cmd/coordinator: stop EC2 buildlet pool

All EC2 builders have been migrated to LUCI and stopped in coordinator.
Stop the pool as well. Its permissions have been revoked and it prints
errors continuously. Also drop an unhelpful printf.

For golang/go#67761.

Change-Id: I6ce48e222a2dc88f7d5a7386f8cc9d5b1e8bac71
Reviewed-on: https://go-review.googlesource.com/c/build/+/612559
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Tim King <taking@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>

cmd/coordinator/coordinator.go

@@ -61,6 +61,7 @@ import (
 	gomoteprotos "golang.org/x/build/internal/gomote/protos"
 	"golang.org/x/build/internal/https"
 	"golang.org/x/build/internal/metrics"
+	"golang.org/x/build/internal/migration"
 	"golang.org/x/build/internal/secret"
 	"golang.org/x/build/kubernetes/gke"
 	"golang.org/x/build/maintner/maintnerd/apipb"
@@ -285,8 +286,8 @@ func main() {
 	if *mode == "prod" || (*mode == "dev" && *devEnableEC2) {
 		// TODO(golang.org/issues/38337) the coordinator will use a package scoped pool
 		// until the coordinator is refactored to not require them.
-		ec2Pool := mustCreateEC2BuildletPool(sc, sp.IsSession)
-		defer ec2Pool.Close()
+		ec2PoolClose := mustCreateEC2BuildletPool(sc, sp.IsSession)
+		defer ec2PoolClose()
 	}
 
 	if *mode == "dev" {
@@ -2248,7 +2249,12 @@ func mustCreateSecretClientOnGCE() *secret.Client {
 	return secret.MustNewClient()
 }
 
-func mustCreateEC2BuildletPool(sc *secret.Client, isRemoteBuildlet func(instName string) bool) *pool.EC2Buildlet {
+func mustCreateEC2BuildletPool(sc *secret.Client, isRemoteBuildlet func(instName string) bool) (close func()) {
+	if migration.StopEC2BuildletPool {
+		log.Println("not creating EC2 buildlet pool")
+		return func() {}
+	}
+
 	awsKeyID, err := sc.Retrieve(context.Background(), secret.NameAWSKeyID)
 	if err != nil {
 		log.Fatalf("unable to retrieve secret %q: %s", secret.NameAWSKeyID, err)
@@ -2268,7 +2274,7 @@ func mustCreateEC2BuildletPool(sc *secret.Client, isRemoteBuildlet func(instName
 	if err != nil {
 		log.Fatalf("unable to create EC2 buildlet pool: %s", err)
 	}
-	return ec2Pool
+	return ec2Pool.Close
 }
 
 func mustRetrieveSSHCertificateAuthority() (privateKey []byte) {

cmd/coordinator/internal/legacydash/ui.go

@@ -16,7 +16,6 @@ import (
 	"html/template"
 	"log"
 	"net/http"
-	"os"
 	"sort"
 	"strconv"
 	"strings"
@@ -1176,7 +1175,6 @@ func shortUser(user string) string {
 }
 
 func httpStatusOfErr(err error) int {
-	fmt.Fprintf(os.Stderr, "Got error: %#v, code %v\n", err, grpc.Code(err))
 	switch grpc.Code(err) {
 	case codes.NotFound:
 		return http.StatusNotFound

internal/migration/migration.go

@@ -9,6 +9,7 @@ package migration
 const (
 	StopLegacyMiscCompileTryBots = true
 	StopInternalModuleProxy      = true
+	StopEC2BuildletPool          = true
 
 	// StopPortedBuilder controls whether ported builders should be stopped,
 	// instead of just made invisible in the web UI.