140 lines
3.3 KiB
Go
140 lines
3.3 KiB
Go
package main
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import (
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"flag"
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"fmt"
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"os"
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"os/signal"
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"path/filepath"
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"syscall"
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"github.com/docker/containerd/osutils"
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"github.com/docker/docker/pkg/term"
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)
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func writeMessage(f *os.File, level string, err error) {
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fmt.Fprintf(f, `{"level": "%s","msg": "%s"}`, level, err)
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}
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// containerd-shim is a small shim that sits in front of a runtime implementation
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// that allows it to be repartented to init and handle reattach from the caller.
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//
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// the cwd of the shim should be the bundle for the container. Arg1 should be the path
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// to the state directory where the shim can locate fifos and other information.
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func main() {
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flag.Parse()
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cwd, err := os.Getwd()
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if err != nil {
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panic(err)
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}
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f, err := os.OpenFile(filepath.Join(cwd, "shim-log.json"), os.O_CREATE|os.O_WRONLY|os.O_APPEND|os.O_SYNC, 0666)
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if err != nil {
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panic(err)
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}
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if err := start(f); err != nil {
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// this means that the runtime failed starting the container and will have the
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// proper error messages in the runtime log so we should to treat this as a
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// shim failure because the sim executed properly
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if err == errRuntime {
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f.Close()
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return
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}
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// log the error instead of writing to stderr because the shim will have
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// /dev/null as it's stdio because it is supposed to be reparented to system
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// init and will not have anyone to read from it
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writeMessage(f, "error", err)
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f.Close()
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os.Exit(1)
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}
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}
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func start(log *os.File) error {
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// start handling signals as soon as possible so that things are properly reaped
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// or if runtime exits before we hit the handler
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signals := make(chan os.Signal, 2048)
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signal.Notify(signals)
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// set the shim as the subreaper for all orphaned processes created by the container
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if err := osutils.SetSubreaper(1); err != nil {
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return err
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}
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// open the exit pipe
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f, err := os.OpenFile("exit", syscall.O_WRONLY, 0)
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if err != nil {
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return err
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}
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defer f.Close()
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control, err := os.OpenFile("control", syscall.O_RDWR, 0)
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if err != nil {
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return err
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}
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defer control.Close()
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p, err := newProcess(flag.Arg(0), flag.Arg(1), flag.Arg(2))
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if err != nil {
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return err
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}
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defer func() {
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if err := p.Close(); err != nil {
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writeMessage(log, "warn", err)
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}
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}()
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if err := p.start(); err != nil {
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p.delete()
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return err
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}
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go func() {
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for {
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var msg, w, h int
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if _, err := fmt.Fscanf(control, "%d %d %d\n", &msg, &w, &h); err != nil {
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continue
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}
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switch msg {
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case 0:
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// close stdin
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if p.stdinCloser != nil {
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p.stdinCloser.Close()
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}
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case 1:
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if p.console == nil {
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continue
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}
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ws := term.Winsize{
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Width: uint16(w),
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Height: uint16(h),
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}
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term.SetWinsize(p.console.Fd(), &ws)
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}
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}
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}()
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var exitShim bool
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for s := range signals {
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switch s {
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case syscall.SIGCHLD:
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exits, _ := osutils.Reap()
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for _, e := range exits {
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// check to see if runtime is one of the processes that has exited
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if e.Pid == p.pid() {
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exitShim = true
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writeInt("exitStatus", e.Status)
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}
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}
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}
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// runtime has exited so the shim can also exit
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if exitShim {
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p.delete()
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p.Wait()
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return nil
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}
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}
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return nil
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}
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func writeInt(path string, i int) error {
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f, err := os.Create(path)
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if err != nil {
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return err
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}
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defer f.Close()
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_, err = fmt.Fprintf(f, "%d", i)
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return err
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}
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