cmd/locktrigger/main.go - website - Git at Google

 // Copyright 2021 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.

 // Locktrigger “locks” a given build trigger, making sure that
 // the currently running build is the only trigger running.
 //
 // Usage:
 //
 //	locktrigger -project=$PROJECT_ID -build=$BUILD_ID
 //
 // The $PROJECT_ID and $BUILD_ID are typically written literally in cloudbuild.yaml
 // and then substituted by Cloud Build.
 //
 // When a project uses “continuous deployment powered by Cloud Build”,
 // the deployment is a little bit too continuous: when multiple commits
 // land in a short time window, Cloud Build will run all the triggered
 // build jobs in parallel. If each job does “gcloud app deploy”, there
 // is no guarantee which will win: perhaps an older commit will complete
 // last, resulting in the newest commit not actually being the final
 // deployed version of the site. This should probably be fixed in
 // “continuous deployment powered by Cloud Build”, but until then,
 // locktrigger works around the problem.
 //
 // All triggered builds must run locktrigger to guarantee mutual exclusion.
 // When there is contention—that is, when multiple builds are running and
 // they all run locktrigger—the build corresponding to the newest commit
 // is permitted to continue running, and older builds are canceled.
 //
 // When locktrigger exits successfully, then, at that moment, the current
 // build is (or recently was) the only running build for its trigger.
 // Of course, another build may start immediately after locktrigger exits.
 // As long as that build also runs locktrigger, then either it will cancel
 // itself (if it is older than we are), or it will cancel us before proceeding
 // (if we are older than it is).
 package main

 import (
 	"bytes"
 	"context"
 	"flag"
 	"fmt"
 	"log"
 	"os"
 	"os/exec"
 	"strings"
 	"time"

 	cloudbuild "cloud.google.com/go/cloudbuild/apiv1/v2"
 	"cloud.google.com/go/cloudbuild/apiv1/v2/cloudbuildpb"
 	"google.golang.org/api/iterator"
 )

 var (
 	project = flag.String("project", "", "GCP project `name` (required)")
 	build   = flag.String("build", "", "GCP build `id` (required)")
 	repo    = flag.String("repo", "", "`URL` of repository (required)")
 )

 func usage() {
 	fmt.Fprintf(os.Stderr, "usage: locktrigger -project=name -build=id -repo=URL\n")
 	os.Exit(2)
 }

 func main() {
 	flag.Usage = usage
 	flag.Parse()
 	log.SetPrefix("locktrigger: ")
 	log.SetFlags(0)

 	if *project == "" || *build == "" || *repo == "" {
 		usage()
 	}

 	ctx := context.Background()
 	c, err := cloudbuild.NewClient(ctx)
 	if err != nil {
 		log.Fatal(err)
 	}
 	defer c.Close()

 	// Find commit hash of local Git
 	myHash := run("git", "rev-parse", "HEAD")
 	log.Printf("my hash: %v", myHash)

 	// Find build object for current build, check that it matches.
 	self := getBuild(c, ctx, *build)
 	if hash := self.Substitutions["COMMIT_SHA"]; hash != myHash {
 		log.Fatalf("build COMMIT_SHA does not match local hash: %v != %v", hash, myHash)
 	}
 	log.Printf("my build: %v", self.Id)
 	if self.BuildTriggerId == "" {
 		log.Fatalf("build has no trigger ID")
 	}
 	log.Printf("my trigger: %v", self.BuildTriggerId)

 	// List all builds for our trigger that are still running.
 	req := &cloudbuildpb.ListBuildsRequest{
 		ProjectId: *project,
 		// Note: Really want "status=WORKING buildTriggerId="+self.BuildTriggerId,
 		// but that fails with an InvalidArgument error for unknown reasons.
 		// status=WORKING will narrow the list down to something reasonable,
 		// and we filter the unrelated triggers below.
 		Filter: "status=WORKING",
 	}
 	it := c.ListBuilds(ctx, req)
 	foundSelf := false
 	shallow := false
 	if _, err := os.Stat(run("git", "rev-parse", "--git-dir") + "/shallow"); err == nil {
 		shallow = true
 	}
 	for {
 		b, err := it.Next()
 		if err == iterator.Done {
 			break
 		}
 		if err != nil {
 			log.Fatalf("reading builds: %v (%q)", err, req.Filter)
 		}
 		if b.BuildTriggerId != self.BuildTriggerId {
 			continue
 		}

