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Prefer dotnet MSBuild.dll for out-of-proc worker nodes in CLI scenarios #13452

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Merged
rainersigwald merged 2 commits into from
Mar 30, 2026
Merged

Prefer dotnet MSBuild.dll for out-of-proc worker nodes in CLI scenarios #13452

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d9bf159
Prefer dotnet MSBuild.dll for worker nodes when hosted by dotnet.exe
YuliiaKovalova Mar 27, 2026
dd9439d
fix error
YuliiaKovalova Mar 27, 2026
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30 changes: 27 additions & 3 deletions src/Build/BackEnd/Components/Communications/NodeProviderOutOfProcBase.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -228,6 +228,33 @@ protected IList<NodeContext> GetNodes(
msbuildLocation = _componentHost.BuildParameters.NodeExeLocation;
}

// Extract the expected NodeMode from the command line arguments
NodeMode? expectedNodeMode = NodeModeHelper.ExtractFromCommandLine(commandLineArgs);

#if RUNTIME_TYPE_NETCORE
// When MSBuild is hosted by dotnet.exe (e.g. `dotnet build`), NodeExeLocation may resolve
// to the AppHost (MSBuild.exe on Windows, MSBuild on Unix) because BuildEnvironmentHelper
// prefers the AppHost over MSBuild.dll. Launching worker nodes as MSBuild.exe AppHost
// processes is measurably slower than using dotnet MSBuild.dll. Prefer MSBuild.dll so
// worker nodes are launched via dotnet.exe, matching the parent process.
// This only applies to regular out-of-proc worker nodes (nodemode:1), not task host nodes
// (nodemode:2) which may need the AppHost for COM host object support.
if (expectedNodeMode == NodeMode.OutOfProcNode
&& !String.IsNullOrEmpty(msbuildLocation)
&& Path.GetFileName(msbuildLocation).Equals(Constants.MSBuildExecutableName, StringComparison.OrdinalIgnoreCase))
{
string currentProcessName = Path.GetFileName(EnvironmentUtilities.ProcessPath);
if (currentProcessName?.Equals(Constants.DotnetProcessName, StringComparison.OrdinalIgnoreCase) == true)
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{
string dllPath = Path.Combine(Path.GetDirectoryName(msbuildLocation), Constants.MSBuildAssemblyName);
if (File.Exists(dllPath))
{
msbuildLocation = dllPath;
}
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}
}
#endif

if (String.IsNullOrEmpty(msbuildLocation))
{
string msbuildExeName = Environment.GetEnvironmentVariable("MSBUILD_EXE_NAME");
Expand All @@ -240,9 +267,6 @@ protected IList<NodeContext> GetNodes(
}

bool nodeReuseRequested = Handshake.IsHandshakeOptionEnabled(nodeLaunchData.Handshake.HandshakeOptions, HandshakeOptions.NodeReuse);

// Extract the expected NodeMode from the command line arguments
NodeMode? expectedNodeMode = NodeModeHelper.ExtractFromCommandLine(commandLineArgs);

// Get all process of possible running node processes for reuse and put them into ConcurrentQueue.
// Processes from this queue will be concurrently consumed by TryReusePossibleRunningNodes while
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