Adjust tracer home resolution to honor architecture-specific profiler paths by lucaspimentel · Pull Request #7567 · DataDog/dd-trace-dotnet

lucaspimentel · 2025-09-25T20:40:17Z

Summary

iterate profiler path environment variables per runtime so we prefer the value matching the current process architecture
add .NET Core logic to prefer CORECLR_PROFILER_PATH_ before falling back to CORECLR_PROFILER_PATH when deriving the tracer home
add .NET Framework logic to prefer COR_PROFILER_PATH_ before falling back to COR_PROFILER_PATH when deriving the tracer home

Testing

dotnet build tracer/src/Datadog.Trace.ClrProfiler.Managed.Loader/Datadog.Trace.ClrProfiler.Managed.Loader.csproj

https://chatgpt.com/codex/tasks/task_b_68d59245fcec832180db94dd256130ba

… paths

dd-trace-dotnet-ci-bot · 2025-09-25T21:42:34Z

Execution-Time Benchmarks Report ⏱️

Execution-time results for samples comparing the following branches/commits:

Execution-time benchmarks measure the whole time it takes to execute a program. And are intended to measure the one-off costs. Cases where the execution time results for the PR are worse than latest master results are shown in red. The following thresholds were used for comparing the execution times:

Welch test with statistical test for significance of 5%
Only results indicating a difference greater than 5% and 5 ms are considered.

Note that these results are based on a single point-in-time result for each branch. For full results, see the dashboard.

Graphs show the p99 interval based on the mean and StdDev of the test run, as well as the mean value of the run (shown as a diamond below the graph).

gantt
    title Execution time (ms) FakeDbCommand (.NET Framework 4.8) 
    dateFormat  X
    axisFormat %s
    todayMarker off
    section Bailout
    This PR (7567) - mean (72ms)  : 71, 73
     .   : milestone, 72,
    master - mean (77ms)  : 68, 86
     .   : milestone, 77,

    section Baseline
    This PR (7567) - mean (68ms)  : 65, 71
     .   : milestone, 68,
    master - mean (71ms)  : 66, 75
     .   : milestone, 71,

    section CallTarget+Inlining+NGEN
    This PR (7567) - mean (1,056ms)  : 1000, 1112
     .   : milestone, 1056,
    master - mean (1,063ms)  : 998, 1128
     .   : milestone, 1063,

gantt
    title Execution time (ms) FakeDbCommand (.NET Core 3.1) 
    dateFormat  X
    axisFormat %s
    todayMarker off
    section Bailout
    This PR (7567) - mean (114ms)  : 111, 116
     .   : milestone, 114,
    master - mean (109ms)  : 107, 111
     .   : milestone, 109,

    section Baseline
    This PR (7567) - mean (113ms)  : 110, 115
     .   : milestone, 113,
    master - mean (108ms)  : 105, 112
     .   : milestone, 108,

    section CallTarget+Inlining+NGEN
    This PR (7567) - mean (747ms)  : 722, 771
     .   : milestone, 747,
    master - mean (769ms)  : 726, 813
     .   : milestone, 769,

gantt
    title Execution time (ms) FakeDbCommand (.NET 6) 
    dateFormat  X
    axisFormat %s
    todayMarker off
    section Bailout
    This PR (7567) - mean (100ms)  : 99, 102
     .   : milestone, 100,
    master - mean (108ms)  : 101, 115
     .   : milestone, 108,

    section Baseline
    This PR (7567) - mean (100ms)  : 98, 102
     .   : milestone, 100,
    master - mean (105ms)  : 96, 113
     .   : milestone, 105,

    section CallTarget+Inlining+NGEN
    This PR (7567) - mean (778ms)  : 733, 823
     .   : milestone, 778,
    master - mean (799ms)  : 743, 855
     .   : milestone, 799,

gantt
    title Execution time (ms) FakeDbCommand (.NET 8) 
    dateFormat  X
    axisFormat %s
    todayMarker off
    section Bailout
    This PR (7567) - mean (93ms)  : 91, 94
     .   : milestone, 93,
    master - mean (97ms)  : 92, 102
     .   : milestone, 97,