 		// Check whether this build is an older or newer commit.
 		// If this build is older, cancel it.
 		// If this build is newer, cancel ourselves.
 		if b.Id == self.Id {
 			foundSelf = true
 			continue
 		}
 		hash := b.Substitutions["COMMIT_SHA"]
 		if hash == "" {
 			log.Fatalf("cannot find COMMIT_SHA for build %v", b.Id)
 		}
 		if hash == myHash {
 			log.Fatalf("found another build %v at same commit %v", b.Id, hash)
 		}

 		// Fetch the full Git repo so we can answer the history questions.
 		// This is delayed until now to avoid the expense of fetching the full repo
 		// if we are the only build that is running.
 		if shallow {
 			log.Printf("git fetch --unshallow")
 			run("git", "fetch", "--unshallow", *repo)
 			shallow = false
 		}

 		// Contention.
 		// Find the common ancestor between us and that build,
 		// to tell whether we're older, it's older, or we're unrelated.
 		log.Printf("checking %v", hash)
 		switch run("git", "merge-base", myHash, hash) {
 		default:
 			log.Fatalf("unexpected build for unrelated commit %v", hash)

 		case myHash:
 			// myHash is older than b's hash. Cancel self.
 			log.Printf("canceling self, for build %v commit %v", b.Id, hash)
 			cancel(c, ctx, self.Id)

 		case hash:
 			// b's hash is older than myHash. Cancel b.
 			log.Printf("canceling build %v commit %v", b.Id, hash)
 			cancel(c, ctx, b.Id)
 		}
 	}

 	// If we listed all the in-progress builds, we should have seen ourselves.
 	if !foundSelf {
 		log.Fatalf("reading builds: didn't find self")
 	}
 }

 // getBuild returns the build info for the build with the given id.
 func getBuild(c *cloudbuild.Client, ctx context.Context, id string) *cloudbuildpb.Build {
 	req := &cloudbuildpb.GetBuildRequest{
 		ProjectId: *project,
 		Id:        id,
 	}
 	b, err := c.GetBuild(ctx, req)
 	if err != nil {
 		log.Fatalf("getbuild %v: %v", id, err)
 	}
 	return b
 }

 // cancel cancels the build with the given id.
 func cancel(c *cloudbuild.Client, ctx context.Context, id string) {
 	req := &cloudbuildpb.CancelBuildRequest{
 		ProjectId: *project,
 		Id:        id,
 	}
 	_, err := c.CancelBuild(ctx, req)
 	if err != nil {
 		// Not Fatal: maybe cancel failed because the build exited.
 		// Waiting for it to stop running below will take care of that case.
 		log.Printf("cancel %v: %v", id, err)
 	}

 	// Wait for build to report being stopped,
 	// in case cancel only queues the cancellation and doesn't actually wait,
 	// or in case cancel failed.
 	// Willing to wait a few minutes.
 	now := time.Now()
 	for time.Since(now) < 3*time.Minute {
 		b := getBuild(c, ctx, id)
 		if b.Status != cloudbuildpb.Build_WORKING {
 			log.Printf("canceled %v: now %v", id, b.Status)
 			return
 		}
 		time.Sleep(10 * time.Second)
 	}
 	log.Fatalf("cancel %v: did not stop", id)
 }

 // run runs the given command line and returns the standard output, with spaces trimmed.
 func run(args ...string) string {
 	var stdout, stderr bytes.Buffer
 	cmd := exec.Command(args[0], args[1:]...)
 	cmd.Stdout = &stdout
 	cmd.Stderr = &stderr
 	if err := cmd.Run(); err != nil {
 		log.Fatalf("exec %v: %v\n%s%s", args, err, stdout.String(), stderr.String())
 	}
 	return strings.TrimSpace(stdout.String())
 }
	// Copyright 2021 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.

