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robustio: copy from cmd/go/internal/robustio (#239)
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// 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. | ||
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// 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 | ||
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// 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) | ||
} | ||
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// 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) | ||
} | ||
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// 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) | ||
} | ||
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// 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) | ||
} |
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// 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. | ||
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package robustio | ||
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import ( | ||
"errors" | ||
"syscall" | ||
) | ||
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const errFileNotFound = syscall.ENOENT | ||
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// 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 | ||
} |
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// 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. | ||
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//go:build windows || darwin | ||
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package robustio | ||
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import ( | ||
"errors" | ||
"math/rand" | ||
"os" | ||
"syscall" | ||
"time" | ||
) | ||
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const arbitraryTimeout = 2000 * time.Millisecond | ||
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// 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 | ||
} | ||
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var errno syscall.Errno | ||
if errors.As(err, &errno) && (lowestErrno == 0 || errno < lowestErrno) { | ||
bestErr = err | ||
lowestErrno = errno | ||
} else if bestErr == nil { | ||
bestErr = err | ||
} | ||
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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))) | ||
} | ||
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return bestErr | ||
} | ||
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// 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) | ||
}) | ||
} | ||
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// 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) | ||
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// 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 | ||
} | ||
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func removeAll(path string) error { | ||
return retry(func() (err error, mayRetry bool) { | ||
err = os.RemoveAll(path) | ||
return err, isEphemeralError(err) | ||
}) | ||
} |
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// 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. | ||
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//go:build !windows && !darwin | ||
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package robustio | ||
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import ( | ||
"os" | ||
) | ||
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func rename(oldpath, newpath string) error { | ||
return os.Rename(oldpath, newpath) | ||
} | ||
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func readFile(filename string) ([]byte, error) { | ||
return os.ReadFile(filename) | ||
} | ||
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func removeAll(path string) error { | ||
return os.RemoveAll(path) | ||
} | ||
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func isEphemeralError(err error) bool { | ||
return false | ||
} |
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// 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. | ||
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package robustio | ||
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import ( | ||
"errors" | ||
"syscall" | ||
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"github.com/rogpeppe/go-internal/internal/syscall/windows" | ||
) | ||
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const errFileNotFound = syscall.ERROR_FILE_NOT_FOUND | ||
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// 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 | ||
} |