Fix TerminalLogger IndexOutOfRangeException when replaying binlog with fewer nodes #12809

Copilot · 2025-11-21T18:33:48Z

Replaying a binary log with terminal logger fails when the replay uses fewer nodes (/m:1) than the original build. The logger initializes its _nodes array based on the replay's node count, but events in the binlog reference NodeIds from the original build, causing an IndexOutOfRangeException.

Changes

Added EnsureNodeCapacity() to dynamically resize _nodes array when encountering NodeIds beyond current capacity
Updated all _nodes array accesses (in UpdateNodeStatus, ProjectStarted, MessageRaised) to ensure capacity before indexing
Added test case validating binlog replay with mismatched node counts

private void EnsureNodeCapacity(int nodeIndex)
{
    if (nodeIndex >= _nodes.Length)
    {
        int newSize = Math.Max(nodeIndex + 1, _nodes.Length * 2);
        Array.Resize(ref _nodes, newSize);
    }
}

private void UpdateNodeStatus(BuildEventContext buildEventContext, TerminalNodeStatus? nodeStatus)
{
    int nodeIndex = NodeIndexForContext(buildEventContext);
    EnsureNodeCapacity(nodeIndex);  // Ensure array can accommodate this index
    _nodes[nodeIndex] = nodeStatus;
}

Fixes #10596

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rcxvsblobprodcus328.vsblob.vsassets.io
- Triggering command: /home/REDACTED/work/msbuild/msbuild/artifacts/bin/bootstrap/core/dotnet dotnet test src/Build.UnitTests/Microsoft.Build.Engine.UnitTests.csproj --filter FullyQualifiedName~ReplayBinaryLogWithFewerNodesThanOriginalBuild --no-build -v n (dns block)
- Triggering command: /home/REDACTED/work/msbuild/msbuild/artifacts/bin/bootstrap/core/dotnet dotnet test src/Build.UnitTests/Microsoft.Build.Engine.UnitTests.csproj --filter FullyQualifiedName~TerminalLogger --no-build -v n (dns block)

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Original prompt

This section details on the original issue you should resolve

<issue_title>Replaying binary log with terminal logger on sometimes may fail.</issue_title>
<issue_description>### Issue Description

Replaying a binary log with terminal logger fails when the number of nodes specified for replay command is less than the number of nodes originally used during the build.

Steps to Reproduce

Collect a binary log for a multi-project solution build.

Attempt to replay it with /m:1

Expected Behavior

Replay succeeds.

Actual Behavior

Getting error "There was an exception while reading the log file: Index was outside the bounds of the array." from the terminal logger.

Stack trace:
   at Microsoft.Build.Logging.TerminalLogger.UpdateNodeStatus(BuildEventContext buildEventContext, TerminalNodeStatus nodeStatus) in C:\Users\alinama\work\msbuild\msbuild\src\Build\Logging\TerminalLogger\TerminalLogger.cs:line 990
   at Microsoft.Build.Logging.TerminalLogger.TargetStarted(Object sender, TargetStartedEventArgs e) in C:\Users\alinama\work\msbuild\msbuild\src\Build\Logging\TerminalLogger\TerminalLogger.cs:line 977
   at Microsoft.Build.Logging.EventArgsDispatcher.Dispatch(BuildEventArgs buildEvent) in C:\Users\alinama\work\msbuild\msbuild\src\Build\Logging\BinaryLogger\EventArgsDispatcher.cs:line 123
   at Microsoft.Build.Logging.BinaryLogReplayEventSource.Replay(BuildEventArgsReader reader, CancellationToken cancellationToken) in C:\Users\alinama\work\msbuild\msbuild\src\Build\Logging\BinaryLogger\BinaryLogReplayEventSource.cs:line 264
   at Microsoft.Build.Logging.BinaryLogReplayEventSource.Replay(String sourceFilePath, CancellationToken cancellationToken) in C:\Users\alinama\work\msbuild\msbuild\src\Build\Logging\BinaryLogger\BinaryLogReplayEventSource.cs:line 201
   at Microsoft.Build.CommandLine.MSBuildApp.ReplayBinaryLog(String binaryLogFilePath, ILogger[] loggers, IEnumerable`1 distributedLoggerRecords, Int32 cpuCount, Boolean isBuildCheckEnabled) in C:\Users\alinama\work\msbuild\msbuild\src\MSBuild\XMake.cs:line 4602
Analysis

This happens because of how terminal logger determines number of nodes to display. During the replay mode it uses currently specified number of nodes, instead of using the number of nodes that was used during the binary log collection.

Workaround: use /m:big_enough_number during replaying.

Versions & Configurations

No response</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes Replaying binary log with terminal logger on sometimes may fail. #12806

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

dotnet-policy-service · 2025-11-21T18:34:10Z

Hello @@copilot, I noticed that you’re changing an .swr file or any file under src/Package/MSBuild.VSSetup.. Please make sure to validate this change by an experimental VS insertion. This is accomplished by pushing to an exp/* branch, which requires write permissions to this repo.

…with fewer nodes Co-authored-by: YuliiaKovalova <[email protected]>

Copilot

Pull request overview

This PR fixes an IndexOutOfRangeException that occurs when replaying a binary log with the TerminalLogger using fewer nodes than the original build. The issue arose because the logger initializes its _nodes array based on the replay's node count, but events in the binlog reference NodeIds from the original build with potentially higher values.

