAddsSeparator) {
+  const auto home_path = WStr("C:\\tracer_home");
+  const auto expected_path = WStr("C:\\tracer_home\\netcoreapp3.1\\OpenTelemetry.Instrumentation.StartupHook.dll");
+
+  const auto startup_hook_path = GetExpectedStartupHookPath(home_path);
+
+  ASSERT_EQ(expected_path, startup_hook_path);
+}
+
+TEST(StartupHookTest, StartupHookIsEnabled) {
+  const auto startup_hooks = WStr("C:\\tracer_home\\netcoreapp3.1\\OpenTelemetry.Instrumentation.StartupHook.dll");
+  const auto home_path = WStr("C:\\tracer_home");
+
+  const auto is_enabled = IsStartupHookEnabled(startup_hooks, home_path);
+
+  ASSERT_TRUE(is_enabled);
+}
+
+TEST(StartupHookTest, StartupHookIsNotEnabledWhenStartupHooksIsEmpty) {
+  const auto startup_hooks = WStr("");
+  const auto home_path = WStr("C:\\tracer_home");
+
+  const auto is_enabled = IsStartupHookEnabled(startup_hooks, home_path);
+
+  ASSERT_FALSE(is_enabled);
+}
+
+TEST(StartupHookTest, StartupHookIsNotEnabledWhenNoStartupHooksDefined) {
+  const WSTRING startup_hooks;
+  const auto home_path = WStr("C:\\tracer_home");
+
+  const auto is_enabled = IsStartupHookEnabled(startup_hooks, home_path);
+
+  ASSERT_FALSE(is_enabled);
+}
+
+TEST(StartupHookTest, StartupHookIsNotEnabledWhenStartupHookDoesNotContainOpenTelemetryHook) {
+  const auto startup_hooks = WStr("C:\\other_folder\\StartupHook.dll");
+  const auto home_path = WStr("C:\\tracer_home");
+
+  const auto is_enabled = IsStartupHookEnabled(startup_hooks, home_path);
+
+  ASSERT_FALSE(is_enabled);
+}
+
+TEST(StartupHookTest, StartupHookIsNotEnabledWhenNotInTheCorrectLocation) {
+  const auto startup_hooks = WStr("C:\\other_folder\\netcoreapp3.1\\OpenTelemetry.Instrumentation.StartupHook.dll");
+  const auto home_path = WStr("C:\\tracer_home");
+
+  const auto is_enabled = IsStartupHookEnabled(startup_hooks, home_path);
+
+  ASSERT_FALSE(is_enabled);
+}
+
+TEST(StartupHookTest, StartupHookIsEnabledWhenMultipleStartupHooksDefined) {
+  std::stringstream ss;
+  ss << "C:\\folder1\\StartupHook.dll" << DIR_SEPARATOR
+     << "C:\\tracer_home\\netcoreapp3.1\\OpenTelemetry.Instrumentation.StartupHook.dll"
+     << DIR_SEPARATOR << "C:\\folder2\\StartupHook.dll";
+
+  const auto startup_hooks = ToWSTRING(ss.str());
+  const auto home_path = WStr("C:\\tracer_home");
+
+  const auto is_enabled = IsStartupHookEnabled(startup_hooks, home_path);
+
+  ASSERT_TRUE(is_enabled);
+}

test/integration-tests/IntegrationTests.Helpers/EnvironmentHelper.cs

@@ -142,34 +142,31 @@ namespace IntegrationTests.Helpers
             int agentPort,
             int aspNetCorePort,
             StringDictionary environmentVariables,
-            string processToProfile = null,
+            bool enableStartupHook,
-            bool isStartupHook = false)
+            string processToProfile = null)
         {
             string profilerEnabled = _requiresProfiling ? "1" : "0";
+            string profilerPath = GetProfilerPath();
 
-            if (isStartupHook)
+            if (IsCoreClr())
             {
-                string hookPath = GetStartupHookOutputPath();
+                // enableStartupHook should be true by default, and the parameter should only be set
+                // to false when testing the case that instrumentation should not be available.
+                if (enableStartupHook)
+                {
+                    string hookPath = GetStartupHookOutputPath();
+                    environmentVariables["DOTNET_STARTUP_HOOKS"] = hookPath;
+                }
 
