dashboard/buildlet: add Makefiles, and add Windows stage0 bootstrap binary

Change-Id: I69938af38fb5c45c01598e9171e851a1c29790bc
Reviewed-on: https://go-review.googlesource.com/2268
Reviewed-by: Andrew Gerrand <adg@golang.org>

dashboard/buildlet/.gitignore

@@ -0,0 +1,3 @@
+buildlet
+buildlet.*-*
+stage0/buildlet-stage0.*

dashboard/buildlet/Makefile

@@ -0,0 +1,14 @@
+buildlet: buildlet.go
+	go build --tags=buildlet
+
+buildlet.openbsd-amd64: buildlet.go
+	GOOS=openbsd GOARCH=amd64 go build -o $@ --tags=buildlet
+	cat $@ | (cd ../coordinator/buildongce && go run create.go --write_object=go-builder-data/$@)
+
+buildlet.plan9-386: buildlet.go
+	GOOS=plan9 GOARCH=386 go build -o $@ --tags=buildlet
+	cat $@ | (cd ../coordinator/buildongce && go run create.go --write_object=go-builder-data/$@)
+
+buildlet.windows-amd64: buildlet.go
+	GOOS=windows GOARCH=amd64 go build -o $@ --tags=buildlet
+	cat $@ | (cd ../coordinator/buildongce && go run create.go --write_object=go-builder-data/$@)

dashboard/buildlet/buildlet.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build buildlet
+
 // The buildlet is an HTTP server that untars content to disk and runs
 // commands it has untarred, streaming their output back over HTTP.
 // It is part of Go's continuous build system.
@@ -29,7 +31,6 @@ import (
 	"io"
 	"io/ioutil"
 	"log"
-	"net"
 	"net/http"
 	"os"
 	"os/exec"
@@ -37,7 +38,8 @@ import (
 	"runtime"
 	"strings"
 	"sync"
-	"time"
+
+	"google.golang.org/cloud/compute/metadata"
 )
 
 var (
@@ -46,7 +48,7 @@ var (
 )
 
 func defaultListenAddr() string {
-	if OnGCE() {
+	if metadata.OnGCE() {
 		// In production, default to
 		return ":80"
 	}
@@ -55,7 +57,7 @@ func defaultListenAddr() string {
 
 func main() {
 	flag.Parse()
-	if !OnGCE() && !strings.HasPrefix(*listenAddr, "localhost:") {
+	if !metadata.OnGCE() && !strings.HasPrefix(*listenAddr, "localhost:") {
 		log.Printf("** WARNING ***  This server is unsafe and offers no security. Be careful.")
 	}
 	if *scratchDir == "" {
@@ -239,37 +241,3 @@ func (he httpError) httpStatus() int { return he.statusCode }
 func badRequest(msg string) error {
 	return httpError{http.StatusBadRequest, msg}
 }
-
-// metaClient to fetch GCE metadata values.
-var metaClient = &http.Client{
-	Transport: &http.Transport{
-		Dial: (&net.Dialer{
-			Timeout:   750 * time.Millisecond,
-			KeepAlive: 30 * time.Second,
-		}).Dial,
-		ResponseHeaderTimeout: 750 * time.Millisecond,
-	},
-}
-
-var onGCE struct {
-	sync.Mutex
-	set bool
-	v   bool
-}
-
-// OnGCE reports whether this process is running on Google Compute Engine.
-func OnGCE() bool {
-	defer onGCE.Unlock()
-	onGCE.Lock()
-	if onGCE.set {
-		return onGCE.v
-	}
-	onGCE.set = true
-
-	res, err := metaClient.Get("http://metadata.google.internal")
-	if err != nil {
-		return false
-	}
-	onGCE.v = res.Header.Get("Metadata-Flavor") == "Google"
-	return onGCE.v
-}

dashboard/buildlet/stage0/Makefile

@@ -0,0 +1,3 @@
+buildlet-stage0.windows-amd64: stage0.go
+	GOOS=windows GOARCH=amd64 go build -o $@ --tags=stage0
+	cat $@ | (cd ../../coordinator/buildongce && go run create.go --write_object=go-builder-data/$@)

dashboard/buildlet/stage0/stage0.go

@@ -0,0 +1,78 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build stage0
+
+// The stage0 command looks up the buildlet's URL from the GCE metadata
+// service, downloads it, and runs it. It's used primarily by Windows,
+// since it can be written in a couple lines of shell elsewhere.
+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"time"
+
+	"google.golang.org/cloud/compute/metadata"
+)
+
+const attr = "buildlet-binary-url"
+
+func main() {
+	buildletURL, err := metadata.InstanceAttributeValue(attr)
+	if err != nil {
+		sleepFatalf("Failed to look up %q attribute value: %v", attr, err)
+	}
+	target := filepath.FromSlash("./buildlet.exe")
+	if err := download(target, buildletURL); err != nil {
+		sleepFatalf("Downloading %s: %v", buildletURL, err)
+	}
+	cmd := exec.Command(target)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	if err := cmd.Run(); err != nil {
+		sleepFatalf("Error running buildlet: %v", err)
+	}
+}
+
+func sleepFatalf(format string, args ...interface{}) {
+	log.Printf(format, args...)
+	time.Sleep(time.Minute) // so user has time to see it in cmd.exe, maybe
+	os.Exit(1)
+}
+
+func download(file, url string) error {
+	log.Printf("Downloading %s to %s ...\n", url, file)
+	res, err := http.Get(url)
+	if err != nil {
+		return fmt.Errorf("Error fetching %v: %v", url, err)
+	}
+	if res.StatusCode != 200 {
+		return fmt.Errorf("HTTP status code of %s was %v", url, res.Status)
+	}
+	tmp := file + ".tmp"
+	os.Remove(tmp)
+	os.Remove(file)
+	f, err := os.Create(tmp)
+	if err != nil {
+		return err
+	}
+	n, err := io.Copy(f, res.Body)
+	res.Body.Close()
+	if err != nil {
+		return fmt.Errorf("Error reading %v: %v", url, err)
+	}
+	f.Close()
+	err = os.Rename(tmp, file)
+	if err != nil {
+		return err
+	}
+	log.Printf("Downloaded %s (%d bytes)", file, n)
+	return nil
+}