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init.go
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init.go
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// Copyright 2016 IBM Corporation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package supervisor
import (
"os"
"os/exec"
"os/signal"
"syscall"
"github.com/Sirupsen/logrus"
)
// Init launches new sidecar process with same args and env vars as current process
// and runs zombie process cleanup for any inherited orphans
func Init() {
cmd := exec.Command(os.Args[0], os.Args[1:]...)
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
if err := cmd.Start(); err != nil {
logrus.Errorf("Sidecar failed to start: %v", err)
os.Exit(1)
}
handleSignals(cmd.Process)
}
func handleSignals(proc *os.Process) {
// Trap all signals
sigChan := make(chan os.Signal, 1)
signal.Notify(sigChan)
for sig := range sigChan {
switch sig {
case syscall.SIGCHLD:
reapZombies(proc)
default:
forwardSignal(proc, sig)
}
}
}
// reapZombies cleans up any zombies sidecar may have inherited from terminated children
// - on SIGCHLD send wait4() (ref http://linux.die.net/man/2/waitpid)
func reapZombies(proc *os.Process) {
for {
var waitStatus syscall.WaitStatus
pid, err := syscall.Wait4(-1, &waitStatus, syscall.WNOHANG, nil)
if proc != nil && proc.Pid == pid {
logrus.Debugf("Sidecar exited with exit code %v", waitStatus.ExitStatus())
os.Exit(waitStatus.ExitStatus())
}
// Spurious wakeup
if err == syscall.EINTR {
continue
}
logrus.Debug("Zombie reaped")
// Done
break
}
}
func forwardSignal(proc *os.Process, sig os.Signal) {
if proc != nil {
proc.Signal(sig)
}
}