beam/examples/beamsh: basic execution of commands, with in-process beam and dummy handlers

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)

beam/examples/beamsh/beamsh.go

@@ -1,19 +1,127 @@
 package main
 
 import (
+	"io"
 	"fmt"
 	"os"
 	"github.com/dotcloud/docker/pkg/dockerscript"
+	"github.com/dotcloud/docker/pkg/beam"
+	"strings"
+	"sync"
+	"net"
+	"bytes"
+	"path"
 )
 
 func main() {
 	script, err := dockerscript.Parse(os.Stdin)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "parse error: %v\n", err)
+		Fatal("parse error: %v\n", err)
-		os.Exit(1)
 	}
-	fmt.Printf("%d commands:\n", len(script))
+	Logf("%d commands:\n", len(script))
-	for i, cmd := range script {
+	client, engine, err := beam.USocketPair()
-		fmt.Printf("%%%d: %s\n", i, cmd)
+	if err != nil {
+		Fatal(err)
+	}
+	go func() {
+		Serve(engine)
+		engine.Close()
+	}()
+	for _, cmd := range script {
+		job, err := beam.SendPipe(client, []byte(strings.Join(cmd.Args, " ")))
+		if err != nil {
+			Fatal(err)
+		}
+		// Synchronize on the job handler
+		for {
+			_, _, err := beam.Receive(job)
+			if err == io.EOF {
+				break
+			} else if err != nil {
+				Fatalf("error reading from job handler: %#v\n", err)
+			}
+		}
+		Logf("[%s] done\n", strings.Join(cmd.Args, " "))
+	}
+	client.Close()
+}
+
+func CmdCat(args []string, f *os.File) {
+	for _, name := range args[1:] {
+		f, err := os.Open(name)
+		if err != nil {
+			continue
+		}
+		io.Copy(os.Stdout, f)
+		f.Close()
 	}
 }
+
+func CmdEcho(args []string, f *os.File) {
+	fmt.Println(strings.Join(args[1:], " "))
+}
+
+func CmdDie(args []string, f *os.File) {
+	Fatal(strings.Join(args[1:], " "))
+}
+
+func Serve(endpoint *net.UnixConn) error {
+	var tasks sync.WaitGroup
+	defer tasks.Wait()
+	for {
+		payload, attachment, err := beam.Receive(endpoint)
+		if err != nil {
+			return err
+		}
+		tasks.Add(1)
+		go func(payload []byte, attachment *os.File) {
+			defer tasks.Done()
+			defer func() {
+				if attachment != nil {
+					attachment.Close()
+				}
+			}()
+			// FIXME: send structured message instead of a text script
+			cmds, err := dockerscript.Parse(bytes.NewReader(payload))
+			if err != nil {
+				Logf("error parsing beam message: %s\n", err)
+				if attachment != nil {
+					attachment.Close()
+				}
+				return
+			}
+			if len(cmds) == 0 {
+				Logf("ignoring empty command\n", err)
+			}
+			// We don't care about multiple commands or children
+			args := cmds[0].Args
+			Logf("beam message: %v\n", args)
+			if args[0] == "die" {
+				CmdDie(args, attachment)
+			} else if args[0] == "cat" {
+				CmdCat(args, attachment)
+			} else if args[0] == "echo" {
+				CmdEcho(args, attachment)
+			}
+		}(payload, attachment)
+	}
+	return nil
+}
+
+
+func Logf(msg string, args ...interface{}) (int, error) {
+	if len(msg) == 0 || msg[len(msg) - 1] != '\n' {
+		msg = msg + "\n"
+	}
+	msg = fmt.Sprintf("[%v] [%v] %s", os.Getpid(), path.Base(os.Args[0]), msg)
+	return fmt.Printf(msg, args...)
+}
+
+func Fatalf(msg string, args ...interface{})  {
+	Logf(msg, args)
+	os.Exit(1)
+}
+
+func Fatal(args ...interface{}) {
+	Fatalf("%v", args[0])
+}