Fix IIS/Windows Service console race condition (#7691) #7793
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- Detect when running in IIS/Windows Service environments where Console.Out and Console.Error are redirected to the same StreamWriter.Null singleton - Skip console output entirely in these environments to prevent race conditions that cause IndexOutOfRangeException and cascade failures - Improve DefaultLogger error handling to prevent feedback loops - Add unit tests for non-console scenarios The race condition occurs because: 1. IIS/Services redirect both Console.Out and Console.Error to StreamWriter.Null 2. StreamWriter.Null is a singleton, not thread-safe for concurrent access 3. Multiple threads writing to both streams cause IndexOutOfRangeException 4. Console output goes nowhere in these environments anyway Fixes akkadotnet#7691
- Make console detection more precise: only skip output when both Console.Out AND Console.Error point to StreamWriter.Null (the exact race condition scenario) - Remove unnecessary try-catch in DefaultLogger.Print() since Tell() is unlikely to throw - Keep improved error message for debugging when logger is not initialized
Aaronontheweb
commented
Sep 2, 2025
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| [Fact] | ||
| public void StandardOutWriter_should_handle_concurrent_writes_without_race_conditions() |
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This whole test class is probably a tad useless IMHO given the racy and rare nature of this bug but it's worth a shot
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| public void StandardOutWriter_should_handle_null_and_empty_messages() |
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Probably the most useful test of the bunch tbh
| // and Console.Error point to the SAME StreamWriter.Null singleton instance. | ||
| // This is the exact condition that causes the race condition. | ||
| // Note: We check both because in these environments, both are always set to the same instance | ||
| if (Console.Out == StreamWriter.Null && Console.Error == StreamWriter.Null) |
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Comment in the code explains it best
This was referenced Sep 3, 2025
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…adotnet#7793) * Fix IIS/Windows Service console race condition (akkadotnet#7691) - Detect when running in IIS/Windows Service environments where Console.Out and Console.Error are redirected to the same StreamWriter.Null singleton - Skip console output entirely in these environments to prevent race conditions that cause IndexOutOfRangeException and cascade failures - Improve DefaultLogger error handling to prevent feedback loops - Add unit tests for non-console scenarios The race condition occurs because: 1. IIS/Services redirect both Console.Out and Console.Error to StreamWriter.Null 2. StreamWriter.Null is a singleton, not thread-safe for concurrent access 3. Multiple threads writing to both streams cause IndexOutOfRangeException 4. Console output goes nowhere in these environments anyway Fixes akkadotnet#7691 * Refine console detection and simplify error handling - Make console detection more precise: only skip output when both Console.Out AND Console.Error point to StreamWriter.Null (the exact race condition scenario) - Remove unnecessary try-catch in DefaultLogger.Print() since Tell() is unlikely to throw - Keep improved error message for debugging when logger is not initialized
Aaronontheweb
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that referenced
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Sep 5, 2025
* Fix IIS/Windows Service console race condition (#7691) - Detect when running in IIS/Windows Service environments where Console.Out and Console.Error are redirected to the same StreamWriter.Null singleton - Skip console output entirely in these environments to prevent race conditions that cause IndexOutOfRangeException and cascade failures - Improve DefaultLogger error handling to prevent feedback loops - Add unit tests for non-console scenarios The race condition occurs because: 1. IIS/Services redirect both Console.Out and Console.Error to StreamWriter.Null 2. StreamWriter.Null is a singleton, not thread-safe for concurrent access 3. Multiple threads writing to both streams cause IndexOutOfRangeException 4. Console output goes nowhere in these environments anyway Fixes #7691 * Refine console detection and simplify error handling - Make console detection more precise: only skip output when both Console.Out AND Console.Error point to StreamWriter.Null (the exact race condition scenario) - Remove unnecessary try-catch in DefaultLogger.Print() since Tell() is unlikely to throw - Keep improved error message for debugging when logger is not initialized
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Changes
The race condition occurs because:
Fixes #7691
Checklist
For significant changes, please ensure that the following have been completed (delete if not relevant):