From 2c88e7f58ae1ca6f811b818d0d985b4622556532 Mon Sep 17 00:00:00 2001 From: Roger Peppe Date: Wed, 13 Dec 2023 11:29:26 +0000 Subject: [PATCH] robustio: copy from cmd/go/internal/robustio (#239) Copied from Go commit b18b05881691861c4279a50010829150f1684fa9. --- robustio/robustio.go | 53 +++++++++++++++++++++ robustio/robustio_darwin.go | 21 +++++++++ robustio/robustio_flaky.go | 91 ++++++++++++++++++++++++++++++++++++ robustio/robustio_other.go | 27 +++++++++++ robustio/robustio_windows.go | 28 +++++++++++ 5 files changed, 220 insertions(+) create mode 100644 robustio/robustio.go create mode 100644 robustio/robustio_darwin.go create mode 100644 robustio/robustio_flaky.go create mode 100644 robustio/robustio_other.go create mode 100644 robustio/robustio_windows.go diff --git a/robustio/robustio.go b/robustio/robustio.go new file mode 100644 index 00000000..15b33773 --- /dev/null +++ b/robustio/robustio.go @@ -0,0 +1,53 @@ +// Copyright 2019 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Package robustio wraps I/O functions that are prone to failure on Windows, +// transparently retrying errors up to an arbitrary timeout. +// +// Errors are classified heuristically and retries are bounded, so the functions +// in this package do not completely eliminate spurious errors. However, they do +// significantly reduce the rate of failure in practice. +// +// If so, the error will likely wrap one of: +// The functions in this package do not completely eliminate spurious errors, +// but substantially reduce their rate of occurrence in practice. +package robustio + +// Rename is like os.Rename, but on Windows retries errors that may occur if the +// file is concurrently read or overwritten. +// +// (See golang.org/issue/31247 and golang.org/issue/32188.) +func Rename(oldpath, newpath string) error { + return rename(oldpath, newpath) +} + +// ReadFile is like os.ReadFile, but on Windows retries errors that may +// occur if the file is concurrently replaced. +// +// (See golang.org/issue/31247 and golang.org/issue/32188.) +func ReadFile(filename string) ([]byte, error) { + return readFile(filename) +} + +// RemoveAll is like os.RemoveAll, but on Windows retries errors that may occur +// if an executable file in the directory has recently been executed. +// +// (See golang.org/issue/19491.) +func RemoveAll(path string) error { + return removeAll(path) +} + +// IsEphemeralError reports whether err is one of the errors that the functions +// in this package attempt to mitigate. +// +// Errors considered ephemeral include: +// - syscall.ERROR_ACCESS_DENIED +// - syscall.ERROR_FILE_NOT_FOUND +// - internal/syscall/windows.ERROR_SHARING_VIOLATION +// +// This set may be expanded in the future; programs must not rely on the +// non-ephemerality of any given error. +func IsEphemeralError(err error) bool { + return isEphemeralError(err) +} diff --git a/robustio/robustio_darwin.go b/robustio/robustio_darwin.go new file mode 100644 index 00000000..99fd8ebc --- /dev/null +++ b/robustio/robustio_darwin.go @@ -0,0 +1,21 @@ +// Copyright 2019 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package robustio + +import ( + "errors" + "syscall" +) + +const errFileNotFound = syscall.ENOENT + +// isEphemeralError returns true if err may be resolved by waiting. +func isEphemeralError(err error) bool { + var errno syscall.Errno + if errors.As(err, &errno) { + return errno == errFileNotFound + } + return false +} diff --git a/robustio/robustio_flaky.go b/robustio/robustio_flaky.go new file mode 100644 index 00000000..c56e36ca --- /dev/null +++ b/robustio/robustio_flaky.go @@ -0,0 +1,91 @@ +// Copyright 2019 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +//go:build windows || darwin + +package robustio + +import ( + "errors" + "math/rand" + "os" + "syscall" + "time" +) + +const arbitraryTimeout = 2000 * time.Millisecond + +// retry retries ephemeral errors from f up to an arbitrary timeout +// to work around filesystem flakiness on Windows and Darwin. +func retry(f func() (err error, mayRetry bool)) error { + var ( + bestErr error + lowestErrno syscall.Errno + start time.Time + nextSleep time.Duration = 1 * time.Millisecond + ) + for { + err, mayRetry := f() + if err == nil || !mayRetry { + return err + } + + var errno syscall.Errno + if errors.As(err, &errno) && (lowestErrno == 0 || errno < lowestErrno) { + bestErr = err + lowestErrno = errno + } else if bestErr == nil { + bestErr = err + } + + if start.IsZero() { + start = time.Now() + } else if d := time.Since(start) + nextSleep; d >= arbitraryTimeout { + break + } + time.Sleep(nextSleep) + nextSleep += time.Duration(rand.Int63n(int64(nextSleep))) + } + + return bestErr +} + +// rename is like os.Rename, but retries ephemeral errors. +// +// On Windows it wraps os.Rename, which (as of 2019-06-04) uses MoveFileEx with +// MOVEFILE_REPLACE_EXISTING. +// +// Windows also provides a different system call, ReplaceFile, +// that provides similar semantics, but perhaps preserves more metadata. (The +// documentation on the differences between the two is very sparse.) +// +// Empirical error rates with MoveFileEx are lower under modest concurrency, so +// for now we're sticking with what the os package already provides. +func rename(oldpath, newpath string) (err error) { + return retry(func() (err error, mayRetry bool) { + err = os.Rename(oldpath, newpath) + return err, isEphemeralError(err) + }) +} + +// readFile is like os.ReadFile, but retries ephemeral errors. +func readFile(filename string) ([]byte, error) { + var b []byte + err := retry(func() (err error, mayRetry bool) { + b, err = os.ReadFile(filename) + + // Unlike in rename, we do not retry errFileNotFound here: it can occur + // as a spurious error, but the file may also genuinely not exist, so the + // increase in robustness is probably not worth the extra latency. + return err, isEphemeralError(err) && !errors.Is(err, errFileNotFound) + }) + return b, err +} + +func removeAll(path string) error { + return retry(func() (err error, mayRetry bool) { + err = os.RemoveAll(path) + return err, isEphemeralError(err) + }) +} diff --git a/robustio/robustio_other.go b/robustio/robustio_other.go new file mode 100644 index 00000000..da9a46e4 --- /dev/null +++ b/robustio/robustio_other.go @@ -0,0 +1,27 @@ +// Copyright 2019 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +//go:build !windows && !darwin + +package robustio + +import ( + "os" +) + +func rename(oldpath, newpath string) error { + return os.Rename(oldpath, newpath) +} + +func readFile(filename string) ([]byte, error) { + return os.ReadFile(filename) +} + +func removeAll(path string) error { + return os.RemoveAll(path) +} + +func isEphemeralError(err error) bool { + return false +} diff --git a/robustio/robustio_windows.go b/robustio/robustio_windows.go new file mode 100644 index 00000000..961de4ef --- /dev/null +++ b/robustio/robustio_windows.go @@ -0,0 +1,28 @@ +// Copyright 2019 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package robustio + +import ( + "errors" + "syscall" + + "github.com/rogpeppe/go-internal/internal/syscall/windows" +) + +const errFileNotFound = syscall.ERROR_FILE_NOT_FOUND + +// isEphemeralError returns true if err may be resolved by waiting. +func isEphemeralError(err error) bool { + var errno syscall.Errno + if errors.As(err, &errno) { + switch errno { + case syscall.ERROR_ACCESS_DENIED, + syscall.ERROR_FILE_NOT_FOUND, + windows.ERROR_SHARING_VIOLATION: + return true + } + } + return false +}