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From cd7d76a6d1ecb1856f6ed666fb5c30dc105aa94e Mon Sep 17 00:00:00 2001
From: Jason Wessel <jason.wessel@windriver.com>
Date: Tue, 5 Dec 2017 18:28:28 -0800
Subject: [PATCH] runc-docker: Allow "run start ..." to daemonize with $SIGUSR1_PARENT_PID
The runc-docker has all the code in it to properly run a stop hook if
you use it in the foreground. It doesn't work in the back ground
because there is no way for a golang application to fork a child exit
out of the parent process because all the golang threads stay with the
parent.
This patch has three parts that happen ONLY when $SIGUSR1_PARENT_PID
is set.
1) The code was copied which performs the normal the signal handling
block which is used for the foreground operation of runc.
2) At the point where runc start would normally exit, it closes
stdin/stdout/stderr so it would be possible to daemonize "runc start ...".
3) The code to send a SIGUSR1 to the parent process was added. The
idea being that a parent process would simply exit at that point
because it was blocking until runc performed everything it was
required to perform.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
---
signals.go | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++----
utils_linux.go | 2 +-
2 files changed, 51 insertions(+), 5 deletions(-)
Index: git/src/import/signals.go
===================================================================
--- git.orig/src/import/signals.go
+++ git/src/import/signals.go
@@ -6,6 +6,7 @@
"os"
"os/signal"
"syscall" // only for Signal
+ "strconv"
"github.com/opencontainers/runc/libcontainer"
"github.com/opencontainers/runc/libcontainer/system"
@@ -56,9 +57,6 @@
func (h *signalHandler) forward(process *libcontainer.Process, tty *tty, detach bool) (int, error) {
// make sure we know the pid of our main process so that we can return
// after it dies.
- if detach && h.notifySocket == nil {
- return 0, nil
- }
pid1, err := process.Pid()
if err != nil {
@@ -68,12 +66,61 @@
if h.notifySocket != nil {
if detach {
h.notifySocket.run(pid1)
- return 0, nil
} else {
go h.notifySocket.run(0)
}
}
+ if (detach) {
+ // This allows the parent process to daemonize this process
+ // so long as stdin/stderr/stdout are closed
+ if envVal := os.Getenv("SIGUSR1_PARENT_PID"); envVal != "" {
+ // Close stdin/stdout/stderr
+ os.Stdin.Close()
+ os.Stdout.Close()
+ os.Stderr.Close()
+ // Notify parent to detach
+ i, err := strconv.Atoi(envVal)
+ if (err != nil) {
+ return 0, nil
+ }
+ unix.Kill(i, unix.SIGUSR1)
+ // Loop waiting on the child to signal or exit,
+ // after which all stop hooks will be run
+ for s := range h.signals {
+ switch s {
+ case unix.SIGCHLD:
+ exits, err := h.reap()
+ if err != nil {
+ logrus.Error(err)
+ }
+ for _, e := range exits {
+ logrus.WithFields(logrus.Fields{
+ "pid": e.pid,
+ "status": e.status,
+ }).Debug("process exited")
+ if e.pid == pid1 {
+ // call Wait() on the process even though we already have the exit
+ // status because we must ensure that any of the go specific process
+ // fun such as flushing pipes are complete before we return.
+ process.Wait()
+ if h.notifySocket != nil {
+ h.notifySocket.Close()
+ }
+ return e.status, nil
+ }
+ }
+ default:
+ logrus.Debugf("sending signal to process %s", s)
+ if err := unix.Kill(pid1, s.(syscall.Signal)); err != nil {
+ logrus.Error(err)
+ }
+ }
+ }
+ }
+ return 0, nil
+ }
+
// Perform the initial tty resize. Always ignore errors resizing because
// stdout might have disappeared (due to races with when SIGHUP is sent).
_ = tty.resize()
Index: git/src/import/utils_linux.go
===================================================================
--- git.orig/src/import/utils_linux.go
+++ git/src/import/utils_linux.go
@@ -338,7 +338,7 @@
if err != nil {
r.terminate(process)
}
- if detach {
+ if (detach && os.Getenv("SIGUSR1_PARENT_PID") == "") {
return 0, nil
}
r.destroy()
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