	// Locktrigger “locks” a given build trigger, making sure that
	// the currently running build is the only trigger running.
	//
	// Usage:
	//
	// locktrigger -project=$PROJECT_ID -build=$BUILD_ID
	//
	// The $PROJECT_ID and $BUILD_ID are typically written literally in cloudbuild.yaml
	// and then substituted by Cloud Build.
	//
	// When a project uses “continuous deployment powered by Cloud Build”,
	// the deployment is a little bit too continuous: when multiple commits
	// land in a short time window, Cloud Build will run all the triggered
	// build jobs in parallel. If each job does “gcloud app deploy”, there
	// is no guarantee which will win: perhaps an older commit will complete
	// last, resulting in the newest commit not actually being the final
	// deployed version of the site. This should probably be fixed in
	// “continuous deployment powered by Cloud Build”, but until then,
	// locktrigger works around the problem.
	//
	// All triggered builds must run locktrigger to guarantee mutual exclusion.
	// When there is contention—that is, when multiple builds are running and
	// they all run locktrigger—the build corresponding to the newest commit
	// is permitted to continue running, and older builds are canceled.
	//
	// When locktrigger exits successfully, then, at that moment, the current
	// build is (or recently was) the only running build for its trigger.
	// Of course, another build may start immediately after locktrigger exits.
	// As long as that build also runs locktrigger, then either it will cancel
	// itself (if it is older than we are), or it will cancel us before proceeding
	// (if we are older than it is).
	package main

	import (
	"bytes"
	"context"
	"flag"
	"fmt"
	"log"
	"os"
	"os/exec"
	"strings"
	"time"

	cloudbuild "cloud.google.com/go/cloudbuild/apiv1/v2"
	"cloud.google.com/go/cloudbuild/apiv1/v2/cloudbuildpb"
	"google.golang.org/api/iterator"
	)

	var (
	project = flag.String("project", "", "GCP project `name` (required)")
	build = flag.String("build", "", "GCP build `id` (required)")
	repo = flag.String("repo", "", "`URL` of repository (required)")
	)

	func usage() {
	fmt.Fprintf(os.Stderr, "usage: locktrigger -project=name -build=id -repo=URL\n")
	os.Exit(2)
	}

	func main() {
	flag.Usage = usage
	flag.Parse()
	log.SetPrefix("locktrigger: ")
	log.SetFlags(0)

	if project == "" \|\| build == "" \|\| *repo == "" {
	usage()
	}

	ctx := context.Background()
	c, err := cloudbuild.NewClient(ctx)
	if err != nil {
	log.Fatal(err)
	}
	defer c.Close()

	// Find commit hash of local Git
	myHash := run("git", "rev-parse", "HEAD")
	log.Printf("my hash: %v", myHash)

	// Find build object for current build, check that it matches.
	self := getBuild(c, ctx, *build)
	if hash := self.Substitutions["COMMIT_SHA"]; hash != myHash {
	log.Fatalf("build COMMIT_SHA does not match local hash: %v != %v", hash, myHash)
	}
	log.Printf("my build: %v", self.Id)
	if self.BuildTriggerId == "" {
	log.Fatalf("build has no trigger ID")
	}
	log.Printf("my trigger: %v", self.BuildTriggerId)

	// List all builds for our trigger that are still running.
	req := &cloudbuildpb.ListBuildsRequest{
	ProjectId: *project,
	// Note: Really want "status=WORKING buildTriggerId="+self.BuildTriggerId,
	// but that fails with an InvalidArgument error for unknown reasons.
	// status=WORKING will narrow the list down to something reasonable,
	// and we filter the unrelated triggers below.
	Filter: "status=WORKING",
	}
	it := c.ListBuilds(ctx, req)
	foundSelf := false
	shallow := false
	if _, err := os.Stat(run("git", "rev-parse", "--git-dir") + "/shallow"); err == nil {
	shallow = true
	}
	for {
	b, err := it.Next()
	if err == iterator.Done {
	break
	}
	if err != nil {
	log.Fatalf("reading builds: %v (%q)", err, req.Filter)
	}
	if b.BuildTriggerId != self.BuildTriggerId {
	continue
	}