-                environmentVariables["DOTNET_STARTUP_HOOKS"] = hookPath;
+                environmentVariables["CORECLR_ENABLE_PROFILING"] = profilerEnabled;
-                environmentVariables["OTEL_DOTNET_TRACER_INSTRUMENTATIONS"] = "HttpClient";
+                environmentVariables["CORECLR_PROFILER"] = EnvironmentTools.ProfilerClsId;
+                environmentVariables["CORECLR_PROFILER_PATH"] = profilerPath;
             }
             else
             {
-                string profilerPath = GetProfilerPath();
+                environmentVariables["COR_ENABLE_PROFILING"] = profilerEnabled;
-
+                environmentVariables["COR_PROFILER"] = EnvironmentTools.ProfilerClsId;
-                if (IsCoreClr())
+                environmentVariables["COR_PROFILER_PATH"] = profilerPath;
-                {
-                    environmentVariables["CORECLR_ENABLE_PROFILING"] = profilerEnabled;
-                    environmentVariables["CORECLR_PROFILER"] = EnvironmentTools.ProfilerClsId;
-                    environmentVariables["CORECLR_PROFILER_PATH"] = profilerPath;
-                }
-                else
-                {
-                    environmentVariables["COR_ENABLE_PROFILING"] = profilerEnabled;
-                    environmentVariables["COR_PROFILER"] = EnvironmentTools.ProfilerClsId;
-                    environmentVariables["COR_PROFILER_PATH"] = profilerPath;
-                }
             }
 
             if (DebugModeEnabled)

test/integration-tests/IntegrationTests.Helpers/InstrumentedProcessHelper.cs

@@ -3,16 +3,17 @@ using System.Diagnostics;
 
 namespace IntegrationTests.Helpers
 {
-    public class ProfilerHelper
+    public class InstrumentedProcessHelper
     {
-        public static Process StartProcessWithProfiler(
+        public static Process StartInstrumentedProcess(
             string executable,
             EnvironmentHelper environmentHelper,
             string arguments = null,
             bool redirectStandardInput = false,
             int traceAgentPort = 9696,
             int aspNetCorePort = 5000,
-            string processToProfile = null)
+            string processToProfile = null,
+            bool enableStartupHook = true)
         {
             if (environmentHelper == null)
             {
@@ -24,7 +25,7 @@ namespace IntegrationTests.Helpers
 
             var startInfo = new ProcessStartInfo(executable, $"{arguments ?? string.Empty}");
 
-            environmentHelper.SetEnvironmentVariables(traceAgentPort, aspNetCorePort, startInfo.EnvironmentVariables, processToProfile);
+            environmentHelper.SetEnvironmentVariables(traceAgentPort, aspNetCorePort, startInfo.EnvironmentVariables, enableStartupHook, processToProfile);
 
             startInfo.UseShellExecute = false;
             startInfo.CreateNoWindow = true;

test/integration-tests/IntegrationTests.Helpers/StartupHookHelper.cs

@@ -1,38 +0,0 @@
-using System;
-using System.Diagnostics;
-
-namespace IntegrationTests.Helpers
-{
-    public class StartupHookHelper
-    {
-        public static Process StartProcessWithStartupHook(
-            string executable,
-            EnvironmentHelper environmentHelper,
-            string arguments = null,
-            bool redirectStandardInput = false,
-            int traceAgentPort = 9696,
-            int aspNetCorePort = 5000,
-            string processToProfile = null)
-        {
-            if (environmentHelper == null)
-            {
-                throw new ArgumentNullException(nameof(environmentHelper));
-            }
-
-            // clear all relevant environment variables to start with a clean slate
-            EnvironmentHelper.ClearProfilerEnvironmentVariables();
-
-            var startInfo = new ProcessStartInfo(executable, $"{arguments ?? string.Empty}");
-
-            environmentHelper.SetEnvironmentVariables(traceAgentPort, aspNetCorePort, startInfo.EnvironmentVariables, processToProfile, true);
-
-            startInfo.UseShellExecute = false;
-            startInfo.CreateNoWindow = true;
-            startInfo.RedirectStandardOutput = true;
-            startInfo.RedirectStandardError = true;
-            startInfo.RedirectStandardInput = redirectStandardInput;
-
-            return Process.Start(startInfo);
-        }
-    }
-}

test/integration-tests/IntegrationTests.Helpers/TestHelper.cs

@@ -89,7 +89,7 @@ namespace IntegrationTests.Helpers
             return new Container(container);
         }
 
-        public Process StartSample(int traceAgentPort, string arguments, string packageVersion, int aspNetCorePort, string framework = "", bool startupHook = false)
+        public Process StartSample(int traceAgentPort, string arguments, string packageVersion, int aspNetCorePort, string framework = "", bool enableStartupHook = true)
         {
             // get path to sample app that the profiler will attach to
             string sampleAppPath = EnvironmentHelper.GetSampleApplicationPath(packageVersion, framework);
@@ -102,31 +102,19 @@ namespace IntegrationTests.Helpers
             var executable = EnvironmentHelper.IsCoreClr() ? EnvironmentHelper.GetSampleExecutionSource() : sampleAppPath;
             var args = EnvironmentHelper.IsCoreClr() ? $"{sampleAppPath} {arguments ?? string.Empty}" : arguments;
 
