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k3s/pkg/cli/cmds/log_linux.go

106 lines
2.5 KiB

//go:build linux && cgo
// +build linux,cgo
package cmds
import (
"io"
"os"
"os/exec"
"os/signal"
"syscall"
systemd "github.com/coreos/go-systemd/v22/daemon"
"github.com/erikdubbelboer/gspt"
"github.com/k3s-io/k3s/pkg/version"
"github.com/natefinch/lumberjack"
"github.com/pkg/errors"
"golang.org/x/sys/unix"
)
// forkIfLoggingOrReaping handles forking off the actual k3s process if it is necessary to
// capture log output, or reap child processes. Reaping is only necessary when running
// as pid 1.
func forkIfLoggingOrReaping() error {
var stdout, stderr io.Writer = os.Stdout, os.Stderr
enableLogRedirect := LogConfig.LogFile != "" && os.Getenv("_K3S_LOG_REEXEC_") == ""
enableReaping := os.Getpid() == 1
if enableLogRedirect {
var l io.Writer = &lumberjack.Logger{
Filename: LogConfig.LogFile,
MaxSize: 50,
MaxBackups: 3,
MaxAge: 28,
Compress: true,
}
if LogConfig.AlsoLogToStderr {
l = io.MultiWriter(l, os.Stderr)
}
stdout = l
stderr = l
}
if enableLogRedirect || enableReaping {
gspt.SetProcTitle(os.Args[0] + " init")
pwd, err := os.Getwd()
if err != nil {
return errors.Wrap(err, "failed to get working directory")
}
if enableReaping {
// If we're running as pid 1 we need to reap child processes or defunct containerd-shim
// child processes will accumulate.
unix.Prctl(unix.PR_SET_CHILD_SUBREAPER, uintptr(1), 0, 0, 0)
go reapChildren()
}
args := append([]string{version.Program}, os.Args[1:]...)
env := append(os.Environ(), "_K3S_LOG_REEXEC_=true", "NOTIFY_SOCKET=")
cmd := &exec.Cmd{
Path: "/proc/self/exe",
Dir: pwd,
Args: args,
Env: env,
Stdin: os.Stdin,
Stdout: stdout,
Stderr: stderr,
SysProcAttr: &syscall.SysProcAttr{
Pdeathsig: unix.SIGTERM,
},
}
if err := cmd.Start(); err != nil {
return err
}
// The child process won't be allowed to notify, so we send one for it as soon as it's started,
// and then wait for it to exit and pass along the exit code.
systemd.SdNotify(true, "READY=1\n")
cmd.Wait()
os.Exit(cmd.ProcessState.ExitCode())
}
return nil
}
// reapChildren calls Wait4 whenever SIGCHLD is received
func reapChildren() {
sigs := make(chan os.Signal, 1)
signal.Notify(sigs, syscall.SIGCHLD)
for {
select {
case <-sigs:
}
for {
var wstatus syscall.WaitStatus
_, err := syscall.Wait4(-1, &wstatus, 0, nil)
for err == syscall.EINTR {
_, err = syscall.Wait4(-1, &wstatus, 0, nil)
}
if err == nil || err == syscall.ECHILD {
break
}
}
}
}