    section Baseline
    This PR (7567) - mean (92ms)  : 90, 94
     .   : milestone, 92,
    master - mean (96ms)  : 90, 101
     .   : milestone, 96,

    section CallTarget+Inlining+NGEN
    This PR (7567) - mean (660ms)  : 645, 676
     .   : milestone, 660,
    master - mean (675ms)  : 649, 700
     .   : milestone, 675,

gantt
    title Execution time (ms) HttpMessageHandler (.NET Framework 4.8) 
    dateFormat  X
    axisFormat %s
    todayMarker off
    section Bailout
    This PR (7567) - mean (201ms)  : 196, 206
     .   : milestone, 201,
    master - mean (208ms)  : 196, 220
     .   : milestone, 208,

    section Baseline
    This PR (7567) - mean (198ms)  : 192, 204
     .   : milestone, 198,
    master - mean (203ms)  : 194, 213
     .   : milestone, 203,

    section CallTarget+Inlining+NGEN
    This PR (7567) - mean (1,192ms)  : 1107, 1277
     .   : milestone, 1192,
    master - mean (1,230ms)  : 1143, 1318
     .   : milestone, 1230,

gantt
    title Execution time (ms) HttpMessageHandler (.NET Core 3.1) 
    dateFormat  X
    axisFormat %s
    todayMarker off
    section Bailout
    This PR (7567) - mean (285ms)  : 275, 296
     .   : milestone, 285,
    master - mean (298ms)  : 283, 313
     .   : milestone, 298,

    section Baseline
    This PR (7567) - mean (284ms)  : 276, 292
     .   : milestone, 284,
    master - mean (298ms)  : 282, 313
     .   : milestone, 298,

    section CallTarget+Inlining+NGEN
    This PR (7567) - mean (952ms)  : 915, 988
     .   : milestone, 952,
    master - mean (995ms)  : 956, 1034
     .   : milestone, 995,

gantt
    title Execution time (ms) HttpMessageHandler (.NET 6) 
    dateFormat  X
    axisFormat %s
    todayMarker off
    section Bailout
    This PR (7567) - mean (287ms)  : 281, 293
     .   : milestone, 287,
    master - mean (301ms)  : 285, 316
     .   : milestone, 301,

    section Baseline
    This PR (7567) - mean (288ms)  : 281, 295
     .   : milestone, 288,
    master - mean (300ms)  : 279, 321
     .   : milestone, 300,

    section CallTarget+Inlining+NGEN
    This PR (7567) - mean (1,013ms)  : 982, 1043
     .   : milestone, 1013,
    master - mean (1,040ms)  : 993, 1088
     .   : milestone, 1040,

gantt
    title Execution time (ms) HttpMessageHandler (.NET 8) 
    dateFormat  X
    axisFormat %s
    todayMarker off
    section Bailout
    This PR (7567) - mean (276ms)  : 270, 281
     .   : milestone, 276,
    master - mean (292ms)  : 271, 312
     .   : milestone, 292,

    section Baseline
    This PR (7567) - mean (275ms)  : 268, 283
     .   : milestone, 275,
    master - mean (291ms)  : 269, 314
     .   : milestone, 291,

    section CallTarget+Inlining+NGEN
    This PR (7567) - mean (873ms)  : 845, 900
     .   : milestone, 873,
    master - mean (933ms)  : 842, 1024
     .   : milestone, 933,

