Bug: When WatchStaticMappings=true throws exceptions on updating the mapping files #183

New Issue

adam · 2025-12-29T08:23:33+01:00

adam commented

2025-12-29 08:23:33 +01:00

Originally created by @muzammilkm on GitHub (Jun 20, 2019).

When WatchStaticMappings = true in settings throws exceptions & application abnormally gets aborted on updating the mapping files while Mock Server is running.

Exception:

System.IO.IOException: The process cannot access the file ''  because it is being used by another process.
 at System.IO.FileStream.ValidateFileHandle(SafeFileHandle fileHandle)
   at System.IO.FileStream.CreateFileOpenHandle(FileMode mode, FileShare share, FileOptions options)
   at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options)
   at System.IO.StreamReader..ctor(String path, Encoding encoding, Boolean detectEncodingFromByteOrderMarks, Int32 bufferSize)
   at System.IO.StreamReader..ctor(String path, Encoding encoding, Boolean detectEncodingFromByteOrderMarks)
   at System.IO.File.InternalReadAllText(String path, Encoding encoding)
   at System.IO.File.ReadAllText(String path)
   at WireMock.Server.FluentMockServer.ReadStaticMappingAndAddOrUpdate(String path) in /Server/FluentMockServer.Admin.cs:line 217
   at System.IO.FileSystemWatcher.NotifyFileSystemEventArgs(WatcherChangeTypes changeType, String name)
   at System.IO.FileSystemWatcher.ParseEventBufferAndNotifyForEach(Byte[] buffer)
   at System.IO.FileSystemWatcher.ReadDirectoryChangesCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* overlappedPointer)
   at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP)

This happens due to editor lock duration while writing to disk(saving). I tried capturing the duration for various editors

VS Code: ~400 ms - ~100 ms
Sublime: ~250ms - ~100 ms
Notepad: ~50ms - ~10ms.

Finding the lock duration & work around for this issue, added in WireMock.Net\Server\FluentMockServer.Admin.cs in ReadStaticMappingAndAddOrUpdate method at line 215:

Stopwatch sw = new Stopwatch();
sw.Start();
while (IsFileLocked(path) && sw.ElapsedMilliseconds < EnhancedFileSystemWatcherTimeoutMs) 
{
}
sw.Stop();
 _logger.Debg("Waited for {0} ms", sw.ElapsedMilliseconds);
if (sw.ElapsedMilliseconds > EnhancedFileSystemWatcherTimeoutMs)
{
    _logger.Error("Abort. waited for {0} ms", sw.ElapsedMilliseconds);
    return;
}

Refer for IsFileLocked
Avoiding File Concurrency when using System.IO.FileSystemWatcher

Originally created by @muzammilkm on GitHub (Jun 20, 2019). When WatchStaticMappings = true in settings throws exceptions & application abnormally gets aborted on updating the mapping files while Mock Server is running. **Exception:** ``` System.IO.IOException: The process cannot access the file '' because it is being used by another process. at System.IO.FileStream.ValidateFileHandle(SafeFileHandle fileHandle) at System.IO.FileStream.CreateFileOpenHandle(FileMode mode, FileShare share, FileOptions options) at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options) at System.IO.StreamReader..ctor(String path, Encoding encoding, Boolean detectEncodingFromByteOrderMarks, Int32 bufferSize) at System.IO.StreamReader..ctor(String path, Encoding encoding, Boolean detectEncodingFromByteOrderMarks) at System.IO.File.InternalReadAllText(String path, Encoding encoding) at System.IO.File.ReadAllText(String path) at WireMock.Server.FluentMockServer.ReadStaticMappingAndAddOrUpdate(String path) in /Server/FluentMockServer.Admin.cs:line 217 at System.IO.FileSystemWatcher.NotifyFileSystemEventArgs(WatcherChangeTypes changeType, String name) at System.IO.FileSystemWatcher.ParseEventBufferAndNotifyForEach(Byte[] buffer) at System.IO.FileSystemWatcher.ReadDirectoryChangesCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* overlappedPointer) at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP) ``` This happens due to editor lock duration while writing to disk(saving). I tried capturing the duration for various editors VS Code: ~400 ms - ~100 ms Sublime: ~250ms - ~100 ms Notepad: ~50ms - ~10ms. Finding the lock duration & work around for this issue, added in WireMock.Net\Server\FluentMockServer.Admin.cs in ReadStaticMappingAndAddOrUpdate method at line 215: ```C# Stopwatch sw = new Stopwatch(); sw.Start(); while (IsFileLocked(path) && sw.ElapsedMilliseconds < EnhancedFileSystemWatcherTimeoutMs) { } sw.Stop(); _logger.Debg("Waited for {0} ms", sw.ElapsedMilliseconds); if (sw.ElapsedMilliseconds > EnhancedFileSystemWatcherTimeoutMs) { _logger.Error("Abort. waited for {0} ms", sw.ElapsedMilliseconds); return; } ``` Refer for [IsFileLocked](https://stackoverflow.com/questions/876473/is-there-a-way-to-check-if-a-file-is-in-use) [Avoiding File Concurrency when using System.IO.FileSystemWatcher](https://www.intertech.com/Blog/avoiding-file-concurrency-using-system-io-filesystemwatcher/)

adam added the bug label 2025-12-29 08:23:33 +01:00

adam closed this issue

2025-12-29 08:23:33 +01:00

adam commented

2025-12-29 08:23:34 +01:00

@StefH commented on GitHub (Jun 20, 2019):

I noticed this also in another scenario. I will check the code...

@StefH commented on GitHub (Jun 20, 2019): I noticed this also in another scenario. I will check the code...

adam commented

2025-12-29 08:23:35 +01:00

@StefH commented on GitHub (Jun 20, 2019):

Should be solved in next preview version at MyGet...