mirror of
https://github.com/k3s-io/k3s.git
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dc18ef2e51
Using MAINPID breaks systemd's exit detection, as it stops watching the original pid, but is unable to watch the new pid as it is not a child of systemd itself. The best we can do is just notify when execing the child process. We also need to consolidate forking into a sigle place so that we don't end up with multiple levels of child processes if both redirecting log output and reaping child processes. Signed-off-by: Brad Davidson <brad.davidson@rancher.com>
105 lines
2.5 KiB
Go
105 lines
2.5 KiB
Go
// +build linux,cgo
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package cmds
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import (
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"io"
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"os"
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"os/exec"
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"os/signal"
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"syscall"
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systemd "github.com/coreos/go-systemd/daemon"
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"github.com/erikdubbelboer/gspt"
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"github.com/natefinch/lumberjack"
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"github.com/pkg/errors"
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"github.com/rancher/k3s/pkg/version"
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"golang.org/x/sys/unix"
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)
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// forkIfLoggingOrReaping handles forking off the actual k3s process if it is necessary to
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// capture log output, or reap child processes. Reaping is only necessary when running
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// as pid 1.
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func forkIfLoggingOrReaping() error {
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var stdout, stderr io.Writer = os.Stdout, os.Stderr
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enableLogRedirect := LogConfig.LogFile != "" && os.Getenv("_K3S_LOG_REEXEC_") == ""
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enableReaping := os.Getpid() == 1
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if enableLogRedirect {
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var l io.Writer = &lumberjack.Logger{
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Filename: LogConfig.LogFile,
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MaxSize: 50,
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MaxBackups: 3,
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MaxAge: 28,
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Compress: true,
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}
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if LogConfig.AlsoLogToStderr {
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l = io.MultiWriter(l, os.Stderr)
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}
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stdout = l
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stderr = l
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}
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if enableLogRedirect || enableReaping {
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gspt.SetProcTitle(os.Args[0] + " init")
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pwd, err := os.Getwd()
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if err != nil {
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return errors.Wrap(err, "failed to get working directory")
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}
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if enableReaping {
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// If we're running as pid 1 we need to reap child processes or defunct containerd-shim
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// child processes will accumulate.
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unix.Prctl(unix.PR_SET_CHILD_SUBREAPER, uintptr(1), 0, 0, 0)
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go reapChildren()
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}
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args := append([]string{version.Program}, os.Args[1:]...)
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env := append(os.Environ(), "_K3S_LOG_REEXEC_=true", "NOTIFY_SOCKET=")
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cmd := &exec.Cmd{
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Path: os.Args[0],
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Dir: pwd,
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Args: args,
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Env: env,
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Stdin: os.Stdin,
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Stdout: stdout,
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Stderr: stderr,
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SysProcAttr: &syscall.SysProcAttr{
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Setsid: true,
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},
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}
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if err := cmd.Start(); err != nil {
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return err
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}
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// The child process won't be allowed to notify, so we send one for it as soon as it's started,
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// and then wait for it to exit and pass along the exit code.
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systemd.SdNotify(true, "READY=1\n")
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cmd.Wait()
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os.Exit(cmd.ProcessState.ExitCode())
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}
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return nil
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}
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//reapChildren calls Wait4 whenever SIGCHLD is received
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func reapChildren() {
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sigs := make(chan os.Signal, 1)
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signal.Notify(sigs, syscall.SIGCHLD)
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for {
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select {
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case <-sigs:
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}
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for {
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var wstatus syscall.WaitStatus
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_, err := syscall.Wait4(-1, &wstatus, 0, nil)
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for err == syscall.EINTR {
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_, err = syscall.Wait4(-1, &wstatus, 0, nil)
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}
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if err == nil || err == syscall.ECHILD {
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break
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}
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}
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}
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}
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