Add basic logging to file support

This currently logs to a json file with the stream type.  This is slow
and hard on the cpu and memory so we need to swich this over to
something like protobufs for the binary logs but this is just a start.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

linux/linux.go

@@ -5,7 +5,6 @@ package linux
 import (
 	"encoding/json"
 	"fmt"
-	"io"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -363,25 +362,29 @@ func (r *libcontainerRuntime) Type() string {
 	return "libcontainer"
 }
 
-func (r *libcontainerRuntime) Create(id, bundlePath string, stdio *runtime.Stdio) (runtime.Container, error) {
+func (r *libcontainerRuntime) Create(id, bundlePath string) (runtime.Container, *runtime.IO, error) {
 	spec, rspec, err := r.loadSpec(
 		filepath.Join(bundlePath, "config.json"),
 		filepath.Join(bundlePath, "runtime.json"),
 	)
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	config, err := r.createLibcontainerConfig(id, bundlePath, spec, rspec)
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	container, err := r.factory.Create(id, config)
 	if err != nil {
-		return nil, fmt.Errorf("create container: %v", err)
+		return nil, nil, fmt.Errorf("create container: %v", err)
 	}
-	process, err := r.newProcess(spec.Process, stdio)
+	process, err := r.newProcess(spec.Process)
 	if err != nil {
-		return nil, err
+		return nil, nil, err
+	}
+	i, err := process.InitializeIO(int(spec.Process.User.UID))
+	if err != nil {
+		return nil, nil, err
 	}
 	c := &libcontainerContainer{
 		c:                   container,
@@ -392,20 +395,28 @@ func (r *libcontainerRuntime) Create(id, bundlePath string, stdio *runtime.Stdio
 		},
 		path: bundlePath,
 	}
-	return c, nil
+	return c, &runtime.IO{
+		Stdin:  i.Stdin,
+		Stdout: i.Stdout,
+		Stderr: i.Stderr,
+	}, nil
 }
 
-func (r *libcontainerRuntime) StartProcess(ci runtime.Container, p specs.Process, stdio *runtime.Stdio) (runtime.Process, error) {
+func (r *libcontainerRuntime) StartProcess(ci runtime.Container, p specs.Process) (runtime.Process, *runtime.IO, error) {
 	c, ok := ci.(*libcontainerContainer)
 	if !ok {
-		return nil, runtime.ErrInvalidContainerType
+		return nil, nil, runtime.ErrInvalidContainerType
 	}
-	process, err := r.newProcess(p, stdio)
+	process, err := r.newProcess(p)
 	if err != nil {
-		return nil, err
+		return nil, nil, err
+	}
+	i, err := process.InitializeIO(int(p.User.UID))
+	if err != nil {
+		return nil, nil, err
 	}
 	if err := c.c.Start(process); err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	lp := &libcontainerProcess{
 		process: process,
@@ -413,42 +424,29 @@ func (r *libcontainerRuntime) StartProcess(ci runtime.Container, p specs.Process
 	}
 	pid, err := process.Pid()
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	c.additionalProcesses[pid] = lp
-	return lp, nil
+	return lp, &runtime.IO{
+		Stdin:  i.Stdin,
+		Stdout: i.Stdout,
+		Stderr: i.Stderr,
+	}, nil
 }
 
 // newProcess returns a new libcontainer Process with the arguments from the
 // spec and stdio from the current process.
-func (r *libcontainerRuntime) newProcess(p specs.Process, stdio *runtime.Stdio) (*libcontainer.Process, error) {
-	var (
-		stderr, stdout io.Writer
-	)
-	if stdio != nil {
-		if stdio.Stdout != "" {
-			f, err := os.OpenFile(stdio.Stdout, os.O_CREATE|os.O_WRONLY, 0755)
-			if err != nil {
-				return nil, fmt.Errorf("open stdout: %v", err)
-			}
-			stdout = f
-		}
-		if stdio.Stderr != "" {
-			f, err := os.OpenFile(stdio.Stderr, os.O_CREATE|os.O_WRONLY, 0755)
-			if err != nil {
-				return nil, fmt.Errorf("open stderr: %v", err)
-			}
-			stderr = f
-		}
+func (r *libcontainerRuntime) newProcess(p specs.Process) (*libcontainer.Process, error) {
+	// TODO: support terminals
+	if p.Terminal {
+		return nil, runtime.ErrTerminalsNotSupported
 	}
 	return &libcontainer.Process{
 		Args: p.Args,
 		Env:  p.Env,
 		// TODO: fix libcontainer's API to better support uid/gid in a typesafe way.
-		User:   fmt.Sprintf("%d:%d", p.User.UID, p.User.GID),
-		Cwd:    p.Cwd,
-		Stderr: stderr,
-		Stdout: stdout,
+		User: fmt.Sprintf("%d:%d", p.User.UID, p.User.GID),
+		Cwd:  p.Cwd,
 	}, nil
 }