feat: host builder metadata envs (#2195)

Author: lkingland

pkg/oci/builder_test.go

@@ -330,3 +330,92 @@ type fileInfo struct {
 	Executable bool
 	Linkname   string
 }
+
+// TestBuilder_StaticEnvs ensures that certain "static" environment variables
+// comprising Function metadata are added to the config.
+func TestBuilder_StaticEnvs(t *testing.T) {
+	root, done := Mktemp(t)
+	defer done()
+
+	staticEnvs := []string{
+		"FUNC_CREATED",
+		"FUNC_VERSION",
+	}
+
+	f, err := fn.New().Init(fn.Function{Root: root, Runtime: "go"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := NewBuilder("", true).Build(context.Background(), f, TestPlatforms); err != nil {
+		t.Fatal(err)
+	}
+
+	// Assert
+	// Check if the OCI container defines at least one of the static
+	// variables on each of the constituent containers.
+	// ---
+	// Get the images list (manifest descripors) from the index
+	ociPath := path(f.Root, fn.RunDataDir, "builds", "last", "oci")
+	data, err := os.ReadFile(filepath.Join(ociPath, "index.json"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	var index struct {
+		Manifests []struct {
+			Digest string `json:"digest"`
+		} `json:"manifests"`
+	}
+	if err := json.Unmarshal(data, &index); err != nil {
+		t.Fatal(err)
+	}
+	for _, manifestDesc := range index.Manifests {
+
+		// Dereference the manifest descriptor into the referenced image manifest
+		manifestHash := strings.TrimPrefix(manifestDesc.Digest, "sha256:")
+		data, err := os.ReadFile(filepath.Join(ociPath, "blobs", "sha256", manifestHash))
+		if err != nil {
+			t.Fatal(err)
+		}
+		var manifest struct {
+			Config struct {
+				Digest string `json:"digest"`
+			} `json:"config"`
+		}
+		if err := json.Unmarshal(data, &manifest); err != nil {
+			t.Fatal(err)
+		}
+
+		// From the image manifest get the image's config.json
+		configHash := strings.TrimPrefix(manifest.Config.Digest, "sha256:")
+		data, err = os.ReadFile(filepath.Join(ociPath, "blobs", "sha256", configHash))
+		if err != nil {
+			t.Fatal(err)
+		}
+		var config struct {
+			Config struct {
+				Env []string `json:"Env"`
+			} `json:"config"`
+		}
+		if err := json.Unmarshal(data, &config); err != nil {
+			panic(err)
+		}
+
+		containsEnv := func(ss []string, name string) bool {
+			for _, s := range ss {
+				if strings.HasPrefix(s, name) {
+					return true
+				}
+			}
+			return false
+		}
+
+		for _, expected := range staticEnvs {
+			t.Logf("checking for %q in slice %v", expected, config.Config.Env)
+			if containsEnv(config.Config.Env, expected) {
+				continue // to check the rest
+			}
+			t.Fatalf("static env %q not found in resultant container", expected)
+		}
+	}
+}

pkg/oci/containerize.go

@@ -8,9 +8,11 @@ import (
 	"io"
 	"io/fs"
 	"os"
+	"os/exec"
 	slashpath "path"
 	"path/filepath"
 	"strings"
+	"time"
 
 	v1 "github.com/google/go-containerregistry/pkg/v1"
 	"github.com/google/go-containerregistry/pkg/v1/tarball"
@@ -428,7 +430,7 @@ func newConfig(cfg *buildConfig, p v1.Platform, layers ...v1.Layer) (desc v1.Des
 		Variant: p.Variant,
 		Config: v1.Config{
 			ExposedPorts: map[string]struct{}{"8080/tcp": {}},
-			Env:          cfg.f.Run.Envs.Slice(),
+			Env:          newConfigEnvs(cfg),
 			Cmd:          []string{"/func/f"}, // NOTE: Using Cmd because Entrypoint can not be overridden
 			WorkingDir:   "/func/",
 			StopSignal:   "SIGKILL",
@@ -482,6 +484,46 @@ func newConfig(cfg *buildConfig, p v1.Platform, layers ...v1.Layer) (desc v1.Des
 	return
 }
 
+// newConfigEnvs returns the final set of environment variables to build into
+// the container.  This consists of func-provided build metadata envs as well
+// as any environment variables provided on the function itself.
+func newConfigEnvs(cfg *buildConfig) []string {
+	envs := []string{}
+
+	// FUNC_CREATED
+	// Formats container timestamp as RFC3339; a stricter version of the ISO 8601
+	// format used by the container image manifest's 'Created' attribute.
+	envs = append(envs, "FUNC_CREATED="+cfg.t.Format(time.RFC3339))
+
+	// FUNC_VERSION
+	// If source controlled, and if being built from a system with git, the
+	// environment FUNC_VERSION will be populated.  Otherwise it will exist
+	// (to indicate this logic was executed) but have an empty value.
+	if cfg.verbose {
+		fmt.Printf("cd %v && export FUNC_VERSION=$(git describe --tags)\n", cfg.f.Root)
+	}
+	cmd := exec.CommandContext(cfg.ctx, "git", "describe", "--tags")
+	cmd.Dir = cfg.f.Root
+	output, err := cmd.Output()
+	if err != nil {
+		if cfg.verbose {
+			fmt.Fprintf(os.Stderr, "unable to determine function version. %v", err)
+		}
+		envs = append(envs, "FUNC_VERSION=")
+	} else {
+		envs = append(envs, "FUNC_VERSION="+strings.TrimSpace(string(output)))
+	}
+
+	// TODO: OTHERS?
+	// Other metadata that may be useful. Perhaps:
+	//   - func client version (func cli) used when building this file?
+	//   - user/environment which triggered this build?
+	//   - A reflection of the function itself?  Image, registry, etc. etc?
+
+	// ENVs defined on the Function
+	return append(envs, cfg.f.Run.Envs.Slice()...)
+}
+
 func newImageIndex(cfg *buildConfig, imageDescs []v1.Descriptor) (index v1.IndexManifest, err error) {
 	index = v1.IndexManifest{
 		SchemaVersion: 2,