-            if (startupHook)
+            return InstrumentedProcessHelper.StartInstrumentedProcess(
-            {
+                executable,
-                return StartupHookHelper.StartProcessWithStartupHook(
+                EnvironmentHelper,
-                    executable,
+                args,
-                    EnvironmentHelper,
+                traceAgentPort: traceAgentPort,
-                    args,
+                aspNetCorePort: aspNetCorePort,
-                    traceAgentPort: traceAgentPort,
+                processToProfile: executable,
-                    aspNetCorePort: aspNetCorePort,
+                enableStartupHook: enableStartupHook);
-                    processToProfile: executable);
-            }
-            else
-            {
-                return ProfilerHelper.StartProcessWithProfiler(
-                    executable,
-                    EnvironmentHelper,
-                    args,
-                    traceAgentPort: traceAgentPort,
-                    aspNetCorePort: aspNetCorePort,
-                    processToProfile: executable);
-            }
         }
 
-        public ProcessResult RunSampleAndWaitForExit(int traceAgentPort, string arguments = null, string packageVersion = "", string framework = "", int aspNetCorePort = 5000, bool startupHook = false)
+        public ProcessResult RunSampleAndWaitForExit(int traceAgentPort, string arguments = null, string packageVersion = "", string framework = "", int aspNetCorePort = 5000, bool enableStartupHook = true)
         {
-            var process = StartSample(traceAgentPort, arguments, packageVersion, aspNetCorePort: aspNetCorePort, framework: framework, startupHook: startupHook);
+            var process = StartSample(traceAgentPort, arguments, packageVersion, aspNetCorePort: aspNetCorePort, framework: framework, enableStartupHook: enableStartupHook);
             var name = process.ProcessName;
 
             using var helper = new ProcessHelper(process);

test/integration-tests/IntegrationTests.StartupHook/StartupHookTests.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Linq;
 using IntegrationTests.Helpers;
 using IntegrationTests.Helpers.Mocks;
@@ -18,6 +19,8 @@ namespace IntegrationTests.StartupHook
         public StartupHookTests(ITestOutputHelper output)
             : base("StartupHook", output)
         {
+            SetEnvironmentVariable("OTEL_SERVICE_NAME", ServiceName);
+            SetEnvironmentVariable("OTEL_DOTNET_TRACER_INSTRUMENTATIONS", "HttpClient");
             _expectations.Add(new WebServerSpanExpectation(ServiceName, null, "SayHello", "SayHello", null));
             _expectations.Add(new WebServerSpanExpectation(ServiceName, null, "HTTP GET", "HTTP GET", null, "GET"));
         }
@@ -26,9 +29,22 @@ namespace IntegrationTests.StartupHook
         [Trait("Category", "EndToEnd")]
         public void SubmitsTraces()
         {
-            SetEnvironmentVariable("OTEL_SERVICE_NAME", ServiceName);
+            const int expectedSpanCount = 2;
 
-            RunTestAndValidateResults(2);
+            var spans = RunTestApplication(enableStartupHook: true);
+
+            AssertExpectedSpansReceived(expectedSpanCount, spans);
+        }
+
+        [Fact]
+        [Trait("Category", "EndToEnd")]
+        public void InstrumentationNotAvailableWhenStartupHookIsNotEnabled()
+        {
+            const int expectedSpanCount = 0;
+
+            var spans = RunTestApplication(enableStartupHook: false);
+
+            AssertExpectedSpansReceived(expectedSpanCount, spans);
         }
 
         [Theory]
@@ -45,30 +61,34 @@ namespace IntegrationTests.StartupHook
                 expectedSpanCount = 0;
             }
 
-            SetEnvironmentVariable("OTEL_SERVICE_NAME", ServiceName);
             SetEnvironmentVariable("OTEL_PROFILER_EXCLUDE_PROCESSES", $"dotnet,dotnet.exe,{applicationNameToExclude}");
 
-            RunTestAndValidateResults(expectedSpanCount);
+            var spans = RunTestApplication(enableStartupHook: true);
+
+            AssertExpectedSpansReceived(expectedSpanCount, spans);
         }
 