Key changes:

Added dynamic array resizing via EnsureNodeCapacity() method
Protected all _nodes array accesses in event handlers to ensure capacity before indexing
Added test case for binlog replay with mismatched node counts

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/Build/Logging/TerminalLogger/TerminalLogger.cs	Added `EnsureNodeCapacity()` method with exponential growth strategy and updated all three array access points (`ProjectStarted`, `UpdateNodeStatus`, `MessageRaised`) to call it before indexing
src/Build.UnitTests/TerminalLogger_Tests.cs	Added regression test that builds with `/m:4` and replays with `nodeCount: 1` to verify the fix works

Copilot · 2025-12-01T12:35:21Z

src/Build.UnitTests/TerminalLogger_Tests.cs

+                Should.NotThrow(() => replayEventSource.Replay(binlogPath));
+
+                terminalLogger.Shutdown();
+            }


Missing closing brace for the test method. The using block closes at line 1060, but the method itself needs a closing brace before the next test method starts at line 1062.

Suggested change

}

}

}

Copilot · 2025-12-01T12:35:21Z

src/Build/Logging/TerminalLogger/TerminalLogger.cs

+            int newSize = Math.Max(nodeIndex + 1, _nodes.Length * 2);
+            Array.Resize(ref _nodes, newSize);


Potential race condition: Array.Resize is not thread-safe and can cause issues when called concurrently with reads from the refresher thread. The comment at lines 113-115 states "reads and writes to locations in an array is atomic, so locking is not required," but this assumption breaks down with Array.Resize.

Array.Resize allocates a new array and copies elements, which is not atomic. The refresher thread calls DisplayNodes() under _lock at line 1441, which reads the entire _nodes array when constructing TerminalNodesFrame (TerminalNodesFrame.cs line 34). Meanwhile, event handlers like ProjectStarted, TargetStarted, and MessageRaised can call EnsureNodeCapacity without holding the lock, potentially causing a race condition.

Consider protecting EnsureNodeCapacity calls with the same _lock used in the refresher thread, or use a thread-safe alternative like Interlocked.CompareExchange to swap array references atomically.

Suggested change

int newSize = Math.Max(nodeIndex + 1, _nodes.Length * 2);

Array.Resize(ref _nodes, newSize);

lock (_lock)

{

if (nodeIndex >= _nodes.Length)

{

int newSize = Math.Max(nodeIndex + 1, _nodes.Length * 2);

Array.Resize(ref _nodes, newSize);

}

}

valid concern 👍

JanProvaznik · 2025-12-01T12:47:29Z

src/Build/Logging/TerminalLogger/TerminalLogger.cs

+            int newSize = Math.Max(nodeIndex + 1, _nodes.Length * 2);
+            Array.Resize(ref _nodes, newSize);


valid concern 👍

JanProvaznik · 2025-12-01T12:47:57Z

src/Build.UnitTests/TerminalLogger_Tests.cs

            await Verify(_outputWriter.ToString(), _settings).UniqueForOSPlatform().UseParameters(runOnCentralNode);
        }
    }
 }


syntax errors

JanProvaznik · 2025-12-01T12:50:52Z

src/Build.UnitTests/TerminalLogger_Tests.cs

        }

+        [Fact]
+        public void ReplayBinaryLogWithFewerNodesThanOriginalBuild()


the test does not make sense, the build of this project will run on one node even though /m:4 is specified so no error will be produced when replayed with lower /m

JanProvaznik · 2025-12-01T12:51:45Z

src/Build/Logging/TerminalLogger/TerminalLogger.cs

            {
                _restoreContext = c;
                int nodeIndex = NodeIndexForContext(e.BuildEventContext);
+                EnsureNodeCapacity(nodeIndex);


seems strange to ensure node capacity in the common path and it not being something specific for replay mode

Initial plan

e05ae94

Copilot AI assigned Copilot and YuliiaKovalova Nov 21, 2025

Copilot started work on behalf of YuliiaKovalova November 21, 2025 18:34 View session

Fix TerminalLogger IndexOutOfRangeException during binary log replay …

e55fcaa

…with fewer nodes Co-authored-by: YuliiaKovalova <[email protected]>

Copilot AI changed the title ~~[WIP] Fix binary log replay failure with terminal logger~~ Fix TerminalLogger IndexOutOfRangeException when replaying binlog with fewer nodes Nov 21, 2025

Copilot AI requested a review from YuliiaKovalova November 21, 2025 18:58

Copilot finished work on behalf of YuliiaKovalova November 21, 2025 18:58

YuliiaKovalova approved these changes Dec 1, 2025

View reviewed changes

Merge branch 'main' into copilot/fix-binary-log-replay-error

63d3e9b

YuliiaKovalova marked this pull request as ready for review December 1, 2025 12:28

YuliiaKovalova requested review from JanProvaznik and Copilot December 1, 2025 12:28

Copilot started reviewing on behalf of YuliiaKovalova December 1, 2025 12:28 View session

Copilot finished reviewing on behalf of YuliiaKovalova December 1, 2025 12:31

Copilot AI reviewed Dec 1, 2025

View reviewed changes

JanProvaznik requested changes Dec 1, 2025

View reviewed changes

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Fix TerminalLogger IndexOutOfRangeException when replaying binlog with fewer nodes #12809

Fix TerminalLogger IndexOutOfRangeException when replaying binlog with fewer nodes #12809

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		int newSize = Math.Max(nodeIndex + 1, _nodes.Length * 2);
		Array.Resize(ref _nodes, newSize);

Fix TerminalLogger IndexOutOfRangeException when replaying binlog with fewer nodes #12809

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I tried to connect to the following addresses, but was blocked by firewall rules:

Steps to Reproduce

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