Mount Go build cache into crossbuild container (#9094)

* Mount Go build cache into crossbuild container

* Run crossbuild container as host user

* Update dev-tools/mage/crossbuild.go

Co-authored-by: Victor Martinez <victormartinezrubio@gmail.com>

* Fix formatting

* Control mounting mod cache with env variable

* Control mounting build cache with env variable

* Use a volume for Go build cache

---------

Co-authored-by: Victor Martinez <victormartinezrubio@gmail.com>
(cherry picked from commit fd4de6b)

Author: 2 people

dev-tools/mage/clean.go

@@ -25,7 +25,7 @@ var DefaultCleanPaths = []string{
 	"_meta/kibana/7/index-pattern/{{.BeatName}}.json",
 }
 
-// Clean clean generated build artifacts.
+// Clean clean generated build artifacts and caches.
 func Clean(pathLists ...[]string) error {
 	if len(pathLists) == 0 {
 		pathLists = [][]string{DefaultCleanPaths}
@@ -38,5 +38,8 @@ func Clean(pathLists ...[]string) error {
 			}
 		}
 	}
+	if CrossBuildMountBuildCache {
+		return sh.Run("docker", "volume", "rm", "-f", CrossBuildBuildCacheVolumeName)
+	}
 	return nil
 }

dev-tools/mage/crossbuild.go

@@ -274,6 +274,9 @@ func (b GolangCrossBuilder) Build() error {
 		return fmt.Errorf("failed to determine repo root and package sub dir: %w", err)
 	}
 
+	uid := os.Getuid()
+	gid := os.Getgid()
+
 	mountPoint := filepath.ToSlash(filepath.Join("/go", "src", repoInfo.CanonicalRootImportPath))
 	// use custom dir for build if given, subdir if not:
 	cwd := repoInfo.SubDir
@@ -315,8 +318,8 @@ func (b GolangCrossBuilder) Build() error {
 
 	if runtime.GOOS != "windows" {
 		args = append(args,
-			"--env", "EXEC_UID="+strconv.Itoa(os.Getuid()),
-			"--env", "EXEC_GID="+strconv.Itoa(os.Getgid()),
+			"--env", fmt.Sprintf("EXEC_UID=%d", uid),
+			"--env", fmt.Sprintf("EXEC_GID=%d", gid),
 		)
 	}
 	if versionQualified {
@@ -328,6 +331,14 @@ func (b GolangCrossBuilder) Build() error {
 		args = append(args, "-v", hostDir+":/go/pkg/mod:ro")
 	}
 
+	buildCacheLocation := "/tmp/.cache/go-build"
+	if CrossBuildMountBuildCache {
+		// Mount the go build cache volume into the container.
+		args = append(args,
+			"-v", fmt.Sprintf("%s:%s", CrossBuildBuildCacheVolumeName, buildCacheLocation),
+		)
+	}
+
 	// Mount /opt/git-mirrors (if present) to resolve git alternates in CI
 	if _, err := os.Stat("/opt/git-mirrors"); err == nil {
 		args = append(args, "-v", "/opt/git-mirrors:/opt/git-mirrors:ro")
@@ -344,6 +355,7 @@ func (b GolangCrossBuilder) Build() error {
 	args = append(args,
 		"--rm",
 		"--env", "GOFLAGS=-mod=readonly",
+		"--env", fmt.Sprintf("GOCACHE=%s", buildCacheLocation), // ensure this is writable by the user
 		"--env", "MAGEFILE_VERBOSE="+verbose,
 		"--env", "MAGEFILE_TIMEOUT="+EnvOr("MAGEFILE_TIMEOUT", ""),
 		"--env", fmt.Sprintf("SNAPSHOT=%v", Snapshot),

dev-tools/mage/settings.go

@@ -72,7 +72,11 @@ var (
 
 	// CrossBuildMountModcache mounts $GOPATH/pkg/mod into
 	// the crossbuild images at /go/pkg/mod, read-only,  when set to true.
-	CrossBuildMountModcache = true
+	CrossBuildMountModcache = EnvOr("CROSSBUILD_MOUNT_MODCACHE", "true") == "true"
+
+	// CrossBuildMountBuildCache mounts the Go build cache into golang-crossbuild containers
+	CrossBuildMountBuildCache      = EnvOr("CROSSBUILD_MOUNT_GOCACHE", "true") == "true"
+	CrossBuildBuildCacheVolumeName = "elastic-agent-crossbuild-build-cache"
 
 	BeatName        = EnvOr("BEAT_NAME", defaultName)
 	BeatServiceName = EnvOr("BEAT_SERVICE_NAME", BeatName)