-        private void RunTestAndValidateResults(int expectedSpanCount)
+        private IImmutableList<IMockSpan> RunTestApplication(bool enableStartupHook)
         {
             int agentPort = TcpPortProvider.GetOpenPort();
 
             using (var agent = new MockZipkinCollector(Output, agentPort))
-            using (var processResult = RunSampleAndWaitForExit(agent.Port, startupHook: true))
+            using (var processResult = RunSampleAndWaitForExit(agent.Port, enableStartupHook: enableStartupHook))
             {
                 Assert.True(processResult.ExitCode >= 0, $"Process exited with code {processResult.ExitCode} and exception: {processResult.StandardError}");
-                var span = agent.WaitForSpans(2, 500);
+                return agent.WaitForSpans(2, 500);
+            }
+        }
 
-                Assert.True(span.Count() == expectedSpanCount, $"Expecting {expectedSpanCount} spans, received {span.Count()}");
+        private void AssertExpectedSpansReceived(int expectedSpanCount, IImmutableList<IMockSpan> spans)
-                if (expectedSpanCount > 0)
+        {
-                {
+            Assert.True(spans.Count() == expectedSpanCount, $"Expecting {expectedSpanCount} spans, received {spans.Count()}");
-                    Assert.Single(span.Select(s => s.Service).Distinct());
+            if (expectedSpanCount > 0)
+            {
+                Assert.Single(spans.Select(s => s.Service).Distinct());
 
-                    var spanList = span.ToList();
+                var spanList = spans.ToList();
-                    AssertExpectationsMet(_expectations, spanList);
+                AssertExpectationsMet(_expectations, spanList);
-                }
             }
         }
 

test/test-applications/integrations/Samples.GraphQL/Program.cs

@@ -28,7 +28,7 @@ namespace Samples.GraphQL
             var logger = host.Services.GetRequiredService<ILogger<Program>>();
             logger.LogInformation($"Instrumentation.ProfilerAttached = {IsProfilerAttached()}");
 
-            var prefixes = new[] { "COR_", "CORECLR_", "OTEL_" };
+            var prefixes = new[] { "COR_", "CORECLR_", "DOTNET_", "OTEL_" };
             var envVars = from envVar in Environment.GetEnvironmentVariables().Cast<DictionaryEntry>()
                           from prefix in prefixes
                           let key = (envVar.Key as string)?.ToUpperInvariant()

test/test-applications/integrations/Samples.GraphQL/Properties/launchSettings.json

@@ -17,6 +17,7 @@
         "CORECLR_ENABLE_PROFILING": "1",
         "CORECLR_PROFILER": "{918728DD-259F-4A6A-AC2B-B85E1B658318}",
         "CORECLR_PROFILER_PATH": "$(SolutionDir)bin\\tracer-home\\win-x64\\OpenTelemetry.ClrProfiler.Native.dll",
+        "DOTNET_STARTUP_HOOKS": "$(SolutionDir)bin\\tracer-home\\netcoreapp3.1\\OpenTelemetry.Instrumentation.StartupHook.dll",
 
         "OTEL_DOTNET_TRACER_HOME": "$(SolutionDir)bin\\tracer-home\\",
         "OTEL_INTEGRATIONS": "$(SolutionDir)bin\\tracer-home\\integrations.json",

test/test-applications/integrations/Samples.MongoDB/Properties/launchSettings.json

@@ -6,6 +6,7 @@
         "CORECLR_ENABLE_PROFILING": "1",
         "CORECLR_PROFILER": "{918728DD-259F-4A6A-AC2B-B85E1B658318}",
         "CORECLR_PROFILER_PATH": "$(SolutionDir)bin\\tracer-home\\win-x64\\OpenTelemetry.ClrProfiler.Native.dll",
+        "DOTNET_STARTUP_HOOKS": "$(SolutionDir)bin\\tracer-home\\netcoreapp3.1\\OpenTelemetry.Instrumentation.StartupHook.dll",
 
         "OTEL_DOTNET_TRACER_HOME": "$(SolutionDir)bin\\tracer-home\\",
         "OTEL_INTEGRATIONS": "$(SolutionDir)bin\\tracer-home\\integrations.json",

test/test-applications/integrations/aspnet/Samples.AspNet/Controllers/HomeController.cs

@@ -12,7 +12,7 @@ namespace Samples.AspNet.Controllers
     {
         public ActionResult Index()
         {
-            var prefixes = new[] { "COR_", "CORECLR_", "OTEL_" };
+            var prefixes = new[] { "COR_", "CORECLR_", "DOTNET_", "OTEL_" };
 
             var envVars = from envVar in Environment.GetEnvironmentVariables().Cast<DictionaryEntry>()
                           from prefix in prefixes