Garrett D'Amore
ecd994be06
This changes a few things to try to ensure that we never wind up with a result of ERROR_FILE_NOT_FOUND, due to a race between closing the last pipe instance and opening the next. First we keep an "open" client instance (unused) while the listener is open, so that we are guaranteed to always have an active pipe instance. This means attempts to open while no other instances exist result in ERROR_PIPE_BUSY instead of ERROR_FILE_NOT_FOUND. Second we have changed the loop for dialing to eliminate a race condition that is more or less inherent in WaitNamedPipe when synchronizing with CreateFile. The real timeout needs to be some larger value than the WaitNamedPipe timeout, and furthermore WaitNamedPipe is not very nice with the Go runtime, since it is a blocking system call. Instead we just put the goroutine to sleep for 10 milliseconds, and keep retrying the CreateFile until the maximum timeout is reached. If no timeout is specified we assume a reasonable and large default of 5 seconds, which is similar to a TCP connection timeout. This isn't perfect, as a client attempting to connect to an extremely busy pipe server can be starved out by other clients coming in while it is in that brief sleep, but this potential race was already present with WaitNamedPipe. The numerous retries (by default 500 retries!) mean its pretty unlikely to occur, and if a single client hits the race once, it has an excellent chance of getting in the next cycle. (A real "fix" that is completely race free and fair would require changes in the underlying Named Pipe implementation, or some other kind of external coordination.)
go-winio
This repository contains utilities for efficiently performing Win32 IO operations in Go. Currently, this is focused on accessing named pipes and other file handles, and for using named pipes as a net transport.
This code relies on IO completion ports to avoid blocking IO on system threads, allowing Go to reuse the thread to schedule another goroutine. This limits support to Windows Vista and newer operating systems. This is similar to the implementation of network sockets in Go's net package.
Please see the LICENSE file for licensing information.
This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.
Thanks to natefinch for the inspiration for this library. See https://github.com/natefinch/npipe for another named pipe implementation.