Concurrent restore of project.json contention on lock.json

[ericstj]

Our build happens to try to restore project.json from two separate threads/processes. This can result in an IOException when trying to write the .lock.json.

[pranavkm]

@ericstj, do you have the stack trace for the error?

[ericstj]

Here you go. I forced it by dropping 6 projects in the same directory with different csproj's and same project.json.

System.IO.IOException: The process cannot access the file 'd:\corefx\src\Microsoft.CSharp\src\project.lock.json' because it is being used by another process. (TaskId:14)
   at System.IO.Win32FileStream.Init(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs) (TaskId:14)
   at System.IO.Win32FileSystem.Open(String fullPath, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options, FileStream parent) (TaskId:14)
   at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options) (TaskId:14)
   at Microsoft.Framework.Runtime.DependencyManagement.LockFileFormat.Write(String filePath, LockFile lockFile) (TaskId:14)
   at Microsoft.Framework.PackageManager.RestoreCommand.WriteLockFile(String projectLockFilePath, Project project, List`1 graphItems, PackageRepository repository, IEnumerable`1 frameworks) (TaskId:14)
   at Microsoft.Framework.PackageManager.RestoreCommand.<RestoreForProject>d__75.MoveNext() (TaskId:14)
--- End of stack trace from previous location where exception was thrown --- (TaskId:14)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) (TaskId:14)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) (TaskId:14)
   at Microsoft.Framework.PackageManager.RestoreCommand.<>c__DisplayClass74_0.<<ExecuteCommand>b__0>d.MoveNext() (TaskId:14)
--- End of stack trace from previous location where exception was thrown --- (TaskId:14)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) (TaskId:14)
   at Microsoft.Framework.PackageManager.RestoreCommand.<ExecuteCommand>d__74.MoveNext() (TaskId:14)
---------- (TaskId:14)
Restore failed (TaskId:14)
The process cannot access the file 'd:\corefx\src\Microsoft.CSharp\src\project.lock.json' because it is being used by another process. (TaskId:14)

[pranavkm]

cc @anurse

[davidfowl]

So we're not supporting this. But we're going to fail better