	// Check whether this build is an older or newer commit.
	// If this build is older, cancel it.
	// If this build is newer, cancel ourselves.
	if b.Id == self.Id {
	foundSelf = true
	continue
	}
	hash := b.Substitutions["COMMIT_SHA"]
	if hash == "" {
	log.Fatalf("cannot find COMMIT_SHA for build %v", b.Id)
	}
	if hash == myHash {
	log.Fatalf("found another build %v at same commit %v", b.Id, hash)
	}

	// Fetch the full Git repo so we can answer the history questions.
	// This is delayed until now to avoid the expense of fetching the full repo
	// if we are the only build that is running.
	if shallow {
	log.Printf("git fetch --unshallow")
	run("git", "fetch", "--unshallow", *repo)
	shallow = false
	}

	// Contention.
	// Find the common ancestor between us and that build,
	// to tell whether we're older, it's older, or we're unrelated.
	log.Printf("checking %v", hash)
	switch run("git", "merge-base", myHash, hash) {
	default:
	log.Fatalf("unexpected build for unrelated commit %v", hash)

	case myHash:
	// myHash is older than b's hash. Cancel self.
	log.Printf("canceling self, for build %v commit %v", b.Id, hash)
	cancel(c, ctx, self.Id)

	case hash:
	// b's hash is older than myHash. Cancel b.
	log.Printf("canceling build %v commit %v", b.Id, hash)
	cancel(c, ctx, b.Id)
	}
	}

	// If we listed all the in-progress builds, we should have seen ourselves.
	if !foundSelf {
	log.Fatalf("reading builds: didn't find self")
	}
	}

	// getBuild returns the build info for the build with the given id.
	func getBuild(c cloudbuild.Client, ctx context.Context, id string) cloudbuildpb.Build {
	req := &cloudbuildpb.GetBuildRequest{
	ProjectId: *project,
	Id: id,
	}
	b, err := c.GetBuild(ctx, req)
	if err != nil {
	log.Fatalf("getbuild %v: %v", id, err)
	}
	return b
	}

	// cancel cancels the build with the given id.
	func cancel(c *cloudbuild.Client, ctx context.Context, id string) {
	req := &cloudbuildpb.CancelBuildRequest{
	ProjectId: *project,
	Id: id,
	}
	_, err := c.CancelBuild(ctx, req)
	if err != nil {
	// Not Fatal: maybe cancel failed because the build exited.
	// Waiting for it to stop running below will take care of that case.
	log.Printf("cancel %v: %v", id, err)
	}

	// Wait for build to report being stopped,
	// in case cancel only queues the cancellation and doesn't actually wait,
	// or in case cancel failed.
	// Willing to wait a few minutes.
	now := time.Now()
	for time.Since(now) < 3*time.Minute {
	b := getBuild(c, ctx, id)
	if b.Status != cloudbuildpb.Build_WORKING {
	log.Printf("canceled %v: now %v", id, b.Status)
	return
	}
	time.Sleep(10 * time.Second)
	}
	log.Fatalf("cancel %v: did not stop", id)
	}

	// run runs the given command line and returns the standard output, with spaces trimmed.
	func run(args ...string) string {
	var stdout, stderr bytes.Buffer
	cmd := exec.Command(args[0], args[1:]...)
	cmd.Stdout = &stdout
	cmd.Stderr = &stderr
	if err := cmd.Run(); err != nil {
	log.Fatalf("exec %v: %v\n%s%s", args, err, stdout.String(), stderr.String())
	}
	return strings.TrimSpace(stdout.String())
	}