Add event support to execution subsystem

The implementation relies on nats.io

Signed-off-by: Kenfe-Mickael Laventure <mickael.laventure@gmail.com>

execution/executors/oci/io.go

@@ -0,0 +1,61 @@
+package oci
+
+import (
+	"io"
+	"os"
+
+	"github.com/crosbymichael/go-runc"
+)
+
+type OIO struct {
+	master  *os.File // master holds a fd to the created pty if any
+	console string   // console holds the path the the slave linked to master
+	rio     runc.IO  // rio holds the open fifos for stdios
+}
+
+func newOIO(stdin, stdout, stderr string, console bool) (o OIO, err error) {
+	defer func() {
+		if err != nil {
+			o.cleanup()
+		}
+	}()
+
+	if o.rio.Stdin, err = os.OpenFile(stdin, os.O_RDONLY, 0); err != nil {
+		return
+	}
+	if o.rio.Stdout, err = os.OpenFile(stdout, os.O_WRONLY, 0); err != nil {
+		return
+	}
+	if o.rio.Stderr, err = os.OpenFile(stderr, os.O_WRONLY, 0); err != nil {
+		return
+	}
+
+	if console {
+		o.master, o.console, err = newConsole(0, 0)
+		if err != nil {
+			return
+		}
+		go io.Copy(o.master, o.rio.Stdin)
+		go func() {
+			io.Copy(o.rio.Stdout, o.master)
+			o.master.Close()
+		}()
+	}
+
+	return
+}
+
+func (o OIO) cleanup() {
+	if o.master != nil {
+		o.master.Close()
+	}
+	if o.rio.Stdin != nil {
+		o.rio.Stdin.(*os.File).Close()
+	}
+	if o.rio.Stdout != nil {
+		o.rio.Stdout.(*os.File).Close()
+	}
+	if o.rio.Stderr != nil {
+		o.rio.Stderr.(*os.File).Close()
+	}
+}