util/io: add RedirectStderr
Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>
This commit is contained in:
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814b90efe5
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17
util/io/redirect.go
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17
util/io/redirect.go
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package io
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import (
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"os"
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"sync"
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)
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var osStderrMu sync.Mutex
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var OrigStderr = func() *os.File {
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fd, err := dupFD(os.Stderr.Fd())
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if err != nil {
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panic(err)
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}
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return os.NewFile(fd, os.Stderr.Name())
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}()
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40
util/io/redirect_test.go
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40
util/io/redirect_test.go
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package io
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import (
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"bytes"
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"fmt"
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"io"
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"os"
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"regexp"
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"testing"
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"time"
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)
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var ErrorPattern = regexp.MustCompile(`"error"`)
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func TestRedirect(t *testing.T) {
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r, w, err := os.Pipe()
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if err != nil {
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t.Fatal(err)
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}
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ch := make(chan string)
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go func() {
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buf := bytes.NewBuffer(nil)
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_, _ = io.Copy(buf, r)
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ch <- buf.String()
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}()
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if err = RedirectStderr(w); err != nil {
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t.Fatal(err)
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}
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os.Stderr.Write([]byte(`test redirect`))
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time.Sleep(1 * time.Millisecond)
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r.Close()
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str := <-ch
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if ErrorPattern.MatchString(str) {
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t.Fatal(fmt.Errorf(str))
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}
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}
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48
util/io/redirect_unix.go
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48
util/io/redirect_unix.go
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//go:build !windows
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// +build !windows
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package io
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import (
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"os"
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"golang.org/x/sys/unix"
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)
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// dupFD is used to initialize OrigStderr (see stderr_redirect.go).
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func dupFD(fd uintptr) (uintptr, error) {
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// Warning: failing to set FD_CLOEXEC causes the duplicated file descriptor
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// to leak into subprocesses created by exec.Command. If the file descriptor
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// is a pipe, these subprocesses will hold the pipe open (i.e., prevent
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// EOF), potentially beyond the lifetime of this process.
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//
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// This can break go test's timeouts. go test usually spawns a test process
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// with its stdin and stderr streams hooked up to pipes; if the test process
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// times out, it sends a SIGKILL and attempts to read stdin and stderr to
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// completion. If the test process has itself spawned long-lived
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// subprocesses that hold references to the stdin or stderr pipes, go test
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// will hang until the subprocesses exit, rather defeating the purpose of
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// a timeout.
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nfd, err := unix.FcntlInt(fd, unix.F_DUPFD_CLOEXEC, 0)
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if err != nil {
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return 0, err
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}
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return uintptr(nfd), nil
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}
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// RedirectStderr is used to redirect internal writes to fd 2 to the
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// specified file. This is needed to ensure that harcoded writes to fd
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// 2 by e.g. the Go runtime are redirected to a log file of our
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// choosing.
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//
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// We also override os.Stderr for those other parts of Go which use
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// that and not fd 2 directly.
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func RedirectStderr(f *os.File) error {
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osStderrMu.Lock()
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defer osStderrMu.Unlock()
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if err := unix.Dup2(int(f.Fd()), unix.Stderr); err != nil {
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return err
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}
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os.Stderr = f
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return nil
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}
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32
util/io/redirect_windows.go
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32
util/io/redirect_windows.go
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package io
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import (
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"os"
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"golang.org/x/sys/windows"
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)
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// dupFD is used to initialize OrigStderr (see stderr_redirect.go).
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func dupFD(fd uintptr) (uintptr, error) {
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// Adapted from https://github.com/golang/go/blob/go1.8/src/syscall/exec_windows.go#L303.
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p := windows.CurrentProcess()
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var h windows.Handle
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return uintptr(h), windows.DuplicateHandle(p, windows.Handle(fd), p, &h, 0, true, windows.DUPLICATE_SAME_ACCESS)
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}
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// RedirectStderr is used to redirect internal writes to the error
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// handle to the specified file. This is needed to ensure that
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// harcoded writes to the error handle by e.g. the Go runtime are
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// redirected to a log file of our choosing.
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//
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// We also override os.Stderr for those other parts of Go which use
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// that and not fd 2 directly.
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func RedirectStderr(f *os.File) error {
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osStderrMu.Lock()
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defer osStderrMu.Unlock()
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if err := windows.SetStdHandle(windows.STD_ERROR_HANDLE, windows.Handle(f.Fd())); err != nil {
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return err
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}
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os.Stderr = f
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return nil
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}
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