~_This PR is stacked on #7594. Merge that PR first._~ ## Summary of changes Make `DD_DOTNET_TRACER_HOME` optional. If not set, try to figure out the path from `COR_PROFILER_PATH`/`CORECLR_PROFILER_PATH` and friends. ## Reason for change One less env var for users to set manually. Easier onboarding, less error-prone. I recently worked on an escalation where `DD_DOTNET_TRACER_HOME` was set to the wrong path so the tracer was not loading. ## Implementation details The implementation makes `DD_DOTNET_TRACER_HOME` optional by adding fallback logic to derive the tracer home path from the profiler path environment variables: 1. **New method `GetTracerHomePath`** (`Startup.cs:150-178`): - First checks for explicit `DD_DOTNET_TRACER_HOME` setting (preserves backward compatibility) - Falls back to computing the path from architecture-specific profiler path env vars (e.g., `CORECLR_PROFILER_PATH_64`, `COR_PROFILER_PATH_64`) - If not found, tries the generic profiler path env var (e.g., `CORECLR_PROFILER_PATH`, `COR_PROFILER_PATH`) 2. **New method `ComputeTracerHomePathFromProfilerPath`** (`Startup.cs:180-218`): - Takes a profiler path like `C:\tracer\win-x64\Datadog.Trace.ClrProfiler.Native.dll` - Extracts the parent directory - If the parent directory name matches a known architecture folder (e.g., `win-x64`, `linux-arm64`, `osx`), goes up one more level - Returns the computed tracer home path 3. **Platform-specific helper methods**: - `GetProfilerPathEnvVarNameForArch()`: Returns the architecture-specific env var name (`CORECLR_PROFILER_PATH_64` on .NET Core x64, `COR_PROFILER_PATH_32` on .NET Framework x86, etc.) - `GetProfilerPathEnvVarNameFallback()`: Returns the generic env var name (`CORECLR_PROFILER_PATH` or `COR_PROFILER_PATH`) 4. **Architecture directory detection**: - Maintains a `HashSet<string>` of known architecture directories (`win-x64`, `win-x86`, `linux-x64`, `linux-arm64`, etc) ## Test coverage **Unit tests** (`tracer/test/Datadog.Trace.Tests/ClrProfiler/Managed/Loader/`): - Environment variable reading and fallback logic (`StartupNetCoreTests.cs`, `StartupNetFrameworkTests.cs`) - `GetTracerHomePath()` with explicit `DD_DOTNET_TRACER_HOME` (with/without whitespace) - `GetTracerHomePath()` with architecture-specific profiler path fallback - `GetTracerHomePath()` with generic profiler path fallback - `ComputeTracerHomePathFromProfilerPath()` with all architecture directories - Edge cases: empty values, whitespace, missing variables, null handling **Integration tests**: - Added `WhenOmittingTracerHome_InstrumentsApp()` test in `InstrumentationTests.cs` that explicitly omits `DD_DOTNET_TRACER_HOME` and verifies instrumentation works via fallback logic - Modified all smoke tests (`SmokeTests/SmokeTestBase.cs`) to omit `DD_DOTNET_TRACER_HOME` by default, providing comprehensive real-world validation of the fallback behavior across multiple regression scenarios ## Other details  ⚠️ Based on #7567, which was originally [generated by OpenAI Codex](https://chatgpt.com/codex/tasks/task_b_68d59245fcec832180db94dd256130ba), but I made substantial changes to clean up and refactor.  --------- Co-authored-by: Claude <noreply@anthropic.com>

Adjust tracer home resolution to honor architecture-specific profiler…

6a343d3

… paths

lucaspimentel added the codex label Sep 25, 2025 — with ChatGPT Codex Connector

lucaspimentel added 3 commits September 25, 2025 17:56

cleaning up Codex's code

251bc21

skip known directories

7a65c02

refactor getting the parent directory

02eb489

lucaspimentel mentioned this pull request Sep 25, 2025

[onboarding] make DD_DOTNET_TRACER_HOME optional in managed loader #7568

Merged

lucaspimentel closed this Sep 25, 2025

lucaspimentel deleted the codex/remove-dd_dotnet_tracer_home-dependency branch October 3, 2025 21:20

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Adjust tracer home resolution to honor architecture-specific profiler paths#7567

Adjust tracer home resolution to honor architecture-specific profiler paths#7567
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codex/remove-dd_dotnet_tracer_home-dependency

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lucaspimentel commented Sep 25, 2025

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